EDTO fuel - variable reserve at CP?
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EDTO fuel - variable reserve at CP?
Could I please ask the group for your thoughts on an issue WRT the use of contingency fuel/variable reserve on an EDTO flight plan?
Picture an A330 EDTO 180 minute flight with a few EDTO segments throughout a 10-hour flight. The final segment, with the destination is one of the final EDTO alternates. The last segment has closely-intersecting 180-minute circles and the ETP between the final alternates is a CP (fuel critical).
The computer flight plan indicates that the critical fuel scenario on this final segment is 2 engines operating, 10000’ depressurised. The excess fuel available at the Critical Point (CP) to accommodate the critical fuel scenario is zero, and, on the specific flight plan I am using as an example, an extra 4500kg is carried as EDTO “build-up” to bring the available fuel up to that required for diversion at the CP. This would be a “normal” EDTO flight planning scenario on the route.
I have noticed that in the fuel flight plan, the variable reserve (some call it contingency fuel) of 2000kg (capped) is part of the fuel available at the CP. I am informed by the training system that it is normal flight planning procedure that the variable reserve is included in this fuel available at CP, i.e., if the diversion fuel to the EDTO alternate is, say 22000kg, then, included in this is the 2000kg or ‘original ‘ variable reserve.
My query and concern is this: if any or all of the variable reserve is burned in the 7 hours preceding the arrival at the CP, then you will be up to 2000kg shy of diversion fuel given the depressurisation scenario.
When I asked the question of the planning department, they said this was acceptable risk (I am aware that the whole EDTO operation is based on statistical data and risk management. I get that). What worries me is that, after engine start, I taxy to 34L in Sydney, then there is a weather delay and a runway change to 16R and before takeoff I have eaten substantially into by variable reserve (maybe even close to the 2000kg). So, before I even depart, I know that I am going to be 2000kg short of diversion fuel at the CP (and this is before the 7 hours ahead, complete with potential weather deviations, flight level unavailability, icing, etc.). Is this sensible? It seems beyond the realms of good risk management.
Does your company use the Variable Reserve as a component of your CP fuel scenario?
Am I missing something here, or is this really just a con job to reduce fuel uplift?
Picture an A330 EDTO 180 minute flight with a few EDTO segments throughout a 10-hour flight. The final segment, with the destination is one of the final EDTO alternates. The last segment has closely-intersecting 180-minute circles and the ETP between the final alternates is a CP (fuel critical).
The computer flight plan indicates that the critical fuel scenario on this final segment is 2 engines operating, 10000’ depressurised. The excess fuel available at the Critical Point (CP) to accommodate the critical fuel scenario is zero, and, on the specific flight plan I am using as an example, an extra 4500kg is carried as EDTO “build-up” to bring the available fuel up to that required for diversion at the CP. This would be a “normal” EDTO flight planning scenario on the route.
I have noticed that in the fuel flight plan, the variable reserve (some call it contingency fuel) of 2000kg (capped) is part of the fuel available at the CP. I am informed by the training system that it is normal flight planning procedure that the variable reserve is included in this fuel available at CP, i.e., if the diversion fuel to the EDTO alternate is, say 22000kg, then, included in this is the 2000kg or ‘original ‘ variable reserve.
My query and concern is this: if any or all of the variable reserve is burned in the 7 hours preceding the arrival at the CP, then you will be up to 2000kg shy of diversion fuel given the depressurisation scenario.
When I asked the question of the planning department, they said this was acceptable risk (I am aware that the whole EDTO operation is based on statistical data and risk management. I get that). What worries me is that, after engine start, I taxy to 34L in Sydney, then there is a weather delay and a runway change to 16R and before takeoff I have eaten substantially into by variable reserve (maybe even close to the 2000kg). So, before I even depart, I know that I am going to be 2000kg short of diversion fuel at the CP (and this is before the 7 hours ahead, complete with potential weather deviations, flight level unavailability, icing, etc.). Is this sensible? It seems beyond the realms of good risk management.
Does your company use the Variable Reserve as a component of your CP fuel scenario?
Am I missing something here, or is this really just a con job to reduce fuel uplift?
Etops is a planning exercise.
Upload more discretionary fuel if you're worried and anticipate enroute diversions and extended ground delays.
Sounds to me like it's a refile flight plan. It's perfectly acceptable to refile based on an etp or pnr.
Upload more discretionary fuel if you're worried and anticipate enroute diversions and extended ground delays.
Sounds to me like it's a refile flight plan. It's perfectly acceptable to refile based on an etp or pnr.
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Thanks, GG. It's a normal flight plan, not a refile.
I'm happy to carry discretionary fuel, but, occasionally being payload limited makes this a tough call.
I'm happy to carry discretionary fuel, but, occasionally being payload limited makes this a tough call.
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Etops is a planning exercise
Yes, it is largely a planning exercise, but it's a planning exercise to ensure you have sufficient fuel so that you don't end up in the drink. Same as a normal flight!
If the worst emergency happens, at the worst point along the route, then you MUST still be able to land on a piece of concrete. My operator states that, at the CP, I need to have fuel to fly to my ERA (they give me 5% contingency as well) with a fuel allowance for severe icing and APU burn, hold for 15 mins and make a landing.
My flight plan does use the variable reserve at departure as part of the fuel required, as you state.
So, to answer your question, if I have burned all my variable reserve before takeoff, I would get airborne and have a look at how the flight was progressing. As you said, if the critical CP is the last one, then you have about 8 hours to come up with an alternative plan, which may include finding a new ERA.
But, if it looked like I was to going to get to the CP with insufficient fuel to divert (as above), I would not go there: as an commercial operator of a Perf A aircraft, I have an obligation to my passengers not to put them in harm's way. I cannot knowingly fly to the CP with the full understanding that if the worst were to happen, we would end up swimming due to a lack of fuel. You would need to find another ERA or re-route or pick up some gas somewhere.
You are at min fuel before push back in this scenario. As far as what others find "perfectly acceptable", who cares?
If your variable reserve is used before you get to the CP and you now have insufficient fuel, but the planning department says that's ok, why bother calculating it then? I mean, really, it either means something or it doesn't. (And I am tipping that it does not mean the equal time to ditching point)
And by the way, what an interesting example you cite. Going somewhere?
If your variable reserve is used before you get to the CP and you now have insufficient fuel, but the planning department says that's ok, why bother calculating it then? I mean, really, it either means something or it doesn't. (And I am tipping that it does not mean the equal time to ditching point)
And by the way, what an interesting example you cite. Going somewhere?
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I am informed by the training system that it is normal flight planning procedure that the variable reserve is included in this fuel available at CP, i.e., if the diversion fuel to the EDTO alternate is, say 22000kg, then, included in this is the 2000kg or ‘original ‘ variable reserve.
the etp1d fuel calculation has its own variable reserve (contingency) within that 22t.
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I'm with OK4 Wire. It can't simply be written off as an "ETOPS planning exercise". You either have enough fuel or you don't.
In your example I would see it as a Diversion Decision Point plan and if insufficient fuel was found to be available at the critical point, divert for fuel.
Regards using the contingency fuel for the fuel available at the CP, I would think most companies would do it. In some cases it would be simply be due to a matter of fuel capacity, not commercial reasoning.
A different cost index can sometimes help.
In your example I would see it as a Diversion Decision Point plan and if insufficient fuel was found to be available at the critical point, divert for fuel.
Regards using the contingency fuel for the fuel available at the CP, I would think most companies would do it. In some cases it would be simply be due to a matter of fuel capacity, not commercial reasoning.
A different cost index can sometimes help.
Etops IS a planning exercise, however you can't enter the etops entry point without fuel to divert to an adequate. Meaning you'd have to come up with another plan or divert prior to etops entry.
The only time you might get a please explain with extra fuels upliift, is if you have to offload payload to do it.
The only time you might get a please explain with extra fuels upliift, is if you have to offload payload to do it.
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Waren9 - sorry, my scenario was badly worded.
The fuel at start is 65 tons (this includes 2 tons variable reserve).
My fuel at CP is planned at 22.8 tons (still including variable reserve).
Because the CP diversion fuel is critical, there is an EDTO fuel build-up included in the start fuel and hence in this 22.8 tons. Thus the flight plan shows the CP fuel and the diversion fuel to be 22.8 tons.
Yes, the 22.8 diversion fuel contains 5% PDA buffer and another 5% wind factor buffer, but this extra 2.3 tons buffer is supposed to be there at the CP with the fuel tanks reading 22.8 tons! If you have burned your variable reserve on the way to the CP, then you are going to have 20.8 at the CP and flame the engines out on the roll-out at the alternate.
A bit too fine for my liking.
The fuel at start is 65 tons (this includes 2 tons variable reserve).
My fuel at CP is planned at 22.8 tons (still including variable reserve).
Because the CP diversion fuel is critical, there is an EDTO fuel build-up included in the start fuel and hence in this 22.8 tons. Thus the flight plan shows the CP fuel and the diversion fuel to be 22.8 tons.
Yes, the 22.8 diversion fuel contains 5% PDA buffer and another 5% wind factor buffer, but this extra 2.3 tons buffer is supposed to be there at the CP with the fuel tanks reading 22.8 tons! If you have burned your variable reserve on the way to the CP, then you are going to have 20.8 at the CP and flame the engines out on the roll-out at the alternate.
A bit too fine for my liking.
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then it sounds like how it is presented is misleading. by definition the normal ops fuel reqd from last etp cannot be the same as the etp1d fuel reqd when there is a 4.5t build up.
each scenario has its own contingency calculation
even if you burn your capped 2t contingency along route, the etp1d contingency is still required to be available in whatever amount is required for diversion.
each scenario has its own contingency calculation
even if you burn your capped 2t contingency along route, the etp1d contingency is still required to be available in whatever amount is required for diversion.
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Select a new Adequate if you have concerns. Airbourne there is no requirement to have this fuel on board at your CP. General airmanship applies. The CPE is at flight planning, the adequate is at flight planning. If you're concerned about your fuel state once taxiing, nominate a new Adequate that's above landing minima and fits the requirements to continue to that adequate with your required fuel. It's not a requirement as technically you're now airborne, but if you're concerned about this then just change your nominated adequate.
Something else worth considering, if you're seriously concerned about EDTO fuel reserves. The CP calculations, at least where I work, are on a pure straight-line basis. There's no allowance for doing a 180, and no consideration of whether there might be a 20000' mountain range between CP and the adequate airport. So what you think is enough, may well not be. Also the required reserves are very low - can you imagine turning up at Biak in the middle of the night, engine out, with only 15 minutes and approach fuel? 
On the other hand: this is really a risk-mitigation exercise against a very low-probabiity failure. We're required to have EDTO CP fuel before departure, but once airborne, it's no longer a requirement. While I agree that we should always have enough fuel to get safely to an airport regardless of what happens, the fact is that we don't. It's just that the things we don't allow for are of extremely low probablity. I'd suggest that a depressurisation exactly at CP is also a very low probabliity. If you're aready operating in accordance with CARs and your company's SOPs, do you need to insist on covering that very low probability? That's up to you, but think about this scenario:
You're operating Sydney-Honolulu with 300 pax. The destination weather is fine, and there's a contigency build-up for CP, so the result is that the plan has you arriving in HNL with stacks of fuel - let's say 1.5 hrs on top of normal reserves.
Enroute, all is going pretty well. The destination weather is still great, and there's nothing the matter with the jet, but you see that you'll be 200 kg short of the flight plan contigency fuel at CP. You are, of course, completely legal to continue to HNL, and the chances of a depressurisation happening at exactly CP are tiny. So, do you continue legally to HNL, or do you take your serviceable jet and its 300 pax to Cassidy (Christmas Island)? How do you see the subsequent discussion with the Chief Pilot going if you choose to divert?
Not trying to tell you what you should or shouldn't do, just throwing it out there for consideration.
On the other hand: this is really a risk-mitigation exercise against a very low-probabiity failure. We're required to have EDTO CP fuel before departure, but once airborne, it's no longer a requirement. While I agree that we should always have enough fuel to get safely to an airport regardless of what happens, the fact is that we don't. It's just that the things we don't allow for are of extremely low probablity. I'd suggest that a depressurisation exactly at CP is also a very low probabliity. If you're aready operating in accordance with CARs and your company's SOPs, do you need to insist on covering that very low probability? That's up to you, but think about this scenario:
You're operating Sydney-Honolulu with 300 pax. The destination weather is fine, and there's a contigency build-up for CP, so the result is that the plan has you arriving in HNL with stacks of fuel - let's say 1.5 hrs on top of normal reserves.
Enroute, all is going pretty well. The destination weather is still great, and there's nothing the matter with the jet, but you see that you'll be 200 kg short of the flight plan contigency fuel at CP. You are, of course, completely legal to continue to HNL, and the chances of a depressurisation happening at exactly CP are tiny. So, do you continue legally to HNL, or do you take your serviceable jet and its 300 pax to Cassidy (Christmas Island)? How do you see the subsequent discussion with the Chief Pilot going if you choose to divert?
Not trying to tell you what you should or shouldn't do, just throwing it out there for consideration.
My 2 cents, since you asked
At all times you must have the stat. fuel with appropriate reserves, in this case dep2
If you find the trend 'going south' during the flight, and if you anticipate lower EET fuel targets, then you lower your CI accordingly.
Most ETOPs plans have the critical scenario at the end, so this not new.
Some of the build-up may be destination alterates, that may be traded away inflight, but changing the CI accordingly is the most practical.
At all times you must have the stat. fuel with appropriate reserves, in this case dep2
If you find the trend 'going south' during the flight, and if you anticipate lower EET fuel targets, then you lower your CI accordingly.
Most ETOPs plans have the critical scenario at the end, so this not new.
Some of the build-up may be destination alterates, that may be traded away inflight, but changing the CI accordingly is the most practical.
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Where I work, this fuel is only a preflight requirement, not inflight ( unless dest wx is very poor and is covered by an approved variation)
Additionally, this 'on' and 'return' fuel is based on a simultaneous engine failure and depressurisation at the exact point enroute...
The odds of this?
Additionally, this 'on' and 'return' fuel is based on a simultaneous engine failure and depressurisation at the exact point enroute...
The odds of this?
I don't have the regs Infront of me, but to my understanding it states some jibba Jabba like the pilot In command must at all times have sufficient fuel to xx and land with reserves intact. Variable reserve must always be 10% of the flight fuel to destination (unless refileing which we aren't considering) So to burn all your variable prior to departure is a no no. As the flight progresses the 10% requirement reduces as the fuel to destination reduces.
So when you arrive at said etp, 3 hours away from destination, I'd expect 15t-ish flight fuel, plus 1500 variable to be remaining. Any of this could be used toward edto calcs
So when you arrive at said etp, 3 hours away from destination, I'd expect 15t-ish flight fuel, plus 1500 variable to be remaining. Any of this could be used toward edto calcs
Last edited by Gear in transit; 27th Apr 2015 at 04:58. Reason: Shhhpelling
Itchy butt man,
The CF scenario in my airline is based on the most limiting of the three scenarios too.
Engine failure at CP with drift down to SE cruise altitude.
Depressurisation and flight at 10k
Engine failure and depressurisation at CP.
I suppose you could say the plan is refiled from that point assuming the VR hasn't been burnt and is available.
If you've burnt the fuel then you didn't add enough fuel to cover possible enroute weather deviations and taxi fuel when busy.
The CF scenario in my airline is based on the most limiting of the three scenarios too.
Engine failure at CP with drift down to SE cruise altitude.
Depressurisation and flight at 10k
Engine failure and depressurisation at CP.
I suppose you could say the plan is refiled from that point assuming the VR hasn't been burnt and is available.
If you've burnt the fuel then you didn't add enough fuel to cover possible enroute weather deviations and taxi fuel when busy.
Does your company use the Variable Reserve as a component of your CP fuel scenario?