Post by Tom/CalClassic on Aug 30, 2010 16:34:10 GMT -5
Planning Descent with no DME:
calclassic.proboards.com/index.cg....ead=3042&page=1
From FSAviator:
<<FsAviator, thanks for your reply. If you have time to do so, could you elaborate on timing descent as well?>>
Asking me to 'elaborate' is always dangerous :->
I have been very busy with other things, but I am happy to return this thread to focus on the original question and the misconception it was based on. In this very long post I will try to explain the priorities of arrival planning in piston engined propliners, and what drives them. Where necessary I will focus attention on essential differences between real life and use of MSFS. Along the way I will try to highlight why I believe propliner enthusiasts are in danger of (literally) wandering off course and in doing so I will try to address all the engine management issues which arose in a thread which only asked a question about 4D navigation.
It is easy to assert in a web page, forum, or product tutorial that a procedure, or a rule of thumb, will work. Proving that it won't and explaining why a different strategy is required is much more complex and demanding. To understand why ToD must be time based it is necessary to follow the 'chain reaction' of the arrival phase through the reactions that it causes from start to finish. It's going to be a long ride. I must start with a statement of the principles behind the required technique, and only later provide the worked numerical examples which demonstrate the need for the principle stated earlier.
Successful arrival phase planning and execution requires us to understand why some operating targets are paramount, (relate to safety critical issues), and therefore always initiate the sequence of crew actions that then either cause, else limit, the next step of the chain reaction, while other subordinate crew actions are only necessary responses to earlier inputs, by a different member of the flight deck crew, to deliver the same operating targets within the same operating limits.
Flight simulation is the demonstration of real world compliant flight skills in a virtual environment.
During flight simulation compliance with safety criteria is always paramount, and must be ensured before devoting time to profit maximisation or efficient operation of engines. We must therefore start by coming to terms with the reality that arrival planning and execution is all about ensuring safety, above all else, by avoiding *unseen* obstacles by mandatory distances, whether flying head up in sunshine, or head down in cloud.
Most of the unseen obstacles we must learn to avoid are the airspace reserved for other airfields and conflicting air traffic on other routes. In real life avoidance of those traffic conflictions is planned and executed as the highest priority. It is not reactive, and it is not ignored. In MSFS we may not see the traffic conflicts we must avoid, even if the weather is good, but they are there, and if we intend to incorporate realism we can and should successfully avoid those safety critical conflicts. It should be obvious (but apparently is not) that arrival phase planning and execution in MSFS must also avoid controlled flight into terrain when descending in solid cloud.
Consequently demonstrating the skill to avoid real world traffic conflictions, not just terrain, by achieving real world 4D navigational compliance, is the key to realistic (propliner) flight simulation. Because navigation compliance is always the primary task, with profit maximisation as the secondary task, tertiary tasks like engine micro management are constrained and conditioned by the primary and secondary tasks. The FE is not in charge. He matches engine output to the decisions made by CAPT during planning of the arrival phase, and the subsequent actions of PF during execution of the arrival phase.
During (solo desk top) propliner simulation we are always first and foremost CAPT. We use our learned skills to decide what must be done to achieve 4D navigation compliance on today's route. Only then can we become PF using our learned skills to impose the progressive aircraft energy state (IAS and matched VSI) targets, synchronised with progressive variable geometry (VG) state targets, which will achieve the plan we formulated earlier as CAPT. Last and least we can also perform the tertiary role of FE or PNF to manage engines, also in pursuit of the 4D navigation plan we decided upon during our prior captaincy decision making cycle. An arrival plan always includes both VSI and IAS targets and may include Mach limits. Engine management is not independent of those energy state targets and limits. Our engine management plan is driven by our energy state targets and limits, not engine limits. If we fail to formulate a prior realistic (or any) energy state and synchronised variable geometry state arrival plan, when we later assume the tertiary roles of FE or PNF, engine management also becomes randomised.
In real life Time of Descent (ToD) is decided and imposed by ATC, although they may offer the clearance; 'N123MS cleared to the Initial Approach Fix. When ready descend to altitude xxxxx........'. In real life ATC decide when airliners descend, what altitude it is safe to descend to, what course they must fly while descending. MSFS delivers none of that reality.
When we simulate the realistic operation of propliners in MSFS we must formulate the necessary arrival plan. If we desire realism the 4D navigation plan we devise as CAPT must be the one that ATC would impose in real life. Microsoft do not supply that plan. That plan is supplied to us by the real world ATC authority, or a contractor such as Jeppesen, in the form of published instrument arrival and approach 'plates' (IAPs) or 'charts' (IACs), which real pilots must download before flight so that they can study and understand the different 4D navigation compliance required after ToD and for each destination. If we seek realism within propliner simulation we must do the same. Those flight safety downloads are usually free and the relevant URLS are provided from;
www.calclassic.com/propliner_tutorial_charts.htm
The 2008 Propliner Tutorial explains how to use them within MSFS.
If we desire realism we need to know where the real ATC authority require us to route to, and what altitude we are allowed to descend to, in order to ensure that we avoid military danger areas, nature reserves, air defence interception zones, prohibited airspace, and all the routes and airspace being used by other aeroplanes that we must avoid whether we are navigating head up in sunlight, or head down in cloud. Almost all of the obstacles that real pilots must avoid are invisible, all of the time. On some days the terrain is invisible as well. That is what drives the arrival plan, and the timing of descent from cruise (ToD), in real life and in MSFS.
So in MSFS, in order to calculate ToD, we always need to know what constitutes 4D navigational compliance after ToD, so that we can time when we must terminate our cruise phase and begin our arrival phase. Our primary task during propliner simulation is always to perform the planning and decision making role of CAPT. Execution comes later to deliver the plan we formulate first.
During the arrival phase our task as CAPT is compliant avoidance of many always invisible things. So when we are in cloud and the terrain is just one more invisible thing we must avoid it does not matter at all. ToD is just the first waypoint in that 4D compliance and it is always a TIME not a place.
Time of Descent (ToD) is planned so that our subsequent descent profile towards the real Initial Approach Fix (IAF), *not the airfield visual circuit*, passes clear of all obstacles, (visible or invisible), laterally as well as vertically, whether or not we are in cloud today / tonight. The real IAF is placed so that our descent path misses the mountain. It matters where the real IAF is. Time of Descent planning and subsequent descent procedures which rely on the terrain between ToD and the IAF being visible have no relevance to propliner simulation. At some point in our virtual propliner captaincy career we must learn to formulate 4D navigation plans which will work in bad weather so that we can progress to flying propliner schedules, whatever the weather.
Each real arrival procedure has a Minimum Sector (or airway transition) Altitude (MSA), below which we must not descend until we reach our IAF. We TIME descent so that we level and maintain that real world MSA when we are no more than a few *minutes* short of the real world IAF. Propliner enthusiasts cannot hope to plan that correctly, or later execute that correctly, unless they bother to download the real ATC procedure to discover where the real IAF is for today's destination, and the MSA at which they must cross it! Ignoring where we are required to position the aircraft on today's route, and the altitude we must descend to before we cross it, will always cause descent at the wrong time, and in the wrong direction, to the wrong altitude.
Aerial navigation is 4D not 2D. Consequently DME is always irrelevant to ToD planning whether or not we have it in our cockpit today. Some real world procedures may appear to disagree with that statement, but I will explain why they don't below. ToD always depends on the weather today, never where we are. If we must lose 10,000 feet to reach our MSA before the IAF, (in a piston engined propliner), since we always plan to descend at minus 500 VSI (see later), we always descend 20 minutes before the IAF. We don't need a graph, or a diagram, or a calculator!
Because we always PLAN to descend at minus 500 VSI, we descend 20 minutes before the IAF, if we are cruising 10,000 feet above the MSA for that IAF,
If our cruising velocity is 180 KTAS and there is a 0 KTS headwind we must descend at 60 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS headwind we must descend at 40 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS tailwind we must descend at 80 DME today.
DME has no role to play at all. It does not influence *when* we must descend. GPS also has no role to play at all. The gauge we use to plan and execute descent is called a *clock*. Aerial navigation is 4D not 2D. That is not just a meaningless phrase, it means that aerial navigation is performed using a clock and a flight plan both carefully calibrated and updated using a concept called 'minutes' with an estimate for the (every) next waypoint in minutes, not some other useless random gauge that does not display minutes.
If we need to lose 10,000 feet we descend 20 minutes before the IAF *every* day using the *clock* and our DME is different and irrelevant every day, because the wind and weather are different every day. 2D navigation techniques that we may have learned in powered terrestrial vehicles, involving consideration of place and distance and speed are utterly useless in aeroplanes. Aerial navigation must be 4D and is based instead on TIME.
We must level at MSA a few *minutes* before the IAF and in most classic era propliners we must reduce our profile drag (IAS) far below prior cruise IAS before we cross the IAF else we won't be able to use our autopilot to fly the approach procedure. So we need to level a few *minutes* before the IAF. The miles (or kilometres) involved vary with the wind every day and we never care. We never allow ourselves to be confused by statute miles or nautical miles or kilometres, because none of them ever have any relevance! A minute is a minute in a DC-3 or a Fiat G.12, in every jurisdiction, and on any date. It matters! The real procedures are international. A clock is a clock. There is nothing new to learn in a new cockpit or a new jurisdiction. It matters!
So having always planned descent at minus 500 VSI as soon as it is safe to do so, (see later), we always increase to minus 700 VSI. In any piston propliner, anywhere, because that causes us to level out at MSA a few minutes before the IAF, at any weight, in any weather, in any jurisdiction. We need those constant minutes to reduce our IAS and vary our geometry. Distances are not the point. What we must accomplish takes a fixed TIME to accomplish.
We must employ the 'Keep It Simple Stupid' (KISS) concepts of planning and execution whenever we are operating an aeroplane (even in a simulator).
In a metric cockpit minus 500 VSI is (treated as) minus 2.5 metres/sec and so minus 700 VSI is minus 3.5 m/s.
The Minimum Sector Altitude cited on the real IAP we downloaded, and we are now descending to, is only safe to a distance of 25 miles from our destination. There may be much higher mountains between ToD and the IAF! We must not descend too soon, else we level out on the wrong side of the mountains, below the mountain peaks. We must not descend too late because we must be level at MSA and at target IAS, in our target variable geometry state, before we cross the IAF. We must learn and practice compliant 4D navigation skills in good visibility so that we can replicate them in cloud when we fly the same schedule tomorrow with a very different wind vector. *Nothing must differ*. 'Keep It Simple Stupid'
Descending too soon and too late are not concepts relating to distance. They are concepts relating to TIME. Aviation cannot work any other way because in an aeroplane, (unlike a powered terrestrial vehicle), our speed (KTS) never matches our velocity (KTAS) or our profile drag (KIAS), because unlike a powered terrestrial vehicle aeroplanes are blown about by the wind. We are blown variably every minute and every day so we must operate aeroplanes using strategies which are safe regardless! We must use TIME as the basis of aerial navigation. We must navigate aeroplanes using a clock and a flight plan, both calibrated and updated in minutes, any date, any aeroplane, any jurisdiction.
All of the above is about safety which is always paramount in our planning as CAPT. When we have a headwind we must descend later *not* at the same DME, else we descend into the wrong side of the mountains between ToD and the IAF. Sure we must descend down a conical funnel and that funnel always ends at real MSA, at the real IAF, but it starts some place different every day on the same route. It starts the same number of minutes before the IAF every day so that the funnel is compliantly raised or lowered to allow for the wind. No complex calculations, no rules of thumb, just the fully correct and *simpler* mathematical solution, in every jurisdiction, at any date, in any weather, at any weight, at any prior cruise IAS, at any prior cruise TAS, and at any prior cruise KTS, all of the time! If we need to lose 10,000 feet in a piston propliner ToD is 20 minutes before the IAF every day and everywhere. Pretending that descent planning in piston propliners is complicated, is really dumb. If it were complicated humans would screw up too often. 'Keep It Simple Stupid'
All the above is an essential but simple part of the captaincy decision making cycle on every flight.
1) Where is the next compliant real world fix on this real flight?
2) What (minimum) real world altitude is compliant over that fix?
3) When must I begin the altitude change to achieve that compliance?
In a piston propliner the answer is *always* two minutes per thousand feet of altitude variation. After initiating the altitude change at the correct TIME we 'may' elect to climb or descend a *little* faster than plus or minus 500 VSI,and by default we will actually descend at minus 700 VSI (both during the arrival phase to the Initial Approach Fix, and during the later approach phase from our Final Approach Fix). Provided we never exceed minus 700 VSI we will not impact the invisible mountain as we descend in cloud. It matters! The real ATC authority positioned the real IAF and FAF accordingly and so we will never lose control of our IAS or our glidepath, or have the slightest difficulty progressing the aeroplane through the required synchronised variable geometry state changes, if we fly the real route in real 4D compliance, just like real pilots.
Flight sim enthusiasts constantly make the mistake of supposing that making up some nonsense is easier than following the real procedures, It never will be because many millions of dollars have been spent making the real procedure the one that is easiest to navigate in 4D while avoiding all of the things that must be avoided, while carefully allowing the TIME real aircrew (and we) need to achieve all the IAS and synchronised variable geometry state changes mandated. The real Initial Approach Fix is placed carefully not randomly. The real Final Approach Fix (if different) is also placed carefully, not randomly. The different compliant altitude for crossing those two fixes, and the compliant IAS for crossing those two fixes, has been calculated carefully not randomly. The propliners and their engines, whose operation we are simulating, were designed to achieve exactly that regulatory compliance and not some random made up nonsense. Achieving real world 4D navigation compliance is not only satisfying, because it is what flight simulators exist to teach, it is also the key to making piston propliner operation unrushed and as easy as it can be.
If we are to have any hope of achieving realistic engine management we need to subordinate the tertiary role of the FE (or PNF) to the secondary role of PF as he maximises profit while CAPT imposes safety by planning and telling PF (the helmsman) how to achieve 4D navigational compliance at all times. In MSFS we must acquire the skill to explain 4D navigation compliance to ourselves. We must acquire the skills needed to be captain first, helmsman second, and engineer last.
Now the apparent exception I mentioned earlier. After long range DME was rolled out, from the early 1950s onwards, there were a few places in which descent below MSA was allowed prior to the IAF upon reaching a specific DME from the relevant navaid. What to do if our cockpit today has no DME is obvious. We cannot descend below MSA until the IAF. Note that this has nothing to do with ToD. After long range DME exists, if our cockpit also has a receiver, the real world procedures allow descent below MSA before the IAF by reference to DME. ToD on the other hand is when we depart cruising level for the MSA. DME is not involved in calculation of compliant descent from cruise. It cannot be.
This is all further explained and illustrated in full in Part 3 of the 2008 Propliner Tutorial citing an arrival to KIZG over the White Mountains with a fully worked tutorial exercise which should be flown in the FS9 Grumman Goose after applying the Calclassic update. During training we need lots of TIME to keep up with events and we should not train in over complex, over rapid aeroplanes, or aeroplanes with defective flight dynamics or inadequate handling notes. I am not going to repeat all of the necessary detail here and the required IAP which must be studied is part of the 2008 Propliner Tutorial download;
www.calclassic.com/tutorials
www.calclassic.com/propliner_tutorial_charts.htm
The issue of how fast to close throttles raised later in this thread is consequently being debated in a vacuum of intention that does not exist in the real world.
All complex piston engines with complex gas compressors have restrictions concerning either rate of throttle closure in very cold air (re shock cooling), or they have minimum safe in flight manifold pressure values in any air (sometimes re plug fouling), or both. Liquid cooled engines are buffered by slower change of coolant temperature and will typically have only a minimum in flight engine pressure value. Many, but not all, liquid cooled engines will tolerate rapid throttle closure from no more than max cruise MAP/BOOST/C/ATA *to the cited high minimum*.
Conversely the injunction against closing the throttles of complex supercompressed air cooled engine rapidly 'typically' cites 'no more than 3 inches per minute', but it is only generic MSFS shorthand for a potentially more complex reality. It is anyway only a tertiary priority that approximates reality well enough and allows us to struggle with the problems involved in planning and executing descent from high altitude in complex classic era propliners.
Nobody has any reason to care how engine pressure is calibrated by different cultures. We do not need to know why the targets and limits are what they are, even though I am now explaining exactly that here. We only need to comply. In order to comply we need MSFS propliners with on screen handling notes which explain what constitutes compliance. The cited minima may be nothing to do with shock cooling, or plug fouling, or any similar issue, since each phase of every flight has target engine RPM values, and it is possible that in order to avoid outputting damaging torque the minimum in flight engine operating pressure value is set for that purpose versus target RPM, not shock cooling, or plug fouling etc.
However many propliner enthusiasts then confuse operating limits with operating targets, slavishly applying engine limits as targets because many propliner enthusiasts now give too much priority to the tertiary task of engine management while failing to achieve the primary goal of compliant 4D navigation, and the secondary goal of energy state (IAS & VSI) compliance during synchronised variable geometry state compliance. Propliner enthusiasts who allow navigation, and energy state, and variable geometry state, to randomise cannot have an engine management plan that is not also randomised. The engine management plan is the consequence of the navigation plan, the energy state plan and the variable geometry state plan we decided upon earlier as CAPT. Engine criteria are never the driver of the arrival plan. The tertiary goal of FE (or PNF) is to help deliver the energy state target within the 4D navigation target which CAPT decided and imposed on PF.
With practice, practice, practice, propliner enthusiasts should not struggle to understand and achieve real world 4D navigation compliance. The questions;
1) Where is the next compliant real world fix on this real flight?
2) What real world (minimum) altitude is compliant over that fix?
3) When must I begin the altitude change to achieve that compliance?
are not too complex for anyone involved in propliner simulation to understand or resolve. Failure to do so is always the consequence of never developing the intention to succeed. Once we develop the intention to incorporate realism into our propliner simulation, by downloading the real procedures and following them, we soon can. Our skills challenge then moves on to profit maximisation during accomplished 4D navigation compliance.
To maximise profit after ToD we must target prior cruise IAS, (whatever it was at current weight in the current weather today), since to maximise profit we must fly a 'cruise descent' pegging our profile drag at the profit perfect prior cruise value. On reaching ToD PF initiates descent at minus 500 VSI. At constant power profile drag (IAS) would rise. It is the job of FE (or PNF) to prevent that rise in profile drag by careful retardation of throttle *subject to the cited engine limits*.
Whatever cooling type our engines have, we never have the intention to close throttle rapidly from cruise power to minimum safe power because engine management is only ever tertiary. We use the throttles to maximise profit by making every effort to sustain prior cruise IAS at minus 500 VSI. We could suddenly retard to zero boost safely in an Argonaut, but we never have that intention anyway. The engine management plan is a consequence of the navigation plan and energy state plan for this arrival phase which we devised as CAPT after studying the real 4D navigation compliance procedures.
Engine management during the arrival phase is just a function of the more important profile drag (IAS) plan to maximise profit and conserve our precious holding and diversion fuel. If prior cruise just before ToD was at a profile drag of 182 KIAS today we seek to *prolong* that Newtonian perfection of equilibrium *which was decided and imposed by the weather around us today*, and in a perfect world we wish to prolong 'cruise descent' at prior cruise profile drag (IAS), for as long as possible. We use throttle to deliver the IAS plan. We do not simply reduce throttle as fast as possible! In some particular weather at some particular weight that might be correct, but we are required to behave more intelligently than that.
When FE manages to sustain prior cruise IAS at minus 500 VSI, (without exceeding prior cruise IAS), and without throttling down faster than the operating limit cited for that engine, PF must now, and only now, increase his energy state target to minus 700 VSI and FE (or PNF) must then reduce throttle further *to attempt to sustain prior cruise IAS* all over again at minus 700 VSI. Throttles are closed, or opened, during descent to deliver our arrival phase IAS target, while descending at our arrival phase VSI target, not randomly and not automatically to a limit value unrelated to the captain's (our) energy state plan.
Allowing profile drag (IAS) to rise beyond prior cruise profile drag during an arrival just squanders fuel. That unwanted extra profile drag isn't free. If we allow our profile drag (IAS) to exceed prior cruise profile drag we used diversion fuel to add unwanted extra profile drag (IAS) and the drag we added is slowing us down. We must never confuse a rise in profile drag (IAS) with a rise in velocity (TAS). There is no aeroplane speed indicator in classic propliners! Allowing our profile drag (IAS) to exceed the prior cruise value squanders our holding and diversion fuel. The job of FE (or PNF) during the piston propliner arrival phase is to sustain prior cruise IAS, first at minus 500 VSI, and after that has been achieved, we seek to replicate that IAS operating target all over again at minus 700 VSI.
If we have super compressed air cooled engines, and if the descent is from high cold air, we have a grave risk of shock cooling. IAS = profile drag is the same thing as cooling drag. We must avoid adding more and more cooling (IAS) over air cooled engines in high cold air. In an Argonaut we have more flexibility to vary throttle quickly than in an DC6B and we also have more flexibility concerning IAS. We can progress from minus 500 VSI to minus 700 VSI more quickly in an Argonaut, but our minimum safe engine running pressure is much more restrictive in an Argonaut. For instance a DC6B crew can eventually reduce to 20 inches, but an Argonaut crew must sustain a minimum of zero boost (30 inches).
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Descent and Holding: Argonaut
ABOVE FL200 <= 200 KIAS (Mmo)
NEVER EXCEED 223 KIAS (Vmo)
DO NOT SHOCK COOL ENGINES
BOOST => ZERO <<<<<<<<<
RPM => 2200 whilst => FL130
Passing (below) FL130
BOOST => ZERO
RPM = 2000
..........
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Later in the descent the Argonaut will have more power applied and more unwanted profile drag wasting more fuel, but the high unwanted IAS won't damage liquid cooled engines because the Rolls Royce engine control computer alters radiator gill status and oil cooler gill status and mixture, entirely automatically, preserving engine temperature to that which Rolls Royce deem most satisfactory. The crew of an Argonaut control none of the engine cooling devices. With an air cooled engine in a DC6B if we allow IAS to rise we impose unwanted direct cooling and that unwanted cooling is proportional to 'IAS squared' !
Since IAS rising above prior cruise IAS is also squandering fuel it is doubly bad with supercompressed air cooled engines. Now remember if we mismanage rate of throttle movement, it may be the gas compressor running at many times engine RPM that is going to fail, (especially in high blower), not the engine itself, while it is the engine that suffers if we eventually reduce running pressure too low and cause plug fouling, or a gear box that will shatter if we apply too much torque to it with a forbidden MAP v RPM combination. This isn't just about 'shock cooling'. That is just 'MSFS shorthand' for all the things that can damage an engine, or the gas compressor, or the several gear boxes and associated automatic clutches, in air of any temperature. Supercompressed engines always have a minimum safe in flight pressure and may have a rate of throttle closure injunction, but during the arrival phase we use throttle to sustain prior cruise IAS, and it is that which drives throttle motion, subject to cited injunctions.
The real problem may be nothing to do with engine temperature anyway. It may relate to unsafe torque. For us in MSFS the issue is simply compliance with the handling notes using the units of engine pressure measurement cited whether MAP in a US cockpit, or BOOST in a British cockpit, or C (=Kg/cm^2) in an Italian cockpit. or ATA in a German cockpit, or decimetres of mercury in a Soviet cockpit. Complex supercompressed air cooled engines, which may not be radials, require more care to avoid damage, but often allow safe running at lower engine pressure 'eventually'.
Now having said all that in many complex piston propliners once we (eventually) invoke minus 700 VSI the existence of engine operating limits (either rate or minimum) will (eventually) prevent FE (else PNF) from providing the throttle closure that would prevent our profile drag from rising above prior cruise IAS and (eventually) later in the descent it nearly always will. Nevertheless as PF we must invoke minus 700 VSI (eventually) in order to be level at our Minimum Sector Altitude a few minutes before the Initial Approach Fix, so that we have TIME to achieve our target IAS, and our target variable geometry state for crossing the IAF, maintaining our MSA, whatever the wind and weather today. So when simulating operation of a DC6B the procedures are;
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Descent:
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS
DO NOT EXCEED Vno = 251 KIAS
COWL FLAPS = CLOSED
RPM = 2000
REDUCE MAP in stages of 3 inches (per minute)
MINIMUM 20 INCHES MAP <<<<<<<<<<
See CARB HEAT below
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TerminalHolding:
Approaching IAF / Hold
COWL FLAPS = 1 degree
2000 RPM
REDUCE < 160 KIAS
FLAP = STAGE 1
REDUCE < 150 KIAS
Crossing IAF entering Hold
FLAP = STAGE 2
MAINTAIN 140 KIAS
Check CHT < 232C
Plan 2100 PPH
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Our energy state targets and our variable geometry state targets are mandatory and invariant and are as cited in the supplied handling notes. ToD varies only with altitude to be lost prior to the IAF today. Engine management is driven by our operating targets cited above. If we assume this DC6B has R-2800-CB16 engines max cruise MAP is 36 inches and we will never have more applied just before ToD. Our safe in flight minimum is 20. The first 3 inch reduction is at ToD to 33 and we may need to make five more over five minutes to reach min safe MAP = 20 inches. We never exceed minus 700 VSI, so even if we need to lose only 3500 feet from max cruise power to IAF we can achieve 20 MAP before the IAF and having planned descent at minus 500 VSI, but executed at up to minus 700, we level out at MSA prior to the IAF. Now in level flight we watch IAS decay through 160 KIAS and we apply FLAP 1. We watch IAS decay through 150 KIAS and we apply FLAP 2. As IAS decays rapidly to 140 KIAS with FLAP 2 deployed in level flight we must throttle up to sustain 140 KIAS to the IAF.
We need TIME to achieve compliance. We TIME descent in every possible way with a flight plan calibrated in minutes, a clock calibrated in minutes, and a VSI calibrated per minute. ToD is never a place it is always a TIME. This is not a ghastly mistake repeated for 100 years in every cockpit. It is how aviation works. Aerial navigation is 4D.
Varying wing geometry, from cruise geometry, sooner than necessary also wastes precious holding and diversion fuel. We vary wing geometry at the correct TIME in the arrival phase sequence above, and we have TIME. We created TIME. During the subsequent (potentially much later) approach phase we must use high RPM, and in order to rotate the engine at high RPM we must supply high engine pressures with the throttle. The only way we can then achieve the necessary negative VSI while at the same time reducing IAS to Vref is to meet all of our prior IAS targets, in each compliant location, at the compliant altitude, for that specific destination, in the compliant variable geometry state.
If we desire realism nothing is random. Everything must be compliant. Everything must be sequenced and synchronised correctly. We cannot achieve compliant flight (realism) if we never attempt compliant flight.
Compliant flight, and therefore realistic flight simulation, does not revolve around the tertiary task of the FE. It revolves around compliant 4D navigation imposed by ATC in real life, but by ourselves as CAPT in MSFS, and then achieved by ourselves as PF in MSFS, with the FE role on the periphery of the compliance task. FE compliance with *limits* is easy. PF and FE compliance with the energy state and variable geometry targets is harder and must be given much more of our attention. But before any of that we must perform the primary role of CAPT and formulate the 4D arrival plan, using the real world procedures downloaded from the internet. Thousands of them, delivering huge variety to our MSFS experience. Once we decide to incorporate realism into simulation every arrival is different and every subsequent approach is different, and much more interesting to fly.
We must descend at the compliant TIME, moving from the cruise phase to the arrival phase, else we cannot achieve our 4D navigation and IAS targets several minutes before the carefully positioned real IAF. If we must cross the later Final Approach Fix (FAF) at a different altitude to the IAF and / or at a different IAS the arrival phase must be followed by a holding phase as we adjust both IAS and altitude *before we proceed to the approach phase*, already in the correct place (FAF), at the correct altitude shown on the approach plate we downloaded, at the correct IAS, in the correct variable geometry state, with the correct thrust (RPM), having set engine pressure to deliver those criteria at that *real 4D* location in space time. From that prior compliance achieving Vref compliance in a very different variable geometry state as we cross the airfield boundary fence is as easy as it possibly can be.
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Approach and Circuit: DC6B
Cross FAF = 140 KIAS & FLAP 2 deployed
COWL FLAPS = 2 degrees
2400 RPM
MAP => 24 inches
LANDING LIGHTS = DEPLOY + ON
On reaching Minimum Descent Altitude
(see propliner tutorial parts 4 & 7)
REDUCE = 130 KIAS
ON reaching Glideslope
(straight in or base)
GEAR = DOWN
FLAP = STAGE 3
FLAP = STAGE 4
REDUCE < 120 KIAS
FLAP = STAGE 5
Cross THRESHOLD 105 KIAS (@ 88,000lbs)
FLARE and LAND
**********************************
Of course the on screen handling notes also explain what we must do if the landing runway is not the instrument runway which we approach to locate our destination, before locating the different landing runway visually and flying a compliant, not random, visual circuit pattern to the landing runway. We must think hard about where the glideslope for the *landing* runway begins and we never reduce below 130 KIAS or make VG status changes beyond FLAP 2 until we reach it *at the compliant altitude, in the compliant location* having already imposed every other compliance required.
Each operating target links to another and another. Sure there are limits to be avoided along the way, but the targets we must achieve are the focus of any simulation. Avoiding limits is the really easy part of any simulation. The point is to achieve the target outputs, one after another, in the correct sequence, at the correct time, and that requires much more skill than just avoiding the limits, whether they are IAS limits, or Mach limits, or engine limits, or navigation compliance limits.
What is being increasingly disregarded by many propliner enthusiasts is that navigation has limits too. Those limits are just as mandatory and even more essential to flight safety. The primary cause of death in real airliners is controlled flight into terrain, (failure to achieve compliant 4D navigation), not engine malfunction. Most airliners have more than enough engines, but they each have only one CAPT to impose compliant navigation. Real aircrew suffer from exactly the same problem as MSFS propliner enthusiasts. They fixate on what is happening to some aircraft system or other and lose control of 4D navigation. They confuse primary, secondary and tertiary safety compliance priorities. It is just another form of pilot error. It is however the most fatal form of airline pilot error in real life. The MSFS propliner community have become too fascinated with micro management of engines and are proceeding in a flawed direction if their goal is realism. Sure engine compliance is part of the process, but it is tertiary. Compliance with the safe limits of 4D navigation is the primary goal.
Notice how quickly this thread wandered away from the crucial topic of 4D navigation compliance, to be just another thread about micro managing engines in pursuit of no specific 4D navigation targets, and no specific energy state management targets. Nobody seemed to be able to notice that the ability to close a Merlin throttle quickly is irrelevant because what must be done with that throttle is driven by primary (4D navigation) and secondary (energy state) operating targets, not engine limits. The propliner community are increasingly putting the cart before the horse allowing navigation targets, VSI targets, IAS targets, and synchronised variable geometry state targets to wander randomly, while fixating on engine micro management.
The supplied handling notes explain all the energy state targets and how to synchronise our variable geometry state targets for a good reason. The supplied 'realistic' flight dynamics are not compatible with just any old made up nonsense which has too many crew actions squashed into far too few minutes! Real aircrew need TIME to accomplish all the real operating targets, whilst easily avoiding the real operating limits, and only the real procedures deliver the TIME needed to comply. 4D navigational compliance is not a burden. It is the missing solution that many propliner enthusiasts fail to incorporate in their simulation
FS developers have no idea where propliner enthusiasts will fly tomorrow. We cannot supply the thousands of necessary, departure, arrival and approach charts needed. Propliner enthusiasts must take responsibility for downloading them and finding out where their IAF is and what altitude they must cross it. As virtual CAPT propliner enthusiasts must find out where the real FAF is and what altitude they must cross it too. My job is limited to citing within the supplied handling notes what IAS and what synchronised variable geometry state propliner enthusiasts must achieve before reaching those real (not random) 4D locations. If propliner enthusiasts just make up any old nonsense and allow propliners to wander anywhere at all in 4D they will never keep their energy state and variable geometry state under control and will forever wander aimlessly having no idea how to avoid terrain or any other obstacles in bad weather when they are invisible.
Unfortunately the entire MSFS community also has very limited understanding of transonic shock issues. Many third party MSFS developers pretend that propliners have no transonic shock limits, else that it is acceptable to operate a propliner beyond Mach (max operating) = Mmo. Since the phase in which this issue is paramount is just after ToD, the Mmo limit of the propliner whose operation we are simulating today is often the driver of how we must manage descent just after ToD, and therefore drives the need to be very cautious and never exceed minus 500 VSI until we are sure that first minus 500 VSI, and then minus 700 VSI, will not cause IAS to exceed Mmo. Those low VSI limits in turn drive ToD.
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Descent: DC6B
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS <<<<<<<<<<<<<<
DO NOT EXCEED Vno = 251 KIAS
COWL FLAPS = CLOSED
RPM = 2000
REDUCE MAP in stages of 3 inches (per minute)
MINIMUM 20 INCHES MAP
See CARB HEAT below
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It is mismanaging energy state that will kill everybody aboard, not a hot or cold engine that will only cost money to fix. The propliner community are losing their focus and like real aircrew are being increasingly distracted by systems management, when we should be concentrating on compliance with 4D navigation, and energy state limits and targets. The aeroplanes we discuss here were designed when nobody knew how to prevent transonic shock, delay transonic shock, or reduce the consequence of transonic shock. Some real aerodynamicists just thought they did. Some propliners had Mmo barely above Mach 0.2 !
Remember fatal transonic shock arising from all the misshapen junk attached to our beautiful aerofoil can occur long, long, before that beautiful aerofoil reaches it critical Mach number which causes it to induce persistent transonic drag. In these badly designed ancient aeroplanes there is no correlation at all between Mmo and Mcrit. Classic era piston engined propliners never induce measurable transonic drag because they all depart controlled flight due to transonic shock just beyond Mmo long, long, before they can ever reach Mcrit for their smooth aerofoil.
Even propliners with Mmo above Mach 0.4 are at critical risk in early descent from high level cruise, so descent must be early and shallow, but not too early, or too shallow. TIME of Descent is crucial in propliners. Pretending that some have no Mach limits, or that they exist but don't matter, is confusing the propliner community into complacency concerning VSI after ToD, leading in turn to complacency concerning timing of ToD. In reality ToD has little leeway given engine limits versus Mach limits versus need to reach MSA only a few minutes before the IAF, (only on the far side of the nearby mountains), then crossing the IAF at target IAS in the target variable geometry state.
The higher we cruise, the lower the profile drag (IAS) that will exceed Mmo in early descent, and so we must restrain IAS in early descent for a third and safety critical reason. So the last part of the puzzle falls into place. In combination these criteria impose very early descent in piston propliners down careful shallow 4D navigation funnels imposed by the real arrival procedures *that solve all our problems* in any weather.
Remember this?
If our cruising velocity is 180 KTAS and there is a 0 KTS headwind we must descend at 60 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS headwind we must descend at 40 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS tailwind we must descend at 80 DME today.
When we descend a complex piston propliner from high cold air we must descend at a precise VSI, targeting a precise IAS, to avoid a fatal Mach number.
We PLAN to take 20 minutes to lose 10,000 feet in any weather, any jurisdiction, in any piston propliner, at any date. While we are in high cold air we may need to actually execute that plan. Elderly frail passengers in vintage era unpressurised propliners cannot tolerate higher rate of change of cabin altitude anyway. The same rule therefore apply to them at any altitude. Not only does descent planning not need to be complicated; it must not be complicated, and it must not depend on distance. It must depend on TIME and the distance must vary hugely from Monday to Tuesday on the same route at the same altitude. We must *not* vary VSI to compensate for headwinds at any altitude. We must vary distance of descent instead. ToD is a constant TIME offset so that we can descend at constant and low VSI to avoid inducing fatal transonic shock in some propliners and to avoid inner ear injury to passengers in unpressurised cabins in others.
Many propliner enthusiasts have become fixated on engine limits while ignoring much more important energy state limits such as VSI and IAS and Mach.
Most of the rest of aerial navigation is 4D for exactly the same reasons. Where something must be invoked depends on wind and weather, but *when* does not.
So the ToD issue this thread was supposed to be about is just the tip of a much neglected iceberg that is very poorly understood because flight simulation enthusiasts are determined to believe they can carry over skills of 2D powered land vehicle navigation into aviation. When they don't work propliner enthusiasts then pretend that aerial navigation has no limits and no targets while fixating on less important targets and limits that are easier to understand and achieve. However when given priority over the things that really matter, that leads to 'made up nonsense, let's pretend' 4D navigation, and random energy state targeting, with unsynchronised timing of variable geometry status changes, followed by rushed approaches. Nobody can develop the skill to avoid high terrain in cloud during the arrival.
There is another whole can of worms that the propliner community are sliding into.
Increasingly propliner enthusiasts micro meddle with mixture during cruise (and even descent) while making no attempt to control their profile drag (IAS). Cruising at the wrong profile drag (IAS), and thus the wrong aircraft pitch, wastes far more fuel than any micro fiddling with mixture can possibly restore, because it causes loss of available cruising velocity (KTAS) from current fuel burn (PPH). The can of worms here is failure to understand the difference between the goal of maximising efficiency and the goal of maximising profit which comes second in priority to the goal of compliant 4D navigation (safety).
The last thing most classic era airlines want CAPT to do is operate a propliner efficiently. The tutorials I have provided explain that the role of CAPT is to decide when to maximise efficiency, when to minimise it, and when to target a specific intermediate efficiency that will maximise profit, not power, not thrust, not efficiency, not range, not endurance, not performance. That is part of what an aeroplane captain does. He decides which of those choices to maximise, role by role, and phase by phase, and instructs the crew on how to deliver his plan. During use of MSFS acting first and foremost as captain of the aeroplane is not optional.
During take off the last thing we want is efficiency. We must move the RPM levers to maximum inefficiency. We need every last pound of thrust whatever it costs. The last thing we want during TOGA is efficiency of thrust production. We need to maximise thrust and performance, not efficiency.
These choices concerning what to maximise do not end with procurement. They blossom after procurement and every aeroplane captain must use the captaincy decision making cycle to decide what must be maximised, from many possibilities. Consequently the 2008 Propliner Tutorial is very long. It addresses that reality and that complexity, but throughout it makes plain that compliant navigation in 4D (safety) comes first, all of the time.
Micro fiddling with mixture etc is a long way down the real list of priorities in the cockpit, whether the micro fiddling is done by FE or PNF. Playing with mixture can never recapture the fuel squandered by operating the aeroplane at the wrong altitude causing it to cruise at the wrong pitch and thus at the wrong profile drag (IAS) because CAPT failed to evaluate and then periodically step climb to current operational ceiling. Cruising at the wrong altitude, in the wrong aeroplane pitch, and thus at at the wrong profile and induced drag, causes loss of velocity and squanders far more fuel than can be saved by FE micro fiddling with mixture. His role is always only tertiary. Propliner enthusiasts must not become over focussed on systems management to the exclusion of the things that really determine miles per gallon.
Flight simulation enthusiasts are also failing to come to terms with the four phases of aviation history (pioneer / vintage / classic / modern), why they matter, and how they differ. Each was invoked by a change of legislation which required captains to alter how they operated (commercial) aeroplanes. The aeroplanes were then designed to match the relevant new regulations and the crew complement and qualifications imposed by those new regulations.
In the vintage phase of aviation history aeroplanes were so badly designed, and regulation so lacking, that the death toll was terrible. Two thirds, or sometimes three quarters, of the propliners of a particular type would crash within ten years of manufacture. They were so badly designed, and were allowed to get away with carrying such low fuel reserves, that they had to be operated efficiently all of the time.
They had no hope of making a profit and all airlines needed huge tax subsidies. The B314A Clipper and M130 China Clipper tutorials available from Calclssic.com, within the relevant downloads, explain that when we simulate their operation, always within an infrastructure stranded in the vintage phase of aviation history, we must constantly seek maximum efficiency by targeting low profile drag = IAS = Vbr, proceeding direct along great circle routes, while cruise climbing continuously to unpressurised ceiling, without restriction, in that dangerously unregulated environment. They need huge expensive crews to even attempt that, and it still wasn't remotely safe, because they still failed to achieve safe navigation far too often. The vintage phase of aviation history, (the lack of classic phase infrastructure), continued over the North Atlantic (including the 'Bermuda Triangle') until 1959, but had ended over the CONUS in 1932, and over Germany in 1936. It mattered!
The classic phase navigation infrastructure, when and where it was implemented, introduced massive regulation, much higher safety criteria, and very different aeroplanes with much smaller crews forced to adopt compliant 4D navigation. Suddenly the new DC-3 created to match the new highly regulated and compliant way of operating commercial aeroplanes with only a tiny crew, all of whom were only pilots, allowed airlines to make a profit without a subsidy and in safety. It matters! While profit and safety in aviation were just ridiculous impossibilities they were neither sought nor required. Once safety and profit were made possible they became compulsory. Classic era propliners can operate efficiently at medium level targeting IAS = Vbr with very low power and manually weakened mixtures, just like a huge vintage era flying boat, but its a dumb way to use one if we are trying to simulate a classic era aviation environment in an Argonaut or an L-049A Constellation.
However we must remember that trans oceanic travel lacked classic era infrastructure for a long time. Consequently the handling notes for the L-049A explain efficient operation targeting in a vintage era aviation infrastructure.
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Max Range Cruise (about 700hp):
COWL FLAPS - CLOSED
MAP = 22 inches
RPM = 1600
Plan 1400 PPH
Yields 185 KTAS at FL150 at MCW
c28000lbs @ 1400 PPH = 20 hours nominal
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Just like a flying boat we restrict power applied (fuel burn). With little fuel burn applied we must stay in thick air and so our velocity is held back to just 185 KTAS, but we can achieve 20 hours endurance with full tanks as we cruise climb continuously around a great circle over an Ocean. It's very efficient, but it will never make a profit. If we replicate that vintage era procedure in a classic era infrastructure everybody will be buying tickets with the L-049A operator who maximises profit by delivering much higher velocity, held back less, in much thinner air, at much higher altitude, using more fuel burn to access that lovely thin air which permits much higher cruising velocity.
Consequently the handling notes for the L-049A also explain profitable operation in a classic era infrastructure.
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Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
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Passengers would rather arrive after 14 hours instead of 20. Where a classic phase infrastructure mandating 4D navigation compliance at all times exists, installed at huge expense by taxpayers, delivering comprehensive ATC provided by taxpayers, at no expense to airlines, the regulator appointed by those taxpayers insists that we must learn to operate much less efficiently, burning much more fuel per hour, at higher power settings, to access much thinner air, to go much faster. Our costs are higher, but our revenue is much higher, and we can actually make a profit. Those taxpayers can then withdraw direct subsidies to airlines. Cruising only a few thousand feet above the much cheaper DC-4s at only 185 KTAS does not justify the huge cost of a pressure hull, or the huge cost of engines rated 2200hp for TOGA and 1800hp continuous. To maximise profit in a classic era infrastructure we must step climb to operational ceiling at current weight in the current weather, unless we have a significant headwind, (see 2008 Propliner Tutorial for relevant strategies).
Vintage phase procedures do not get our passengers above the weather, trap us in icing in cloud at FL150, and horribly slow us down, but the great oceans are stuck in the vintage phase of aviation history until 1959. It matters. It drives the captaincy decision making cycle during use of MSFS. We don't operate a 1946 Constellation like a 1936 China Clipper if the local taxpayer has provided a profitable, much safer, and much faster alternative.
Due to the negotiating power of the relevant trade union to impose a maximum of ten flying hours per shift, TWA actually operated their L-049As at max cruise power over the CONUS to get maximum miles per pilot per shift;
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Max Cruise (about 1400hp):
SUBJECT to CHT & OIL gauges in GREEN ARC
COWL FLAPS = AS REQUIRED
MAP = 31 inches
RPM = 2300
Plan 2800 PPH
Yields 276 KTAS at FL230 at MCW
***********************************
Micro fiddling to reduce fuel consumption, and avoiding using high blower after paying an arm and a leg to buy one, flying barely above the altitude where dirt cheap unpressurised propliners like the DC4 are allowed to cruise, is not the way to maximise profit in a classic era propliner flown within a classic era infrastructure!
To maximise profit we go out of our way to avoid efficiency in the cruise, just as we did during Take Off. Once the classic phase of aviation history arrives *in the jurisdiction we are flying in right here, right now* we must target profit not efficiency. This is *not* a function of the aeroplane we are simulating. It is a function of the infrastructure we are navigating within in and the associated legislation. Of course we may not be able to generate Max Cruise Power at pressurisation = certification ceiling (FL250). TWA targeted FL230 on internal flights over the CONUS once light enough because that maximised TAS which maximised (passenger) miles (purchased) per aircrew shift.
The pressurised classic era propliners are so complex and so expensive that those very expensive assets, (capital assets or labour assets), must be worked very hard. Efficiency as defined in textbooks about 'dynamics' are no longer the point. The curves we must now pursue are in textbooks about 'economics'. Our operating targets change with the legislation for the jurisdiction we are crossing right here, right now, not the aeroplane we are in or the gauges it has in its cockpit.
UK and USSR tax payers did not install a classic era infrastructure over the UK or USSR, or across the dwindling British Empire until the late 1950s. Consequently British and Soviet airlines continued to procure vintage era propliners to be operated within vintage era regulations. It matters! 4D navigation compliance was not part of vintage phase of aviation history and the death toll was terrible, but 4D navigation compliance is at the heart of classic phase aviation. We must teach ourselves to proceed accordingly, or choose which aeroplanes we simulate where and when in a realistic way if we desire realism.
Realism is a variable which depends on compliance with relevant legislation which always matched the available navigation infrastructure in that *jurisdiction*. The entire planet was not under the jurisdiction of the US, or Germany. or the UK or the USSR. Propliner enthusiasts need to think harder about those issues and how the navigation infrastructure drives legislation, and in turn drives realistic simulation of a particular phase of aviation history in a particular jurisdiction. It also drove propliner design and procurement. Then we all need to come to terms with the reality that New York had been located in classic era infrastructure, with classic era 4D navigation compliance procedures applicable since 1932, even though we may have spent twelve hours in vintage era airspace earlier in the same flight across the North Atlantic in 1958. The price of realism is complexity of both planning and execution.
The complexity involved in delivering propliner realism to ourselves takes a long to explain because everything is linked to something else which has driven it to be the way it is and a long chain of cause and effect must be understood, before it can be replicated in a virtual environment.
The norm for most airlines in a classic phase infrastructure was however to target neither maximum efficiency, nor maximum performance, but something in between giving rise to the concepts of economical cruise power or normal cruise power . At any date a particular airline has specific fuel versus labour costs, including aircrew labour costs and engineer / mechanic engine maintenance costs, and also has a specific *target consumer*. That causes economical = normal cruise criteria to alter year by year, route by route, and role by role.
Continued in next post...
calclassic.proboards.com/index.cg....ead=3042&page=1
From FSAviator:
<<FsAviator, thanks for your reply. If you have time to do so, could you elaborate on timing descent as well?>>
Asking me to 'elaborate' is always dangerous :->
I have been very busy with other things, but I am happy to return this thread to focus on the original question and the misconception it was based on. In this very long post I will try to explain the priorities of arrival planning in piston engined propliners, and what drives them. Where necessary I will focus attention on essential differences between real life and use of MSFS. Along the way I will try to highlight why I believe propliner enthusiasts are in danger of (literally) wandering off course and in doing so I will try to address all the engine management issues which arose in a thread which only asked a question about 4D navigation.
It is easy to assert in a web page, forum, or product tutorial that a procedure, or a rule of thumb, will work. Proving that it won't and explaining why a different strategy is required is much more complex and demanding. To understand why ToD must be time based it is necessary to follow the 'chain reaction' of the arrival phase through the reactions that it causes from start to finish. It's going to be a long ride. I must start with a statement of the principles behind the required technique, and only later provide the worked numerical examples which demonstrate the need for the principle stated earlier.
Successful arrival phase planning and execution requires us to understand why some operating targets are paramount, (relate to safety critical issues), and therefore always initiate the sequence of crew actions that then either cause, else limit, the next step of the chain reaction, while other subordinate crew actions are only necessary responses to earlier inputs, by a different member of the flight deck crew, to deliver the same operating targets within the same operating limits.
Flight simulation is the demonstration of real world compliant flight skills in a virtual environment.
During flight simulation compliance with safety criteria is always paramount, and must be ensured before devoting time to profit maximisation or efficient operation of engines. We must therefore start by coming to terms with the reality that arrival planning and execution is all about ensuring safety, above all else, by avoiding *unseen* obstacles by mandatory distances, whether flying head up in sunshine, or head down in cloud.
Most of the unseen obstacles we must learn to avoid are the airspace reserved for other airfields and conflicting air traffic on other routes. In real life avoidance of those traffic conflictions is planned and executed as the highest priority. It is not reactive, and it is not ignored. In MSFS we may not see the traffic conflicts we must avoid, even if the weather is good, but they are there, and if we intend to incorporate realism we can and should successfully avoid those safety critical conflicts. It should be obvious (but apparently is not) that arrival phase planning and execution in MSFS must also avoid controlled flight into terrain when descending in solid cloud.
Consequently demonstrating the skill to avoid real world traffic conflictions, not just terrain, by achieving real world 4D navigational compliance, is the key to realistic (propliner) flight simulation. Because navigation compliance is always the primary task, with profit maximisation as the secondary task, tertiary tasks like engine micro management are constrained and conditioned by the primary and secondary tasks. The FE is not in charge. He matches engine output to the decisions made by CAPT during planning of the arrival phase, and the subsequent actions of PF during execution of the arrival phase.
During (solo desk top) propliner simulation we are always first and foremost CAPT. We use our learned skills to decide what must be done to achieve 4D navigation compliance on today's route. Only then can we become PF using our learned skills to impose the progressive aircraft energy state (IAS and matched VSI) targets, synchronised with progressive variable geometry (VG) state targets, which will achieve the plan we formulated earlier as CAPT. Last and least we can also perform the tertiary role of FE or PNF to manage engines, also in pursuit of the 4D navigation plan we decided upon during our prior captaincy decision making cycle. An arrival plan always includes both VSI and IAS targets and may include Mach limits. Engine management is not independent of those energy state targets and limits. Our engine management plan is driven by our energy state targets and limits, not engine limits. If we fail to formulate a prior realistic (or any) energy state and synchronised variable geometry state arrival plan, when we later assume the tertiary roles of FE or PNF, engine management also becomes randomised.
In real life Time of Descent (ToD) is decided and imposed by ATC, although they may offer the clearance; 'N123MS cleared to the Initial Approach Fix. When ready descend to altitude xxxxx........'. In real life ATC decide when airliners descend, what altitude it is safe to descend to, what course they must fly while descending. MSFS delivers none of that reality.
When we simulate the realistic operation of propliners in MSFS we must formulate the necessary arrival plan. If we desire realism the 4D navigation plan we devise as CAPT must be the one that ATC would impose in real life. Microsoft do not supply that plan. That plan is supplied to us by the real world ATC authority, or a contractor such as Jeppesen, in the form of published instrument arrival and approach 'plates' (IAPs) or 'charts' (IACs), which real pilots must download before flight so that they can study and understand the different 4D navigation compliance required after ToD and for each destination. If we seek realism within propliner simulation we must do the same. Those flight safety downloads are usually free and the relevant URLS are provided from;
www.calclassic.com/propliner_tutorial_charts.htm
The 2008 Propliner Tutorial explains how to use them within MSFS.
If we desire realism we need to know where the real ATC authority require us to route to, and what altitude we are allowed to descend to, in order to ensure that we avoid military danger areas, nature reserves, air defence interception zones, prohibited airspace, and all the routes and airspace being used by other aeroplanes that we must avoid whether we are navigating head up in sunlight, or head down in cloud. Almost all of the obstacles that real pilots must avoid are invisible, all of the time. On some days the terrain is invisible as well. That is what drives the arrival plan, and the timing of descent from cruise (ToD), in real life and in MSFS.
So in MSFS, in order to calculate ToD, we always need to know what constitutes 4D navigational compliance after ToD, so that we can time when we must terminate our cruise phase and begin our arrival phase. Our primary task during propliner simulation is always to perform the planning and decision making role of CAPT. Execution comes later to deliver the plan we formulate first.
During the arrival phase our task as CAPT is compliant avoidance of many always invisible things. So when we are in cloud and the terrain is just one more invisible thing we must avoid it does not matter at all. ToD is just the first waypoint in that 4D compliance and it is always a TIME not a place.
Time of Descent (ToD) is planned so that our subsequent descent profile towards the real Initial Approach Fix (IAF), *not the airfield visual circuit*, passes clear of all obstacles, (visible or invisible), laterally as well as vertically, whether or not we are in cloud today / tonight. The real IAF is placed so that our descent path misses the mountain. It matters where the real IAF is. Time of Descent planning and subsequent descent procedures which rely on the terrain between ToD and the IAF being visible have no relevance to propliner simulation. At some point in our virtual propliner captaincy career we must learn to formulate 4D navigation plans which will work in bad weather so that we can progress to flying propliner schedules, whatever the weather.
Each real arrival procedure has a Minimum Sector (or airway transition) Altitude (MSA), below which we must not descend until we reach our IAF. We TIME descent so that we level and maintain that real world MSA when we are no more than a few *minutes* short of the real world IAF. Propliner enthusiasts cannot hope to plan that correctly, or later execute that correctly, unless they bother to download the real ATC procedure to discover where the real IAF is for today's destination, and the MSA at which they must cross it! Ignoring where we are required to position the aircraft on today's route, and the altitude we must descend to before we cross it, will always cause descent at the wrong time, and in the wrong direction, to the wrong altitude.
Aerial navigation is 4D not 2D. Consequently DME is always irrelevant to ToD planning whether or not we have it in our cockpit today. Some real world procedures may appear to disagree with that statement, but I will explain why they don't below. ToD always depends on the weather today, never where we are. If we must lose 10,000 feet to reach our MSA before the IAF, (in a piston engined propliner), since we always plan to descend at minus 500 VSI (see later), we always descend 20 minutes before the IAF. We don't need a graph, or a diagram, or a calculator!
Because we always PLAN to descend at minus 500 VSI, we descend 20 minutes before the IAF, if we are cruising 10,000 feet above the MSA for that IAF,
If our cruising velocity is 180 KTAS and there is a 0 KTS headwind we must descend at 60 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS headwind we must descend at 40 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS tailwind we must descend at 80 DME today.
DME has no role to play at all. It does not influence *when* we must descend. GPS also has no role to play at all. The gauge we use to plan and execute descent is called a *clock*. Aerial navigation is 4D not 2D. That is not just a meaningless phrase, it means that aerial navigation is performed using a clock and a flight plan both carefully calibrated and updated using a concept called 'minutes' with an estimate for the (every) next waypoint in minutes, not some other useless random gauge that does not display minutes.
If we need to lose 10,000 feet we descend 20 minutes before the IAF *every* day using the *clock* and our DME is different and irrelevant every day, because the wind and weather are different every day. 2D navigation techniques that we may have learned in powered terrestrial vehicles, involving consideration of place and distance and speed are utterly useless in aeroplanes. Aerial navigation must be 4D and is based instead on TIME.
We must level at MSA a few *minutes* before the IAF and in most classic era propliners we must reduce our profile drag (IAS) far below prior cruise IAS before we cross the IAF else we won't be able to use our autopilot to fly the approach procedure. So we need to level a few *minutes* before the IAF. The miles (or kilometres) involved vary with the wind every day and we never care. We never allow ourselves to be confused by statute miles or nautical miles or kilometres, because none of them ever have any relevance! A minute is a minute in a DC-3 or a Fiat G.12, in every jurisdiction, and on any date. It matters! The real procedures are international. A clock is a clock. There is nothing new to learn in a new cockpit or a new jurisdiction. It matters!
So having always planned descent at minus 500 VSI as soon as it is safe to do so, (see later), we always increase to minus 700 VSI. In any piston propliner, anywhere, because that causes us to level out at MSA a few minutes before the IAF, at any weight, in any weather, in any jurisdiction. We need those constant minutes to reduce our IAS and vary our geometry. Distances are not the point. What we must accomplish takes a fixed TIME to accomplish.
We must employ the 'Keep It Simple Stupid' (KISS) concepts of planning and execution whenever we are operating an aeroplane (even in a simulator).
In a metric cockpit minus 500 VSI is (treated as) minus 2.5 metres/sec and so minus 700 VSI is minus 3.5 m/s.
The Minimum Sector Altitude cited on the real IAP we downloaded, and we are now descending to, is only safe to a distance of 25 miles from our destination. There may be much higher mountains between ToD and the IAF! We must not descend too soon, else we level out on the wrong side of the mountains, below the mountain peaks. We must not descend too late because we must be level at MSA and at target IAS, in our target variable geometry state, before we cross the IAF. We must learn and practice compliant 4D navigation skills in good visibility so that we can replicate them in cloud when we fly the same schedule tomorrow with a very different wind vector. *Nothing must differ*. 'Keep It Simple Stupid'
Descending too soon and too late are not concepts relating to distance. They are concepts relating to TIME. Aviation cannot work any other way because in an aeroplane, (unlike a powered terrestrial vehicle), our speed (KTS) never matches our velocity (KTAS) or our profile drag (KIAS), because unlike a powered terrestrial vehicle aeroplanes are blown about by the wind. We are blown variably every minute and every day so we must operate aeroplanes using strategies which are safe regardless! We must use TIME as the basis of aerial navigation. We must navigate aeroplanes using a clock and a flight plan, both calibrated and updated in minutes, any date, any aeroplane, any jurisdiction.
All of the above is about safety which is always paramount in our planning as CAPT. When we have a headwind we must descend later *not* at the same DME, else we descend into the wrong side of the mountains between ToD and the IAF. Sure we must descend down a conical funnel and that funnel always ends at real MSA, at the real IAF, but it starts some place different every day on the same route. It starts the same number of minutes before the IAF every day so that the funnel is compliantly raised or lowered to allow for the wind. No complex calculations, no rules of thumb, just the fully correct and *simpler* mathematical solution, in every jurisdiction, at any date, in any weather, at any weight, at any prior cruise IAS, at any prior cruise TAS, and at any prior cruise KTS, all of the time! If we need to lose 10,000 feet in a piston propliner ToD is 20 minutes before the IAF every day and everywhere. Pretending that descent planning in piston propliners is complicated, is really dumb. If it were complicated humans would screw up too often. 'Keep It Simple Stupid'
All the above is an essential but simple part of the captaincy decision making cycle on every flight.
1) Where is the next compliant real world fix on this real flight?
2) What (minimum) real world altitude is compliant over that fix?
3) When must I begin the altitude change to achieve that compliance?
In a piston propliner the answer is *always* two minutes per thousand feet of altitude variation. After initiating the altitude change at the correct TIME we 'may' elect to climb or descend a *little* faster than plus or minus 500 VSI,and by default we will actually descend at minus 700 VSI (both during the arrival phase to the Initial Approach Fix, and during the later approach phase from our Final Approach Fix). Provided we never exceed minus 700 VSI we will not impact the invisible mountain as we descend in cloud. It matters! The real ATC authority positioned the real IAF and FAF accordingly and so we will never lose control of our IAS or our glidepath, or have the slightest difficulty progressing the aeroplane through the required synchronised variable geometry state changes, if we fly the real route in real 4D compliance, just like real pilots.
Flight sim enthusiasts constantly make the mistake of supposing that making up some nonsense is easier than following the real procedures, It never will be because many millions of dollars have been spent making the real procedure the one that is easiest to navigate in 4D while avoiding all of the things that must be avoided, while carefully allowing the TIME real aircrew (and we) need to achieve all the IAS and synchronised variable geometry state changes mandated. The real Initial Approach Fix is placed carefully not randomly. The real Final Approach Fix (if different) is also placed carefully, not randomly. The different compliant altitude for crossing those two fixes, and the compliant IAS for crossing those two fixes, has been calculated carefully not randomly. The propliners and their engines, whose operation we are simulating, were designed to achieve exactly that regulatory compliance and not some random made up nonsense. Achieving real world 4D navigation compliance is not only satisfying, because it is what flight simulators exist to teach, it is also the key to making piston propliner operation unrushed and as easy as it can be.
If we are to have any hope of achieving realistic engine management we need to subordinate the tertiary role of the FE (or PNF) to the secondary role of PF as he maximises profit while CAPT imposes safety by planning and telling PF (the helmsman) how to achieve 4D navigational compliance at all times. In MSFS we must acquire the skill to explain 4D navigation compliance to ourselves. We must acquire the skills needed to be captain first, helmsman second, and engineer last.
Now the apparent exception I mentioned earlier. After long range DME was rolled out, from the early 1950s onwards, there were a few places in which descent below MSA was allowed prior to the IAF upon reaching a specific DME from the relevant navaid. What to do if our cockpit today has no DME is obvious. We cannot descend below MSA until the IAF. Note that this has nothing to do with ToD. After long range DME exists, if our cockpit also has a receiver, the real world procedures allow descent below MSA before the IAF by reference to DME. ToD on the other hand is when we depart cruising level for the MSA. DME is not involved in calculation of compliant descent from cruise. It cannot be.
This is all further explained and illustrated in full in Part 3 of the 2008 Propliner Tutorial citing an arrival to KIZG over the White Mountains with a fully worked tutorial exercise which should be flown in the FS9 Grumman Goose after applying the Calclassic update. During training we need lots of TIME to keep up with events and we should not train in over complex, over rapid aeroplanes, or aeroplanes with defective flight dynamics or inadequate handling notes. I am not going to repeat all of the necessary detail here and the required IAP which must be studied is part of the 2008 Propliner Tutorial download;
www.calclassic.com/tutorials
www.calclassic.com/propliner_tutorial_charts.htm
The issue of how fast to close throttles raised later in this thread is consequently being debated in a vacuum of intention that does not exist in the real world.
All complex piston engines with complex gas compressors have restrictions concerning either rate of throttle closure in very cold air (re shock cooling), or they have minimum safe in flight manifold pressure values in any air (sometimes re plug fouling), or both. Liquid cooled engines are buffered by slower change of coolant temperature and will typically have only a minimum in flight engine pressure value. Many, but not all, liquid cooled engines will tolerate rapid throttle closure from no more than max cruise MAP/BOOST/C/ATA *to the cited high minimum*.
Conversely the injunction against closing the throttles of complex supercompressed air cooled engine rapidly 'typically' cites 'no more than 3 inches per minute', but it is only generic MSFS shorthand for a potentially more complex reality. It is anyway only a tertiary priority that approximates reality well enough and allows us to struggle with the problems involved in planning and executing descent from high altitude in complex classic era propliners.
Nobody has any reason to care how engine pressure is calibrated by different cultures. We do not need to know why the targets and limits are what they are, even though I am now explaining exactly that here. We only need to comply. In order to comply we need MSFS propliners with on screen handling notes which explain what constitutes compliance. The cited minima may be nothing to do with shock cooling, or plug fouling, or any similar issue, since each phase of every flight has target engine RPM values, and it is possible that in order to avoid outputting damaging torque the minimum in flight engine operating pressure value is set for that purpose versus target RPM, not shock cooling, or plug fouling etc.
However many propliner enthusiasts then confuse operating limits with operating targets, slavishly applying engine limits as targets because many propliner enthusiasts now give too much priority to the tertiary task of engine management while failing to achieve the primary goal of compliant 4D navigation, and the secondary goal of energy state (IAS & VSI) compliance during synchronised variable geometry state compliance. Propliner enthusiasts who allow navigation, and energy state, and variable geometry state, to randomise cannot have an engine management plan that is not also randomised. The engine management plan is the consequence of the navigation plan, the energy state plan and the variable geometry state plan we decided upon earlier as CAPT. Engine criteria are never the driver of the arrival plan. The tertiary goal of FE (or PNF) is to help deliver the energy state target within the 4D navigation target which CAPT decided and imposed on PF.
With practice, practice, practice, propliner enthusiasts should not struggle to understand and achieve real world 4D navigation compliance. The questions;
1) Where is the next compliant real world fix on this real flight?
2) What real world (minimum) altitude is compliant over that fix?
3) When must I begin the altitude change to achieve that compliance?
are not too complex for anyone involved in propliner simulation to understand or resolve. Failure to do so is always the consequence of never developing the intention to succeed. Once we develop the intention to incorporate realism into our propliner simulation, by downloading the real procedures and following them, we soon can. Our skills challenge then moves on to profit maximisation during accomplished 4D navigation compliance.
To maximise profit after ToD we must target prior cruise IAS, (whatever it was at current weight in the current weather today), since to maximise profit we must fly a 'cruise descent' pegging our profile drag at the profit perfect prior cruise value. On reaching ToD PF initiates descent at minus 500 VSI. At constant power profile drag (IAS) would rise. It is the job of FE (or PNF) to prevent that rise in profile drag by careful retardation of throttle *subject to the cited engine limits*.
Whatever cooling type our engines have, we never have the intention to close throttle rapidly from cruise power to minimum safe power because engine management is only ever tertiary. We use the throttles to maximise profit by making every effort to sustain prior cruise IAS at minus 500 VSI. We could suddenly retard to zero boost safely in an Argonaut, but we never have that intention anyway. The engine management plan is a consequence of the navigation plan and energy state plan for this arrival phase which we devised as CAPT after studying the real 4D navigation compliance procedures.
Engine management during the arrival phase is just a function of the more important profile drag (IAS) plan to maximise profit and conserve our precious holding and diversion fuel. If prior cruise just before ToD was at a profile drag of 182 KIAS today we seek to *prolong* that Newtonian perfection of equilibrium *which was decided and imposed by the weather around us today*, and in a perfect world we wish to prolong 'cruise descent' at prior cruise profile drag (IAS), for as long as possible. We use throttle to deliver the IAS plan. We do not simply reduce throttle as fast as possible! In some particular weather at some particular weight that might be correct, but we are required to behave more intelligently than that.
When FE manages to sustain prior cruise IAS at minus 500 VSI, (without exceeding prior cruise IAS), and without throttling down faster than the operating limit cited for that engine, PF must now, and only now, increase his energy state target to minus 700 VSI and FE (or PNF) must then reduce throttle further *to attempt to sustain prior cruise IAS* all over again at minus 700 VSI. Throttles are closed, or opened, during descent to deliver our arrival phase IAS target, while descending at our arrival phase VSI target, not randomly and not automatically to a limit value unrelated to the captain's (our) energy state plan.
Allowing profile drag (IAS) to rise beyond prior cruise profile drag during an arrival just squanders fuel. That unwanted extra profile drag isn't free. If we allow our profile drag (IAS) to exceed prior cruise profile drag we used diversion fuel to add unwanted extra profile drag (IAS) and the drag we added is slowing us down. We must never confuse a rise in profile drag (IAS) with a rise in velocity (TAS). There is no aeroplane speed indicator in classic propliners! Allowing our profile drag (IAS) to exceed the prior cruise value squanders our holding and diversion fuel. The job of FE (or PNF) during the piston propliner arrival phase is to sustain prior cruise IAS, first at minus 500 VSI, and after that has been achieved, we seek to replicate that IAS operating target all over again at minus 700 VSI.
If we have super compressed air cooled engines, and if the descent is from high cold air, we have a grave risk of shock cooling. IAS = profile drag is the same thing as cooling drag. We must avoid adding more and more cooling (IAS) over air cooled engines in high cold air. In an Argonaut we have more flexibility to vary throttle quickly than in an DC6B and we also have more flexibility concerning IAS. We can progress from minus 500 VSI to minus 700 VSI more quickly in an Argonaut, but our minimum safe engine running pressure is much more restrictive in an Argonaut. For instance a DC6B crew can eventually reduce to 20 inches, but an Argonaut crew must sustain a minimum of zero boost (30 inches).
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Descent and Holding: Argonaut
ABOVE FL200 <= 200 KIAS (Mmo)
NEVER EXCEED 223 KIAS (Vmo)
DO NOT SHOCK COOL ENGINES
BOOST => ZERO <<<<<<<<<
RPM => 2200 whilst => FL130
Passing (below) FL130
BOOST => ZERO
RPM = 2000
..........
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Later in the descent the Argonaut will have more power applied and more unwanted profile drag wasting more fuel, but the high unwanted IAS won't damage liquid cooled engines because the Rolls Royce engine control computer alters radiator gill status and oil cooler gill status and mixture, entirely automatically, preserving engine temperature to that which Rolls Royce deem most satisfactory. The crew of an Argonaut control none of the engine cooling devices. With an air cooled engine in a DC6B if we allow IAS to rise we impose unwanted direct cooling and that unwanted cooling is proportional to 'IAS squared' !
Since IAS rising above prior cruise IAS is also squandering fuel it is doubly bad with supercompressed air cooled engines. Now remember if we mismanage rate of throttle movement, it may be the gas compressor running at many times engine RPM that is going to fail, (especially in high blower), not the engine itself, while it is the engine that suffers if we eventually reduce running pressure too low and cause plug fouling, or a gear box that will shatter if we apply too much torque to it with a forbidden MAP v RPM combination. This isn't just about 'shock cooling'. That is just 'MSFS shorthand' for all the things that can damage an engine, or the gas compressor, or the several gear boxes and associated automatic clutches, in air of any temperature. Supercompressed engines always have a minimum safe in flight pressure and may have a rate of throttle closure injunction, but during the arrival phase we use throttle to sustain prior cruise IAS, and it is that which drives throttle motion, subject to cited injunctions.
The real problem may be nothing to do with engine temperature anyway. It may relate to unsafe torque. For us in MSFS the issue is simply compliance with the handling notes using the units of engine pressure measurement cited whether MAP in a US cockpit, or BOOST in a British cockpit, or C (=Kg/cm^2) in an Italian cockpit. or ATA in a German cockpit, or decimetres of mercury in a Soviet cockpit. Complex supercompressed air cooled engines, which may not be radials, require more care to avoid damage, but often allow safe running at lower engine pressure 'eventually'.
Now having said all that in many complex piston propliners once we (eventually) invoke minus 700 VSI the existence of engine operating limits (either rate or minimum) will (eventually) prevent FE (else PNF) from providing the throttle closure that would prevent our profile drag from rising above prior cruise IAS and (eventually) later in the descent it nearly always will. Nevertheless as PF we must invoke minus 700 VSI (eventually) in order to be level at our Minimum Sector Altitude a few minutes before the Initial Approach Fix, so that we have TIME to achieve our target IAS, and our target variable geometry state for crossing the IAF, maintaining our MSA, whatever the wind and weather today. So when simulating operation of a DC6B the procedures are;
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Descent:
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS
DO NOT EXCEED Vno = 251 KIAS
COWL FLAPS = CLOSED
RPM = 2000
REDUCE MAP in stages of 3 inches (per minute)
MINIMUM 20 INCHES MAP <<<<<<<<<<
See CARB HEAT below
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TerminalHolding:
Approaching IAF / Hold
COWL FLAPS = 1 degree
2000 RPM
REDUCE < 160 KIAS
FLAP = STAGE 1
REDUCE < 150 KIAS
Crossing IAF entering Hold
FLAP = STAGE 2
MAINTAIN 140 KIAS
Check CHT < 232C
Plan 2100 PPH
****************************
Our energy state targets and our variable geometry state targets are mandatory and invariant and are as cited in the supplied handling notes. ToD varies only with altitude to be lost prior to the IAF today. Engine management is driven by our operating targets cited above. If we assume this DC6B has R-2800-CB16 engines max cruise MAP is 36 inches and we will never have more applied just before ToD. Our safe in flight minimum is 20. The first 3 inch reduction is at ToD to 33 and we may need to make five more over five minutes to reach min safe MAP = 20 inches. We never exceed minus 700 VSI, so even if we need to lose only 3500 feet from max cruise power to IAF we can achieve 20 MAP before the IAF and having planned descent at minus 500 VSI, but executed at up to minus 700, we level out at MSA prior to the IAF. Now in level flight we watch IAS decay through 160 KIAS and we apply FLAP 1. We watch IAS decay through 150 KIAS and we apply FLAP 2. As IAS decays rapidly to 140 KIAS with FLAP 2 deployed in level flight we must throttle up to sustain 140 KIAS to the IAF.
We need TIME to achieve compliance. We TIME descent in every possible way with a flight plan calibrated in minutes, a clock calibrated in minutes, and a VSI calibrated per minute. ToD is never a place it is always a TIME. This is not a ghastly mistake repeated for 100 years in every cockpit. It is how aviation works. Aerial navigation is 4D.
Varying wing geometry, from cruise geometry, sooner than necessary also wastes precious holding and diversion fuel. We vary wing geometry at the correct TIME in the arrival phase sequence above, and we have TIME. We created TIME. During the subsequent (potentially much later) approach phase we must use high RPM, and in order to rotate the engine at high RPM we must supply high engine pressures with the throttle. The only way we can then achieve the necessary negative VSI while at the same time reducing IAS to Vref is to meet all of our prior IAS targets, in each compliant location, at the compliant altitude, for that specific destination, in the compliant variable geometry state.
If we desire realism nothing is random. Everything must be compliant. Everything must be sequenced and synchronised correctly. We cannot achieve compliant flight (realism) if we never attempt compliant flight.
Compliant flight, and therefore realistic flight simulation, does not revolve around the tertiary task of the FE. It revolves around compliant 4D navigation imposed by ATC in real life, but by ourselves as CAPT in MSFS, and then achieved by ourselves as PF in MSFS, with the FE role on the periphery of the compliance task. FE compliance with *limits* is easy. PF and FE compliance with the energy state and variable geometry targets is harder and must be given much more of our attention. But before any of that we must perform the primary role of CAPT and formulate the 4D arrival plan, using the real world procedures downloaded from the internet. Thousands of them, delivering huge variety to our MSFS experience. Once we decide to incorporate realism into simulation every arrival is different and every subsequent approach is different, and much more interesting to fly.
We must descend at the compliant TIME, moving from the cruise phase to the arrival phase, else we cannot achieve our 4D navigation and IAS targets several minutes before the carefully positioned real IAF. If we must cross the later Final Approach Fix (FAF) at a different altitude to the IAF and / or at a different IAS the arrival phase must be followed by a holding phase as we adjust both IAS and altitude *before we proceed to the approach phase*, already in the correct place (FAF), at the correct altitude shown on the approach plate we downloaded, at the correct IAS, in the correct variable geometry state, with the correct thrust (RPM), having set engine pressure to deliver those criteria at that *real 4D* location in space time. From that prior compliance achieving Vref compliance in a very different variable geometry state as we cross the airfield boundary fence is as easy as it possibly can be.
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Approach and Circuit: DC6B
Cross FAF = 140 KIAS & FLAP 2 deployed
COWL FLAPS = 2 degrees
2400 RPM
MAP => 24 inches
LANDING LIGHTS = DEPLOY + ON
On reaching Minimum Descent Altitude
(see propliner tutorial parts 4 & 7)
REDUCE = 130 KIAS
ON reaching Glideslope
(straight in or base)
GEAR = DOWN
FLAP = STAGE 3
FLAP = STAGE 4
REDUCE < 120 KIAS
FLAP = STAGE 5
Cross THRESHOLD 105 KIAS (@ 88,000lbs)
FLARE and LAND
**********************************
Of course the on screen handling notes also explain what we must do if the landing runway is not the instrument runway which we approach to locate our destination, before locating the different landing runway visually and flying a compliant, not random, visual circuit pattern to the landing runway. We must think hard about where the glideslope for the *landing* runway begins and we never reduce below 130 KIAS or make VG status changes beyond FLAP 2 until we reach it *at the compliant altitude, in the compliant location* having already imposed every other compliance required.
Each operating target links to another and another. Sure there are limits to be avoided along the way, but the targets we must achieve are the focus of any simulation. Avoiding limits is the really easy part of any simulation. The point is to achieve the target outputs, one after another, in the correct sequence, at the correct time, and that requires much more skill than just avoiding the limits, whether they are IAS limits, or Mach limits, or engine limits, or navigation compliance limits.
What is being increasingly disregarded by many propliner enthusiasts is that navigation has limits too. Those limits are just as mandatory and even more essential to flight safety. The primary cause of death in real airliners is controlled flight into terrain, (failure to achieve compliant 4D navigation), not engine malfunction. Most airliners have more than enough engines, but they each have only one CAPT to impose compliant navigation. Real aircrew suffer from exactly the same problem as MSFS propliner enthusiasts. They fixate on what is happening to some aircraft system or other and lose control of 4D navigation. They confuse primary, secondary and tertiary safety compliance priorities. It is just another form of pilot error. It is however the most fatal form of airline pilot error in real life. The MSFS propliner community have become too fascinated with micro management of engines and are proceeding in a flawed direction if their goal is realism. Sure engine compliance is part of the process, but it is tertiary. Compliance with the safe limits of 4D navigation is the primary goal.
Notice how quickly this thread wandered away from the crucial topic of 4D navigation compliance, to be just another thread about micro managing engines in pursuit of no specific 4D navigation targets, and no specific energy state management targets. Nobody seemed to be able to notice that the ability to close a Merlin throttle quickly is irrelevant because what must be done with that throttle is driven by primary (4D navigation) and secondary (energy state) operating targets, not engine limits. The propliner community are increasingly putting the cart before the horse allowing navigation targets, VSI targets, IAS targets, and synchronised variable geometry state targets to wander randomly, while fixating on engine micro management.
The supplied handling notes explain all the energy state targets and how to synchronise our variable geometry state targets for a good reason. The supplied 'realistic' flight dynamics are not compatible with just any old made up nonsense which has too many crew actions squashed into far too few minutes! Real aircrew need TIME to accomplish all the real operating targets, whilst easily avoiding the real operating limits, and only the real procedures deliver the TIME needed to comply. 4D navigational compliance is not a burden. It is the missing solution that many propliner enthusiasts fail to incorporate in their simulation
FS developers have no idea where propliner enthusiasts will fly tomorrow. We cannot supply the thousands of necessary, departure, arrival and approach charts needed. Propliner enthusiasts must take responsibility for downloading them and finding out where their IAF is and what altitude they must cross it. As virtual CAPT propliner enthusiasts must find out where the real FAF is and what altitude they must cross it too. My job is limited to citing within the supplied handling notes what IAS and what synchronised variable geometry state propliner enthusiasts must achieve before reaching those real (not random) 4D locations. If propliner enthusiasts just make up any old nonsense and allow propliners to wander anywhere at all in 4D they will never keep their energy state and variable geometry state under control and will forever wander aimlessly having no idea how to avoid terrain or any other obstacles in bad weather when they are invisible.
Unfortunately the entire MSFS community also has very limited understanding of transonic shock issues. Many third party MSFS developers pretend that propliners have no transonic shock limits, else that it is acceptable to operate a propliner beyond Mach (max operating) = Mmo. Since the phase in which this issue is paramount is just after ToD, the Mmo limit of the propliner whose operation we are simulating today is often the driver of how we must manage descent just after ToD, and therefore drives the need to be very cautious and never exceed minus 500 VSI until we are sure that first minus 500 VSI, and then minus 700 VSI, will not cause IAS to exceed Mmo. Those low VSI limits in turn drive ToD.
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Descent: DC6B
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS <<<<<<<<<<<<<<
DO NOT EXCEED Vno = 251 KIAS
COWL FLAPS = CLOSED
RPM = 2000
REDUCE MAP in stages of 3 inches (per minute)
MINIMUM 20 INCHES MAP
See CARB HEAT below
*****************************
It is mismanaging energy state that will kill everybody aboard, not a hot or cold engine that will only cost money to fix. The propliner community are losing their focus and like real aircrew are being increasingly distracted by systems management, when we should be concentrating on compliance with 4D navigation, and energy state limits and targets. The aeroplanes we discuss here were designed when nobody knew how to prevent transonic shock, delay transonic shock, or reduce the consequence of transonic shock. Some real aerodynamicists just thought they did. Some propliners had Mmo barely above Mach 0.2 !
Remember fatal transonic shock arising from all the misshapen junk attached to our beautiful aerofoil can occur long, long, before that beautiful aerofoil reaches it critical Mach number which causes it to induce persistent transonic drag. In these badly designed ancient aeroplanes there is no correlation at all between Mmo and Mcrit. Classic era piston engined propliners never induce measurable transonic drag because they all depart controlled flight due to transonic shock just beyond Mmo long, long, before they can ever reach Mcrit for their smooth aerofoil.
Even propliners with Mmo above Mach 0.4 are at critical risk in early descent from high level cruise, so descent must be early and shallow, but not too early, or too shallow. TIME of Descent is crucial in propliners. Pretending that some have no Mach limits, or that they exist but don't matter, is confusing the propliner community into complacency concerning VSI after ToD, leading in turn to complacency concerning timing of ToD. In reality ToD has little leeway given engine limits versus Mach limits versus need to reach MSA only a few minutes before the IAF, (only on the far side of the nearby mountains), then crossing the IAF at target IAS in the target variable geometry state.
The higher we cruise, the lower the profile drag (IAS) that will exceed Mmo in early descent, and so we must restrain IAS in early descent for a third and safety critical reason. So the last part of the puzzle falls into place. In combination these criteria impose very early descent in piston propliners down careful shallow 4D navigation funnels imposed by the real arrival procedures *that solve all our problems* in any weather.
Remember this?
If our cruising velocity is 180 KTAS and there is a 0 KTS headwind we must descend at 60 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS headwind we must descend at 40 DME today.
If our cruising velocity is 180 KTAS and there is a 60 KTS tailwind we must descend at 80 DME today.
When we descend a complex piston propliner from high cold air we must descend at a precise VSI, targeting a precise IAS, to avoid a fatal Mach number.
We PLAN to take 20 minutes to lose 10,000 feet in any weather, any jurisdiction, in any piston propliner, at any date. While we are in high cold air we may need to actually execute that plan. Elderly frail passengers in vintage era unpressurised propliners cannot tolerate higher rate of change of cabin altitude anyway. The same rule therefore apply to them at any altitude. Not only does descent planning not need to be complicated; it must not be complicated, and it must not depend on distance. It must depend on TIME and the distance must vary hugely from Monday to Tuesday on the same route at the same altitude. We must *not* vary VSI to compensate for headwinds at any altitude. We must vary distance of descent instead. ToD is a constant TIME offset so that we can descend at constant and low VSI to avoid inducing fatal transonic shock in some propliners and to avoid inner ear injury to passengers in unpressurised cabins in others.
Many propliner enthusiasts have become fixated on engine limits while ignoring much more important energy state limits such as VSI and IAS and Mach.
Most of the rest of aerial navigation is 4D for exactly the same reasons. Where something must be invoked depends on wind and weather, but *when* does not.
So the ToD issue this thread was supposed to be about is just the tip of a much neglected iceberg that is very poorly understood because flight simulation enthusiasts are determined to believe they can carry over skills of 2D powered land vehicle navigation into aviation. When they don't work propliner enthusiasts then pretend that aerial navigation has no limits and no targets while fixating on less important targets and limits that are easier to understand and achieve. However when given priority over the things that really matter, that leads to 'made up nonsense, let's pretend' 4D navigation, and random energy state targeting, with unsynchronised timing of variable geometry status changes, followed by rushed approaches. Nobody can develop the skill to avoid high terrain in cloud during the arrival.
There is another whole can of worms that the propliner community are sliding into.
Increasingly propliner enthusiasts micro meddle with mixture during cruise (and even descent) while making no attempt to control their profile drag (IAS). Cruising at the wrong profile drag (IAS), and thus the wrong aircraft pitch, wastes far more fuel than any micro fiddling with mixture can possibly restore, because it causes loss of available cruising velocity (KTAS) from current fuel burn (PPH). The can of worms here is failure to understand the difference between the goal of maximising efficiency and the goal of maximising profit which comes second in priority to the goal of compliant 4D navigation (safety).
The last thing most classic era airlines want CAPT to do is operate a propliner efficiently. The tutorials I have provided explain that the role of CAPT is to decide when to maximise efficiency, when to minimise it, and when to target a specific intermediate efficiency that will maximise profit, not power, not thrust, not efficiency, not range, not endurance, not performance. That is part of what an aeroplane captain does. He decides which of those choices to maximise, role by role, and phase by phase, and instructs the crew on how to deliver his plan. During use of MSFS acting first and foremost as captain of the aeroplane is not optional.
During take off the last thing we want is efficiency. We must move the RPM levers to maximum inefficiency. We need every last pound of thrust whatever it costs. The last thing we want during TOGA is efficiency of thrust production. We need to maximise thrust and performance, not efficiency.
These choices concerning what to maximise do not end with procurement. They blossom after procurement and every aeroplane captain must use the captaincy decision making cycle to decide what must be maximised, from many possibilities. Consequently the 2008 Propliner Tutorial is very long. It addresses that reality and that complexity, but throughout it makes plain that compliant navigation in 4D (safety) comes first, all of the time.
Micro fiddling with mixture etc is a long way down the real list of priorities in the cockpit, whether the micro fiddling is done by FE or PNF. Playing with mixture can never recapture the fuel squandered by operating the aeroplane at the wrong altitude causing it to cruise at the wrong pitch and thus at the wrong profile drag (IAS) because CAPT failed to evaluate and then periodically step climb to current operational ceiling. Cruising at the wrong altitude, in the wrong aeroplane pitch, and thus at at the wrong profile and induced drag, causes loss of velocity and squanders far more fuel than can be saved by FE micro fiddling with mixture. His role is always only tertiary. Propliner enthusiasts must not become over focussed on systems management to the exclusion of the things that really determine miles per gallon.
Flight simulation enthusiasts are also failing to come to terms with the four phases of aviation history (pioneer / vintage / classic / modern), why they matter, and how they differ. Each was invoked by a change of legislation which required captains to alter how they operated (commercial) aeroplanes. The aeroplanes were then designed to match the relevant new regulations and the crew complement and qualifications imposed by those new regulations.
In the vintage phase of aviation history aeroplanes were so badly designed, and regulation so lacking, that the death toll was terrible. Two thirds, or sometimes three quarters, of the propliners of a particular type would crash within ten years of manufacture. They were so badly designed, and were allowed to get away with carrying such low fuel reserves, that they had to be operated efficiently all of the time.
They had no hope of making a profit and all airlines needed huge tax subsidies. The B314A Clipper and M130 China Clipper tutorials available from Calclssic.com, within the relevant downloads, explain that when we simulate their operation, always within an infrastructure stranded in the vintage phase of aviation history, we must constantly seek maximum efficiency by targeting low profile drag = IAS = Vbr, proceeding direct along great circle routes, while cruise climbing continuously to unpressurised ceiling, without restriction, in that dangerously unregulated environment. They need huge expensive crews to even attempt that, and it still wasn't remotely safe, because they still failed to achieve safe navigation far too often. The vintage phase of aviation history, (the lack of classic phase infrastructure), continued over the North Atlantic (including the 'Bermuda Triangle') until 1959, but had ended over the CONUS in 1932, and over Germany in 1936. It mattered!
The classic phase navigation infrastructure, when and where it was implemented, introduced massive regulation, much higher safety criteria, and very different aeroplanes with much smaller crews forced to adopt compliant 4D navigation. Suddenly the new DC-3 created to match the new highly regulated and compliant way of operating commercial aeroplanes with only a tiny crew, all of whom were only pilots, allowed airlines to make a profit without a subsidy and in safety. It matters! While profit and safety in aviation were just ridiculous impossibilities they were neither sought nor required. Once safety and profit were made possible they became compulsory. Classic era propliners can operate efficiently at medium level targeting IAS = Vbr with very low power and manually weakened mixtures, just like a huge vintage era flying boat, but its a dumb way to use one if we are trying to simulate a classic era aviation environment in an Argonaut or an L-049A Constellation.
However we must remember that trans oceanic travel lacked classic era infrastructure for a long time. Consequently the handling notes for the L-049A explain efficient operation targeting in a vintage era aviation infrastructure.
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Max Range Cruise (about 700hp):
COWL FLAPS - CLOSED
MAP = 22 inches
RPM = 1600
Plan 1400 PPH
Yields 185 KTAS at FL150 at MCW
c28000lbs @ 1400 PPH = 20 hours nominal
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Just like a flying boat we restrict power applied (fuel burn). With little fuel burn applied we must stay in thick air and so our velocity is held back to just 185 KTAS, but we can achieve 20 hours endurance with full tanks as we cruise climb continuously around a great circle over an Ocean. It's very efficient, but it will never make a profit. If we replicate that vintage era procedure in a classic era infrastructure everybody will be buying tickets with the L-049A operator who maximises profit by delivering much higher velocity, held back less, in much thinner air, at much higher altitude, using more fuel burn to access that lovely thin air which permits much higher cruising velocity.
Consequently the handling notes for the L-049A also explain profitable operation in a classic era infrastructure.
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Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
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Passengers would rather arrive after 14 hours instead of 20. Where a classic phase infrastructure mandating 4D navigation compliance at all times exists, installed at huge expense by taxpayers, delivering comprehensive ATC provided by taxpayers, at no expense to airlines, the regulator appointed by those taxpayers insists that we must learn to operate much less efficiently, burning much more fuel per hour, at higher power settings, to access much thinner air, to go much faster. Our costs are higher, but our revenue is much higher, and we can actually make a profit. Those taxpayers can then withdraw direct subsidies to airlines. Cruising only a few thousand feet above the much cheaper DC-4s at only 185 KTAS does not justify the huge cost of a pressure hull, or the huge cost of engines rated 2200hp for TOGA and 1800hp continuous. To maximise profit in a classic era infrastructure we must step climb to operational ceiling at current weight in the current weather, unless we have a significant headwind, (see 2008 Propliner Tutorial for relevant strategies).
Vintage phase procedures do not get our passengers above the weather, trap us in icing in cloud at FL150, and horribly slow us down, but the great oceans are stuck in the vintage phase of aviation history until 1959. It matters. It drives the captaincy decision making cycle during use of MSFS. We don't operate a 1946 Constellation like a 1936 China Clipper if the local taxpayer has provided a profitable, much safer, and much faster alternative.
Due to the negotiating power of the relevant trade union to impose a maximum of ten flying hours per shift, TWA actually operated their L-049As at max cruise power over the CONUS to get maximum miles per pilot per shift;
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Max Cruise (about 1400hp):
SUBJECT to CHT & OIL gauges in GREEN ARC
COWL FLAPS = AS REQUIRED
MAP = 31 inches
RPM = 2300
Plan 2800 PPH
Yields 276 KTAS at FL230 at MCW
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Micro fiddling to reduce fuel consumption, and avoiding using high blower after paying an arm and a leg to buy one, flying barely above the altitude where dirt cheap unpressurised propliners like the DC4 are allowed to cruise, is not the way to maximise profit in a classic era propliner flown within a classic era infrastructure!
To maximise profit we go out of our way to avoid efficiency in the cruise, just as we did during Take Off. Once the classic phase of aviation history arrives *in the jurisdiction we are flying in right here, right now* we must target profit not efficiency. This is *not* a function of the aeroplane we are simulating. It is a function of the infrastructure we are navigating within in and the associated legislation. Of course we may not be able to generate Max Cruise Power at pressurisation = certification ceiling (FL250). TWA targeted FL230 on internal flights over the CONUS once light enough because that maximised TAS which maximised (passenger) miles (purchased) per aircrew shift.
The pressurised classic era propliners are so complex and so expensive that those very expensive assets, (capital assets or labour assets), must be worked very hard. Efficiency as defined in textbooks about 'dynamics' are no longer the point. The curves we must now pursue are in textbooks about 'economics'. Our operating targets change with the legislation for the jurisdiction we are crossing right here, right now, not the aeroplane we are in or the gauges it has in its cockpit.
UK and USSR tax payers did not install a classic era infrastructure over the UK or USSR, or across the dwindling British Empire until the late 1950s. Consequently British and Soviet airlines continued to procure vintage era propliners to be operated within vintage era regulations. It matters! 4D navigation compliance was not part of vintage phase of aviation history and the death toll was terrible, but 4D navigation compliance is at the heart of classic phase aviation. We must teach ourselves to proceed accordingly, or choose which aeroplanes we simulate where and when in a realistic way if we desire realism.
Realism is a variable which depends on compliance with relevant legislation which always matched the available navigation infrastructure in that *jurisdiction*. The entire planet was not under the jurisdiction of the US, or Germany. or the UK or the USSR. Propliner enthusiasts need to think harder about those issues and how the navigation infrastructure drives legislation, and in turn drives realistic simulation of a particular phase of aviation history in a particular jurisdiction. It also drove propliner design and procurement. Then we all need to come to terms with the reality that New York had been located in classic era infrastructure, with classic era 4D navigation compliance procedures applicable since 1932, even though we may have spent twelve hours in vintage era airspace earlier in the same flight across the North Atlantic in 1958. The price of realism is complexity of both planning and execution.
The complexity involved in delivering propliner realism to ourselves takes a long to explain because everything is linked to something else which has driven it to be the way it is and a long chain of cause and effect must be understood, before it can be replicated in a virtual environment.
The norm for most airlines in a classic phase infrastructure was however to target neither maximum efficiency, nor maximum performance, but something in between giving rise to the concepts of economical cruise power or normal cruise power . At any date a particular airline has specific fuel versus labour costs, including aircrew labour costs and engineer / mechanic engine maintenance costs, and also has a specific *target consumer*. That causes economical = normal cruise criteria to alter year by year, route by route, and role by role.
Continued in next post...
