Final Reserve and FPF

[Lantirn]

Hello everyone.


Final reserve is a planning figure for 30 mins required for dispatch, lets say for the A320 its around 1100kgs.


I am wondering if that should change inflight if one encounters fuel penalty failures inflight.


Lets say you lose green hydraulic fluid and after gear extension you cant retract it and you have to divert to a close airport (not your day). So you have increased fuel consumption, almost double. Leveling off you realise that you burn around 4000kg/hr.


Does the "planning" fuel value of 1100kgs for landing still applies as a threshold for fuel mayday declaration? Or you factor the fuel penalty and make that mayday call threshold at 2000kgs to adjust?


Obviously you will declare urgency or emergency in bad weather under time pressure with technical issues for other reasons and the fuel mayday may come late towards the end of the flight.


But my question is more academic. Are you obliged to adjust the final reserve fuel value for the emergency fuel declaration with increased fuel consumption?


My guess is that you should adjust and count the FPF because ATC has an estimate of your endurance from your flightplan. Declaring a fuel mayday late would compromise safety.


Have searched ICAO FPFM (9976) and Annex 6 but still nothing there.

[pineteam]

I have no reference but you definitely need to take the fuel penalty into account. The Mayday Fuel is based on remaining flight time by definition not a definite value in fuel quantity which makes sense. At anytime during flight if you believe you are going to land with less than 30 min of fuel, you must call Mayday fuel.

[TheEdge]

At anytime during flight if you believe you are going to land with less than 30 min of fuel, you must call Mayday fuel.

And be ready to handover your licence

[vilas]

Hello everyone.


Final reserve is a planning figure for 30 mins required for dispatch, lets say for the A320 its around 1100kgs.


I am wondering if that should change inflight if one encounters fuel penalty failures inflight.


Lets say you lose green hydraulic fluid and after gear extension you cant retract it and you have to divert to a close airport (not your day). So you have increased fuel consumption, almost double. Leveling off you realise that you burn around 4000kg/hr.


Does the "planning" fuel value of 1100kgs for landing still applies as a threshold for fuel mayday declaration? Or you factor the fuel penalty and make that mayday call threshold at 2000kgs to adjust?


Obviously you will declare urgency or emergency in bad weather under time pressure with technical issues for other reasons and the fuel mayday may come late towards the end of the flight.


But my question is more academic. Are you obliged to adjust the final reserve fuel value for the emergency fuel declaration with increased fuel consumption?
My guess is that you should adjust and count the FPF because ATC has an estimate of your endurance from your flightplan. Declaring a fuel mayday late would compromise safety.
Have searched ICAO FPFM (9976) and Annex 6 but still nothing there.
The 30mts is holding fuel. There will also be alternate fuel added to that. If you are at your destination and can't retract gear then you won't be going anywhere as you wouldn't be carrying that much fuel which is 180% of normal. But if it's a turn back after takeoff and stuck with gear down diversion it may be possible. Offcours the fuel required will be affected by FPF.

[FullWings]

And be ready to handover your licence
Errm, why? Circumstances may force that upon you and as long as you have followed a reasonable decision making process, there isn’t an issue. ASR/MOR, certainly.

To answer the OP, you are in a non-normal situation, so it would be eminently sensible to reconsider your reserves (normally 30mins clean, 1500’ AAL, PLW @ALT). If you had dispatched IAW the DDG with the gear locked down, your increased fuel burn at all stages of flight would have to be accounted for in the flight plan, including the final reserve figure.

[Lantirn]

Thanks all. I wanted a confirmation and your views. It seems that fact is missed in the simulator.

[FlightDetent]

Thanks all. I wanted a confirmation and your views. It seems that fact is missed in the simulator. Another fact missed often in case of the L/G down mentioned above is the penalty algorithm.

It is penalty of 180 percent which comes on top of the normal burn.

Assuming normal FRF 1250 and ALTN fuel of 1750,

​​​​​​3 + 3 x 1.8 = 8.4 T.

If that was for G HYD LO PR with doors hanging, there's another +15% IIRC.

[Lantirn]

Another fact missed often in case of the L/G down mentioned above is the penalty algorithm.

It is penalty of 180 percent which comes on top of the normal burn.

Assuming normal FRF 1250 and ALTN fuel of 1750,

​​​​​​3 + 3 x 1.8 = 8.4 T.

If that was for G HYD LO PR with doors hanging, there's another +15% IIRC.

True, thats correct if you assume QRH FPF factors. This is conservative and of course its the safest.

Real consumption is much less, close to x2.1 (ref Bomb on board QRH)

Plus, with flysmart in-flight calculation you can have more realistic consumption calculation according to your selection in the EFB (Select NSC)

After some emails between my company and airbus to clarify, airbus replied that flysmart is more accurate and approved app to calculate such computations in-flight

So thats good news

[FlightDetent]

Haha, already have the QRH open because of the other thread. Bomb is for level flight after descent with CF 1 + L/G down, suggesting 'LO SPD'.

This brings another question, which flaps and speed profile would one choose to minimize fuel burn. It's an edge case only relevant for loss of G HYD at take-off with weather below minima (TKOF alternate).

The idea of calculating this for a MisAPCH from DES after a failure is a bit vain because you won't have 3x the fuel normally needed to ALTN, so no point of diverting.

The other combinations seem only theoretical such as diversion en route (EMERG ELEC) but G/A from the chosen airport, after which a leg to a different backup field needs to be flown.

[Lantirn]

Haha, already have the QRH open because of the other thread. Bomb is for level flight after descent with CF 1 + L/G down, suggesting 'LO SPD'.

This brings another question, which flaps and speed profile would one choose to minimize fuel burn. It's an edge case only relevant for loss of G HYD at take-off with weather below minima (TKOF alternate).

The conf1+LG down on bomb on board is not for low fuel consumption but rather to minimize damage and ensure basic flap and gear extension in case of bomb explosion in LRBL position!

The idea of calculating this for a MisAPCH from DES after a failure is a bit vain because you won't have 3x the fuel normally needed to ALTN, so no point of diverting.

The other combinations seem only theoretical such as diversion en route (EMERG ELEC) but G/A from the chosen airport, after which a leg to a different backup field needs to be flown.

You will be amazed by seeing the difference in the actual consumption from the flysmart when calculating these penalties. Firstly, when calculating from cruise phase (CRZ-DES), the penalty is far less than when calculating for alternate (CLB-CRZ-DES). Secondly, closer distances mean less difference compared to the normal fuel. That means when the distance between airports is really close, like destination to alternate 80 track miles, the fuel difference figures are much smaller than you think between normal and non standard configurations.

For instance, flying to a 75 track NM ALTN field without failure is 700kgs. With gear down as per QRH its around 2000kgs. Whereas, flysmart in flight for alternate (CLB-CRZ-DES) calculates 1200kgs.

[FlightDetent]

Yes, I was too concise. The bomb 'slow' does not say how slow, just gives you 1/G as a hint. You land a the nearest available and better have fuel for that. But also can go slower, which is better and the same concept why the gear is down. 2+G and F speed is nice for structural considerations but the burnoff might be incompatible with distance to diversion field.

For the preciously discussed case, ​​​​​​if you needed to divert after MisApch with gravity gear, what conf and speed to choose - that was my thought (at the absence of hints). Easy answer to that, clean but gear out.

The examples you give sound logical after thinking about them a bit. BTW did you had the chance to check the dispatch for gear down performance data and compare them to FlySmart with failure?
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[Lantirn]

BTW did you had the chance to check the dispatch for gear down performance data and compare them to FlySmart with failure?
​​​​​

Sadly airbus removed the relevant performance section. These tables are not anymore in my FCOM. But yes, I remember that they were pretty accurate.

[sonicbum]

This brings another question, which flaps and speed profile would one choose to minimize fuel burn. It's an edge case only relevant for loss of G HYD at take-off with weather below minima (TKOF alternate).




Hi,

You are considering L/G down with doors closed correct? i.e. loss of G HYD during takeoff roll or shortly after and the inability to raise the gear.
Flysmart gives You data for LRC in terms of CAS, MAX and OPT altitude and a combination to obtain the Maximum specific range.

[sonicbum]

Hello everyone.


Final reserve is a planning figure for 30 mins required for dispatch, lets say for the A320 its around 1100kgs.


I am wondering if that should change inflight if one encounters fuel penalty failures inflight.


Lets say you lose green hydraulic fluid and after gear extension you cant retract it and you have to divert to a close airport (not your day). So you have increased fuel consumption, almost double. Leveling off you realise that you burn around 4000kg/hr.


Does the "planning" fuel value of 1100kgs for landing still applies as a threshold for fuel mayday declaration? Or you factor the fuel penalty and make that mayday call threshold at 2000kgs to adjust?


Obviously you will declare urgency or emergency in bad weather under time pressure with technical issues for other reasons and the fuel mayday may come late towards the end of the flight.


But my question is more academic. Are you obliged to adjust the final reserve fuel value for the emergency fuel declaration with increased fuel consumption?


My guess is that you should adjust and count the FPF because ATC has an estimate of your endurance from your flightplan. Declaring a fuel mayday late would compromise safety.


Have searched ICAO FPFM (9976) and Annex 6 but still nothing there.

Hi,

the mayday fuel is time based, hence whatever increases your fuel consumption (gear stuck down, slats/flaps and so on) will affect how much time you can be in the air with a given amount of fuel. You will need to reassess all your critical fuel scenarios such as the final reserve fuel for instance. On the A320 a single hydraulic failure is not an emergency but the inability to land with at least 30 min of fuel in your tanks (if that is the case) will become one, like in your example.

[Lantirn]

Thanks all for your time.

By the way. Do anyone knows what's the company final reserve for Lufthansa? Have heard that they have adjusted it to 45mins of fuel, which I find awesome.

I was looking recently a study that occurred some years ago in their simulators about an approach in LFMN and then a nose gear would not come down with a hydraulic failure, plus on the second approach they had flaps locked.

This study after some mathematical forecasts concluded that the final reserve of 30mins was not enough to be safe according to todays high complexity on the flightdecks, and that its more applicable to the old jet era. A recommendation to adjust to 45 mins would dramatically minimize the risk of fuel starvation.

[sonicbum]

Thanks all for your time.

By the way. Do anyone knows what's the company final reserve for Lufthansa? Have heard that they have adjusted it to 45mins of fuel, which I find awesome.

I was looking recently a study that occurred some years ago in their simulators about an approach in LFMN and then a nose gear would not come down with a hydraulic failure, plus on the second approach they had flaps locked.

This study after some mathematical forecasts concluded that the final reserve of 30mins was not enough to be safe according to todays high complexity on the flightdecks, and that its more applicable to the old jet era. A recommendation to adjust to 45 mins would dramatically minimize the risk of fuel starvation.

Don't know about Lufthansa but it would make sense to increase the final reserve to 45 min at least. If I am not mistaken in FAA land it's 45 min of final reserve computed at cruising thrust ?
Legally landing with 30 mins of gas in the tanks of a large category transport aircraft is not ideal but it is definitely not going to change.

[Sergei.a320]

My company recently updated Flight Ops Manual and Fuel policy is 30’ of final reserve at dispatch phase, but they require to call “Minimum Fuel “ when Land ANSA would be with fuel less than for 45’…:}