Accidents and Close Calls Discussion on accidents, close calls, and other unplanned aviation events, so we can learn from them, and be better pilots ourselves.

Concorde 4590

Old 8th Nov 2017, 16:45
  #21 (permalink)  
 
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Well I have watched the video (great material btw, highly recommended for anyone interested in this tragic accident). I am in full agreement with Capt. Hutchinson that there were many contributing factors and that the "infamous" titanium strip was just a piece of the puzzle. I would go as far a to say that the BEA report, however comprehensive, is definitely not weighting all those factors adequately. And I would venture to say that they were both very unlucky and very lucky (they could have very well collided with the 747).

I also agree that the actions of the crew, especially pre-takeoff but also during the emergency, were subpar and not conforming to established procedures.

Yet, given the circumstances and the law of physics, and without the benefit of hindsight, there is zero chance that they would have walked away from this one. The only better outcome I can imagine is a more or less controlled crash landing in a field or on the Bourget runway, thus sparing the lives of the people in the hotel. Which, admittedly, is not negligible...
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Old 8th Nov 2017, 19:16
  #22 (permalink)  
 
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The action that caused the crash was the engine shut down. Had this action not been taken, whether it would still have crashed has not and never will be resolved. In that respect the speculation lies on whether the decision would have remained to make for Le Bourget and made a successful landing there.
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Old 8th Nov 2017, 20:09
  #23 (permalink)  
 
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Originally Posted by Chronus View Post
The action that caused the crash was the engine shut down. Had this action not been taken, whether it would still have crashed has not and never will be resolved. In that respect the speculation lies on whether the decision would have remained to make for Le Bourget and made a successful landing there.
But engine 1 surged and flamed out due to ingestion of hot gasses from the fire shortly after engine 2 was shut down......I'd say it was certain that engine 2 would have flamed out along with engine 1 if it had still been running.

In the circumstances, and in hindsight (the crew could never have known this at the time) their best chance was an RTO. Once they got in the air, with engine 2 shut down as soon as their speed dropped below 205kts (gear down 3 engine Vzrc) they were going down whatever.........their only chance would have been a forced landing in whatever clear area they could see straight ahead. I don't think either option would have ended well.

atakacs I agree the titanium strip was very convenient for the investigation. Personally I think the BEA report was a bit of a whitewash. It should have investigated the effect of the missing spacer much more thoroughly. It also should have investigated human factors and the culture within the Air France Concorde operation that allowed the aircraft to depart overweight.
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Old 9th Nov 2017, 13:59
  #24 (permalink)  
 
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atakacs: "atakacs I agree the titanium strip was very convenient for the investigation. Personally I think the BEA report was a bit of a whitewash. It should have investigated the effect of the missing spacer much more thoroughly. It also should have investigated human factors and the culture within the Air France Concorde operation that allowed the aircraft to depart overweight."

If the gear was vibrating badly, would an RTO have been initiated? The loss of #2 doomed the aircraft, regardless whether done by engineer or flame out. I agree the causes were plentiful, and the Titanium strip in my opinion was exaggerated.
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Old 9th Nov 2017, 22:22
  #25 (permalink)  
 
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Originally Posted by Concours77 View Post
If the gear was vibrating badly, would an RTO have been initiated?
If it was vibrating badly, then yes. But in this case it wasn't vibrating....at least not enough to be heard on the CVR.

The missing spacer allowed the tyre to track 3 degrees right or left of centre. My feeling is that the tyre would have been tracking off centre...ie scrubbing sideways slightly. When it hit the Titanium strip at 175kts, did the sideways scrubbing cause the tyre to tear more dramatically? Would it have burst at all if it had been tracking straight when it hit the strip or at least have failed less catastrophically? We'll never know but will always wonder.
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Old 9th Nov 2017, 22:51
  #26 (permalink)  
 
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If the gear was vibrating badly, would an RTO have been initiated?
Never having flown Concorde (sadly), this is an educated guess based on 15000 heavy jet hours (Boeing and Bus).

No, probably. A vibration with no other indications would not normally warrant a stop. My current type requires a (low speed) stop for a tyre failure but otherwise an indication on a gauge is generally required. Having said that, there’s nothing to prevent a stop call for any reason from the commander if he sees fit.
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Old 10th Nov 2017, 05:21
  #27 (permalink)  
 
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Loss of control

Loss of control was purely from flying too slow.
Co pilot was calling “speed” which indicated that he thought the captain had the wrong priority.
Captain was flying a pitch attitude that meant speed was decreasing.
Centre of lift moves forward until elevons cannot stop the pitch up and the aircraft “flips”.
Had two delta model aircraft that did the same...both unstable in pitch at low speed.
If he had flown as low as possible he would have delayed the crash but it was probably inevitable from the time he decided to prematurely get into the air but at least he would have crashed in control.
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Old 10th Nov 2017, 13:10
  #28 (permalink)  
 
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Originally Posted by Buster15 View Post
Probably best for you to read the official investigation report carried out by the French BEA. You can easily access it by Internet search.
Oh really? Because the BEA included all information and has a reputation for being unbiased... lol
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Old 21st Nov 2017, 02:54
  #29 (permalink)  
 
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Originally Posted by atakacs View Post
Not sure to follow you train of thought. Do you mean that if the aircraft was 1.5t lighter it would have accelerated faster, thus not hitting the titanium strip ?
My assumption (Knowing assumptions are dangerous) is that the crew did one of two things, or perhaps both.

1) The aircraft was overweight. This caused a number of speed related problems.
They did not recalculate takeoff speeds. According to various interviews and info regarding the accident, the captain took on something like 1 ton of extra fuel in addition to the extra baggage. They had planned for extended taxi time either due to traffic or for positioning on a different runway.

However, they did not end up burning that fuel before attempting the takeoff. The assumption is that they tried to take off at speeds calculated for a lower fuel AND baggage load.

2) The aircraft took off with a tailwind without recalculating the v-speeds AND without factoring in the tailwind component as it would affect the aircraft at the higher takeoff weight.

So one can surmise that they not only had some kind of gear problem during the takeoff roll that may have prevented them from accelerating at the normal speed, and they may have had steering difficulty while on the roll, but they also rotated far too soon due to not recalculating, maybe as much as 10 knots under the correct speed, plus the fact that they were overweight, with a tailwind not helping things, and then the engines were shut down, all while being on fire and with possible damage or debris causing drag all over one side of the aircraft.
The extra tailwind component could have been the difference between staying up and going down. They must have been below their engine out safety speed. Had they calculated correctly, the aircraft -may- have been salvageable if the fire did not consume the aircraft in the air. Had they lifted off with 5-10 knots more speed as would have been proper, they would have made their engine out speed and thus could have flown out of the death-drag curve, in theory.

In a delta wing aircraft excessively early rotation with insufficient thrust to lower the AoA results in something called aerobraking. Among other things it's used to slow down spacecraft reentering the atmosphere. It is remarkably effective at slowing down airplanes. On the runway it kills acceleration, in the air it turns you into a flying brick.


I feel bad for them but there were a lot of amateur mistakes made in allowing the aircraft to even take off in that condition. There are a million youtube videos of aircraft ranging from cessna to airbus showing the disastrous or near disastrous results of trying to take off while overweight and in bad conditions i.e. density altitude stuff. Tail strikes being the best case scenario, crashing into trees or water at the end of the runway being the more common scenario.

These guys didn't have a chance past V1 IMO. Too many bad choices.
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Old 21st Nov 2017, 12:42
  #30 (permalink)  
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I understood that they lifted off when they did to avoid running off the side of the runway and potentially into the side of a stationary 747.
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Old 30th Nov 2017, 10:22
  #31 (permalink)  
 
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Which begs the question, if they had lost good ground steering why didn't they chop the throttles while below 80 or V1. Of course everything is 20/20 in hindsight but.. One does have to wonder what the FE was doing on the takeoff roll. I wonder what the gear temp gauges were reading at 80 knots.

I dunno. There are too many things that went wrong on that flight. We can only hope that their mistakes help others to avoid repeating them. Unfortunately the official crash investigations seem to have covered up a lot of important information for whatever reason, so a lot of valuable info may be lost and we can only go by speculation, rumor and anecdotes from other Concorde pilots and people at the scene.
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Old 30th Nov 2017, 12:19
  #32 (permalink)  
 
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What this accident served to demonstrate was that a lot of sloppy practices had crept into the system, in maintenance, in flying the aircraft, and in not adhering strictly to weight and balance considerations.

The fact that the aircraft coped admirably with all these issues for many years without a mishap demonstrates that the aircraft was operating well within its limits when everything was done by the book. It was also capable of operating quite a bit beyond the book figures when required. The aircraft acquired something of a reputation for being able to handle anything that was thrown at it.

The conclusion has to be that many crews undertook flights under similar circumstances and repeatedly got away with it. Because of that, this was an accident that was bound to happen sooner or later. The Titanium strip was just an initiator in a chain of events that stretched from well before the aircraft boarded passengers to the decision not to reject take off. Nobody involved in the chain of events comes out squeaky clean.
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Old 30th Nov 2017, 14:35
  #33 (permalink)  
 
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Originally Posted by paradoxbox View Post
Which begs the question, if they had lost good ground steering why didn't they chop the throttles while below 80 or V1.
Although the missing tyre spacer was causing the wheel to shimmy, it didn't cause much steering difficulty.

The directional control problems only occurred after they hit the titanium strip, caused by the reduction of thrust on engines 1 and 2 and the drag from the burst tyre. The tyre burst at 175kts......way beyond V1. That being said, in hindsight a RTO with high speed runway excursion would probably have been their best (albeit small) chance.

As to sloppy practices.....If they were flying Concorde like that you can guarantee they were flying other aircraft like it too. The report didn't probe the culture within the airline that allowed the sloppy practices to creep in. I'd like to hope Air France did probe and develop culture/training to eradicate it.
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Old 8th Jan 2018, 13:03
  #34 (permalink)  
 
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Flight Engineer

Hi All

Just recently I watched a documentary that stated that the Flight Engineer shut the engine (on fire) down without any order to do so.

The thinking behind not shutting down an engine on fire at that critical T/O juncture that was that even an engine on fire is producing some thrust.....

Also the missing spacer on the left hand main gear meant that the Concorde veered to the left obviously and that to miss the Air France 747 waiting to cross the live runway, they rotated at a much lower speed than would have been the case normally.

Also mentioned was that under normal circumstances all Concorde flight crew only fuelled up to around 82/83% of maximum to allow for some expansion space in the tanks. The Captain on the day did recognise that he was over loaded and insisted that full (as in full) fuel was added thus leaving no spare expansion space in the tanks. (Btw I know that seems like a contradiction)

Once that piece of rubber hit the underside of the left wing, the shock wave had nowhere to go and then we see the fuel leak and subsequent fire caused by a spark from the main gear electrics.
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Old 10th Jan 2018, 15:06
  #35 (permalink)  
 
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The other reason you don't shut a running (or partially running) engine down like that, even if it's displaying a fire warning, is that you'll lose the services it provides in the form of electrical power and hydraulics.

On Concorde the undercarriage is operated by the 'green' hydraulic system. The 'Green' system is driven by pumps on engines 1 & 2. Shutting down No.2 when No.1 had failed meant they could not raise the gear, greatly adding to the drag.
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Old 10th Jan 2018, 19:00
  #36 (permalink)  
 
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A very valid point.

But I'm still of the opinion that once the tank ruptured the way it did and the fuel ignited this flight was doomed no matter what. The only better outcome they could have possibly achieved is to avoid the hotel (which, I guess, is already worth this discussion).
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Old 10th Jan 2018, 21:27
  #37 (permalink)  
 
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Originally Posted by Shaggy Sheep Driver View Post
On Concorde the undercarriage is operated by the 'green' hydraulic system. The 'Green' system is driven by pumps on engines 1 & 2. Shutting down No.2 when No.1 had failed meant they could not raise the gear, greatly adding to the drag.
The gear wouldn't retract due to an undetermined fault with the left gear.....either damage to wiring around the left gear or damage to the gear door, the investigation couldn't establish exactly what.

But they established the Green hydraulic system was functional when the gear lever was selected up and although it probably lost pressure at some later point in the flight, it couldn't be determined exactly when.

Green hydraulics or not, the gear was going nowhere.
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Old 28th Jan 2018, 13:05
  #38 (permalink)  
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I attended a lecture on the accident which was given by a former BA Concorde driver (Mr Cough knows him and may well have attended the same evening presentation, it was many years ago). IIRC, AF overfilled the fuel tanks. There was a switch that limited the tanks to about 97% occupancy however the switch was overridden and they squeezed in as much as they could. As a result, there was no air gap above the fuel and the slab of rubber hitting the tank set up a shock wave that blew out a panel further aft. Had the fuelling complied with the manual, would the tank have remained intact ? It's probably impossible to say for sure.

Are there any tech people who can comment on the tank limit and why such a limit was imposed in the operating handbook ? Are there similar limits for other aircraft and again, why are those limits there ?
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Old 28th Jan 2018, 13:30
  #39 (permalink)  
 
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Originally Posted by hoss183 View Post
Oh really? Because the BEA included all information and has a reputation for being unbiased... lol
No doubt you missed the previous post to which this response was submitted.
Whether you agree or disagree, the investigation was extremely comprehensive and covered all the relevant findings.
Regarding a number of points relating to the titanium strip being a convenient finding, this is totally incorrect. That strip was clearly the prime cause. Without that the tyre would not have disintegrated as it did. Yes there had been a number of previous tyre failures on t/o but the mass of the rubber that was released was larger and that as we now know was the cause of the damage to the wing underside resulting in the massive fuel loss.
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Old 28th Jan 2018, 17:07
  #40 (permalink)  
 
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The metal strip would have been of no consequence (would not have been run over) if the missing spacer hadn't steered the aeroplane to the left, and eventually off the side of the runway breaking edge lights.

The tank would not have burst had it not been overfilled.

Several factors HAD to come together for the accident to happen. The metal strip is no more 'prime' than any of the others.
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