suninmyeyes - excellent post, especially the second para about us not saying half of what really goes on, since we just then get attacked by all the MS FSim experts :ugh:

NoD

suninmyeyes...second paragraph,,:ok: sadly it will be lost in the noise

suninmyeyes - you've just written my retort for the next wanton comment I get...which may well be tomorrow night at work:}
Good stuff:ok:

Sorry I can't afford the ghost writing fees.

In the meantime, can those who don't have a clue just be thankful Messrs Burkhill and Coward did.

Fuel temperature variations
 

Is it a fact that the port wing probe is at the coldest point in the fuel's route from tank to engine?

If the pipework - for example in the pylons - could be colder, then any tests based on bulk fuel temperature would be optimistic.

no water checks carried out
 

bae146 is clearly stating that at british airways the water sump checks were never carried out, just stamped as being done. I recall earlier in this post baengineering saying the same thing! Clearly water was building up in this centre tank from poor maintenance practice that was widespread at cc.

All i can say is the sooner the media gets this out to the wider public the better. Also why has ba lied in the report? Making out they were doing a study on water sumping just before the incident! It would be amusing if the gravity of the situation were not so significant. A large aircraft nearly down over london.

Any other ba engineers wish to comment?

And here is what is written in the AAIB report:

Probably that the FO didn't have 18 years of 747 behind him... but to me THIS is how he saved the day...

To dxzh:

Thank you for your gentleman's post. I really appreciated your comments and your open minded point of view. I'm sorry not to elaborate more on it as it is bedtime but you made your way to convince me. :ok:

Well said Rainboe! Similar to you, I have some 23 years' experience on wide-bodies and nearly 30 years on four-engine jet transports and I can see a massive contrast between the opinions from the informed professionals and that of some of the inexperienced wannabees. I have been lurking for most of this thread, just amazed at some of the uninformed rubbish that has been posted - suninmyeyes, you are spot on with your recent post.

dxzh has some very sensible and constructive ideas to put forward - especially the recent response to sispanys ria, which was excellent reading - and suninmyeyes' subsequent comment says it just the way it is.

On the subject of the recent AAIB Interim Report, I congratulate them on a detailed and comprehensive update on the progress of the investigation. I, for one, have total confidence in their competence as an investigative body.

Now, back to lurking on this thread ...


JD
:)

33333333333333333333

Misinformation
 

BlueRay:

This misinformation is based on earlier misinformation and provides a good example of why many professionals will no longer contribute.

Firstly, the posts you are referencing did not refer to specific procedures which had been signed-off without implementation. Secondly, they were clearly from someone with an axe to grind, probably a disaffected (Ex?) employee.

I suggest that before you start reaching such conclusions you read the entire thread. This would give a much broader understanding and would allow you to judge the quality and credibility of individual posts within the bigger picture.

Dear, I think I sent you enough PMs to tell you that nobody here recommended to push the nose down. But since you only listen to experienced people, I understand my words didn't reach your brain. What you are now saying is EXACTLY what I told you in my PM: holding attitude (also meaning AOA and speed). Unfortunately the crew didn't have an opportunity to understand the situation before they loose too much of speed and the consequence is that they left the AP until stick shaker...
I'm sure you are experienced enough to understand that letting the AP following the GS is exactly the contrary of what you recommend: the AP didnt' hold the attitude but increased it up to 14 degrees nose up.

Once again I agree... while this is what was done... and that it contributed to increase the attitude to follow the GS (what you do not recommend as an experienced heavy jet pilot).

Sadly your 18 years experience didn't taught you how to hold control over your words. You should read dxzh's post, you would learn a lot on how to share a different point of view.


This is exactly what the FO did at 170 ft... Please note that this nose down input is the consequence of letting the AP increase the attitude till stall...

Basically they did all the contrary of what you recommend (as an experienced heavy jet professional) :

They didn't hold the attitude
They did retract the flaps
They made a nose down input at low speed/altitude

As dxzh said very nicely, it's too bad that the newspaper needs to decide wether the crew made it right or wrong. In most cases, the truth is in between and we (as experienced professional) should be able to understand it clearly. It is absolutely not a matter of judging the crew, since they obviously are not the cause of the accident. Still, their actions could be analyzed for the sake of safety in finding how their actions could have been improved. According to Rainboe's attitude, I guess there wasn't so much of CRM during his 18 years of heavy 747 operations...

There has to be some definition of 'pushing' or letting the nose down. It just can't have been a very pronounced maneuver.

Any attempt to sustain 14 degrees up as the speed came back towards the shake would be catastrophic, obviously. Somehow, that had to be corrected, and one would hope by just allowing the nose to come down a bit...accepting going below the glide, and trying to nail an attitude that was a last-ditch compromise.

I'll leave the flap setting out of the equation, as it may or may not have been just being part of that compromise.

Suninmyeyes I completely agree with your sentiments as expressed in para 2, however and very sadly there will always be professionals and professionals, so its not always that easy to leave it to the professionals....

On another note a quick question. Does the 777 fuel tank contain sensors for ice as well as water?

Each tank has a water sensor. This works by sending a signal down through the fuel which is reflected off the tank bottom surface. The time the signal takes to make the journey is measured. If there is water or ice in the tank the signal will be reflected from the fuel/water (or ice) interface. The resultant shorter signal journey will trigger the water in fuel maint message. So yes the water sensing system will react to ice as well as water.


But retracting the flaps from 30 to 25 will only take a couple of seconds, and they had all hydraulics working so no loss of hyd pressure.

I would dearly love this sniping between factions to stop! I said eons ago on this thread that I do not know what I would have done in that situation.

As I said before, given a significant loss of available energy on the approach (as any pilot, powered or glider should know) there is an altitude above which it is beneficial to reduce flap and/or lower the nose to maintain best glide performance. There is an altitude below which is is beneficial to use the remaining energy to 'stretch' the glide. They, deliberately or inadvertently, chose the second. I suspect that at the moment of stick shake and a/p disconnect at 170' there was an awkward feeling that the choice may not have been right. All said and done, no-one died and the aircraft crashed on the airfield.

However, we cannot judge with the information we have available. I sincerely hope that some sort of 'official' analysis is produced somewhere of the 'best' solution so that it can be added to that mysterious store of 'background' knowledge all pilots have. Until then, rantings about stuffing the nose down, hydraulics being sucked dry are pointless.

Hear, hear!


JD
:)

For all the bitching about the "attitude" / "GS" / "Speed".

Firstly, by leaving the AP in, you had 2(3) crew to discuss/action the best options in resolving the real problem, which lay in the engines... :{

For those of you who advocate lowering the nose to maintain the approach speed (~140K) the aircraft would have ended up well short* - unless you can also show us the profile as to when to now raise the nose / sacrifice airspeed.

The Flaps were retracted ~240' (IIRC) from 30 to 25. The 30 setting is almost all drag. I suspect this was inspired - the rate of loss of IAS would have been higher with Flap 30, so the stall / stick shake / end point would again have been earlier*.

I guess that with idling engines, a suitably trained and pre-notifed crew, it could be shown to have got to the threshold before landing. Lower nose, Flaps 25 (maybe 20?), even some ground effect - but it is barking mad to even suggest this crew should have tried it :ugh: Contrary to the emergency handling procedures we are all taught, and irrelevant as a "lesson" because next time it occurs 1NM further out on the approach all would change and it would not make the threshold* :{

The actions by this crew just got the aircraft over the A30 and onto wet / soft ground, and "landed" with a tolerable RoD that saved everybody.

*Now just go and look at the A30, traffic, and the trees along the SE side. If the aircraft had come down before there, or even "over" the road / trees at very low altitude, the results would likely have been catastrophic...

NoD

PS suggest we do not even discuss the Sim here - I really cannot believe it is accurately modelled for engines out / ground effect etc.

Swedish Steve thanks for the reply - the point I'm trying to clarify in my head is that will the sensor react differently to water than ice . It has been discussed quite openly that the water was a contributing factor after it had melted from ice, my point being that it appears that excessesive water in the tanks can be detected as a cause for concern but not neccesarily ice....

I tried to estimate the obstacle clearance of BA038's flight path by comparing the FDR trace and Google Earth. It appears to have crossed A30 about 5 sec before touchdown at about 100 ft height. At that point there is a low (15-20 ft?) building 50 metres from the runway centerline as well as streetlight poles.

The next significant obstacle is a group of houses 700 metres from the touchdown point, where the plane was 14 sec from touchdown at 230 ft, nose high just before the stick shaker activated.

With full respect for the crew's action in a situation they had obviously never been trained for:

The hypothetical question is, would a slightly lower faster approach, reducing the margin to the houses, have left the plane with enough additional energy to flare over the road and (presumably) come down softer than the actual 1400 fpm vertical speed?

A second question. What if the airplane would have "sounded the alarm" at the earliest possible time, which according to the trace was about 54 sec before touchdown for the right engine and 45 sec for the left, as the EEC entered "Control Loop 17"? An immediate flap retraction to 20 degrees at that early point in time might actually have given some real benefit of reduced drag, even considering the ~10 sec retraction time. But how much?

Hear, hear.

For "hypothetical" I would say "irrelevant" :ugh:

So you are suggesting that if the engines give a first indication of failure in an airliner, you want the crew to ignore all drills to do with trying to restore the engines, or even determine if the warning is/are false... and dive below the G/S, retracting flaps by (?) how much. And when would you do this? VMC? IMC? AWOPS? With Terrain under the approach path?

Take a clue from the AAIB - do they seem the slightest bit interested, at this stage, in the crew actions, or why the engines stopped :D

And are you seriously suggesting that as a result of this accident, we should look at training crews in unanticipated double engines failures on Final Approach, or might it be better to stop the engines failing in the first place :ooh:

NoD

Very difficult to say, due to the unpredictability of ground effect, wind gradient, drag characteristics of a 'dirty' airframe, engines that were producing significant thrust, etc. It's something that would require large gonads to experiment with in this situation... If it was *obvious* that a crash into houses/trees/petrol stations was going to take place, then what have you got to lose? Otherwise, a very difficult call. I wouldn't rely on a simulator to give a realistic answer in this scenario either.

It is well known that you can often escape an undershoot situation by using the technique described in the question above. What is slightly less well known is that the aircraft are generally "cleaned up" on recognition of a developing undershoot and the potential energy (height) converted into kinetic (speed), then bled off in the ground effect where the wing is more efficient. If you have gear and drag flap deployed on an airframe where configuration changes are slow and/or require a significant energy input, the act of speeding up to get into ground effect will probably bleed more energy than you'll save later and lead to an even shorter landing. It isn't called "drag flap" for nothing; in an overshoot situation, "pushing against the flaps" is a another well-known remedy.

The were no warnings (aural or visual) that anything untoward was happening. This is just one of the factors that made it a very difficult scenario to deal with. Does going into "Control Loop 17" mean the engine has become unresponsive? I don't have that level of knowledge but I believe it has something to do with surge/stall recovery, not a total failure. From a flight crew perspective, as it happened to one engine first, a warning would be noted but I suspect no action taken, as the 777 is perfectly happy coming in single engine F30, as the WAT limits are high in that config. By the time a warning came through for the other one, you'd be at the same place and time as the crew were on the accident flight.

It is easy to take the precise figures for BA38 and work out all sorts of things the guys might or might not have done. Change those starting conditions by just a small amount and the "best" course of action may change radically... It was a very dynamic situation and there was not enough information available at that instant to make calculated decisions - just instinctive ones. After all, here we are, eight months later, and no-one has definitively worked out what the optimum actions might have been...

No. You might want to look at my post #1736 to get confirmation on that point. This is a secondary issue, but not totally uninteresting, as many before me have shown :ouch: .

As BOAC has stated (and others before), there is an altitude (or point in the approach) above which reducing drag pays off anyway and I'm referring to that phase - I'm not sure this was the case for BA038. The suggestion would admittedly be bad in those cases where the time for the action (say 5 sec) delays the engine restoration drill AND the engines would actually have responded in the last 5 sec before hitting the ground. In all other cases it would do no additional harm. Either the airplane crashes anyway or the engines save it before, or - in the fortunate case - the airplane would increase its chance to make the airfield.

Finding the root cause is paramount. However, if it's not found with certainty, there might be reason to consider the handling of low level dual engines-outs. Time will tell. :ok:

Am I right in assuming that this detection method will only work when there is a distinct boundary condition - ie a layer of water or ice with a layer of fuel on top - as opposed to the situation where the tank just contains a mixed fluid?

You're correct Steve.
Just to make things more precise, graph in P6 says 8 seconds.


Technically and aerodynamically speaking, I don't see where sispanys ria is wrong ?
For every flying machine, the same rule apply and an optimal attitude will stretch your glide.

Would I have done better ?
Certainly not !
Probably a case for heart attack and best case scenario a compulsory underwear change before jumping in the slide ...

I think that crew has been very unlucky to be on that BA038 but in the same time has been very lucky to end it up the way it did.
But the worst for them was probably to have to go for that PR BA BS the very next day.
For the medals, I'm not sure they really care but would rather have all the data in their pocket which I doubt they have been given ...

Yes it detects the boundary. The transmitter is very low in the tank so it is usually immersed in fuel, and the beam goes down to the bottom surface and back.

Reading again ... could someone please clarify the following (on Page 10 of the report): "approx 6500 to 7100 kg of fuel had leaked [] before the spar valves were manually closed". I thought these valves would be closed when the fire handles are pulled. But the quantity above seems quite large (to me!) ... so what does "manually" mean here?

Posts #5-#12 and on will explain.

It really would help if people read the AAIB reports before asking questions. :ugh:

The answer to your question pax2908 is here on pages 5 and 6 of the AAIB Bulletin S1/2008, published back in February, if you would care to read it ...


JD
:)

FullWings and others well explain the practical uncertainties associated with the hypothesised alternative ways of handling the aircraft after the double rollback - particularly given the ever-developing critical position the crew found themselves in at literally the last minute and a slow, low, heavy aircraft in an initially stabilised but very draggy configuration.

The acid test in my simple world is that, if I were put back in the situation the crew found themselves in at that minute of that flight, then I would turn down each and every proffered "improvement" or “lesson” from any well-meaning speculator, who could (inevitably) only aver with less than 100% confidence that their alternative would work, in return for the certainty of the safe landing which the crew delivered on the day.

I think we should all be pretty humble and thankful that the crew did what they did with the poisoned chalice that they were given and that they saved the day. In my view the crew balanced the aircraft on the right side of the stall, they managed the little energy they had and got the right result, a safe landing - remarkable! This was a catastrophe which could have happened, but did not thanks to the crew.

sorry to be out of tune, but now starting to read all this thread !

somewhere written that the crew performed a managed approach .

what is it ?

thanks !

dxzh -
>>> "I think we should all be pretty humble and thankful that the crew did what they did with the poisoned chalice that they were given and that they saved the day. In my view the crew balanced the aircraft on the right side of the stall, they managed the little energy they had and got the right result, a safe landing - remarkable! This was a catastrophe which could have happened, but did not thanks to the crew."


Ah, but how do we know that they might have made the runway had they left the flaps alone? Or might have gotten to the overrun. Granted things turned out alright, but they might've turned out better. We'll never know. And chances are the sim won't really prove anything. I just don't think their actions qualify them for any Flight Safety Award. Unless, that is, it can be proven that reducing the flaps at that critical point in flight was the right thing to do.

DC-ATE, entirely fair comment on your part and I agree "We'll never now" - but I respect the crew nonetheless for what I do know which is that they got the plane down safely having been put into a potentially catastrophic situation by the double rollback - I would not begrudge them any praise for that achievement.

I believe Boeings computer modelling has already proved that reducing the flaps was the right thing to do. Unless landing even shorter and ploughing through a busy road is considered a better outcome.

It has been suggested in this thread that crews are not trained to cope with a total loss of power at low altitude. I would propose that this is not so. Just consider the regular practice, in the simulator, of recovery from windshear or GPWS warning. In both cases, the aircraft is flown in such a way as to trade kinetic energy for potential energy, in a situation where engine power cannot meet the desired flight profile. In other words, trade speed for height. In these situations, kinetic energy is traded for height right back to the stick shaker, at which point attitude is adjusted to fly at intermittent stick shaker speed.
I would suggest that the crew of BA038 did, instinctively, follow exactly what they had been trained to do. Speed was bled back to the shaker speed and then an attitude adjustment was made to keep the aircraft flyable. Energy management.
There seems to be a perception that the stick shaker represents an entry into the stall regime, with loss of lift and control. This is totally wrong. The aircraft remains controllable and flyable at shaker speeds, as there is still a fair margin above the stall speed.

I know about stick shakers having heard them numerous times in the sim; fortunately NEVER under actual conditions!

There is an obvious dissagreement in the handling of this flight with regard to flaps. I don't care what type airplane it is, however, if you raise the flaps, you've taken away lift and increased the stall speed: period. Any other action taken at that point other than lowering the nose will only aggravate the situation. As I stated earlier, I've had the flaps dumped on me and I know the feeling!

Being as I'm retired, I'll leave this now (unless called upon) to all you active types to sort out.

Again, we're ALL glad the outcome was as successful as it was. It probably speaks well for the aircraft also.

Energy budget: height for speed
 

What options did the crew of BA038 have with respect to trading speed/kinetic energy for height/potential energy?

They had a finite reservoir of total energy, unless they could get power back. Worse, in fact, this energy reservoir was being depleted rapidly by drag: bleeding away into the turbulent air behind the flaps.

Going faster would increase drag further, taking away a larger fraction of their total energy per second. Going slower would reduce the loss rate, but too slow and what remains is forfeit in a stall.

The results of the manufacturer's detailed modeling of the precise circumstances: go for a bit less lift and quite a lot less drag, and squeeze the remaining energy out for as long as possible. The crew's intuition seems to have lead them to the same (right?) answer. A remaining question - does the computer modeling take into account the details of ground effect, surface topology and gusty wind in the final seconds?

Sorry DC-ATE, but I disagree. Retracting flap from 30 to 25 on a 777 has virtually no effect on lift, changes the stall speed by a negligible amount, but considerably reduces drag. In the energy management situation I recently described, it is a winner.

OK 777fly, I'll leave it to you to keep these things in the air. Best of luck to you and your fellow pilots. Just glad I'm out of it.

30 vs 25 Flap.
 

@777Fly.

I do not question your response to DC-ATE. or agree with his post. but simply ask...

What is the purpose of the 30 position IF it adds "negligible" lift yet adds considerable drag.

Surely the "negligible" must be closer to "significant" i.e. worth having or otherwise what is the point of such a setting?

I do not wish to rekindle the discussion re whether the crew should or should not have reduced the flap setting (I'm not interested and do not believe that at this point it has any relevance) but just question the premise against which the discussion is based, namely that 25 to 30 is "purely drag".

I am not a pilot. nor an aerodynamic specialist, but as an engineer I find it surprising that a function/position has been provided that increases drag but not lift...unless of course its purpose is as a brake, which may be the case.

So another way. What is the thinking/purpose in selecting 30 vs 25 under normal circumstances other than procedure calsl for it.

Please enlighten us.

snancekl
Effectively the case. On the 757, Vref F25 was only a couple of knots above that of F30 - however, it gave you much mroe drag to keep the power "up" on Final Approach, enabling better speed control / engine response.

The airlines have now seen this and are getting 777 pilots to do F25 landings, and us Airbus guys to do F3 (Flap 3 rather than Flap Full). This keeps the Final Approach power low hence saves (a little) fuel. Depending on type the Approach and speed and Landing Distance increase by a bit, but the main effect for the crew on a steep glideslope / tailwind is dififculty having anything other than idle, against an SOP requirement of "Approach Power".

It makes the selection of F25 fairly instinctive, when day in / day out you are used to seeing a lower power setting for a F25 approach than a F30... someone takes the power away, lets go for the approach that needs less power :D

As has been pointed out elsewhere, most airliners on a go-around call for an immediate reduction of flap setting by one or even 2 stages - yet no increase in datum speed. Again, reason is pronounced reduction in drag (increased climb performance) with little reduction in lift.

NoD