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Old 9th Feb 2010, 17:28   #2881 (permalink)
 
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The lift drag benefit can be examined by checking stall speeds. On every airliner I've checked(6 types), the first notch of flaps reduces stall speed by 50-60%.

Obviously the greater the deflection the more drag vs lift is created.

Any old school fighter pilot can tell you about the value of leading edge devices. "Hard wing" wasn't your friend in a turning(ie high AOA) fight.
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Old 9th Feb 2010, 17:36   #2882 (permalink)
bearfoil
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You must have read Boyd.
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Old 9th Feb 2010, 17:40   #2883 (permalink)
 
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DERG,

That report is not a very good summary, and certainly even ignores to main report's glossing over of the actual water content issue.

.
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Old 9th Feb 2010, 17:48   #2884 (permalink)
 
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post 2898 Basil asked about retracting flaps straight to Flaps 20.

Basil,

Vref 135 from the 777 performance pages is for a 440,000 lbs a/c(I don't recall BA 038's weight).

Stall speeds at 440K -
Flaps 30 108
Flaps 25 110
Flaps 20 115

The flap retraction was done 115-118 kts(I've seen/recall different numbers). If the 777 would allow it there's a chance that a retraction to Flaps 20 at those speeds could have triggered a stall. I have to believe, based on Vso multipliers, that the AOA would have been mucher and I'm guessing it would outweight any configuration drag reduction.

I'd believe that an immediate retraction to Flaps 20 at Vref might be the best plan. Sadly, the AAIB report doesn't give the next guys any knowledge.

How quickly can guys be expected to react? With training and awareness it could be done fairly quickly. How quick does a trained pilot apply rudder with an engine failure?

For non pilots the difference for most Boeing a/c(that I know of) and I'm assuming Airbus' Flaps 2 is that the leading edge slats are in the mid, or takeoff, configuration. Most single engine configurations are based on mid/takeoff slats to reduce the drag associated with greater flap extensions.

My previous post explained how the largest stall speed reduction occurs in the first flap position(Flaps 1, Flaps 2, Slats EXT, etc). The last flap settings are just the opposite, mostly drag, with little stall speed reduction.

That is also why, as Basil mentioned, Flaps 20 is an important step in reducing drag, with a relatively small stall speed increase, to allow the a/c to accelerate rapidly during a go-around.
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Old 9th Feb 2010, 17:53   #2885 (permalink)
 
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"You must have read Boyd." - bearfoil

Ah, brings a smile to my face. Learned his concepts, didn't all G pullers, before I read his book.

I love telling Marines that I have great respect for their branch of the service, especially since they so willing put a statue of a USAF fighter pilot in front of their leadership school. "B.S.!" is often the internal, and sometimes external, reaction.

Then they research it.
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Old 9th Feb 2010, 18:02   #2886 (permalink)
 
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Quote:
How quickly can guys be expected to react? With training and awareness it could be done fairly quickly. How quick does a trained pilot apply rudder with an engine failure?
This is certainly why Boeing issued recommendations on monitoring automated approaches which insists on mandatory manual override as soon as an automatism default is identified.

Retracting flaps from 30 to 25 improves the aircraft L/D "global" configuration, but you still need to fly the right speed to get the best of this new configuration. Flying best L/D speed at flaps 30 will take you further than flying minimum speed with flaps 25.

It's exactly like on a go-around: retracting flaps is improving the aircraft global aircraft config but you still need to fly the right speed to get the best GA performances.

In this particular case the captain's decision to retract flaps reduced the poor gliding performances resulting from flying at minimum speed.

The report clearly demonstrate that it was better than doing nothing, but it sadly fails to show what would have been the benefits of controlling the airspeed.
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Old 9th Feb 2010, 18:05   #2887 (permalink)
 
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interim measures from the report

Safety Recommendation 2008-047
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency, in conjunction with Boeing and Rolls‑Royce, introduce interim measures for the Boeing 777, powered by Trent 800 engines, to reduce the risk of ice formed from water in aviation turbine fuel causing a restriction in the fuel feed system.

it goes onto say...

In addition, an engine response non-normal procedure was added to provide a procedure should the engine fail to respond to a thrust application.
The procedure called for the thrust levers to be set to idle for 30 seconds,
after which each engine thrust lever is moved to max thrust to ensure the restriction has cleared.

oh....
30 seconds....? erm like you have 30 seconds to wait when your are 450' AGL
at 108 kts and both engines no longer have any ooomph in them and the staff car park badges in the windscreens are easy to read hmmmm...
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Old 9th Feb 2010, 18:07   #2888 (permalink)
 
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Quote:
phil gollin
I'm amazed.
I find the report extremely annoying.


I'm not and I don't. I believe the AAIB's report to be well researched, well written and comprehensive in scope. I believe that they have reached the right conclusions and have provided sufficient analysis to justify those conclusions. For those of us with more than a passing interest in fluid dynamics, more detail would have been gratefully read. But one has to draw the line somewhere, and I think that they have got the balance of the report just right. It is a QED report in my view.

Concerning the flap retraction, some would do well to read Capt P Burkhill's thorough explanation of his feel for the 777. Non believers can do the numbers or get someone to do them for you. Or just believe the AAIB. A difference of 51 metres is significant, and life saving in this situation. He obviously had no time to do the numbers; he knew from experience and instinct. A good man.

Anyone baying for the CVR, forget it. The crew probably swore, said good-bye to their loved ones, before they knew they were going to make it. What do you expect?

About the fuel restriction, I can understand that some might be surprised by this and may have a preference for other theories; others may accept it, but doubt the AAIB’s reasoning. This too is entirely understandable and normal. Water occurs naturally in fuel (from the atmosphere), on the ground and at 30,000ft. There is nothing new about that. But fluids can be tricky, especially water, and get trickier with changes in temperature and when ‘piped’. Anyone with an intimate knowledge of Fluid Dynamics knows that. That is why the AAIB were able to focus on this, and why myself and others suspected the fuel delivery architecture some time ago. AAIB, Boeing and Rolls Royce all accepted that a modification of the FOHE was needed, and I understand the all Trent 777 have now been fitted with modified FOHEs. So that's it.
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Old 9th Feb 2010, 18:10   #2889 (permalink)
 
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PG...thanks for your opinion..but

That report will prolly be read by a wider audience than the official version and of course it is an interpretation. It has pics and good precis and is objective.

For people like me it is wunnerful because I can see the parts and understand what went on. It makes sense.

I don't think this will happen again due to the modifications made as result of this accident. That is all I seek. The outcome is postive and the world is safer..whatmore could anyone want?
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Old 9th Feb 2010, 18:15   #2890 (permalink)
 
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Quote:
Anyone baying for the CVR, forget it. The crew probably swore, said good-bye to their loved ones, before they knew they were going to make it. What do you expect?
Instead of swearing some crew communication could have helped to detect that the AP failed to be disconnected as it was believed.
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Old 9th Feb 2010, 18:15   #2891 (permalink)
 
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Quote:
I'd believe that an immediate retraction to Flaps 20 at Vref might be the best plan. Sadly, the AAIB report doesn't give the next guys any knowledge.
Aerodynamic basics would state that there is no set "rule" you can derive. The higher you are, the lower the optimum flap setting would be. As you get lower the lower stall speed with more flap outweighs the drag.

It is not the AAIB's job to (re)write handling manuals:
Quote:
The purpose of the AAIB is:

"To improve aviation safety by determining the causes of air accidents and serious incidents and making safety recommendations intended to prevent recurrence"
...It is not to apportion blame or liability.

Chief Inspector
They went as far in this report to analyse the FC actions as were relevant to the accident - in short, a no notice untrained for emergency, and their actions pretty much resulted in an optimal outcome:
Quote:
...they kept the aircraft flying and under control so that, at impact, it was wings level and at a moderate pitch attitude
Fundamentally this is a design/engineering accident, and little to learn from the FC pov - IMHO it is impractical to expect "drills" to be produced for every eventuality - especially since in this type of accident they would need to be "memory"...

Just my 2ps worth

NoD
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Old 9th Feb 2010, 18:28   #2892 (permalink)
 
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Quote:
IMHO it is impractical to expect "drills" to be produced for every eventuality
It's not a matter of different eventuality but basic fundamentals. Losses of thrust during initial climb requires to control:

- Safe flight path
- Optimum speed
- Configuration (drag)

There is basically no difference when this happen during an approach, there is no need for a "special" procedure. I regret that the AAIB didn't consider including few lines about it.
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Old 9th Feb 2010, 18:31   #2893 (permalink)
 
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Quote:
Instead of swearing some crew communication could have helped to detect that the AP failed to be disconnected as it was believed.
which will, no doubt, bring down the wrath yet again of the god-like pilots on poor old sfly. But, people, she has a point. Throughout my reading of this thread I've been amazed by the pure coolness displayed by these guys in leaving the a/p engaged until it tripped at stick-shaker. What faith in automation!

and now it turns out the F/O "omitted" to disengage it. That doesn't sound like a deliberate (and oh so cool) action.

And surely you guys out there see the point. Might it have been better to hand-fly from the moment the problem was identified? Perhaps not. Certainly the outcome could hardly have been better. But I think we'd all like to know.
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Old 9th Feb 2010, 18:35   #2894 (permalink)
 
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Pettifogger -

The transcripts for USAIR 1549 are available. 3+28 (208 seconds) from impact to impact.

FO Skiles - Oh, sh*t
CA Sully - Oh, yeah

After that they were too busy to make any personal comments. Sully has said that his family never crossed his mind.

I would guess that the BA038 crew had the same focus.
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Old 9th Feb 2010, 18:41   #2895 (permalink)
 
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SFLY
95% of pilots will follow the flight director if flying manually. The flight director will be trying to keep the aircraft on the ILS, exactly what the AP was tryting to do. So why increase the workload, when trying to faultfind an emergency for which there is no drill. For the 15-20 seconds that elapsed between when the FO intended to take out the AP, and when he did, the difference in flight path is hardly worth talkingabout, if you want something pointless to contemplate, why not have a heated debate about whether they should have asked all the passengers to move to the back of the aircraft, in an attempt to reduce control drag!

Last edited by xavier95; 9th Feb 2010 at 23:15.
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Old 9th Feb 2010, 18:59   #2896 (permalink)
 
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Pettifogger ;

" .........the AAIB's report to be well researched, well written and comprehensive in scope. I believe that they have reached the right conclusions and have provided sufficient analysis to justify those conclusions. ......."

The report is hardly "comprehensive in scope" as it does not even begin to try to cover representative tests of the presumed actual fuel/water mixture in the plane at the time of the accident.

Likewise their "analysis" is non-existent as they totally dodge this issue.

The report screams out both a lack of rigourous testing and avoidance of the huge cost that would be involved in both undertaking such research and then applying it to ALL airframe and engine combinations.

Releasing a report with such glaring gaps is plain weird.
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Old 9th Feb 2010, 19:02   #2897 (permalink)
 
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Quote:
Vref 135 from the 777 performance pages is for a 440,000 lbs a/c(I don't recall BA 038's weight).
410,880 lbs

SoS
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Old 9th Feb 2010, 19:06   #2898 (permalink)
 
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This is the longest, and most comprehensive, AAIB report I can recall. I guess as a taxpayer I ought to be glad that the AAIB does not have to pander to idiots who want the report to explain the movements of every component throughout their entire life, the movement of the planets and the variations in the planetary magnetic fields.
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Old 9th Feb 2010, 19:08   #2899 (permalink)
 
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Phil Gollin

While the actions of the crew in the last, doubtless frenetic, seconds of the flight are both interesting and admirable - so far as I am concerned - I have to say I share Phil Gollin's concerns that 'eyes have been taken off the ball.' His well researched and knowledgable post should really have put questions of flaps raised or not, to one side. The reason those two gentlemen, plus all their crew and passengers were in that terrifying situation is because two of the most beautifully engineered machines for producing thrust, didn't. Both at the same time, give or take a few seconds.

I joined this forum because the circumstances of BA038 were, to this uninvolved bystander engineer, quite simply; staggering. Unbelievable. And yet today the report uses the word 'probably'. Entrained ice in the fuel probably caused the engines to 'choke' simultaneously. However, unless I've missed some big numbers somewhere, it seems quite extraodinary that so little water could choke such big engines at such a critical moment in the flight.

It appears to my untrained eye that the engines were consuming fuel at varying rates - in the last twenty odd seconds - but between one and two kilograms per second. Phil Gollin's text stated that it was estimated that there was a total of 5.14 Lt of water in all the fuel in the aeroplane at take off and sucked in during the flight. It just seems too little, because if all the water in the tanks suddenly arrived at the delivery system in the last few seconds, it would still only represent about 10% of the fuel being consumed at the time.

Since entrained water and ice in fuel systems has been endemic all through the history of high altitude, high speed flight and certainly during the whole operating career of the 777 - a lovely aeroplane to my mind - why hasn't it happend before?

Perhaps it has been decided to apply the principle of Occam's Razor and accept that ice is 'probably' the cause. Although I apply the principle myself in my own job often enough, the pricking of my engineer's thumbs suggests to me that something, somewhere has been forgotten.

Roger.
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Old 9th Feb 2010, 20:43   #2900 (permalink)
 
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Mmmayday38:
for some it is still not possible to accept that gut feeling flying may actually produce best possible results.
I still believe that your post BA038 (B777) Thread is a glamorous example of humble and professional human side of flying.

thank you!

long time ago J.Conrad wrote a book on sailors - 'Lord Jim' - from which i have learned one thing: one can not tell how he would have behaved in given situation until he would have lived through such experience himself.

hopefully the Report's recommendations might help in preventing it happening ever again...
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