Post by volkerboehme on Aug 10, 2008 12:08:02 GMT -5
Volker,
Tom and I are still in the process of matching the 'realistic' L-1649A FD to the V 1.0 L-1649A release files. A variety of new files are required to enable realism. The issue you raise cannot be 'resolved' without 'realistic' handling notes matched to 'realistic' FD. In the mean time it can only be 'explained'.
The PT explains that niether climb (fuel) nor descent (fuel) are relevant calculations for propliner flight planning. In particular initial climb in propliners is usually to a fraction of median cruising level followed by many step climbs over many weary hours. The concept of climb fuel planning belongs to the jet era even though I include fuel planning assumptions for each phase of flight in my 'realistic' propliner handling notes.
You did not follow the PT fuel planning methodology and so your post and most of this reply belong in the L-1649A thread. Maybe it should be copied there.
The 'realistic' L-1649A handling notes explain that 'polar' flights lack the normal PT reserves. Diversion is required if a *significant* headwind is forecast or encountered. We must divert to somewhere closer than London to pick up fuel. Consequently we must flight plan to pass over Sondrestromfjord, then Keflavik, then Prestwick, not great circle direct to London. With realistic FD we never have enough fuel to proceed direct London in safety.
Returning to Propliner Tutorial issues and concerning duration of METO (only for obstacle clearance), versus max climb power, (whilst meeting all ATC cross above restrictions), versus climb power thereafter, (all of which are set out in the realistic handling notes), you will need to download the KSFO REBAS 3 Propliner Departure from the FAA website cited in the calclassic charts link. Then you will need to relate the content of Part 5 of the 2008 PT to those power settings and that chart in order to execute the departure. It still has no bearing on fuel planning, but once you have studied the KSFO REBAS 3 Propliner departure which empties into the CHICO transition you will understand the early part of the relevant 4D flight plan better.
Flight planning via V routes which mirror the great circle begins from Chico (CIC VOR) and proceeds BGSF - BIKF - Benbecula (BCL) - EGPK - EGLL. BCL will be our Oceanic landfall fix. We transition from vintage era navigation techniques to classic era navigation techniques once we can identify and receive BCL. Similarly we will use the KEF whilst we can. The return flight will use the same route until off track polar landfall north of Goose, but after BGSF we will be heading for Calgary or Edmonton. We will need to use Vintage era techniques near the magnetic north pole until ywe can ident and track to the YYC or the YEG. We will almost always need to refuel at one of those two locations, sometimes earlier at BGSF. Optimistically marketed as 'non stop' EGLL - KSFO (against the prevailing winds) was timetabled for more than 21 hours to allow that, not because we have 21 hours of route fuel.
The PT explains clearly how to plan the fuel (only) when both 'realistic' handling notes and matching 'realistic' FD are available. You over complicated the process and miscalculated accordingly.
The route fuel is simply route distance multiplied by *planned* fuel burn in pounds per hour (PPH) divided by *planned* TAS. We must not confuse what we plan (to achieve eventually); with how we actually execute our plan in flight; step by lumbering step.
***********************************
Econ Cruise (<= 123,000lbs):
Use at all weights during 'POLAR' flights
COWL FLAPS = CLOSED
RPM = 2200
MAP = 35 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials
WARNING - NEVER EXCEED FL250
PLAN 2900 PPH
Note: - Yields 280 KTAS at FL230
****************************
So in this case 4700(ish) miles * 2900 PPH / 280 KTAS = 48678 lbs of *planned* route fuel.
<<Maximum and default fuel load is 59,064lbs of 145 Octane fuel. 58,621lbs are usable.>>
Now we must calculate the necessary reserve fuel.
HOLDING RESERVE
The Treaty of Chicago mandates a holding reserve of 45 minutes. An airline might decide to carry more, particularly if fog or runway snow clearance operations were expected at destination. We calculate our holding reserve at the lowest relevant fuel flow stated in the handling notes. This may be a long range cruise section associated with high altitude. It matters not. If we plan our fuel correctly we will be down to the weight or fuel state that limits use of the specified MAP and rpm, (and thus the associated planned fuel burn), before we reach the IAF and commence holding.
2900 * 0.75 = 2175lbs
48678 + 2175 = 50853lbs.
We will never depart for a 'polar' flight with less than full fuel so we have a spare (58621 - 50853) = 7768lbs.
A full headwind reserve to deal with a *significant* headwind would be 48678 * 0.15 = 7300lbs.
If we assume almost no diversion fuel at all we do have the necessary headwind reserve, but that would be a dangerous assumption. Runways sometimes get blocked for longer than 45 minutes even in good weather. We may hold for 45 minutes and then need to divert from overhead EGLL.
So we have enough fuel, but the reserves are marginal, in the sense that we only have 'two out of three'. We do not have holding + diversion + headwind reserves so the standard procedure is to divert to pick up fuel well short of destination with a forecast or encountered *significant* headwind. We *do* have enough reserve to deal with an *insignificant perceived headwind*, but it compromises our holding reserve and/or our diversion reserve. We must *divert* from the Bovingdon stack at EGLL once we are down to 2175 lbs even if we could *hold* for only ten minutes before that happened.
More to the point we must *divert* from *anywhere* (even enroute to the Bovingdon stack) once we are down to 2175 lbs even if that happens before the Bovingdon stack. We can turn our holding fuel into diversion fuel at will; so long as we do not hold. Two reserves out of three are 'adequate' but we must execute our plan accordingly.
These things are all defined in the 2008 PT and the fuel planning criteria within are carefully matched to the headwind criteria within. Planning techniques cannot be mixed. They must be matched.
Note that the key to polar operations is never exceeding econ cruise power during a polar flight so that our fuel burn will never exceed the planned 2900 PPH. Significant headwinds cannot and will not be battled. We will divert for fuel. 58621lbs usable at 2900 PPH = 20.2 hours to dry tanks, but we will actually burn less than the *planning* figure in the handling notes. 2900 PPH is a *planning* figure not the average or median burn. It is the final operating target. An L-1649A can easily remain airborne for much longer than 20.2 hours, but that plan is inconsistent with profit. It uses too many engine hours ( x 4).
Note that the POLAR restriction is;
>>>>>>>>>>>>>>>>>>>>>>>>>>
*POLAR FLIGHTS ONLY*
Reaching FL150/160 (eastbound/westbound)
Begin ECON CRUISE and step climbs
***********************************
During the early parts of any eastbound polar flight we will not exceed FL150 (see PT part 2 concerning Long Range operations) and our fuel burn will be only 2600 PPH down at FL150. Propliner realism is all about realistic 4D navigation. Note that the REBAS 3 propliner departure is consitent with our plan to climb both slowly and not much.
We must STEP CLIMB propliners. Step by lumbering step.
We will not exceed FL150 until we reach zero pitch *in econ cruise power*. We will only reach 2900 PPH after about 14 weary hours and four step climbs later; when we make the final step climb to FL230 which is our ISA ceiling in econ cruise power. Only then will we achieve our polar flight target velocity of 280 KTAS. The crew who departed KSFO have been asleep in their bunks for several hours by then.
'Climb fuel planning' is irrelevant because we plan not to climb!
We plan not to reach FL230 until we have burned off 37,000lbs of fuel (160,000 - 123,000), about 14 hours into the flight, because our operational ceiling in this lumbering dinosaur will not be FL230 until then.
**********************************
Econ Cruise (<= 123,000lbs):
Use at all weights during 'POLAR' flights
COWL FLAPS = CLOSED
RPM = 2200
MAP = 35 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials
WARNING - NEVER EXCEED FL250
PLAN 2900 PPH
Note: - Yields 280 KTAS at FL230
****************************
We have no intention of allowing our fuel burn to match the planning assumption until we can achieve our planned TAS by doing so; and it takes about 14 hours in average weather to burn those first 37,000lbs of fuel. Accelerating propliners to their optimum energy state is not a brief or simple process! They are lumbering great dinosaurs. This is the last and the most lumbering of all the great dinosaurs. It will lumber into extinction very quickly step by weary step.
With realistic handling notes, realistic flight dyanmics, and the Propliner Tutorial we can examine why in painful detail, and so (with some effort) we can understand why the aviation dinosaurs became extinct.
FSAviator
Tom and I are still in the process of matching the 'realistic' L-1649A FD to the V 1.0 L-1649A release files. A variety of new files are required to enable realism. The issue you raise cannot be 'resolved' without 'realistic' handling notes matched to 'realistic' FD. In the mean time it can only be 'explained'.
The PT explains that niether climb (fuel) nor descent (fuel) are relevant calculations for propliner flight planning. In particular initial climb in propliners is usually to a fraction of median cruising level followed by many step climbs over many weary hours. The concept of climb fuel planning belongs to the jet era even though I include fuel planning assumptions for each phase of flight in my 'realistic' propliner handling notes.
You did not follow the PT fuel planning methodology and so your post and most of this reply belong in the L-1649A thread. Maybe it should be copied there.
The 'realistic' L-1649A handling notes explain that 'polar' flights lack the normal PT reserves. Diversion is required if a *significant* headwind is forecast or encountered. We must divert to somewhere closer than London to pick up fuel. Consequently we must flight plan to pass over Sondrestromfjord, then Keflavik, then Prestwick, not great circle direct to London. With realistic FD we never have enough fuel to proceed direct London in safety.
Returning to Propliner Tutorial issues and concerning duration of METO (only for obstacle clearance), versus max climb power, (whilst meeting all ATC cross above restrictions), versus climb power thereafter, (all of which are set out in the realistic handling notes), you will need to download the KSFO REBAS 3 Propliner Departure from the FAA website cited in the calclassic charts link. Then you will need to relate the content of Part 5 of the 2008 PT to those power settings and that chart in order to execute the departure. It still has no bearing on fuel planning, but once you have studied the KSFO REBAS 3 Propliner departure which empties into the CHICO transition you will understand the early part of the relevant 4D flight plan better.
Flight planning via V routes which mirror the great circle begins from Chico (CIC VOR) and proceeds BGSF - BIKF - Benbecula (BCL) - EGPK - EGLL. BCL will be our Oceanic landfall fix. We transition from vintage era navigation techniques to classic era navigation techniques once we can identify and receive BCL. Similarly we will use the KEF whilst we can. The return flight will use the same route until off track polar landfall north of Goose, but after BGSF we will be heading for Calgary or Edmonton. We will need to use Vintage era techniques near the magnetic north pole until ywe can ident and track to the YYC or the YEG. We will almost always need to refuel at one of those two locations, sometimes earlier at BGSF. Optimistically marketed as 'non stop' EGLL - KSFO (against the prevailing winds) was timetabled for more than 21 hours to allow that, not because we have 21 hours of route fuel.
The PT explains clearly how to plan the fuel (only) when both 'realistic' handling notes and matching 'realistic' FD are available. You over complicated the process and miscalculated accordingly.
The route fuel is simply route distance multiplied by *planned* fuel burn in pounds per hour (PPH) divided by *planned* TAS. We must not confuse what we plan (to achieve eventually); with how we actually execute our plan in flight; step by lumbering step.
***********************************
Econ Cruise (<= 123,000lbs):
Use at all weights during 'POLAR' flights
COWL FLAPS = CLOSED
RPM = 2200
MAP = 35 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials
WARNING - NEVER EXCEED FL250
PLAN 2900 PPH
Note: - Yields 280 KTAS at FL230
****************************
So in this case 4700(ish) miles * 2900 PPH / 280 KTAS = 48678 lbs of *planned* route fuel.
<<Maximum and default fuel load is 59,064lbs of 145 Octane fuel. 58,621lbs are usable.>>
Now we must calculate the necessary reserve fuel.
HOLDING RESERVE
The Treaty of Chicago mandates a holding reserve of 45 minutes. An airline might decide to carry more, particularly if fog or runway snow clearance operations were expected at destination. We calculate our holding reserve at the lowest relevant fuel flow stated in the handling notes. This may be a long range cruise section associated with high altitude. It matters not. If we plan our fuel correctly we will be down to the weight or fuel state that limits use of the specified MAP and rpm, (and thus the associated planned fuel burn), before we reach the IAF and commence holding.
2900 * 0.75 = 2175lbs
48678 + 2175 = 50853lbs.
We will never depart for a 'polar' flight with less than full fuel so we have a spare (58621 - 50853) = 7768lbs.
A full headwind reserve to deal with a *significant* headwind would be 48678 * 0.15 = 7300lbs.
If we assume almost no diversion fuel at all we do have the necessary headwind reserve, but that would be a dangerous assumption. Runways sometimes get blocked for longer than 45 minutes even in good weather. We may hold for 45 minutes and then need to divert from overhead EGLL.
So we have enough fuel, but the reserves are marginal, in the sense that we only have 'two out of three'. We do not have holding + diversion + headwind reserves so the standard procedure is to divert to pick up fuel well short of destination with a forecast or encountered *significant* headwind. We *do* have enough reserve to deal with an *insignificant perceived headwind*, but it compromises our holding reserve and/or our diversion reserve. We must *divert* from the Bovingdon stack at EGLL once we are down to 2175 lbs even if we could *hold* for only ten minutes before that happened.
More to the point we must *divert* from *anywhere* (even enroute to the Bovingdon stack) once we are down to 2175 lbs even if that happens before the Bovingdon stack. We can turn our holding fuel into diversion fuel at will; so long as we do not hold. Two reserves out of three are 'adequate' but we must execute our plan accordingly.
These things are all defined in the 2008 PT and the fuel planning criteria within are carefully matched to the headwind criteria within. Planning techniques cannot be mixed. They must be matched.
Note that the key to polar operations is never exceeding econ cruise power during a polar flight so that our fuel burn will never exceed the planned 2900 PPH. Significant headwinds cannot and will not be battled. We will divert for fuel. 58621lbs usable at 2900 PPH = 20.2 hours to dry tanks, but we will actually burn less than the *planning* figure in the handling notes. 2900 PPH is a *planning* figure not the average or median burn. It is the final operating target. An L-1649A can easily remain airborne for much longer than 20.2 hours, but that plan is inconsistent with profit. It uses too many engine hours ( x 4).
Note that the POLAR restriction is;
>>>>>>>>>>>>>>>>>>>>>>>>>>
*POLAR FLIGHTS ONLY*
Reaching FL150/160 (eastbound/westbound)
Begin ECON CRUISE and step climbs
***********************************
During the early parts of any eastbound polar flight we will not exceed FL150 (see PT part 2 concerning Long Range operations) and our fuel burn will be only 2600 PPH down at FL150. Propliner realism is all about realistic 4D navigation. Note that the REBAS 3 propliner departure is consitent with our plan to climb both slowly and not much.
We must STEP CLIMB propliners. Step by lumbering step.
We will not exceed FL150 until we reach zero pitch *in econ cruise power*. We will only reach 2900 PPH after about 14 weary hours and four step climbs later; when we make the final step climb to FL230 which is our ISA ceiling in econ cruise power. Only then will we achieve our polar flight target velocity of 280 KTAS. The crew who departed KSFO have been asleep in their bunks for several hours by then.
'Climb fuel planning' is irrelevant because we plan not to climb!
We plan not to reach FL230 until we have burned off 37,000lbs of fuel (160,000 - 123,000), about 14 hours into the flight, because our operational ceiling in this lumbering dinosaur will not be FL230 until then.
**********************************
Econ Cruise (<= 123,000lbs):
Use at all weights during 'POLAR' flights
COWL FLAPS = CLOSED
RPM = 2200
MAP = 35 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials
WARNING - NEVER EXCEED FL250
PLAN 2900 PPH
Note: - Yields 280 KTAS at FL230
****************************
We have no intention of allowing our fuel burn to match the planning assumption until we can achieve our planned TAS by doing so; and it takes about 14 hours in average weather to burn those first 37,000lbs of fuel. Accelerating propliners to their optimum energy state is not a brief or simple process! They are lumbering great dinosaurs. This is the last and the most lumbering of all the great dinosaurs. It will lumber into extinction very quickly step by weary step.
With realistic handling notes, realistic flight dyanmics, and the Propliner Tutorial we can examine why in painful detail, and so (with some effort) we can understand why the aviation dinosaurs became extinct.
FSAviator