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747 Crash At Brussels

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747 Crash At Brussels

Old 1st Jun 2008, 15:56
  #181 (permalink)  
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FE Hoppy;
In such a case "you are on your own".
Concur fully - you're essentially in "test pilot territory". Although it is interesting from a hangar-flying pov, raising the notion as "an issue" is a non-sequitur, largely irrelevant to "airline pilot territory". The outcomes you described are logical conclusions to the forces at work in such circumstances and are not associated with skill level.

WRT to such a discussion and practising RTOs after V1 and then losing a second engine, (what about the twin-engine case?... ), the AF Concorde accident immediately comes to mind. They knew there was mention of fire very late in the takeoff roll. From the preliminary report, (which is all I have a copy of):

"At 14 h 42 min 31 s, the PF commenced takeoff. At 14 h 42 min 54 s, the PNF
called one hundred knots, then V1 nine seconds later.

"A few seconds after that, the right front tyre on the left main landing gear was destroyed,
very probably after having run over a piece of metal. The destruction of
the tyre resulted in large pieces of rubber being thrown against and damaging
parts of the aircraft.

"At 14 h 43 min 13 s, as the PF commenced the rotation, the controller informed
the crew the presence of flames behind the aircraft. The PNF acknowledged this
transmission and the FE announced the failure of engine n° 2. The recorded parameters
show a momentary loss of power on engine n° 1 that was not mentioned
by the crew. Eight seconds later the fire alarm sounded and the FE announced
that he was shutting down engine n° 2. The fire alarm then stopped. The PNF
drew the PF’s attention to the airspeed.

"At 14 h 43 min 30 s, the PF called for landing gear retraction. The controller confirmed
the presence of large flames behind the aircraft."
I don't think any of us need carry the discussion further concerning the decision the captain faced - it was likely understood once they knew the gear couldn't be raised.

edited to provide a link: As a further interesting point, the FAA produced an excellent paper on RTO's some years ago (1994 or so) entitled, "Takeoff Safety Training Aid", Section 2 of which is available here.

Last edited by PJ2; 1st Jun 2008 at 16:26.
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Old 1st Jun 2008, 16:27
  #182 (permalink)  
 
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tgdxb
When I first flew the B747, the cross-wind limits for take-off was 40 knots - now it is 30 knots.My opinion of the statement from " a pilot-instructor" is that it is inaccurate. Heathrow's decision to end the use of runway 05/23 was probably more to do with expansion plans than the need for a cross-wind runway.

PJ2
from your cutting of the Concorde CVR/FDR didn't it state that the pilot had already commenced rotation when the observation from ATC was received? At that point, the Captain would only be aware of a problem with one engine, as practised regularly in the simulator.

We must remember that in the take-off calculations, the determination of V1 is 'theory'. In practice, the actual take-off weight and the actual wind component, temperature and pressure, as well as the runway surface condition, tyre and brake wear, could be detrimentally different. Using the calculated V1, the assumption that a RTO before this speed is reached, would result in the a/c stopping on the runway, also requires rapid recognition and correct actions.
Until the latter is made known, it is all speculation.
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Old 1st Jun 2008, 16:49
  #183 (permalink)  
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point8six;
that the pilot had already commenced rotation when the observation from ATC was received?
Yes. I'd have to take a look at the final report to see if #1 was exhibiting problems at rotation - it certainly did soon after. As you say, and as is the point of the post was, at/near/past V1 "correct" decisions are more closely determined by circumstances and outcomes than the books.

Clearly, practising/training for an RTO after V1 may be something that many may personally advocate for reasons already known, some stated in the thread, but the fact is, successful outcomes are rare, and, there is no basis in certification or numbers in the AOM for such a decision - I think that's the only point.
Until the latter is made known, it is all speculation.
Agree, of course.
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Old 3rd Jun 2008, 17:25
  #184 (permalink)  
 
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N704CK aborted take-off

Discovering the thread to-day, I agree that all relevant information but one were quoted from the local media.

The pilot in charge was well aware that he would take off from runway 20, as he requested permission to back track to the threhold to use the maximum available length instead of joining 20 at the first intersection.

Various computations shown on Luchtzak confirming that the runway length was not too short providing that the entered weight was correct.

Regards

Willy
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Old 4th Jun 2008, 11:26
  #185 (permalink)  
 
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BelgianBoy,
Maybe I miss a point, but reading the extract appended, it very much looks to me like the rwy was not really sufficient. It is approximately 2,900 m long & I remember cockpit crews' comments saying that you may reach V1 on a longer distance than calculated.

Following is extract from Luchtzak:
(Simplistic KISS) recalculation:
70.000 Kg Fuel (FOB) (80.98% Max) = Runway Required (No wind, ISA, Dry, Unsloped) 2583 meters
Extra safety margin V1 @ 144 kts = 5.45 seconds ! (404 meters)

80.000 Kg Fuel (FOB) (83.67% Max) = Runway Required (No wind, ISA, Dry, Unsloped) 2669 meters
Extra Satefy margin V1 @ 144 kts = 4.29 seconds ! (318 meters)

Note: aviators don't practice Rejected Takeoff (RTO) situations AFTER V1 (hostile Test Pilot environment). After passing V1 and (for example) a second engine (N-2) on the same side fails, you're going sideways and definitely not up !! Final result (if you're able to maintain N-2 directional control): visiting the runway end and fence, as in this case.
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Old 4th Jun 2008, 11:58
  #186 (permalink)  
 
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tgdxb, even according to the calculations you provided, it seems to me that the runway was sufficient. Or is there a point I do not understand?
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Old 4th Jun 2008, 12:04
  #187 (permalink)  
 
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HFinn,
I do not want to enter an argument, but here is my rationale:
1) rwy length is 2,900 m
2) calculations @ 70KT or 80 KT fuel load lead to a bit more than 2,900 m (including safety margin to break)
3) furthermore, v1 being a theoretical calculation, there is no guarantee that it will be reached at the calculated distance.
Based on the above--and assuming I am not making a big mistake--it looks to me there was no real safety margin.
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Old 4th Jun 2008, 12:12
  #188 (permalink)  
 
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My rationale is that if runway required is either 2583 or 2669 meters, it is in both cases less than the 2900 m available. It will be an endless discussion whether or not and how theoretical figure V1 is. In any case V1 is what we have to live with, and base our calculations on.
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Old 4th Jun 2008, 12:57
  #189 (permalink)  
 
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N704CK aborted take-off

H Finn,

I consider you put it wright.

Runway 20 didn't offer a great safety margin but should theoretically be long enough for safe take-off.

Reading this morning the report on the Halifax MK crash, I would just remind that if spares were carried on board their weight should be taken into account what we don't know at this stage of the investigations.

All pilots interviewed by the media when 02 and 20 were extensively used stated that the length is sufficient but the safety margin reduced.

Regards

Willy
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Old 4th Jun 2008, 13:04
  #190 (permalink)  
 
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Preliminary report of the Air Accidents Investigation Unit of the Belgian Federal Ministery of Transport at:

in Dutch
http://www.mobilit.fgov.be/data/pbs/p080604an.pdf

in French:
http://www.mobilit.fgov.be/data/pbs/p080604af.pdf

(My) Summary of preliminary findings:

- no apparent problem as regards the use of RW 20/02 for this flight - all flight data correctly entered in flight computer
- brief loss of power on one engine at about (sic) V1 associated with loud bang and flames, as confirmed by crew cq witnesses/controller.
- 2 sec after the bang, thrust was reduced to idle - no reverse thrust commanded - vigourous braking started and maintained until final stop
- preliminary on site endoscopic inspection of engines 3 and 4 - although very incomplete - didn t show any damange in the HP or LP compressor, HP turbine nor of the fan blades
- cargo found correctly stowed after impact - actual cargo on board being compared with load sheet data
- no catastrophic structural damage before final impact (4m drop)
- L1 door blocked due to structural damage on impact, 'service' door used to evacuate

FDR and CVR will now be analysed further , and engines will be recovered from the wreckage and further investigated upon.

If you need more info or translation, just ask!

Last edited by borghha; 4th Jun 2008 at 14:08.
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Old 4th Jun 2008, 17:38
  #191 (permalink)  
 
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"The question in aviation is not how much runway is necessary to take off and land an airplane. The question is how much runway is necessary to make that operation safe." Charles Lindbergh, from his book, "We." 1926
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Old 5th Jun 2008, 07:27
  #192 (permalink)  
 
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"The question in aviation is not how much runway is necessary to take off and land an airplane. The question is how much runway is necessary to make that operation safe." Charles Lindbergh, from his book, "We." 1926
And the answer is given in great detail in CS25 or FAR 25. In this case it would appear there was plenty of room for a safe take off even with a brief reduction in thrust associated with a loud bang and flame.(we call this a surge). There was not however enough room for a safe stop from 2 seconds after "about V1". But to be quite frank there wasn't supposed to be!!!!!


sgg come on down.
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Old 5th Jun 2008, 10:12
  #193 (permalink)  
 
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Why No Reverse?

Why did they not use reverse? Someone earlier stated that the stopping distance from V1 is calculated without considering reverse but it still seems to be a serious failure on the part of the crew. Just because the stopping distance calculation doesn't include the use of reverse, does it make use of reverse imprudent? I don't think so.
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Old 5th Jun 2008, 14:06
  #194 (permalink)  
 
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Pls correct me if I am wrong, but from the threads I get the feeling that the TO distance is virtually the only important parameter, i.e. as long as the a/c can take off within the rwy limits everything is fine. If this is true, why specifying safety margins then?
Apologies if this question sounds dumb but I am not a professional pilot & I am confused. What is the point in specifying a safety margin?
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Old 5th Jun 2008, 14:44
  #195 (permalink)  
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Feeling, tgdxb

Take-off distance is a computed value, based on a number of measured limits. Everything about Flight is about safety. With gobs of experience, a Pilot's calculations and conclusions may "seem" "casual" to an inexperienced observer. Flying has everything to do with Knowledge, which is accumulated. When experience is present, the quality of performance is characterized as wisdom. Knowledge plus experience equals wisdom. Wisdom can seem to be anything but when judged by someone without it. V speeds are velocities, speed and direction expressed as rate. If you think (feel) something may be off, you will have to debate with a like amount of wisdom. It is this paradigm that gets Pilots at times the reputation of arrogance. It is generally undeserved. I mean this with the most respect tgdxb, I understand your position regarding the Airport, and I sympathize.
 
Old 5th Jun 2008, 15:50
  #196 (permalink)  
 
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What is the point in specifying a safety margin?

Safety margins are applied to performance data because the calculations involve many assumptions; the margin also considers some variability in the aircraft (engines, brakes, tyres), runway surface (how slippery is ‘wet’), crew reaction, etc, etc. Certification and operational requirements are place markers on which everyday operations have to be built; where possible they cover a reasonable range of the variables and to a lesser degree, account for opportunities for error. The resultant provides an acceptable margin of safety (for public operation) in all routine operations, judged as not taking unacceptable risks.
Take off distance is not necessarily the same as the distance needed to accelerate and then stop from a critical speed.

A rejected takeoff scenario just before V1 is a critical area where the margins are minimal. The identification of the components of a situation on which the decision to stop is perhaps the weakest area.
A fire warning or engine run down is relatively clear cut, but determining the source and effect of a ‘bang’ is complicated. A takeoff ‘surge’ in large engines is normally associated with a big bang (but not always), and the noise could be a tyre, load shift, or a galley door.
Confirming an engine surge – leading to a sustained loss of power, is very complicated. The indications are not always evident on instruments, or if present not always seen; all of this takes time which is a premium.

Why wasn’t reverse used? We must wait and see what the crew have to say, but humans react in unusual ways in stressful situations. Perhaps more so where the decision to stop is made on a particular belief (engine failure) and then coupled with an erroneous belief (asymmetric reverse not authorised, or reverse not required) then the safety margins rapidly disappear.
Attempting to stop beyond the critical point (V1) is fraught with danger; more so if reverse is not used.
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Old 5th Jun 2008, 17:22
  #197 (permalink)  
 
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N704CK aborted take-off

http://www.lesoir.be/actualite/belgi...5-603435.shtml

In French.

To summarize, the writer states that the Service fédéral de la Mobilité concluded that a loss of power on one engine was experienced during take-off.

Based on the first reports (Pilot in charge and ATC), it is likely that an engine surge occurred which I haven't found in the report published yesterday.

As for the safety margin in the industry, the purpose of taking into account a safety factor which might range from 1,5 to 5 times is to cope with lack of accuracy of the data fed to the computation. Safety coefficients decreased last century with the extended use of computers.

Comments welcome and regards.

Willy
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Old 5th Jun 2008, 17:58
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Why did they not use reverse? Someone earlier stated that the stopping distance from V1 is calculated without considering reverse but it still seems to be a serious failure on the part of the crew. Just because the stopping distance calculation doesn't include the use of reverse, does it make use of reverse imprudent?
Still so much assumption. You're assuming that the crew made a mistake, or failed. How do you know that the crew was or was not able to deploy the reversers at all? Or the reasons? You don't. Therefore, to suggest that not deploying reversers or ground spoilers was a "failure" is an assumption in error, based on a lack of fact.

Wait for the facts.
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Old 5th Jun 2008, 23:25
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I am not saying this is the case in this accident, however there has been a considerable push at my airline (and others I would imagine) to use only idle reverse on landing to 'save fuel and wear and tear on the reversers'

Unfortunately I see this becoming such an ingrained habit, many times I have been in situations where max reverse is appropriate for the conditions, e.g. short, wet, slippery runway and my FO is only using idle reverse.

I prebrief now that in these conditions, as is specified in our flight manual, to use max reverse and get stuck into MAX right away, even so they are hesitant to do so as if they will break something.

This is something I see in both seats, I realize an RTO is a different animal but
that ingrained habit of not using max reverse can be hard to break with for some.

Having 'grown up' on older jets always using max reverse I find it hard to rationalize 'fuel saving and wear and tear' against the possibilty of an overrun.

Long, flat dry runway is one thing, perhaps with noise considerations, otherwise, use EVERY AVAILABLE STOPPING DEVICE.
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Old 6th Jun 2008, 01:14
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That's not the case for this particular operator, which uses reverse freely as needed on any normal landing, and which calls for maximum reverse thrust during a rejected takeoff.
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