Airbus effectively does this, since the PFD "characteristic speeds" are Alpha derived, and hence if weights are wrong, the PFD and FMGC speeds disagree ;) I would imagine B777 type technology has something similar...

NoD

I think the cavitation found in the pumps is probably misleading the line of thought of everyone in this forum. IMHO cavitation could have happened prior to the event in question, like a couple of days (or the sector) before. So leaving the cavitation signs aside:

If the fuel metering device was giving a “false” reading, somewhat bellow true fuel flow, when the A/T commanded an increase of thrust it would have increased initially to the requested value but then the excess of fuel in the burners would made it drop dramatically but not entirely. Thrust decays, FADEC opens fuel valves even further to compensate, but instead of correcting it worsens the problem.

Too far off the mark?

GD&L

Or was the excess of fuel in the burners in this scenario a mix of fuel, ice and water?

Thawing Ice, perhaps shedding from the compressor stages as the engines revved up from approach idle to a new target thrust setting, quenching or partially blocking the annular combustion chambers on both engines? In this case the anticipated EGT increase with reduced gas flow may have been negligible due to the cooling effect of water, hence no RPM increase but instead (partial) rollback to somewhere above idle?


Green-dot

Dated1,
 

I'm fairly convinced the subject of a possible "stretching the glide" will be included in the accident report. As I see it, the report may suggest one of three things:
a) do nothing;
b) recommend additional flight crew training for handling low-level double engine failure;
c) recommend improved autopilot designs that automatically trim the plane for optimum glide range when sensing a power loss situation.

Each of the alternatives need to be judged on basis of the resulting increase in safety compared to the probability of this type of engine failure, as well as the implementation costs. Also we have to await the outcome of the search for the primary engine failure reason. In case that is not found, the case for doing something (b or c) becomes stronger.

Unless autopilot design has fundamentally changed since my days, the (pitch) autopilot would have no way to 'sense' an uncommanded power loss.
It did its job, i.e., keeping the aircraft on the 3 degree glideslope by increasing pitch (and thus AoA) until things got too hairy and it disconnected.
It 'expected' the autothrotlle to keep the speed up.

CJ

ChristiaanJ,
 

that's exactly my point, with today's computer technology it would be no big deal to design a capable integrated autopilot/autothrottle. It's about time, too, considering the technology advances in most airplane systems.

Talking about inputs that an A/P system may get in the future, I can think of two off the top of my head.

1. Fuel Temp.

2. Amout of Water in the Fuel.

AOA
 

Reheat, thanks for a very good article. The most important part is: "AOA information is most important when approaching stall." The U.S. Navy has used it to very good advantage for about 50 years now in making carrier approaches.

Joetom,
Again confusing A/P and A/T.

Have a read of this...noone seems to be thinking of googling past events
200204444

More Info
 

Dont know if this has been seen before, http://www.iasa.com.au/folders/Safet...eculative.html

snowfalcon2Non pilot speaking
My guess as to why these things might take longer to get more closely integrated - is the certification process. How long would it take to get approval of a new set of controls, software, interlocks and all the rest? The manufacturers will work on the basis that it ain't broke and if the customer ain't demanding it ...?

Hi,

http://www.iasa.com.au/folders/Safet...eculative.html

Thank you.
This was published on the IASA site the 01 Feb 08 and rely to a official report.
Wonder if no more official news was released from this date.

Cheers.

You shouldn't need an AOA gauge to understand that at a slow speed reducing speed increases your AOA, which will decrease your gliding distance.

Decreasing speed from 1.3 Vso to close to stick shaker speed will not stretch the glide at altitude. It does in the end game, and allows some airspeed to 'flare' as opposed to hitting the ground at whatever sink rate you have at, or close to, stickshaker.

Reducing flaps from 25/30(Landing slat configuration - full) to 20 (Takeoff slat configuration - mid) might be critical to improving your gliding distance.

Obviously the lowest drag configuration is best, but sometimes the gain achieved via decreased drag doesn't make up for the increased sink rate generated by the need to increase flying speed to your new, and faster, approach speed. Early? Yes. Late? No. Beats me what the actual difference between 'early' vs. 'late' is. That's the gut check time.

How Long??
 

may i ask anyone who knows how long its going to be before the aaib comes out with a FINAL report . they have had 6 months, all the facts , the airplane itself ,and the crew at their disposal. speaking as a 777 driver myself we fly everyday wondering what happened . delay in releasing reports in my experience, i am sorry to say,. sometimes indicates cover up. excuse my poor typin skills

@thinkingpilot

Our best guess is "as soon as they have something"... As far as one can tell they are at loss for an explanation.

And I'm pretty sure "we don't know" won't be good enough for you, especially if you really are a 777 driver :O

PAXboy
 

Yes, basically the requirement has to be included in the aircraft certification standards in order to get things to happen. And for that to happen there usually needs to be evidence of a number of accidents that could have been avoided.

Now in this case I don't immediately remember any other case of a low-level double engine power loss of this "sneaky" type, on approach with autopilot engaged. Those that come to my mind have happened on take-off (SAS 751, MD-82 ice ingestion, and the recent Citation at Farnborough, Kent) which is an altogether different situation. However, the proposed integrated autopilot/autothrottle might also have helped in the "Gimli Glider" case (which occurred at cruise altitude), had the captain not happened to be an experienced sailplane pilot.

Anyway the key issue, as I see it, is whether this type of fault has a high enough probability to justify new safety measures and their associated costs. The investigation will hopefully shed more light on this.

Fundamental changes of method also go through a cost-benefit filter and a "testability" filter.

Given at least a few incidents of unpowered flight, approaches, and landing sequences in heavy jets, it would seem the cost-benefit (with reference to passenger safety, in particular) argument could be made.

As regards testability, however, the questions are harder to answer. The low, slow, zero-power flight envelope is about as dangerous as it gets for flying a large, heavy aircraft. One can do testing at higher altitudes, of course, but realistic "ground effect" and flare phenomena combined might either require some live tests of each type or a major research effort to create a data-set that could be used for simulation of all reasonable types. The potential variables are so many (for a 'general-case' solution) and the cost of error so high, it would take some considerable courage for an airframe manufacturer to add this function set and pronounce it usable. Would be pretty much a lifetime career for some bunch of lawyers to litigate about that forever after.

Even with all the computers, maybe seasoned pilots and 'seat-of pants' flying still are occasionally the best choice, after all?


.

Thinkingpilot

We all share your thoughts on the unseemly delay in the determination of the cause/s of the problem. It's looking as though we will never know and the natives are getting restless!

Then we are intrigued that you as a 777 pilot with less than average keyboard skills can manage to accurately input all of the necessary data using the push buttons, knobs and switches by which you now fly.

Is it a problem or have you had a heavy week?

There is a subsystem installed on each and every aircraft, with the purpose to evaluate the trajectory of the aircraft under those conditions. They call it the pilot.

milt
 

u bet the delay is unseemly. just wondering that we in pprune have so far filled nearly 80 pages of thread and are still none the wiser than we were six months ago. :ugh:re my typin i was being modest about my laziness in picking caps . flying wise im happy to inform u that big jets merely require basic typing data input from keypads . knobs and buttons are much more user friendly:)

Don't worry about Pprune 80 filled pages, some posts are regularly removed...

Still I would appreciate some update regarding the crew's behavior between the initial loss of power and AP disconnection. Any idea about when they noticed it, how they announced it and did they leave the AP on on purpose ?
Come on, this should be known by the time, simply with the CVR, and especially since they received the BA safety medal.
How do BA expect this medal to be considered serious if they don't release the appropriate info ?

Please don't remove this message (unless my question is too much embarrassing of course).

Ah yes, the modern 'I am too idle to do it properly and so the reader can struggle with trying to decipher the text speak, poor grammar and lack of punctuation and capital letters'.

Just plain bad manners in my book but hey, what do you care?

Mouse.

I'm with you all the way. To the old military adage of 'any fool can be cold and uncomfortable', add 'any fool can communicate sloppily'!

Couldn't agree more M.Mouse, moderating a very busy forum, I get pretty peeved with lower case texting whena full keyboard is provided and supported.
Dyslexia one can usually spot and allow for (getting very common), but am intolerant of ALL CAPS and texting styles - its dumbing down and where does it all end, in the gutter with readers having to to do the hard work... there is a good reason written English has punctuation :ugh:

Not that this thread needs it, but add my $0.02 support to advocacy for proper communication. :D

If a poster can't organize his words, does not that call into question the ability to organize thoughts?

What kind of communication are referring to ?

80 pages of posts, unavailable CVRs or crew statements and all we get after 6 months is BA's safety medal for the crew.

Is there at least any information published on when did the crew notice the problem and on what they did do with their 4 free hands while the AP was flying the aircraft from 720 till disconnection at 175 ft ?

I think after 6 months these question deserved to be answered...

Ok folks. I'm in agreement on the txtspk thing but can we stay on topic please? Someone's on their high horse and we'd hate to deny them their moment of glory :rolleyes:



Duck

arsynapsis rear.

Why do you keep banging on about this award? Upset because you didn't get one?

The AAIB have issued their preliminary findings so your comment about waiting six months is really just posturing. I don't know which part of the world you're from but here on the mainland things get done properly. The report will be issued when there's something pertinent to say. You should try that approach sometime.

I have nothing against the award which values only when the related actions are available...

I understand the AAIB may need time to investigate a very complex technical issue, but what does it have to do with the crew actions in the cockpit ? Both are alive and CVR available.

It's little bit surprising to have a crew rewarded before we know why so forgive me if my question disturbs the "mainland"'s standards but in my part of the world we like to understand before admitting. Obviously you don't have any clue about what happen in this cockpit.

So the crew's actions were pertinent enough to be rewarded but not to be mentioned... interesting approach in did.

Moderator,

You recently deleted some of these rubbish comments and my dismissive reply to same. Kindly continue the good work.........

Sure. However, in this case, it seems neither the operator, the training organization nor the supervising authority had deemed it necessary to prepare the pilot for this particular variant of the task. Fortunately for everyone, luck was also involved. :ok:

Who cares if someone can't spell occasionally...stop being uptight...you know when I and a few friends travelled through countries, I wasnt annoyed that they can't speak english...So stop picking on people for being different...

Having sat in on a number of flight briefings on the flight deck, if trouble occures on take off/climb out the auto pilot is engaged to fly the aeroplane while the crew go through their procedures. I GUESS it would be the same for approach?

May I refer you to post 852, which comments on this...

This message is hidden because sispanys ria is on your ignore list.

Another one!

Whatever happened to AVIATE, navigate, communicate?

Whatever happened to AVIATE, navigate, communicate?

Perhaps I should have been a bit clearer. The briefing includes what to do in a situation and if not already engaged - engage the autopilot.

Bold my emphasis

I have often found that there is truth in the saying 'luck is a residue of skill.'

No-one seems to have commented on or asked about the relevance of the B777 fly by wire system in this close to stall situation.
Would things have worked out differently if the aircraft had been an Airbus?