the concorde prang

[towbar]

i know it was on fire, that pieces ruptured the tank bottoms, etc. I
also have my own idea about what caused the ruptures but this is not
about that. THIS is about how the fire caused the crash? Was there
engine failure, control failure?

[Ulick Magee]

One engine was shut down by the crew following a fire warning, shutting
it down was in hindsight a mistake as they couldn't raise the gear and
needed all the thrust they could get. Of course the fire wasn't in the
engine, but the crew weren't to know that.

The adjacent engine ingested hot gases from the fire, and lost much of
its thrust.

With gear down, effectively two engines out, and heavy, they had no
chance unfortunately.

If the tanks hadn't been overfilled (the aircraft took off above MTOW)
the rupture might not have happened.

The investigation concluded that a fire of that severity would
inevitably lead to loss of structural integrity and a crash, even if all
engines were operational.

U

[towbar]

On 2020-03-13 18:59, Ulick Magee wrote:
> On 04/03/2020 13:33, towbar wrote:
>>
>> i know it was on fire, that pieces ruptured the tank bottoms, etc. I
>> also have my own idea about what caused the ruptures but this is not
>> about that. THIS is about how the fire caused the crash? Was there
>> engine failure, control failure?
>
> One engine was shut down by the crew following a fire warning, shutting
> it down was in hindsight a mistake as they couldn't raise the gear and
> needed all the thrust they could get. Of course the fire wasn't in the
> engine, but the crew weren't to know that.
>
> The adjacent engine ingested hot gases from the fire, and lost much of
> its thrust.
>
> With gear down, effectively two engines out, and heavy, they had no
> chance unfortunately.
>
> If the tanks hadn't been overfilled (the aircraft took off above MTOW)
> the rupture might not have happened.

How would we arrive to that conclusion? Run distance?

> The investigation concluded that a fire of that severity would
> inevitably lead to loss of structural integrity and a crash, even if all
> engines were operational.

Thank you, I ate my way through the original native language trascript
back then but have forgotten many details. Two engines out is in fact a
bad omen. I can't cite wing fires but for uncontrolled wheel-well fires
the rule used to be to land in less than 5 minutes so in light of that I
suppose they would have made Bourget, albeit in flames. The overweight
was there in the numbers but was probably not a killing factor.

[Ulick Magee]

On 16/03/2020 22:12, towbar wrote:
> On 2020-03-13 18:59, Ulick Magee wrote:
>>
>> If the tanks hadn't been overfilled (the aircraft took off above MTOW)
>> the rupture might not have happened.
>
> How would we arrive to that conclusion? Run distance?

I was just going by memory, I've since re-read the conclusions of the
report, the overweight was marginal and they concluded (like the missing
gear spacer) it had no influence on the crash. The first officer's
medical was a few days expired, too. These indicated sloppy procedures
at Air France (and Continental, whose strip of metal triggered the burst
tyre.)

They were going to require a very long takeoff roll anyway, being a
fully loaded charter flight (scheduled Concorde flights were rarely
full) and were still quite a bit short of Vr when they hit the metal
strip, so there's no way they could have lifted off before hitting it.

Bad luck there was debris on the runway
Bad luck the scheduled runway inspection was postponed until after their
takeoff
Bad luck to hit the debris
Bad luck to hit the debris in such an orientation it caused serious tyre
damage
Bad luck to hit it while substantially above V1 but still substantially
below Vr
Bad luck they were at, or even slightly above, MTOW
Bad luck the tank didn't receive minor punctures as had happened before,
but a major breach in a very unusual failure mode
Bad luck the fuel ignited, probably due to damaged wheel well wiring
Bad luck they couldn't raise the gear due to gear door or wiring damage

But sometimes all the holes line up...

U

[Ulick Magee]

On 16/03/2020 22:12, towbar wrote:

> On 2020-03-13 18:59, Ulick Magee wrote:
>>
>> If the tanks hadn't been overfilled (the aircraft took off above MTOW)
>> the rupture might not have happened.
>
> How would we arrive to that conclusion? Run distance?

There was a theory put forward that if tank 5 had not been full and had
an air space above the fuel, it might not have ruptured when impacted
(the impact energy causing a compression at the impact point resulted in
an expansion further forward, which caused part of the lower surface of
the tank to burst outwards), however the slight excess over MTOW appears
to have been caused by luggage not fuel, and a fully loaded Concorde
going to New York from Paris was going to need a full or very close to
full fuel load. So the "tanks being overfilled" thing was misremembered
on my part.

U

[towbar]

Thanks, I was busy with food poisoning and coronavirus arguments :-)

When you've been around cockpits long enough (retired for 12 years now)
you know how a crew functions, that not everything is always said, that
there are fingers pointing and grunts or ahumms coughed up instead.
Having once digested the origial french transcript I figured they had
(over)heating wheels before clearance onto the runway. That couldn't
have helped, could even have made the debris 'unnecessary' so to speak.
I know what a piece of tire can do but didn't think how a full tank
could/would behave. I should have because I once accidentally hit a
small but very full diesel tank with a metal bar and a mechanical
thermometer inside it just fell off its mounts which broke, surprisingly
because it had been very well fixed. Due to fluid dynamics I'm not sure
if the tanks would really have needed to be more full than almost full
for something like what you describe to happen.

[Ulick Magee]

On 27/03/2020 01:53, towbar wrote:
>
> When you've been around cockpits long enough (retired for 12 years now)
> you know how a crew functions, that not everything is always said, that
> there are fingers pointing and grunts or ahumms coughed up instead.
> Having once digested the origial french transcript I figured they had
> (over)heating wheels before clearance onto the runway. That couldn't
> have helped, could even have made the debris 'unnecessary' so to speak.
> I know what a piece of tire can do but didn't think how a full tank
> could/would behave. I should have because I once accidentally hit a
> small but very full diesel tank with a metal bar and a mechanical
> thermometer inside it just fell off its mounts which broke, surprisingly
> because it had been very well fixed. Due to fluid dynamics I'm not sure
> if the tanks would really have needed to be more full than almost full
> for something like what you describe to happen.

I understand the aircraft had been parked for some hours before takeoff,
how did the brakes/wheels overheat?

Something that should be borne in mind is Concorde's high V1/Vr speeds
compared to other jet aircraft. This greatly increases the momentum of
any tyre fragments ejected while at or above V1. Also the thing was
basically a flying fuel tank with 100 pax along for the ride... if it
had been produced in large numbers and flown at high utilisation, we
would certainly have seen other serious incidents. There were some close
calls before.
https://en.wikipedia.org/wiki/Air_France_Flight_4590#Previous_tyre_incidents

Still, an amazing technological achievement.


U

[towbar]

On 2020-03-29 15:58, Ulick Magee wrote:
> On 27/03/2020 01:53, towbar wrote:
>>
>> When you've been around cockpits long enough (retired for 12 years now)
>> you know how a crew functions, that not everything is always said, that
>> there are fingers pointing and grunts or ahumms coughed up instead.
>> Having once digested the origial french transcript I figured they had
>> (over)heating wheels before clearance onto the runway. That couldn't
>> have helped, could even have made the debris 'unnecessary' so to speak.
>> I know what a piece of tire can do but didn't think how a full tank
>> could/would behave. I should have because I once accidentally hit a
>> small but very full diesel tank with a metal bar and a mechanical
>> thermometer inside it just fell off its mounts which broke, surprisingly
>> because it had been very well fixed. Due to fluid dynamics I'm not sure
>> if the tanks would really have needed to be more full than almost full
>> for something like what you describe to happen.
>
> I understand the aircraft had been parked for some hours before takeoff,
> how did the brakes/wheels overheat?

I can only suspect that a long taxi at high weight could have been the
cause, and if I remember correctly only one wheel was at or near limits.

> Something that should be borne in mind is Concorde's high V1/Vr speeds
> compared to other jet aircraft. This greatly increases the momentum of
> any tyre fragments ejected while at or above V1. Also the thing was
> basically a flying fuel tank with 100 pax along for the ride... if it
> had been produced in large numbers and flown at high utilisation, we
> would certainly have seen other serious incidents. There were some close
> calls before.
> https://en.wikipedia.org/wiki/Air_France_Flight_4590#Previous_tyre_incidents

210 mph tires were state-of-the art back then but I don't really know
what was being used on the Concorde. The many tire failures were in deed
a serious threat, and the others didn't need any debris on the runway
either. I'm supposing that temperature was a factor in all of them not
knowing in what proportion rotational speed and temperature each may
have played a role. For all rubber in motion the lowest temperature that
offers good flexibility is the sweet spot. Maybe that airplane should
have had deep air conditioning (freezing) units blowing the gear bogies
during preflight (perfect hindsight).

> Still, an amazing technological achievement.

no doubt

[towbar]

in retrospect I wonder if she'd still be flying if the bogies
had been blown refrigerated to -20c at every stopover
untill taxi-out?