Why you might want to dump fuel if you can

[pelmet]

A good example here. Boeing 777 near MTOW and they lost an engine on takeoff. The runway length for landing is 4100m(about 13,500'). Don't be fooled by that. They landed at more than 90 tons above their max landing weight and used up almost all of runway to stop with almost all main tires deflating.

Of course, they did land long but at a very heavy weight, who wants to be doing a single engine go-around. Why not take the time to dump fuel and come in at a much lighter weight. It gives much better options. Significantly less reverse thrust is available meaning mostly brakes will be used. An OAT of up to 39C doesn't help either.

It reminds me of my one overweight landing quite few years back. Although the captain initially wanted to use the shorter runway, I convinced him to use the 10,000' runway. We had a higher than normal Vref and landed long(maybe that is more likely when overweight with its higher approach speeds combined with less drag from reduced flap setting). We ended up using most of the longer runway to stop and probably 500-1000 feet more than the length of the shorter runway. It seems to make a big difference when landing overweight.

https://www.gcaa.gov.ae/en/ePublication ... cident.pdf

[goingnowherefast]

Interesting. The airspeed in the initial climb after the engine failed also dropped to 1 kt above V1, and well below the Vr. The gear was left down until over 500agl.

I don't fly a heavy jet, but I still would think gear up is an important part of an engine failure on take-off drill.

[complexintentions]

Why not take the time to dump fuel and come in at a much lighter weight. It gives much better options.

I’m sure fuel jettison was considered, but to reduce weight for any meaningful amount of braking distance reduction means a very long time during which you are absolutely dependent on your one remaining engine whose precise status is unknown.

The performance calculation tool is very accurate for landing distance with this and most non-normal situations. Of course the figures are dependent on correct technique and touchdown zone position but delaying landing to account for possible pilot error would be hard to defend in either a court of law or public opinion - it IS kind of the whole reason we’re there. Blown tires are a non-factor, it’s assumed all the fuse plugs will blow on an overweight landing.

Comparing the risks and survivability of a slim chance of overrunning a 4100m runway at low speed versus the unknown odds of becoming a 347 ton glider, seems pretty clear to me what the correct choice is from a risk management perspective.


Gear up on a heavy jet on an engine fail is important but not critical to the same degree as on a light piston twin, for example. From the report the crew got about 10kt slow briefly but airspeed is achieved by proper pitch so they probably pitched up a bit too much momentarily. Single engine there’s still plenty of thrust with GE90 engines even with gear down (RR-powered, not so much). V1 and Vr are takeoff speeds not relevant to engine out, the target speed is V2 to V2 +15kt.

[digits_]

I know it is easy to second guess actions, but would there be a reason as to why they leave the gear down longer? Probably distracted by the emergency, but are there any actions they have to do in an engine failure on take-off scenario in a B777 that would delay a gear retraction?

[pelmet]

Why not take the time to dump fuel and come in at a much lighter weight. It gives much better options.

I’m sure fuel jettison was considered, but to reduce weight for any meaningful amount of braking distance reduction means a very long time during which you are absolutely dependent on your one remaining engine whose precise status is unknown.

The performance calculation tool is very accurate for landing distance with this and most non-normal situations. Of course the figures are dependent on correct technique and touchdown zone position but delaying landing to account for possible pilot error would be hard to defend in either a court of law or public opinion - it IS kind of the whole reason we’re there. Blown tires are a non-factor, it’s assumed all the fuse plugs will blow on an overweight landing.

Comparing the risks and survivability of a slim chance of overrunning a 4100m runway at low speed versus the unknown odds of becoming a 347 ton glider, seems pretty clear to me what the correct choice is from a risk management perspective.


Gear up on a heavy jet on an engine fail is important but not critical to the same degree as on a light piston twin, for example. From the report the crew got about 10kt slow briefly but airspeed is achieved by proper pitch so they probably pitched up a bit too much momentarily. Single engine there’s still plenty of thrust with GE90 engines even with gear down (RR-powered, not so much). V1 and Vr are takeoff speeds not relevant to engine out, the target speed is V2 to V2 +15kt.

Thanks for the reply,

I am happy to listen to any other arguments including yours.

Appreciate the comments but the reality is that the other engine is not going to fail. Unfortunate, people have gotten into their mind that they must land right away because they could be a glider if the other engine fail. It is not going to fail(OK, there is a one in a million chance).

Then they start doing things like saying the performance shows they can do it and land way overweight. And then they float and now you have to jam on the brakes and it just gets worse. Dump the fuel and lower the weight unless you have lots of margin, instead of this near panicked idea that we have to get on the ground right away. You are quite safe in the air.

[LETUN]

They had NLG tire delamination causing damage on one engine leading to shut down; I would have assumed damage on both engines and land the jet ASAP. The report says there were impacts on both eng.
Tires are designed to deflate in such circumstances. None issue.
Similar event happened at an airline North of AUH. Captain rejected. Many threw mud at him. Once in the hangar, substantial damage was found on BOTH engines requiring both to be replaced.

[goingnowherefast]

The overweight landing was probably the smart decision knowing what caused the first engine problem. I'd have trust issues with the other engine as well.

Leaving the gear down (unless there was some logical reason) and poor airspeed control are my questions. Don't they practice this maneuver in the sim every 6 months?

They new they had a nose gear problem, maybe they left it extended for that? But then why did they retract it at all? By 500', I assume they were already out of the most critical phase for obstacles and climb performance.

[pelmet]

The overweight landing was probably the smart decision knowing what caused the first engine problem. I'd have trust issues with the other engine as well.

Leaving the gear down (unless there was some logical reason) and poor airspeed control are my questions. Don't they practice this maneuver in the sim every 6 months?

They new they had a nose gear problem, maybe they left it extended for that? But then why did they retract it at all? By 500', I assume they were already out of the most critical phase for obstacles and climb performance.

Perhaps. One can do a quick return if they feel that the other engine is seriously at risk. The flight was over 30 minutes which doesn't really sound like a quick return but maybe it was.

I suppose one could leave the gear down if they thought there was a fire. Otherwise, best to put it up.

[ahramin]

If the performance calculation (which already has a conservative factor) confirms the desired runway is long enough, I would not consider a fuel dump. It is my understanding that this is industry standard and possibly Airbus and Boeing best practice as well.

[pelmet]

If the performance calculation (which already has a conservative factor) confirms the desired runway is long enough, I would not consider a fuel dump. It is my understanding that this is industry standard and possibly Airbus and Boeing best practice as well.

I don't think there is an industry standard. My old company seemed to prefer overweight landings, <i suspect to save fuel. My present company's policy is to dump at least down to max landing weight unless it is a critical issue such as a fire.

If you have any publications confirming industry standard or that Boeing or Airbus consider this best practice, it would be greatly appreciated.

Thanks

[Eric Janson]

Not all large aircraft have fuel dumping capability.

Not possible on the 757.

Some 767 don't have it installed.

Some A330 don't have it installed.

[sportingrifle]

Not trying to Monday morning quarterback here, but the airplane touched down about 4000' from the runway threshold...about 2000' further than it should have. Crew was probably trying to make a very gentle touchdown due to the high weight. Like I said, well done, not criticising, just pointing out that an awareness of the runway length required is important in these sorts of circumstances.

My operator provides guidelines to dump fuel prior to landing in the event of a problem with the airplane. But this is a great example of not being able to cater to every circumstance and the value of pilot judgement and experience. There is no right answer, I would probably dumped but this crew managed a risk equally well with a good outcome.

[pelmet]

My operator provides guidelines to dump fuel prior to landing in the event of a problem with the airplane.

Correct. Some operators prefer it, some don't. I doubt you will find any industry best practice info from Airbus or Boeing stating one way or the other, at minimum for liability purposes, and probably for other reasons as well. And these two manufacturers will certainly tell you that the fuel jettison system was installed with the intent that it be used if felt to be necessary. So I am not sure why someone would state otherwise.

But this is a great example of not being able to cater to every circumstance and the value of pilot judgement and experience. There is no right answer, I would probably dumped but this crew managed a risk equally well with a good outcome.

Thanks, that is why the title of the thread is....'You MIGHT want to dump fuel if you can’. You also might not want to. But as seen in my example, when well overweight, don't assume that runway that seems excessively long, Will not, all of a sudden, significantly shorter than desired due to some mishandling.

Performance numbers are nice but sometimes things don't work out as planned. On final in what was likely quite bumpy conditions, these guys ended up in a choice between a near overrun and a very heavy single engine go-around(although, they may not have realized the former). They already had difficulties with their first climbout out on one engine(showing the performance numbers in critical situations don't mean a lot if not properly flown within tight tolerances), perhaps they didn't want to try again.

As Eric mentioned, not all of the airliners, even some of the big airliners can dump fuel while some turboprops can. That means it can be a long wait to burn off fuel if that lighter landing weight is desired.

[complexintentions]

The overweight landing was probably the smart decision knowing what caused the first engine problem. I'd have trust issues with the other engine as well.

Leaving the gear down (unless there was some logical reason) and poor airspeed control are my questions. Don't they practice this maneuver in the sim every 6 months?

They new they had a nose gear problem, maybe they left it extended for that? But then why did they retract it at all? By 500', I assume they were already out of the most critical phase for obstacles and climb performance.

I wouldn't be too quick to pass judgement on "poor airspeed control". As the reports state, they were very heavy and in the prevailing environmental conditions they were really flying the razor's edge with regards to pitch. I would be willing to bet that the delayed gear retraction was precisely due to the airspeed loss and the concentration on recovering it with what would be very sensitive pitch control while also trying to maintain a positive rate, or at least not descend. In fact raising the gear while struggling with low airspeed can exacerbate the situation while 14 tons of swinging gear and massive doors introduce MORE drag temporarily. If they near-levelled to regain speed the PM probably hesitated to call a positive rate which would normally trigger the call to raise the gear. Speculation, but I've seen this a gazillion times in the sim.

Airspeed Is Life and they prioritized correctly. The report also details a routine configuration cleanup with appropriate speeds so it would seem the loss was momentary and obviously, corrected.

I've got about 9,000 hours on B777 and I would still be challenged to fly such precise pitch at the limits particularly when you throw in the startle factor. Momentary airspeed loss at maximum conditions is almost guaranteed unless you fly it perfectly, and the certification doesn't require or expect perfection. I mean, I know the average AvCanada contributor would have done it perfectly of course, but not everyone is that good.

All hail the mighty power of the GE90-115B's though, to be able to safely fly a 347 ton machine on one engine!

[rookiepilot]

All hail the mighty power of the GE90-115B's though, to be able to safely fly a 347 ton machine on one engine!

That is amazing, actually.

[GRK2]

The overweight landing was probably the smart decision knowing what caused the first engine problem. I'd have trust issues with the other engine as well.

Leaving the gear down (unless there was some logical reason) and poor airspeed control are my questions. Don't they practice this maneuver in the sim every 6 months?

They new they had a nose gear problem, maybe they left it extended for that? But then why did they retract it at all? By 500', I assume they were already out of the most critical phase for obstacles and climb performance.

I wouldn't be too quick to pass judgement on "poor airspeed control". As the reports state, they were very heavy and in the prevailing environmental conditions they were really flying the razor's edge with regards to pitch. I would be willing to bet that the delayed gear retraction was precisely due to the airspeed loss and the concentration on recovering it with what would be very sensitive pitch control while also trying to maintain a positive rate, or at least not descend. In fact raising the gear while struggling with low airspeed can exacerbate the situation while 14 tons of swinging gear and massive doors introduce MORE drag temporarily. If they near-levelled to regain speed the PM probably hesitated to call a positive rate which would normally trigger the call to raise the gear. Speculation, but I've seen this a gazillion times in the sim.

Airspeed Is Life and they prioritized correctly. The report also details a routine configuration cleanup with appropriate speeds so it would seem the loss was momentary and obviously, corrected.

I've got about 9,000 hours on B777 and I would still be challenged to fly such precise pitch at the limits particularly when you throw in the startle factor. Momentary airspeed loss at maximum conditions is almost guaranteed unless you fly it perfectly, and the certification doesn't require or expect perfection. I mean, I know the average AvCanada contributor would have done it perfectly of course, but not everyone is that good.

All hail the mighty power of the GE90-115B's though, to be able to safely fly a 347 ton machine on one engine!

Up until recently I flew the B777 and B787 for the company in question and we were presented with the very situation being discussed here as part of a training profile. It was a no jeopardy exercise and the conditions were identical. (Obviously this was done in the B777 300 simulator) As far as I can recall it was supposed to be a surprise and no briefing was given, although pilots are pilots and the instructors notes (as usual) had been circulated throughout the pilot group prior to the training semester actually starting. So that pretty much took care of the surprise factor. Having said that, it was a valuable training tool as it showed various levels of CRM, and how crews used the tools they had. In some cases the aircraft would slowly sink despite the best handling abilities of the PF, and he or she had the option of asking the augmenting crew (who were simulated to be on the flight deck as if this was a normal ULR flight) to start a fuel dump to lighten the aircraft in order to stop the sink. That allowed the PF and PM to complete the memory items and the Severe Damage checklist without interruption, which allowed for an unhurried use of the decision making matrix being applied here. There was a serious vibration from the remaining engine to add to the situation if memory serves. If the fuel dump option was utilised, it was always stopped before turning final. Others did not and managed the situation in a different manner. There was no right or wrong outcome, the point was to allow decisions to be made and results to be tabulated for debriefing facilitation. A large percentage elected to return and land overweight. The decision to hold and dump, dump while returning if manpower permits, or return without dumping is up to the PIC, and his or her crew. The GCAA and the company are presumed to have properly trained and rested crews on duty and leave the decisions and policy making up to the crew as much as possible. Lessons learned were applied and integrated into the daily operations of the Boeing widebody fleet. As Complex stated, those GE's and that jet are well matched!

[pelmet]

As Eric mentioned, not all of the airliners, even some of the big airliners can dump fuel while some turboprops can. That means it can be a long wait to burn off fuel if that lighter landing weight is desired.

A possible example of holding to burn down to Max landing weight....

"C-GWJK, a Bombardier DHC-8-400 aircraft operated by WestJet Encore, was conducting flight WEN3428 from Halifax/Stanfield Intl (CYHZ), NS to St John's Intl (CYYT), NL. Upon selection of landing gear up shortly after the takeoff, the nose landing gear failed to retract. The flight crew declared an emergency, and performed a low approach for a visual inspection by the control tower. Following a holding of approximately 1 hour to burn fuel, the aircraft landed without incident at CYHZ. The flight crew was able to taxi the aircraft to the gate under its own power. The operator’s maintenance determined that the rigging for the NGLK1 and NGLK2 sensors needed to be reset. A gear swing was completed, and the aircraft released to service"