Landroger

I'm not sure if this is relevant, but didn't a BA 742 have all four donks choked by pumice dust from a volcano in Jakarta? In the eighties? I accept that actual total loss of thrust was not the whole period of the incident and may thus disqualify it from the terms of this discussion. I believe the engines where shut down or flamed out of their own accord, one at a time until there were none. Then, after huge effort on the part of the crew and the fact that the aeroplane had flown out of the plume, engines were restarted one by one.

From memory, the incident happened at FL370 and they got one engine - the one they shut down at the beginning of the incident - restarted at around 12,000 which slowed the descent to about 300ft/min.

Digressing only slightly to the engines themselves, this incident demonstrated, to me at least, just how bomb proof modern High Bypass Fan jets are. I recall seeing photographs of one of those engines after partial tear down and the damage from accreated pumice was massive.

Anyway, I offer all four engines out - BA??? 747 198x?

Roger.

Green-dot

BA009, 747-236B G-BDXH 'City of Edinburgh' June 24, 1982.

The aircraft was at 13,500 ft when the first engine, engine No. 4, burst back to life. Towards 12,000ft the second engine, engine No. 3 restarted. Soon after engines No, 1 and No. 2 relit.



Green-dot

Chronus

The most unfortunate elements common to this and the Concorde crash is that they both nearly made it to a runway. Perhaps looking back at history we may find that systems such as JATO and RATO, necessitated by the lack of technology two manufacture large by pass fan jet engines producing huge power, were effective in assisting heavy metal off the ground. Why such a concept cannot be applied to modern aircraft design. Had these been available I am sure the BA crew would not have had the desperate need to look for assistance from the APU and the AF Concorde would have had that small but crucial burst of energy to give them a fighting chance to make it to Le Bourget. I think in these days of two powerplants and ETOPS, manufacturers ought perhaps consider some form of emergency power back up system that may provide a short but vital source of energy when all else has failed.

CONF iture

Only data from the radar. Early in the process, they had the runway lights in sight. They crossed the extended runway center line, 8 NM final at 13000 feet, so opted for a kind of 360 degrees turn but were still 8000 feet 9 NM final. The only drag available was one set of slats and the landing gear. Not sure about that, but I think they opted for aggressive S turns to dissipate energy. The target speed was 170 knots but had still an extra 30 over the threshold.

A movie on its way …

atakacs

Most interesting

I guess would not be much of an effort to integrate those factors... Good to know anyway

PJ2

atakacs;
The calculation of best L/D speed would be done from standard formulae using specific engineering data regarding the wing, power plant performance data, air data, weight, CofG, etc and presentation is a matter of design and/or convention as glass presentations developed. The basis for the construction of performance tables would be taken out of the books and into the FMGC for real-time presentation on the primary flight displays - that's the 10,000ft, (perhaps 100,000ft!) view.

By way of explanation in re integrating abnormal configurations into speed presentations for crew information with an apology for the return to FMGC (Flight Management Guidance Computer) basics and the thread diversion for a moment, the notion of "prediction" is necessarily based upon known performance quantities such as speed/altitude/rate-of-descent-pilot-entered speed/altitude contraints and so on, - in short, the energy level of the airplane as affected by known configuration changes and the required altitude and/or speed constraints at pilot-entered or FMGC-database waypoints. Because these other quantities are known, FMGC predictions include fuel usage/fuel remaining and ETAs over programmed waypoints as well as at destination and alternate.

Such predictions work extremely well when all is normal. At present and to my knowledge, (the B787 may do so), such information as may be available now, does not take into account the following:

- extended landing gear
- abnormal slat or flap configuration
- engine out
- contaminated wing
- aircraft damage, such as loss of a winglet, etc

The moment an abnormality occurs which affects lift/drag, FMGC predictions regarding times, fuel usage, the achievment of altitude and/or speed constraints etc, are all unreliable and as the FMGC manual states, must not be used. That is when the crew must go back to the books or the QRH.

Bear in mind that this is complex stuff and there will be exceptions/subtleties which we can delve into but which won't change this basis understanding a great deal. I ask others to leap in here if there is something missed, however.

Abnormal slat/flap configurations or extended landing gear will, depending upon configuration, more than double fuel flow and as such, all fuel, time, altitude and speed predictions are lost - rather, they assume a "normal" airplane. This would include the presentation of the best L/D speed so in abnormal circumstances, one returns to the books.

I am guessing when I say that such predictions are certainly possible but computer constraints, (memory, calculating power, cost), actual testing and then certification of same may be part of the constraints in creating new designs which present this kind of data to the crew. There would certainly be a cost-benefit analysis and given that such events are rare, it is probably better to go to the books.

FMGC information, like automation itself, it is tempting to believe all the time what the FMGC is telling the crew but in fact even the FCOM/AOM tells the crew that the FMGC is a guide and not THE performance indicator. The only tool that the crew should rely upon is the official flight plan which is (and must be) the most accurate information for prediction even though it is not in real time. In fact, data in real-time can be very misleading and should be taken in context of the entire flight.

Sorry for the thread-walk.

PJ2

bearfoil

PJ2

No disagreement here, only a philosophical muse relative to the topic you bring to the fore. Appreciating how dynamic and challenging flight can be, I see a trend toward solutions that involve further refinement of problems not solved by automation, but instead caused by them. Reliability is the fulcrum of any solution to an aerodynamic challenge.

Historically, extremely odd and cataclysmic events have shown up to shake the confidence one develops in systems in a lifetime of relying upon them. In BA038, we see one of these (actually two). I deplore the fascination with the flight crew's responses to these two simultaneous events. Their handling was superb, by any measure.

We are left with equipment failure, and evidently having a second engine is not enough. Who'd have predicted dual failure of these two powerplants in simultaneous fashion?

Delta survived a similar (?) occurrence, though the failure happened at altitude, affording a human solution to an engineering (?) problem. At some point, and to the relief of most of us, I would say, a better understanding of systems and piloting relating to how the two work together is needed.

447? Who needs an old fashioned horizon when there are three computers? Pitots? BA038? Who can entertain the "maybe" relative to thrust loss further away from the runway? Was Delta lucky in recovering the one instead of losing the second? As safe as it is, I don't believe stuffing the computer with solutions to oddball scenarios is the way to go. I'd say the pilot part of the process is just fine. What of the mechanical?

misd-agin

More deadsticks,

DL 767 that shutdown the engines departing LAX. Restart worked.

DC-9 diverting from SXM to STX.

'Dead idle stall issues on 757's'. Yes, the engines were still running be they just increased the plane's glide ratio.

Gimbli(sp?) glider. Air Canada 767.

SAS MD-80 with FOD onto frozen lake.

MD-80 with dual compressor stalls, unrecoverable, after takeoff.

A310 enroute from Turkey(?) to N. Germany. Unable to retract gear...deadsticked in Salzburg(?). Believe the fuel gauges, not the FMC computations!

misd-agin

Best dual engine failure best glides speeds SWAGS(Scientific, Wild *ss Guesses)

757/767 - Vref 30 + 90

737 - Vref 15 + 60

Perfect? No. Sometimes 'good enough' is just right until you get the checklist(if you have time).

J52

I was told at that time the saving grace for the BA crew was that the engines were RR (triple spool) and if they had been US manufacturers then probably not restartable under any circumstances due to pumice damage.
Anyone else heard this?

Pumice is really nasty stuff, saw a military plane sand blasted to bare metal after a young pilot wanted to find out what it would be like to fly through a plume from one of NZ'zzzzz volcanoes.

Sir Richard

KLM's Volcanic incident near Anchorage a few years later (Nearly new 744) certainly didn't have RR engines...they landed with a few of them running after multiple flameouts...

KLM 867, 15/12/1989

lomapaseo

There are a lot of old wifs tales being told arround ... all of them just speculation.

restarting is mostly a case of setting the right air speed and altitude conditions. Acceling the engine above idle is another thing. There is no such thing as "rugged" when it comes to fine ash sticking to stuff in the hot section.

You're surely not going to hear bragging from the engine manufacturers about running into volcanic ash any more than encountering birds, rain and hail.

bearfoil

Each Trent 8 selected for the 777 instead of GE saves 2200 pounds. Together, that is 4400 pounds. Weight is everything, where did it go?
Draw one's own conclusions.

bear

barit1

Sir Richard

The KLM 747 at ANC report is NTSB ANC90FA020. I can lend a bit of insight - the volcanic ash ingestion eroded the compressor, and upon passing through the burner, melted into glass droplets that tended to "plate" the nozzle guide vanes of the HP turbine. The combination of these two effects robbed the stall (surge) margin of the HP compressor system, and compressor stalls occurred. Some engines flamed out.

The shock cooling from the flameout caused crazing/cracking of the glass coating on the NGV's, and some of the glass flaked off and exited the tailpipe.

This had the effect of restoring some of the stall margin, and it was possible to restart all engines after that.

This effect has been observed on other engines, notably in test bench ops subjected to dust- or sandstorms. I have little doubt this was the scenario in the BA 747 case.

clivewatson

Do we really need to guess when in a hurry?

From the very beginning of flight training "airspeed" is drummed into us, so perhaps we should be forgiven for having developed into a breed that seems to place so much emphasis on this one data input that is absolutely meaningless when considered on its own. We use reams of charts presenting us with PA, OAT and Weights to determine "speeds" that in reality correspond to an "angle of attack," the value of which is displayed on what I am sure is one of the least used and least understood instruments on a flight deck. As I don't fly either the 777 or A320, I have no idea if they are even fitted with an AOA indicator, but I'll bet few posters have received the benefit of much, if any, instruction on the use of this valuable little dial. I certainly hadn't, until I was fortunate to meet an instructor who knew more than a little bit about how the AOA indicator could help me. For a given aircraft type (and config) the AOA indicator will guide one swiftly to fly at the correct corresponding "speed" for a variety of flight regimes, irrespective of the WAT. Vref and V2 are perhaps the easiest examples to quote as we all know the values to look for; and further the configs are of no relavence (for these two examples). Similarly, in crusing flight (gear and flaps retracted), if one knows the angle of attack values for a given aircraft, calculations are of secondary priority when "speeds" for drift down, holding and even more importantly best glide (for max range in still air) may be needed in a hurry. Even during more leisurely moments, when perhaps ATC might ask if we can make another 2000 feet up, this magic little dial can guide us to an answer in an instant. I am not suggesting for one moment that the BA777 crew should or could have done anything at all different to change the outcome, in fact I congratulate and admire them for doing exactly what they did, especially the flap reduction. Knowing any AOA values for the config they were in at the time, and with the height available would not, I suspect, have made any difference to the outcome.
I am however sure that the outcome of at least twoother major hull losses could have been prevented if the crew had been able to make use of an AOA indicator, if indeed fitted, to either the Birgenair 301that departed with blocked pitot tubes, or the Aero Peru 603 with taped up static vents. (both Boeing 757's).

Smilin_Ed

Clive, I've been thinking for sometime that I should jump in here and mention Angle of Attack. Glad you did. Flying the correct AoA allows you to forget about a whole host of things and simply concentrate on one. The U.S. Navy has been making aircraft carrier approaches using AoA for decades. They never have to worry about weight, temperature, or anything else. Just fly the specified AoA for the configuration (which usually is simply gear down and flaps full down) and you will be at the optimum approach speed. (That, by the way, is not necessarily the best glide speed.) These guys did a fantastic job of making the best out of a truly horrendous situation but we could give the next crew encountering such a situation some help by teaching them a bit about AoA (and providing an AoA indicator).

BTW, AoA at cruise speeds is not very useful. At cruise it's awfully hard to fly an accurate AoA since the faster you go the less AoA changes with speed changes.

clivewatson

Thanks Ed,

I agree that the AOA changes are of lesser magnitude in cruising flight, but similarly so are the "speed" spreads that the manuals would otherwise determine. If the AOA value (for a given type) is known, it is far more expedient to fly it first, then if one needs the comfort of a speed target, then by all means look up the equivalent.if time permits.

The point I was trying to convey (which I am sure you grasped) is that all "speeds" are those which result only when the correct angle of attack is achieved, and for just about anything you wish to do in a given type there is only one corresponding AOA to fly it at, irrespective of the WAT. Best rate, best angle, best glide, min sink, and a LOT more.

The trick here is to learn the AOA's for your type....and I suspect this will only come by ASKING those who are responsible for training on your type.

Incidentally, I recently had reason to conduct two test flights, one in a factory new aircraft, and one on an aircraft fresh out of maintenance. Both schedules included confirming the AOA indication at which the stick shaker and push triggered. In all configurations in both aircraft the events triggered within less than 1% of the manufacturer margins.Clearly it is an accurate indicator.

Its only limitations? It requires electrical power, and anti icing.
Industry limitations? We need to be taught how to make best use of it!

Bis47

If only things were that simple!

Aircraft performance is much more complex than simple aerodynamics theory.

Engine efficciency is an important element, and this one is a function of many intricate factors.
To start with, forget about thrust being in a direct, constant ratio to fuel flow ....
Then, give me please that unique AOA for best rate of climb with a jet ? ...

Wind is another important factor when it comes to flying best range, best angle of climb, best glide ...

When it comes to keeping a decent safety margin above stall, and especially when you don't have two big engines responding immediately to very sensitive sensors, wind gradiant, and gusts are then of prime importance as well ...

Up to now, I don't know of a single instrument, nor of a single computer program that would dispense a crew member of being a knowledgeable pilot.

Shame on the manufacturers for not puting emphasis on the kind of graph that is dispayed here (Page 148 of this thread)
Shame on the authorities for not making it mandatory.

bearfoil

"....and the rest of the flight was uneventful."

Aren't two running engines MEL? Right then.

Max Angle

The "rest of the flight" might well have been a return to land which was "uneventful".