Chris Scott

Quote from snanceki [Today, 07:53, currently #796]:
As I said we will have to be patient. Only then will we be able to draw conclusions and see whether any of the theories put forward prove to be anywhere near (by chance) correct.
[Unquote]

Err… yes. To paraphrase part of something I think I was saying yesterday; those of us amateurs, who are mildly obsessed with trying to find a plausible cause for this thankfully non-fatal accident, find ourselves in the position of would-be diners at a top restaurant; aperitifs have been served and menus distributed, but we are still waiting for the Maître d’Hotel to come and tell us what the plât du jour is, and take our order. As time passes, and there is no sound emanating from reception or cuisine, we start to wonder WIHIH…

CAAAD

Chris Scott

I have not contributed to this thread very much but, like most, have been impressed by its general tone and interest.

But, like you, I do begin to scent a whiff of something peculiar in the investigation.

A Large Transport Aircraft was written off in dramatic circumstances three months ago, and nothing seems to have been done to prevent it from happening again. No ADs, Recommendations, ASBs, nothing.

Even if it had been 100% crew error we would have expected to hear a reminder about this and that in the Flight Manual.

I agree that the professionals should be allowed to get on with the job, but it is not acceptable to keep the travelling public let alone the industry uninformed for such a long time. Perhaps a bit arrogant in fact.

AAIB owe us an update ASAP.

Bis47

IMHO, one of the immediate recommandations that should be given :

Publish the best glide speed in typical flaps/landing gear configurations, and train the crew to react to full engine failure.

Because, for sure, let us putting it straight : the handling of the event was less than perfect and that is something that should be improved. I presume some chief pilots are already working at it ...

AAIB doesn't need to know the causes, for that first step.

Yes, it does happen, from time to time ...
Boeing should be able to provide the data ...
Crews need some numbers, some practice, too.

Long overdue ...

michaelmarsh

It's irrelevant. Large transport aircraft are not intended to glide in the landing configuration. In the case of BA038, it looks as if the approach path was extended to the utmost- any other procedure would have surely resulted in an even shorter landing-in the road.

lowflare

There is a best glide speed for everything flying including a brick...And 113 KTS is far from it because it is closer to a stall and probably beyond it. B777 is not a glider but still is a machine heavier than air, on which all aerodynamics laws apply. Judging (not sentencing) the crew action bringing it almost to a stall on A/P it could have been better handled and surely more followed up by Boeing in some AD, Urgent circular or something similar...

Lowflare

CAAAD

I was not presuming to comment on the conduct of the flight after the problem had been revealed.

My point is that it is high time that we had an update on the circumstances that led to the problem, together with preliminary recommendations to prevent a recurrence.

michaelmarsh

At 600', with less than 60 seconds to touchdown, no power and in the landing configuration, the ONLY action that won't make the situation worse is to hang on to CLmax (the edge of stick-shake) and if landing is inevitable, make the best touch-down you can. This is the standard procedure for extreme down-draft or terrain proximity recovery i.e. max lift and don't change the config. This action appears to be exactly what occured in the case of BA038.
To suggest that one might train crews for an event that has happened once in the history of jet aviation and is, as yet, unexplained, is to fail to understand training priorities.
Why not wait for the findings of the Enquiry?

LLuke

Without knowing the details of what happened, they did (imho) the right/ most natural thing. It all happened in a couple of seconds at low altitude (500 ft?), waiting for the damned engines to respond, going for minimum decent rate, but obviously not allowing it too stall. At the altitude it happened, in landing configuration, it probably wouldn't make sense to dive to the best glide speed. (just my opinion ofcourse) I am sure it has been replayed on the sim already many times...

If both engines go in relax mode at 4000 feet, it is obviously a different story.

Green-dot

What if the aircraft would have made it to the runway with this failure and had landed safely without any structural damage? Obviously the aircraft would have been taken out of service for some serious trouble shooting and would have undergone every operational and functional test available.

What value should be placed on the fact that in the current situation (with the aircraft relatively intact, minus engines and landing gear) it is impossible to do engine runs or landing gear related tests, hence impossible to check their functioning in conjunction (or interfacing) with other aircraft systems? Could something, due to their absence, be missing in the scheme of things? Bench testing components may not always reveal the problem which might have surfaced if the component was installed on the aircraft and tested.

If no definite cause is found, would it be worth to (if only temporarily) repair and complete the aircraft to a fully functioning vehicle to do such tests to possibly try and find the exact cause that way?

Regards,
Green-dot

Bis47

It is definitively false that this is the first occurence of total engine failure in an airliner ... Quite a few occured in the past ... This one is not the last one. Especially if the cause of the accident remains unsolved.

Considering the very special circumstances, and the basic limitations of a two pilots crew in such an extreme emergency, no one should blame the pilots. But ... that is not a valid reason to affirm that the aircraft was flown the best possible way to achieve a maximum glide and a safe touchdown.

The problem, as far as I remember, occured at 700 ft, that is one full minute before touchdown, not "a couple of seconds". The autopilot flew the aircraft down to the stall speed while - we may suppose - both pilots were busy trying to recover some engine thrust. This is the very classical trap indeed : both pilots busy with the hardware, nobody flying the aircraft.

Hard to believe that the auto-pilot had any kind of airmanship to deal with such an unusual situation. Bringing an aircraft to the stall, and letting it fall from 200 ft to the ground without any chance for a minimal flare is "zero airmanship". The auto-pilot was not programmed to achieve the best possible glidespeed, or to let go altitude for speed and recover the initial loss later during the flare ...

From a pure aerodynamic standpoint, we may assume with confidence that it was possible to bring the aircraft over the airport fence with a much lesser rate of descent. Same energy, but not the same trajectory.

Just basic piloting skills ...

Someday - perhaps - somebody will replay the event in a simulator, and experiment some other course of actions. Perhaps ... it is done already?

It should be, and whatever the results, they shoud be made public.

PBL

Biz47,

let me try to summarise.

Your question: was the trajectory optimal?
The current answer: who knows?

The next question: who cares? Is this going to happen again?
The current answers: few people; and, who knows?

The next question: should resources be devoted to finding and teaching the optimal trajectory, should this kind of thing ever happen at 700' again?
Answer: I dunno. Does anybody?

PBL

M.Mouse

Indeed it has been done already.

Your post sums up entirely the basic facts of the last minute of that flight accurately and without emotion, something which has been notably lacking in many comments regarding the flightpath and control, or lack of, in the final 700'.

I am sure I would have been as stunned and possibly overwhelmed as surely 99% of us would have been given the sudden and almost complete unexplained loss of power in that last minute.

I hope and suspect that analysis of the flightpath and alternative scenarios will be made public in due course.

LLuke

I can't comment too much since I really didn't read this thread. I didn't know it was on AP all the way. However I don't think that diving to best glide from 700 ft would have resulted in better range. I always thought all airliners train 'loss of all engines'. Best glide obviously depends on weight. If it happens on short final, your speed isn't going to make a difference, you will *never* make it to the runway (unless you're in a glider a/c ofcourse). Don't even try it. Better spent some time with looking outside and find a nice place to ditch/land. That's exactly what these guys did; finding a nice place. Unfortunately that place is not always ahead of you. The time it took me to write this message is more time than the BA crew had to analyze what the f*ck was happening and what to do. The job they did resulted in a survivable outcome. If a better result was possible, I will be most pleased to read about it in my comfy arm chair, enjoying my drink, when the report comes out :-)

16024

Don't want to make any point at all regarding the correctness of the crews' actions.
Just to chuck in a couple of points about glide speeds.
Michaelmarsh says:
This will give a very high R.O.D. in the glide. It works in windshear or terrain avoidance situations because of the thrust vector in a nose up situation.
Min. sink is at about 1.1 to 1.2 Vs.
But here we are after best glide ratio, which is at about 1.3 to 1.5 Vs.
Lluke says:
Vref is close to 1.3 Vs so you are right there.
Glad I wasn't...

M.Mouse

It was until the speed reduced to 108kts and the aircraft was about to stall.

Try it in a simulator it makes a significant difference.

We do but usually from altitude where variations of speed are less critical and with far more time and distance to judge the descent profile.

I know for a fact that it has been done in a simulator (made the runway that is).


Sitting here we do of course have a luxury that was not afforded to the unlucky crew i.e. time and detailed analysis. For that reason it would be unfair and foolish to criticise them directly or indirectly. My statements are made with that qualification.

LLuke

Glad to hear all this. Guess it also depends on A/C type... On my type I fly with a typical thrust setting of 60-70% N1 depending on flaps setting, wind, weight, etc..; wont make it idle.

Maybe I will surprise my colleagues next time during recurrent (that's on the sim ofcourse) at 700 ft on the ILS

Chris Scott

There is much merit in the above discussion, if only to increase our understanding of L/D ratios, and their implication. We must recognise, though, that the crew must have been hoping for, or even expecting, a sudden recovery in the thrust shortfall. Double (all) engine failure is one thing; slow and/or partial engine acceleration is another.

One of the most relevant data strings that we would-be diners have been starved of so far is the actual thrust from TOD (top of descent) to the point at which the engines noticeably failed to respond to the autothrust command. This missing information has been a major inhibitor to our discussion from day one.

To spell it out: could this have been the first call for thrust above idle? In which case, how long had the problem been lying dorrmant?

M.Mouse

That question has been answered numerous times. It was not the first demand for more power.

Chris Scott

Thanks. Idle thrust always seemed unlikely, going into LHR. But what/who is your source?

PAXboy

Hhmmm, more criticism ...

:- of flight crew who had an unprecedented event and managed (with the automatics) to get everyone home alive when they had less than a minute to assess and react.

:- of the AAIB who cannot publish an update until they are SURE of what they have found. If they are working on something very serious, then anything less than a full explanation may cause panic in the travelling public. And the airline business is in a bad enough way as it is. If they are thinking of saying, "We have a bunch of ideas - and it could have been any one of them" then that will also cause a bad reaction. They do not 'owe' us anything, until they have something they can say with certainty.

And this thread was doing so much better of late.