F-16 Fuel Quantities (was Power generation & "environmentalism")
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The thing is, Migbuster, in your example of the F-16 hitting the tanker, at 800 lbs the guy was definitely at risk of flameout - so it was really close. In BMS, at the moment, with 800 lbs, I can do 50 NM or more and land without too much sweat
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I see you are also a fan of Dos Gringo’s tale of how they flew the whole mission on alt hold…! XD
DROPPIN’ JDAM!
One of the best lines - cracked me up!
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The thing is, Migbuster, in your example of the F-16 hitting the tanker, at 800 lbs the guy was definitely at risk of flameout - so it was really close. In BMS, at the moment, with 800 lbs, I can do 50 NM or more and land without too much sweat
Me to - I throttle back to zero and glide all the way back
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The thing is, Migbuster, in your example of the F-16 hitting the tanker, at 800 lbs the guy was definitely at risk of flameout - so it was really close. In BMS, at the moment, with 800 lbs, I can do 50 NM or more and land without too much sweat
800 lbs I would wager would still be okay. Under 700 and trying to do negative Gs I would expect a flameout. I kinda thought the -1 would cover how low you can get on fuel, but the only references to it were a line stating that usable fuel is equal to totalizer displayed fuel unless due to a fault, and another saying that the DED bingo page fuel should correlate to within 100 pounds of the totalizer fuel.
Which would support the position that you should be able to get to 100 on the totalizer without worrying under normal flight conditions.
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DED data and totalizer are different mesures of the fuel state. IIRC, totalizer sums up values of each fuel gauges, while DED data is what in france is called “detotaliseur”, ie : total fuel at ramp minus fuel consumed, fuel consumed being measured near the engine. The -1 just says both should be more or less equal within a margin - normal.
But you have fuel the feeding system cannot get to in the tanks, and this is why you can still have a flameout while fuel on board is still a few hundreds lbs. This is the whole purpose of emergency and minimum fuel.
As for the mention of useable fuel…… this would imply that everything in the tanks can be pumped to the engine. IMO, that is not the case.
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DED data and totalizer are different mesures of the fuel state. IIRC, totalizer sums up values of each fuel gauges, while DED data is what in france is called “detotaliseur”, ie : total fuel at ramp minus fuel consumed, fuel consumed being measured near the engine. The -1 just says both should be more or less equal within a margin - normal.
But you have fuel the feeding system cannot get to in the tanks, and this is why you can still have a flameout while fuel on board is still a few hundreds lbs. This is the whole purpose of emergency and minimum fuel.
As for the mention of useable fuel…… this would imply that everything in the tanks can be pumped to the engine. IMO, that is not the case.
The aircraft basic weight includes UNUSABLE fuel. There is aircraft fuel which is not counted in the totalizer and is unusable. The totaliser only counts usable fuel. Additional fuel is in the fuel lines at flameout, but cannot be used by the engine and is not included in the totalizer value.
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The aircraft basic weight includes UNUSABLE fuel. There is aircraft fuel which is not counted in the totalizer and is unusable. The totaliser only counts usable fuel. Additional fuel is in the fuel lines at flameout, but cannot be used by the engine and is not included in the totalizer value.
This is what I’m reading too, fuels tanks are the same. So indeed, you might be right ! Need to check more what the risk are of going below minimum fuel.
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From F-16 operation procedures :
3.22.4. Minimum/Emergency Fuel. Declare the following when it becomes apparent that an aircraft
will enter initial or start an instrument final approach at the base of intended landing or alternate, if
required, with:
3.22.4.1. Minimum Fuel:
3.22.4.1.1. All F-16 Blocks 10 through 32 - 800 pounds or less.
3.22.4.1.2. All F-16 Blocks 40 and higher - 1,000 pounds or less.
3.22.4.2. Emergency Fuel:
3.22.4.2.1. All F-16 Blocks 10 through 32 - 600 pounds or less.
3.22.4.2.2. All F-16 Blocks 40 and higher - 800 pounds or less.Definition of minimum fuel and emergency fuel :
http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/info/all_infos/media/2008/info08004.pdfBasically :
emergency fuel : from where you are, you need to proceed directly to the airbase if you want to land with final reserve fuel.
minimum fuel : emergency + some margin : if any delay occurs, you will be in emergency fuel.From this we can deduce the final reserve fuel, under which we can safely assume there IS a risk of flameout.
So all that’s left to do is take a clean F-16 Block 40 or 50, for ex, run it dry up to 1000-1500 lbs more or less (so that you get more or less the total weight you would have in an emergency), go into a 15 NM final (noting precisely your fuel beginning your approach), land, see what is your fuel at touchdown so you can deduce fuel spent on the approach.
Substract fuel spent on approach to emergency fuel, and you have Final reserve fuel, fuel under which you do have risks of flameout. I need to make the test, but I’m pretty sure that will come to around 500-600 lbs for a Block 40 or up, and 300-400 for Block 32 or less. Not neglectable…
Oh, and BTW : :tjacked:
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under positive G’s and with the fuel pumps working the dash reads a lot like you get a flameout from fuel starvation around 0 on the totalizer. Elsewise it is not usable fuel.
That said the fuel flow section does comment that with the fuel pumps off, and less than full reservoirs, any negative G maneuvering can cause air to get to the siphons that run the FFP which can cause fuel starvation to the engine even with usable fuel in the reservoirs.
RE the threadjacking - my demands are as follows: the thread returns to friendly discussion and no people saying they want to build power plants next to peoples homes!
If my demands are not met, then you will never see the thread (in its original condition) again!
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under positive G’s and with the fuel pumps working the dash reads a lot like you get a flameout from fuel starvation around 0 on the totalizer. Elsewise it is not usable fuel.
That said the fuel flow section does comment that with the fuel pumps off, and less than full reservoirs, any negative G maneuvering can cause air to get to the siphons that run the FFP which can cause fuel starvation to the engine even with usable fuel in the reservoirs.
RE the threadjacking - my demands are as follows: the thread returns to friendly discussion and no people saying they want to build power plants next to peoples homes!
If my demands are not met, then you will never see the thread (in its original condition) again!
+1 for the threadjacking
I know for the pumps nad negative Gs, dont worry But its not what I’m talking about.
I actually just ran the test : on a circuit just like defined on the Dash-1 (so downwind, base, final) or on a long final, you burn 300 lbs. So with an emergency fuel at 800 on the beginning (like for a Block 40/50), you land with 500 lbs. So 500 lbs margin.
500 lbs is around 10 min of flight in economic cruise…. so not a critical emergency to me These minimum fuels in F-16 OPERATION PROCEDURE can only mean, for me, that you do run the risk of a flameout below 500 lbs.
And that can be explained by a number of things besides unuseable fuel : gauge errors, vaporized fuel, fuel expanding with temperature, etc…
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+1 for the threadjacking
I know for the pumps nad negative Gs, dont worry But its not what I’m talking about.
I actually just ran the test : on a circuit just like defined on the Dash-1 (so downwind, base, final) or on a long final, you burn 300 lbs. So with an emergency fuel at 800 on the beginning (like for a Block 40/50), you land with 500 lbs. So 500 lbs margin.
500 lbs is around 10 min of flight in economic cruise…. so not a critical emergency to me These minimum fuels in F-16 OPERATION PROCEDURE can only mean, for me, that you do run the risk of a flameout below 500 lbs.
And that can be explained by a number of things besides unuseable fuel : gauge errors, vaporized fuel, fuel expanding with temperature, etc…
Or that they want you to land with a fixed reserve of 500 pounds. Lets face it, beaurocrats would never let it work like that. It would be called flameout fuel then, not emergency fuel.
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The reservoir is 480lbs iirc. Following simple physics, random flameouts may occur when one of the fuel pumps feeding out of that tank runs dry. Would like to see that modelled, it would lead to more fuel discipline among the virtual pilots.
I get nervous everywhere around 1000lbs
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Or that they want you to land with a fixed reserve of 500 pounds. Lets face it, beaurocrats would never let it work like that. It would be called flameout fuel then, not emergency fuel.
Emergency fuel has a fixed definition - I believe its FAA or something. Definition being : minimum fuel needed to get straight to the next runway and land with the Final Fuel Reserve.
In the F-16, I would make sense that the final fuel reserve is the reservoir feeding the tank indeed : the slightest G you get (in any direction), the fuel goes around everywhere and you risk to have a pump stall. Especially with negative Gs, as you said earlier Blu3wolf.
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The reservoir is 480lbs iirc. Following simple physics, random flameouts may occur when one of the fuel pumps feeding out of that tank runs dry. Would like to see that modelled, it would lead to more fuel discipline among the virtual pilots.
I get nervous everywhere around 1000lbs
both reservoirs are 480 lbs +/-30.
Normally fuel pumps are not the primary supply method to the reservoirs, they are a supplement to the siphoning action from the reservoirs. This method does depend on the reservoirs being full though.
Fuel pumps feed equally from both reservoirs to the FFP and from there to the engine.
It does seem to suggest in the emergency section that you can get flameouts if the reservoirs are not full and you select high fuel flow rates over 6000pph.
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both reservoirs are 480 lbs +/-30.
Normally fuel pumps are not the primary supply method to the reservoirs, they are a supplement to the siphoning action from the reservoirs. This method does depend on the reservoirs being full though.
Fuel pumps feed equally from both reservoirs to the FFP and from there to the engine.
It does seem to suggest in the emergency section that you can get flameouts if the reservoirs are not full and you select high fuel flow rates over 6000pph.
Thanks for the update
It sounds logical since high flow rates out of the reservoir may suck in some air too which disturbs the engine so it might literally blow out the flame. I know a similar behaviour with other liquids than fuel (coolants, for example). When you have a high flow rate, it sucks in some air too in some circumstances. Depends on where the pipe is fitted, the height of the liquid above the pipe, viscosity of the liquid and so on.
To sum it up: When fuel is out, the engine will be dead
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split & moved
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Emergency fuel has a fixed definition - I believe its FAA or something. Definition being : minimum fuel needed to get straight to the next runway and land with the Final Fuel Reserve.
In the F-16, I would make sense that the final fuel reserve is the reservoir feeding the tank indeed : the slightest G you get (in any direction), the fuel goes around everywhere and you risk to have a pump stall. Especially with negative Gs, as you said earlier Blu3wolf.
Well, to sum it up, seeing as we now have a new thread:
From the manuals I have here, it would seem to me that you should be able to fly the aircraft under positive G down to 0 fuel on the totalizer +/- 100 lbs so long as fuel flow is under 6000 pph.
The manual has a long series of warnings and cautions written in it, which detail any area that could affect flight safety. There is no hazard written regarding chances of flameout with say 500 lbs remaining, and there IS a section which states that the totalizer only displays usable fuel, and that unusable fuel is not included in the totalizer values.
There IS a warning about high fuel flow, and about negative G. As a reminder to all, WARNINGs in the -1 series of T.O.s indicate “Operating procedures, techniques, etc., which could result in personal injury or loss of life if not carefully followed.”
Limit fuel flow to the minimum required to
sustain flight while the cause of the fuel low
light(s) is determined. Avoid negative g flight
when either reservoir is not full .I would argue that based on this, a fuel low light is not likely to result in a flameout immediately so long as those guidelines are followed. That said under 150 to 100 lbs I would start expecting a flameout any time soon, and under 50 lbs reported I would expect one imminently.
The dash does make comment of ‘air ejectors’ which ensure the reservoirs remain full of fuel at all times, but they certainly would not work as desired with no fuel in the tanks to draw from. With the reservoirs less than completely full, the low fuel lights still do not come on immediately either, but wait until they are about half full (less than 250 lbs in the AFT reservoir, and less than 400 lbs in the FWD reservoir - reversed figures for the D model). This further leads me to conclude that you should get normal operation under normal flight conditions… but then negative G is apparently a problem with a low fuel light. What about high skid/slip? what about high roll rates? Questions not answered by the dash, and for which logical solutions may not be correct either (at least going by previous ‘logical’ guesstimates which have been put into falcon incorrectly).
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split & moved
Well, to sum it up, seeing as we now have a new thread:
From the manuals I have here, it would seem to me that you should be able to fly the aircraft under positive G down to 0 fuel on the totalizer +/- 100 lbs so long as fuel flow is under 6000 pph.
The dash does make comment of ‘air ejectors’ which ensure the reservoirs remain full of fuel at all times, but they certainly would not work as desired with no fuel in the tanks to draw from. With the reservoirs less than completely full, the low fuel lights still do not come on immediately either, but wait until they are about half full (less than 250 lbs in the AFT reservoir, and less than 400 lbs in the FWD reservoir - reversed figures for the D model). This further leads me to conclude that you should get normal operation under normal flight conditions… but then negative G is apparently a problem with a low fuel light. What about high skid/slip? what about high roll rates? Questions not answered by the dash, and for which logical solutions may not be correct either (at least going by previous ‘logical’ guesstimates which have been put into falcon incorrectly).
Personnally, I think that as soon as the tanks are not full, you have the risk of a pump stall - especially, as you said, under negative G. Basically, even with the ENG FEED on NORM, if remaining fuel gets pushed away from the pump, you have a pump stall and air gets into the pump, its flameout. Probably recoverable though, if you get back to straight and level.
With straight and level flight, with low fuel flow, you should get pretty close to 100 -150 lbs without too much of an issue, i agree. But as soon as you get some lateral, axial, or negative G (especially), fuel might get pushed away from the pump, and you risk a flameout. I think the 500 lbs is a fair threshold under which you consider the limitations in Gs are too important to be neglectable anymore for safety of flight.
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Which of course brings up the question of whether positive G maneuvering is a problem ( I would guess it is, but plenty of wrong guesses have made their way into the sim before ), and if so, crucially, HOW MUCH is a problem.
As soon as the reservoirs have some air in them, if all the boost pumps from the reservoirs start sucking air, it follows that shortly afterwards (a few seconds?) the engine will lose power and flameout (and maybe stall as well?). Question is whether the engine can run with less than 3 boost pumps supplying fuel. Answer is clearly yes, as the aircraft can run under positive G with the ENG FEED knob in OFF.
So I guess the next question becomes how little fuel can you have and still get enough fuel… I think advanced liquids simulation inside the tanks is probably more advanced than the sim should get until after it has advanced fluid simulation for the airflow (per packet basis). So, in a simple system, how much side loading can you get and still have adequate fuel supply for half full reservoir, for a quarter full, etc… Notably, high positive G is not likely to be a problem at all, and coordinated flight (automatically provided by ARI) should limit side loads on the aircraft except during rolls.
so to sum that up, I reckon positive symmetric G should be fine, asymmetric G should be a problem, high speed rolls should be a problem, maybe high speed decelerations should be a problem? Negative G should be right out.
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so to sum that up, I reckon positive symmetric G should be fine, asymmetric G should be a problem, high speed rolls should be a problem, maybe high speed decelerations should be a problem? Negative G should be right out.
That would be my guess too. Then there is the issue of fuel flow :IMO, the higher, the more likely problems (flameout) can arise.