Post by volkerboehme on Sept 15, 2010 11:00:19 GMT -5
FSAviator's comments:
This thread relating to use of gear as speed brake during the arrival phase soon wandered to discussion of the wholly unrelated topic of 'stable approaches' in the approach phase. The AAL promotional video linked from the top of this thread is a cut and paste of several different filming sessions, with both real and fake dubbed narrative, but the dubbed narrative and video content makes plain that speed brake was deployed just after ToD, early in the arrival phase and not during the much later approach phase.
The subsequent discussion concerning the relevance of stable approach criteria to propliners deserves to be brought to a firmer conclusion.
Americans usually refer to a stable approach in the past tense (stabilized approach). They are the same thing. The criteria for a stable approach are defined in international law and even though this is only a flight simulation forum we are not free to just guess at the meaning of legally binding concepts since confusion then descends. Since this thread contains no definition of a stable approach it also has no definition of an unstable approach. In piston propliners an 'unstable' approach is either highly desirable, or mandatory, and must not be confused with an undesirable 'bucking bronco' approach, but that is what has happened in this thread.
The stable approach is defined within ICAO Annex 6 which is a United Nations annex to the Treaty of Chicago which all relevant governments have ratified. I must abbreviate the full legal version for MSFS use, but my short definition below retains all relevant content.
****************
During a stable approach the aeroplane must be in landing configuration, established at, and trimmed to sustain, IAS = Vref, with all landing checks complete, in stable progression along the final approach track (FAT), and in stable progression down the *final* approach glideslope no later than;
1) 1000 feet above the landing runway (QFE) if current visibility < 5 miles
2) 500 feet above the landing runway (QFE) if current visibility => 5 miles
******************
I have added the emphasis around *final* and I will explain why below. Each nation which ratifies the Treaty of Chicago must bring its provisions into its federal law and then promulgate the legal requirement within an appropriate legal reference. The legal requirement, (only for those to whom it applies), is then re-iterated from time to time by the relevant regulatory authority. Within the United States most recently within FAA Approach-and-Landing Accident Reduction (ALAR) Briefing Note 7-1.
The legislation does not address the perceived need for stable approaches, but the representations made by the International Federation of Airline Pilots Associations (IFALPA) in support of the perceived need have. I abbreviate and paraphrase for MSFS use again.
*******************
A) slow or imprecise thrust response from turbine engines
B) slow aeroplane response to control inputs in massive aeroplanes which exhibit massive inertia regardless of engine type.
********************
IFALPA and other pressure groups continue to lobby for the criteria to be increased to 1000 feet QFE in all weather conditions and for stable approaches to be mandatory under many more circumstances. Those proposals continue to be *rejected* by the regulatory authorities who continue to endorse and publish 'non precision' = 'unstable' approach procedures.
We must grasp that stable approaches are *not mandatory by default* and are unnecessary or even inappropriate to many types of aircraft. A regulatory authority may require stable approaches in certain types of massive aeroplane or in aeroplanes with certain types of turbine engine, or at certain locations. An employer, (or insurance provider), may require stable approaches in certain types of aeroplane or at certain locations, but a stable approach, once mandated, is compliance with the ICAO Annex 6 criteria above.
Note that the legal criteria have *no relevance to the flight rules* under which the flight is being conducted. They relate to meteorology. A Boeing 747 crew, or if relevant an executive jet crew, cannot exempt themselves by obtaining a VFR clearance.
The unstated assumption, and intention, is that during a stable approach both thrust and thrust lever position can be constant below 1000 QFE. Unless the real crew meet gusts or wind shear that implicit assumption is mostly true. However in any aeroplane the thrust we need to sustain the glideslope on Monday and Tuesday just varies with the wind. We need more thrust to battle a bigger headwind to sustain the same glideslope at the same weight on Monday compared to Tuesday. There is no correct MAP at which to fly an approach even if every approach is at the same weight.
Airline pilots must often make approaches during which visibility falls below 5 miles, (and so should we in MSFS), either because the general visibility below cloud is lower, or because the approach will, or just may, pass through cloud or precipitation as ragged cloud base and precipitation drift on the wind today.
So during a stable approach aircrew who fly aeroplanes which actually exhibit the problems above may be mandated to achieve landing flap and gear configuration well before 1000 AGL, and must also achieve Vref well before 1000 AGL. On Monday and Tuesday, after achieving those three operating targets, they must juggle very differently with the thrust levers to find the precise thrust lever position that also sustains a *continuous* final glidepath all the way to the flare just above the runway, while still above 1000 QFE, in each day's different headwind.
The most important thing to grasp is that a stable approach is incompatible with any approach procedure that allows the crew to sustain a Minimum Descent Height (MDH) below 1000 QFE in 'poor' visibility while proceeding along the final approach track until the runway lights become visible in that poor visibility. A stable approach is incompatible with the intention of almost all published non precision instrument approaches whether based on an NDB or a VOR or a LOC or GPS.
The hidden agenda sought by IFALPA, and others who lobby for wider mandatory adoption of stable approaches is the requirement to install ILS everywhere, (at somebody else's expense), and on every runway that relevant aircraft will ever be allowed to approach. A stable approach is incompatible with the intended approach profile of most currently lawful types of instrument approach. The wider agenda is to criminalise and prevent the spread of GPS approaches, (which never provide stable glidepath guidance in cloud), and to impose more and more 'beam following' both laterally and vertically.
These safety criteria are not invoked for the benefit of ATC, or sought by ATC. ATC must tolerate them and facilitate them when they are mandatory. These criteria *when mandated* prevent ATC from tactically mandating that a higher IAS than Vref to be used for longer during the approach, and for as long as ATC would wish, and thereby diminish runway capacity to the annoyance of ATC. More importantly the requirement for a stable approach precludes ATC from offering many types of lawful instrument approach at that location, which ATC wish to offer, to expedite traffic flow and runway utilisation.
*No vintage or classic era propliner has the relevant problems* and when classic era propliners were designed and delivered airline pilots, (and their lobbyists IFALPA), believed that stable approaches were;
a) unnecessary
b) a bad idea
They believed (then) that it was safe to intercept the *final* glideslope below 1000 QFE, while maintaining MDH during an NDB or RANGE or VOR or LOC or RDF (ZZ) or GPS (Decca) approach, or even from a visual circuit, in even the most massive piston propliners, in visibility much worse than 5 miles, and that IAS should reduce during the last 1000 feet of descent, and that flap should be deployed during the last 1000 feet of descent, and that retrimming below 1000 feet was safe. They never attempted stable approaches and believed they had no earthly reason to try.
An unstable approach is any approach in which IAS, or flap, or gear, or thrust, or trim, are *deliberately* varied, or a turn is made, or any approach in which the crew maintain an MDH, thereby interrupting the continuous glideslope requirement, below the defined height appropriate to the visibility (500 QFE or 1000 QFE). An unstable approach is not a 'bucking bronco' approach. What has been called a 'bucking bronco' approach in this thread is obviously undesirable in any aeroplane. The legal term for a 'bucking bronco' approach is a 'missed approach'. A 'missed approach' does not happen after the crew manage to recognise that the approach is out of control and discontinue it. It happens as soon as the approach compliance criteria are 'missed' by the crew.
The compliance criteria which are specific to a given approach are cited on the Instrument Approach Chart (or Plate) which we must download. The generic compliance criteria for all approaches are defined in ICAO Doc 8168 (and potentially elsewhere). A mismanaged approach (a bucking bronco approach) is one which transgresses those specific or generic legal limits. Of course either Pilot Flying or CAPT can decide that the management of an approach conducted well within the outer legal limits is beyond the ability *of that particular pilot flying* to correct in good time, and may choose to call a missed approach well inside legal constraints.
I decided long ago that explaining the Doc 8168 criteria, (which require instrument rated airline pilots to execute a missed approach), to non aircrew was counter productive. For non aircrew MSFS is a skills *training* tool, not a check ride *examination* tool. While training to fly compliant approaches non aircrew will transgress the real world (simulator) check ride limits and in a desk top flight simulator that is entirely appropriate for those users.
What is required within MSFS is the intention to understand what constitutes 4D navigation approach compliance and an intention to try. Failure to comply in full is a given during relevant skills training by non aircrew. We all have to learn how to achieve compliance, and in a desk top simulator it is appropriate for non aircrew to continue approaches which must be rejected in real life, as we train ourselves to do better. Propliner enthusiasts should continue approaches in MSFS that are defined as missed approaches, and flown as missed approaches, in real life. Within MSFS propliner enthusiasts should however regularly test their own competence to calculate and achieve Vref no later than 50 QFE while descending on the real *final* glideslope, and should reject approaches in which they do not succeed, accordingly.
Unfortunately many MSFS propliner enthusiasts rarely reject approaches which are obviously and grossly non compliant having never attempted compliance with the real published procedure for their destination in the first place. Horrendous 'bucking bronco' approaches, and rushed approaches, should obviously be rejected, even in MSFS, in any type of aeroplane.
However we must grasp that failure to achieve a stable approach, (using the real definition above), by 1000 QFE or 500 QFE, is not relevant to propliner simulation within MSFS because real classic era aircrew never had that intention. The propliner criterion is always (no later than) 50 QFE, never 500 or 1000 and never varies with the weather. Everything in the real legal definition above *does* apply to propliners, but the height at which it applies in a *propliner* is always 50 QFE. We may have the lawful and appropriate intention to fly unstable approaches to very low heights, so long as we achieve the ICAO criteria above by 50 QFE.
In *some* propliners I encourage MSFS propliner enthusiasts to achieve all of those stability criteria earlier in the final approach than 50 QFE, but below I will explain why even that may not be appropriate in some propliners. Anyway we must remember that many real instrument approaches that we should be learning to fly *require* us to descend to maintain an MDH well below a height of 1000 feet as part of the compliant approach. Flying an unstable approach, with a variable glidepath, is a deliberate, appropriate and lawful intention in most real aircraft. In aeroplanes that are neither massive nor turbine powered propliner pilots frequently intend to fly unstable approaches which include flap and gear and IAS and trim changes, and direction changes, and glidepath changes, below a height of 1000 feet in visibility which is, or may deteriorate, below 5 miles. Unfortunately many real pilots confuse the meaning of stable and compliant.
Unstable approaches are the correct, fully compliant approaches, as published and authorised by the real regulatory authority, for many / most aeroplanes which are neither massive nor turbine powered, at hundreds of real locations and to hundreds of runways at airports where only one runway has ILS. The owner of any aeroplane may of course impose the higher requirement for stable approach criteria on anyone they permit to operate their aeroplane, and in some circumstances the owners insurance company may no longer be prepared to insure unstable approaches. Those are special cases.
The Propliner Tutorial and my propliner handling notes therefore mandate unstable and unrushed approaches commenced at the complaint IAS, in the compliant flap and gear state, over the real Final Approach Fix, at the compliant height cited on the real approach plate, followed by unrushed increases in flap state and synchronised unrushed decrease of IAS to Vref, no later than the airfield boundary fence (nominally crossed with the cockpit (altimeter) at 50 QFE ). Most non aircrew unfortunately have no idea what their height is and are prone to confuse height with altitude, (see 2008 Propliner Tutorial).
Stable thrust was *not* part of that piston propliner procedure either, even though it was possible to fly a stable thrust approach in some. A stable thrust approach is not a stable approach. Those concepts must not be confused. When vintage and classic era piston propliners were designed and delivered no one had developed the intention to fly even stable thrust approaches.
Varying thrust precisely with piston engines to sustain the glideslope during unstable and unrushed approaches was deemed to be both 'easy' and 'necessary' by both pilots and aviation regulators (then) and they (then) mandated that IAS must be controlled and varied with elevator (or elevator trim) and that glideslope could be varied, (to comply with the need to sustain MDH), by variation of MAP at cited approach RPM (*subject to a high minimum manifold pressure*) at heights far below 1000 feet, even when approaching in cloud.
***************************
Approach and Circuit: DC6B
Cross FAF = 140 KIAS & FLAP 2 deployed
2400 RPM <<<<<<<<<<<<
MAP => 24 inches <<<<<<<<<<<<
On reaching Minimum Descent Altitude <<<<<<<<<<<
(see propliner tutorial parts 4 & 7) <<<<<<<<<<<
REDUCE = 130 KIAS
ON reaching Glideslope
(straight in or base)
To achieve Vref
GEAR = DOWN
FLAP = STAGE 3
FLAP = STAGE 4
REDUCE < 120 KIAS
FLAP = STAGE 5
Cross THRESHOLD 105 KIAS (Vref @ 88,000lbs)
FLARE and LAND
****************************
It is possible to deploy FLAP 5 and reduce to 105 KIAS while still 1000 feet above the landing runway in a DC6B, and so it is possible and safe to fly a stable approach in a DC6B, but it would be abnormal and it precludes many real instrument approaches that we should be learning to fly compliantly, and which include one or several mandated changes of glideslope below 1000 QFE.
Note that in a DC6B we must never reduce below 120 KIAS until we are established on both the FAT and the *final continuous* glideslope; and that is important. The *final continuous* glideslope is the one that begins from MDH to the landing runway, often far below 1000 QFE.
Non precision instrument approaches which permit and encourage a discontinuous glidepath, (NDB + RANGE + VOR + LOC + RDF + GPS), aside; in a DC6B or any other piston propliner real (instrument rated) aircrew minima allow PF to approach the instrument runway and then 'circle to land' on the into wind runway, or the current noise abatement, (noise misery sharing), runway, with visibility far below 5 miles and with a cloud base wholly incompatible with a high performance circuit at 1500 AGL achieving a stable approach and Vref by 1000 feet.
Most real airline bosses in 2010 still believe that it is safe to vary IAS, and VG status, and trim status, and make turns below 1000 AGL, in many airliners, (including many with turboprop engines), and have no intention of allowing their employees operating such airliners to refuse to accept ATC clearances which require them to execute a published unstable approach, whether non precision and straight in to the instrument runway, or which require a 'circle to land' procedure at less than 1500 feet QFE in visibility less than 5 miles. Most (probably all) modern era military and naval authorities regard the idea that it is unsafe to turn a C-130 below a height of 1000 feet, in a visibility of four miles, as incompatible with the missions they procured it to fly.
From our perspective as pioneer, vintage or classic era propliner simulation enthusiasts we must simulate unstable and unrushed approaches, often involving an approach to the instrument runway until we are below cloud, or can see the airfield, in the prevailing visibility, just well enough to identify the different landing runway and then join and fly an unstable and unrushed, parallax compliant and downwind leg TIMED, visual circuit pattern making many changes to IAS, and thrust, and VG status, and roll status, and trim status, all below 1000 QFE in any weather.
However for us a problem arises when our virtual employer decides to re-engine our CV340 or CV440 with turbine engines to create a CV580. It suddenly acquires much worse thrust response yet its wing was designed long before to use very late changes of variable geometry and very late changes of IAS on approach, and to make turns safely below 1000 AGL. Our employer will still require us to fly unrushed and unstable instrument approaches and may also require us to fly precise parallax compliant unrushed and unstable visual circuit patterns, making turns and other unstable changes below 1000 QFE.
In a CV58 we must employ a stable thrust technique, but a stable thrust approach is not a stable approach. A stable approach is much more restrictive. We would need to hold for much longer, awaiting greater weather improvement, and we would need to divert far more often.
A stable thrust approach with turbine engines is much more demanding than an unstable thrust approach with piston engines. With piston engines we only have a minimum safe power setting. With turbine engines, mounted in a classic era aerofoil, for practical purposes within MSFS, the minimum power is also the maximum power we can apply. We use the same power setting for a very prolonged period (stable thrust technique). This requires us to develop additional skills of *timing* of Variable Geometry status changes, above or below a height of 1000 feet, as we reduce to Vref no later than 50 AGL in an always deliberately unstable and unrushed stable thrust approach.
In a CV58 we control power and thrust using turbine interstage temperature (TIT) as our primary reference.
****************************
Arrival and Holding phases:
TIT = 765C (throughout) <<<<<<<<<<
Before IAF or earlier Hold:
VSI = as required to
REDUCE < 170 KIAS
FLAP = STAGE 1
Descending in Hold:
DO NOT EXCEED 173 KIAS
VSI = to comply
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
FLAP STAGE 2 = OPTIONAL
Do NOT retain FLAP 2 once level
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
****************************
Approach phase:
TIT = 765 (throughout) <<<<<<<<<<<<<
Just before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
FLAP = STAGE 2
130 KIAS
At Glidepath:
GEAR = DOWN
On Glidepath:
To achieve Vref
FLAP = STAGE 3
>>>>>>>>>>>>>>>
OPTIONAL
FLAP = STAGE 4
Vref = 103 KIAS
>>>>>>>>>>>>>>>
Vref = Cross Boundary 109 KIAS (@ 52,000lbs)
(below 50 QFE TIT < 765 allowed) <<<<<<<<<<<<
FLARE and LAND
**************************
Circuit phase:
High Performance Visual Circuit:
(see 2008 Propliner Tutorial)
Before Downwind Join:
TIT = 765 (throughout) <<<<<<<<<<<
REDUCE < 170 KIAS
FLAP = STAGE 1
Late Downwind:
TIT = 765 (throughout) <<<<<<<<<<<<<<
FLAP = STAGE 2
Base Leg:
VSI to begin final turn 700 QFE
TIT = 765 (throughout) <<<<<<<<<<<<<<
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
GEAR = DOWN
*Before* final turn at 700 QFE:
FLAP = STAGE 3
VSI = adjust to
Turn final @ 145 KIAS
Final:
TIT = 765 (throughout) <<<<<<<<<<<<<<<
>>>>>>>>>>>>>>>
OPTIONAL
FLAP = STAGE 4
Vref = 103 KIAS
>>>>>>>>>>>>>>>
Vref = cross boundary 109 KIAS (@ 52,000lbs)
Below 50 QFE TIT < 765 allowed <<<<<<<<<<<<<<
FLARE and LAND
***********************************
The fact that we (intend to) use constant engine status for maybe the last hour of the flight from just after ToD right through the arrival, and holding, and approach, and visual circuit phases, makes the handling notes more complicated and throughout they emphasise the constancy of TIT required (or anyway possible). After our Convair Liner acquires turbine engines we must learn to use VSI and GEAR and FLAP to control IAS having applied enough TIT, just after ToD, to hold in the holding pattern with appropriate VG status, adding *or subtracting* FLAP as required, and then we sustain the glideslope in any headwind deploying when necessary a different VG status, to target each IAS variation in that unstable, unrushed, classic era wing, but stable thrust (stable TIT) turbine approach.
We avoid a missed approach (bucking bronco approach) by deliberately flying an unstable unrushed approach in which we vary IAS by precise TIMED synchronisation of VG status *right down to very low level*.
In any Convair Liner or Martin Liner, with any engines, we always reserve FLAP 4 as our 'get out of jail free card' precisely because we always fly an unstable approach. Depending on how badly we screw up that intention we may need to invoke FLAP 4 to achieve Vref by 50 AGL. We rarely intend to deploy FLAP 4 in any of those aeroplanes, but it may be the means by which we avoid a missed approach.
A stable approach requires us to achieve *landing flap configuration* more than 1000 feet above the landing runway. The people who designed aeroplanes just after WW2 had no idea anybody would ever believe in such a crazy thing. They assumed regulators would never certificate aeroplanes so dangerous that they might require a stable approach or even a stable thrust technique. So did the (then) regulators!
In many classic era propliners as PF we have no idea what flap we will be using for landing until we are very short final and PNF challenges our IAS deviation from Vref, calling for immediate correction, else he will call the missed approach. In an aeroplane where we cannot know what flap status we will need to achieve Vref today, until we are short final, we cannot possibly fly stable approaches.
These issues and others are addressed in greater detail within the Calclassic Convair and Martin Mini Tutorial. With practice, practice, practice MSFS propliner enthusiasts should eventually be able to simulate stable thrust NDB or VOR or LOC approaches (see 2008 Propliner Tutorial) straight in to instrument runways in the CV58 in MSFS, but nailing Vref while landing on any other runway from a visual circuit requires substantial stable thrust skills.
The stable approach required by massive turbine powered airliners has three primary objectives;
1) to eliminate all turns below a height of 1000 feet
2) to eliminate all changes of glideslope below 1000 feet
3) to eliminate the need to TIME turns in a visual pattern to perfection versus stable thrust in varying winds.
None of those objectives has any relevance to any propliner which is hosted or 'supported' by Calclassic.com for use within MSFS. Airliners like the Tu-114 are special cases and must be treated as 'massive modern turbine airliners'. The '2008 Propliner Tutorial' does not apply to any swept wing aircraft of any kind.
FSAviator.
This thread relating to use of gear as speed brake during the arrival phase soon wandered to discussion of the wholly unrelated topic of 'stable approaches' in the approach phase. The AAL promotional video linked from the top of this thread is a cut and paste of several different filming sessions, with both real and fake dubbed narrative, but the dubbed narrative and video content makes plain that speed brake was deployed just after ToD, early in the arrival phase and not during the much later approach phase.
The subsequent discussion concerning the relevance of stable approach criteria to propliners deserves to be brought to a firmer conclusion.
Americans usually refer to a stable approach in the past tense (stabilized approach). They are the same thing. The criteria for a stable approach are defined in international law and even though this is only a flight simulation forum we are not free to just guess at the meaning of legally binding concepts since confusion then descends. Since this thread contains no definition of a stable approach it also has no definition of an unstable approach. In piston propliners an 'unstable' approach is either highly desirable, or mandatory, and must not be confused with an undesirable 'bucking bronco' approach, but that is what has happened in this thread.
The stable approach is defined within ICAO Annex 6 which is a United Nations annex to the Treaty of Chicago which all relevant governments have ratified. I must abbreviate the full legal version for MSFS use, but my short definition below retains all relevant content.
****************
During a stable approach the aeroplane must be in landing configuration, established at, and trimmed to sustain, IAS = Vref, with all landing checks complete, in stable progression along the final approach track (FAT), and in stable progression down the *final* approach glideslope no later than;
1) 1000 feet above the landing runway (QFE) if current visibility < 5 miles
2) 500 feet above the landing runway (QFE) if current visibility => 5 miles
******************
I have added the emphasis around *final* and I will explain why below. Each nation which ratifies the Treaty of Chicago must bring its provisions into its federal law and then promulgate the legal requirement within an appropriate legal reference. The legal requirement, (only for those to whom it applies), is then re-iterated from time to time by the relevant regulatory authority. Within the United States most recently within FAA Approach-and-Landing Accident Reduction (ALAR) Briefing Note 7-1.
The legislation does not address the perceived need for stable approaches, but the representations made by the International Federation of Airline Pilots Associations (IFALPA) in support of the perceived need have. I abbreviate and paraphrase for MSFS use again.
*******************
A) slow or imprecise thrust response from turbine engines
B) slow aeroplane response to control inputs in massive aeroplanes which exhibit massive inertia regardless of engine type.
********************
IFALPA and other pressure groups continue to lobby for the criteria to be increased to 1000 feet QFE in all weather conditions and for stable approaches to be mandatory under many more circumstances. Those proposals continue to be *rejected* by the regulatory authorities who continue to endorse and publish 'non precision' = 'unstable' approach procedures.
We must grasp that stable approaches are *not mandatory by default* and are unnecessary or even inappropriate to many types of aircraft. A regulatory authority may require stable approaches in certain types of massive aeroplane or in aeroplanes with certain types of turbine engine, or at certain locations. An employer, (or insurance provider), may require stable approaches in certain types of aeroplane or at certain locations, but a stable approach, once mandated, is compliance with the ICAO Annex 6 criteria above.
Note that the legal criteria have *no relevance to the flight rules* under which the flight is being conducted. They relate to meteorology. A Boeing 747 crew, or if relevant an executive jet crew, cannot exempt themselves by obtaining a VFR clearance.
The unstated assumption, and intention, is that during a stable approach both thrust and thrust lever position can be constant below 1000 QFE. Unless the real crew meet gusts or wind shear that implicit assumption is mostly true. However in any aeroplane the thrust we need to sustain the glideslope on Monday and Tuesday just varies with the wind. We need more thrust to battle a bigger headwind to sustain the same glideslope at the same weight on Monday compared to Tuesday. There is no correct MAP at which to fly an approach even if every approach is at the same weight.
Airline pilots must often make approaches during which visibility falls below 5 miles, (and so should we in MSFS), either because the general visibility below cloud is lower, or because the approach will, or just may, pass through cloud or precipitation as ragged cloud base and precipitation drift on the wind today.
So during a stable approach aircrew who fly aeroplanes which actually exhibit the problems above may be mandated to achieve landing flap and gear configuration well before 1000 AGL, and must also achieve Vref well before 1000 AGL. On Monday and Tuesday, after achieving those three operating targets, they must juggle very differently with the thrust levers to find the precise thrust lever position that also sustains a *continuous* final glidepath all the way to the flare just above the runway, while still above 1000 QFE, in each day's different headwind.
The most important thing to grasp is that a stable approach is incompatible with any approach procedure that allows the crew to sustain a Minimum Descent Height (MDH) below 1000 QFE in 'poor' visibility while proceeding along the final approach track until the runway lights become visible in that poor visibility. A stable approach is incompatible with the intention of almost all published non precision instrument approaches whether based on an NDB or a VOR or a LOC or GPS.
The hidden agenda sought by IFALPA, and others who lobby for wider mandatory adoption of stable approaches is the requirement to install ILS everywhere, (at somebody else's expense), and on every runway that relevant aircraft will ever be allowed to approach. A stable approach is incompatible with the intended approach profile of most currently lawful types of instrument approach. The wider agenda is to criminalise and prevent the spread of GPS approaches, (which never provide stable glidepath guidance in cloud), and to impose more and more 'beam following' both laterally and vertically.
These safety criteria are not invoked for the benefit of ATC, or sought by ATC. ATC must tolerate them and facilitate them when they are mandatory. These criteria *when mandated* prevent ATC from tactically mandating that a higher IAS than Vref to be used for longer during the approach, and for as long as ATC would wish, and thereby diminish runway capacity to the annoyance of ATC. More importantly the requirement for a stable approach precludes ATC from offering many types of lawful instrument approach at that location, which ATC wish to offer, to expedite traffic flow and runway utilisation.
*No vintage or classic era propliner has the relevant problems* and when classic era propliners were designed and delivered airline pilots, (and their lobbyists IFALPA), believed that stable approaches were;
a) unnecessary
b) a bad idea
They believed (then) that it was safe to intercept the *final* glideslope below 1000 QFE, while maintaining MDH during an NDB or RANGE or VOR or LOC or RDF (ZZ) or GPS (Decca) approach, or even from a visual circuit, in even the most massive piston propliners, in visibility much worse than 5 miles, and that IAS should reduce during the last 1000 feet of descent, and that flap should be deployed during the last 1000 feet of descent, and that retrimming below 1000 feet was safe. They never attempted stable approaches and believed they had no earthly reason to try.
An unstable approach is any approach in which IAS, or flap, or gear, or thrust, or trim, are *deliberately* varied, or a turn is made, or any approach in which the crew maintain an MDH, thereby interrupting the continuous glideslope requirement, below the defined height appropriate to the visibility (500 QFE or 1000 QFE). An unstable approach is not a 'bucking bronco' approach. What has been called a 'bucking bronco' approach in this thread is obviously undesirable in any aeroplane. The legal term for a 'bucking bronco' approach is a 'missed approach'. A 'missed approach' does not happen after the crew manage to recognise that the approach is out of control and discontinue it. It happens as soon as the approach compliance criteria are 'missed' by the crew.
The compliance criteria which are specific to a given approach are cited on the Instrument Approach Chart (or Plate) which we must download. The generic compliance criteria for all approaches are defined in ICAO Doc 8168 (and potentially elsewhere). A mismanaged approach (a bucking bronco approach) is one which transgresses those specific or generic legal limits. Of course either Pilot Flying or CAPT can decide that the management of an approach conducted well within the outer legal limits is beyond the ability *of that particular pilot flying* to correct in good time, and may choose to call a missed approach well inside legal constraints.
I decided long ago that explaining the Doc 8168 criteria, (which require instrument rated airline pilots to execute a missed approach), to non aircrew was counter productive. For non aircrew MSFS is a skills *training* tool, not a check ride *examination* tool. While training to fly compliant approaches non aircrew will transgress the real world (simulator) check ride limits and in a desk top flight simulator that is entirely appropriate for those users.
What is required within MSFS is the intention to understand what constitutes 4D navigation approach compliance and an intention to try. Failure to comply in full is a given during relevant skills training by non aircrew. We all have to learn how to achieve compliance, and in a desk top simulator it is appropriate for non aircrew to continue approaches which must be rejected in real life, as we train ourselves to do better. Propliner enthusiasts should continue approaches in MSFS that are defined as missed approaches, and flown as missed approaches, in real life. Within MSFS propliner enthusiasts should however regularly test their own competence to calculate and achieve Vref no later than 50 QFE while descending on the real *final* glideslope, and should reject approaches in which they do not succeed, accordingly.
Unfortunately many MSFS propliner enthusiasts rarely reject approaches which are obviously and grossly non compliant having never attempted compliance with the real published procedure for their destination in the first place. Horrendous 'bucking bronco' approaches, and rushed approaches, should obviously be rejected, even in MSFS, in any type of aeroplane.
However we must grasp that failure to achieve a stable approach, (using the real definition above), by 1000 QFE or 500 QFE, is not relevant to propliner simulation within MSFS because real classic era aircrew never had that intention. The propliner criterion is always (no later than) 50 QFE, never 500 or 1000 and never varies with the weather. Everything in the real legal definition above *does* apply to propliners, but the height at which it applies in a *propliner* is always 50 QFE. We may have the lawful and appropriate intention to fly unstable approaches to very low heights, so long as we achieve the ICAO criteria above by 50 QFE.
In *some* propliners I encourage MSFS propliner enthusiasts to achieve all of those stability criteria earlier in the final approach than 50 QFE, but below I will explain why even that may not be appropriate in some propliners. Anyway we must remember that many real instrument approaches that we should be learning to fly *require* us to descend to maintain an MDH well below a height of 1000 feet as part of the compliant approach. Flying an unstable approach, with a variable glidepath, is a deliberate, appropriate and lawful intention in most real aircraft. In aeroplanes that are neither massive nor turbine powered propliner pilots frequently intend to fly unstable approaches which include flap and gear and IAS and trim changes, and direction changes, and glidepath changes, below a height of 1000 feet in visibility which is, or may deteriorate, below 5 miles. Unfortunately many real pilots confuse the meaning of stable and compliant.
Unstable approaches are the correct, fully compliant approaches, as published and authorised by the real regulatory authority, for many / most aeroplanes which are neither massive nor turbine powered, at hundreds of real locations and to hundreds of runways at airports where only one runway has ILS. The owner of any aeroplane may of course impose the higher requirement for stable approach criteria on anyone they permit to operate their aeroplane, and in some circumstances the owners insurance company may no longer be prepared to insure unstable approaches. Those are special cases.
The Propliner Tutorial and my propliner handling notes therefore mandate unstable and unrushed approaches commenced at the complaint IAS, in the compliant flap and gear state, over the real Final Approach Fix, at the compliant height cited on the real approach plate, followed by unrushed increases in flap state and synchronised unrushed decrease of IAS to Vref, no later than the airfield boundary fence (nominally crossed with the cockpit (altimeter) at 50 QFE ). Most non aircrew unfortunately have no idea what their height is and are prone to confuse height with altitude, (see 2008 Propliner Tutorial).
Stable thrust was *not* part of that piston propliner procedure either, even though it was possible to fly a stable thrust approach in some. A stable thrust approach is not a stable approach. Those concepts must not be confused. When vintage and classic era piston propliners were designed and delivered no one had developed the intention to fly even stable thrust approaches.
Varying thrust precisely with piston engines to sustain the glideslope during unstable and unrushed approaches was deemed to be both 'easy' and 'necessary' by both pilots and aviation regulators (then) and they (then) mandated that IAS must be controlled and varied with elevator (or elevator trim) and that glideslope could be varied, (to comply with the need to sustain MDH), by variation of MAP at cited approach RPM (*subject to a high minimum manifold pressure*) at heights far below 1000 feet, even when approaching in cloud.
***************************
Approach and Circuit: DC6B
Cross FAF = 140 KIAS & FLAP 2 deployed
2400 RPM <<<<<<<<<<<<
MAP => 24 inches <<<<<<<<<<<<
On reaching Minimum Descent Altitude <<<<<<<<<<<
(see propliner tutorial parts 4 & 7) <<<<<<<<<<<
REDUCE = 130 KIAS
ON reaching Glideslope
(straight in or base)
To achieve Vref
GEAR = DOWN
FLAP = STAGE 3
FLAP = STAGE 4
REDUCE < 120 KIAS
FLAP = STAGE 5
Cross THRESHOLD 105 KIAS (Vref @ 88,000lbs)
FLARE and LAND
****************************
It is possible to deploy FLAP 5 and reduce to 105 KIAS while still 1000 feet above the landing runway in a DC6B, and so it is possible and safe to fly a stable approach in a DC6B, but it would be abnormal and it precludes many real instrument approaches that we should be learning to fly compliantly, and which include one or several mandated changes of glideslope below 1000 QFE.
Note that in a DC6B we must never reduce below 120 KIAS until we are established on both the FAT and the *final continuous* glideslope; and that is important. The *final continuous* glideslope is the one that begins from MDH to the landing runway, often far below 1000 QFE.
Non precision instrument approaches which permit and encourage a discontinuous glidepath, (NDB + RANGE + VOR + LOC + RDF + GPS), aside; in a DC6B or any other piston propliner real (instrument rated) aircrew minima allow PF to approach the instrument runway and then 'circle to land' on the into wind runway, or the current noise abatement, (noise misery sharing), runway, with visibility far below 5 miles and with a cloud base wholly incompatible with a high performance circuit at 1500 AGL achieving a stable approach and Vref by 1000 feet.
Most real airline bosses in 2010 still believe that it is safe to vary IAS, and VG status, and trim status, and make turns below 1000 AGL, in many airliners, (including many with turboprop engines), and have no intention of allowing their employees operating such airliners to refuse to accept ATC clearances which require them to execute a published unstable approach, whether non precision and straight in to the instrument runway, or which require a 'circle to land' procedure at less than 1500 feet QFE in visibility less than 5 miles. Most (probably all) modern era military and naval authorities regard the idea that it is unsafe to turn a C-130 below a height of 1000 feet, in a visibility of four miles, as incompatible with the missions they procured it to fly.
From our perspective as pioneer, vintage or classic era propliner simulation enthusiasts we must simulate unstable and unrushed approaches, often involving an approach to the instrument runway until we are below cloud, or can see the airfield, in the prevailing visibility, just well enough to identify the different landing runway and then join and fly an unstable and unrushed, parallax compliant and downwind leg TIMED, visual circuit pattern making many changes to IAS, and thrust, and VG status, and roll status, and trim status, all below 1000 QFE in any weather.
However for us a problem arises when our virtual employer decides to re-engine our CV340 or CV440 with turbine engines to create a CV580. It suddenly acquires much worse thrust response yet its wing was designed long before to use very late changes of variable geometry and very late changes of IAS on approach, and to make turns safely below 1000 AGL. Our employer will still require us to fly unrushed and unstable instrument approaches and may also require us to fly precise parallax compliant unrushed and unstable visual circuit patterns, making turns and other unstable changes below 1000 QFE.
In a CV58 we must employ a stable thrust technique, but a stable thrust approach is not a stable approach. A stable approach is much more restrictive. We would need to hold for much longer, awaiting greater weather improvement, and we would need to divert far more often.
A stable thrust approach with turbine engines is much more demanding than an unstable thrust approach with piston engines. With piston engines we only have a minimum safe power setting. With turbine engines, mounted in a classic era aerofoil, for practical purposes within MSFS, the minimum power is also the maximum power we can apply. We use the same power setting for a very prolonged period (stable thrust technique). This requires us to develop additional skills of *timing* of Variable Geometry status changes, above or below a height of 1000 feet, as we reduce to Vref no later than 50 AGL in an always deliberately unstable and unrushed stable thrust approach.
In a CV58 we control power and thrust using turbine interstage temperature (TIT) as our primary reference.
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Arrival and Holding phases:
TIT = 765C (throughout) <<<<<<<<<<
Before IAF or earlier Hold:
VSI = as required to
REDUCE < 170 KIAS
FLAP = STAGE 1
Descending in Hold:
DO NOT EXCEED 173 KIAS
VSI = to comply
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
FLAP STAGE 2 = OPTIONAL
Do NOT retain FLAP 2 once level
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
****************************
Approach phase:
TIT = 765 (throughout) <<<<<<<<<<<<<
Just before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
FLAP = STAGE 2
130 KIAS
At Glidepath:
GEAR = DOWN
On Glidepath:
To achieve Vref
FLAP = STAGE 3
>>>>>>>>>>>>>>>
OPTIONAL
FLAP = STAGE 4
Vref = 103 KIAS
>>>>>>>>>>>>>>>
Vref = Cross Boundary 109 KIAS (@ 52,000lbs)
(below 50 QFE TIT < 765 allowed) <<<<<<<<<<<<
FLARE and LAND
**************************
Circuit phase:
High Performance Visual Circuit:
(see 2008 Propliner Tutorial)
Before Downwind Join:
TIT = 765 (throughout) <<<<<<<<<<<
REDUCE < 170 KIAS
FLAP = STAGE 1
Late Downwind:
TIT = 765 (throughout) <<<<<<<<<<<<<<
FLAP = STAGE 2
Base Leg:
VSI to begin final turn 700 QFE
TIT = 765 (throughout) <<<<<<<<<<<<<<
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
GEAR = DOWN
*Before* final turn at 700 QFE:
FLAP = STAGE 3
VSI = adjust to
Turn final @ 145 KIAS
Final:
TIT = 765 (throughout) <<<<<<<<<<<<<<<
>>>>>>>>>>>>>>>
OPTIONAL
FLAP = STAGE 4
Vref = 103 KIAS
>>>>>>>>>>>>>>>
Vref = cross boundary 109 KIAS (@ 52,000lbs)
Below 50 QFE TIT < 765 allowed <<<<<<<<<<<<<<
FLARE and LAND
***********************************
The fact that we (intend to) use constant engine status for maybe the last hour of the flight from just after ToD right through the arrival, and holding, and approach, and visual circuit phases, makes the handling notes more complicated and throughout they emphasise the constancy of TIT required (or anyway possible). After our Convair Liner acquires turbine engines we must learn to use VSI and GEAR and FLAP to control IAS having applied enough TIT, just after ToD, to hold in the holding pattern with appropriate VG status, adding *or subtracting* FLAP as required, and then we sustain the glideslope in any headwind deploying when necessary a different VG status, to target each IAS variation in that unstable, unrushed, classic era wing, but stable thrust (stable TIT) turbine approach.
We avoid a missed approach (bucking bronco approach) by deliberately flying an unstable unrushed approach in which we vary IAS by precise TIMED synchronisation of VG status *right down to very low level*.
In any Convair Liner or Martin Liner, with any engines, we always reserve FLAP 4 as our 'get out of jail free card' precisely because we always fly an unstable approach. Depending on how badly we screw up that intention we may need to invoke FLAP 4 to achieve Vref by 50 AGL. We rarely intend to deploy FLAP 4 in any of those aeroplanes, but it may be the means by which we avoid a missed approach.
A stable approach requires us to achieve *landing flap configuration* more than 1000 feet above the landing runway. The people who designed aeroplanes just after WW2 had no idea anybody would ever believe in such a crazy thing. They assumed regulators would never certificate aeroplanes so dangerous that they might require a stable approach or even a stable thrust technique. So did the (then) regulators!
In many classic era propliners as PF we have no idea what flap we will be using for landing until we are very short final and PNF challenges our IAS deviation from Vref, calling for immediate correction, else he will call the missed approach. In an aeroplane where we cannot know what flap status we will need to achieve Vref today, until we are short final, we cannot possibly fly stable approaches.
These issues and others are addressed in greater detail within the Calclassic Convair and Martin Mini Tutorial. With practice, practice, practice MSFS propliner enthusiasts should eventually be able to simulate stable thrust NDB or VOR or LOC approaches (see 2008 Propliner Tutorial) straight in to instrument runways in the CV58 in MSFS, but nailing Vref while landing on any other runway from a visual circuit requires substantial stable thrust skills.
The stable approach required by massive turbine powered airliners has three primary objectives;
1) to eliminate all turns below a height of 1000 feet
2) to eliminate all changes of glideslope below 1000 feet
3) to eliminate the need to TIME turns in a visual pattern to perfection versus stable thrust in varying winds.
None of those objectives has any relevance to any propliner which is hosted or 'supported' by Calclassic.com for use within MSFS. Airliners like the Tu-114 are special cases and must be treated as 'massive modern turbine airliners'. The '2008 Propliner Tutorial' does not apply to any swept wing aircraft of any kind.
FSAviator.