Rise and Fall of Concorde
Sylvia Else
specific subject.
The program was more interesting than I expected. The fact that BA
discovered that it was charging less for tickets than its passengers
thought they were paying was quite surprising.
A couple of comments that were made, then not followed up.
One was that the aircraft was 1.5 tonnes (or perhaps tons), overweight
when it started the takeoff roll, partly because of a 500kg unaccounted
for baggage load, and partly due to less fuel being used during taxying
than expected. However, there was talk of the flight engineer moving
fuel to compensate. It wasn't clear to me whether what they really meant
was that the aircraft was above the weight originally anticipated, or
whether it was actually above its certified takeoff weight.
The other was that it left the ground while travelling too slowly. The
latter could I suppose be the crew's response to the aircraft drifting
off the runway.
It was mentioned that the gear wouldn't retract, but again there was no
further discussion.
So could the Concorde have gained height on two engines if it had been
1.5 tonnes lighter, and rotated at the correct speed, even with gear
that wouldn't retract?
I'm sceptical about kerosene being ignited by a spark in a situation
where it's pouring out of a fuel tank.
Sylvia.
JB
> One was that the aircraft was 1.5 tonnes (or perhaps tons), overweight
> when it started the takeoff roll, partly because of a 500kg unaccounted
> for baggage load, and partly due to less fuel being used during taxying
> than expected. However, there was talk of the flight engineer moving
> fuel to compensate. It wasn't clear to me whether what they really meant
> was that the aircraft was above the weight originally anticipated, or
> whether it was actually above its certified takeoff weight.
The aircraft was over the performance limited weight for the
conditions. If I recall the original report correctly, they basically
should have gone to the other end of the runway. In practical terms
though, it most likely made little difference to the performance.
>
> The other was that it left the ground while travelling too slowly. The
> latter could I suppose be the crew's response to the aircraft drifting
> off the runway.
Early rotation in a delta is especially dangerous, as it puts you into
a very high drag area. If you don't have enough power to accelerate
out of it, then, well you know the results.
>
> It was mentioned that the gear wouldn't retract, but again there was no
> further discussion.
I don't think they've ever been able to resolve just why it wouldn't
retract.
>
> So could the Concorde have gained height on two engines if it had been
> 1.5 tonnes lighter, and rotated at the correct speed, even with gear
> that wouldn't retract?
>
No. And even if the gear did retract, I'd expect it still would have
crashed. But, it may have done so a little later.
> I'm sceptical about kerosene being ignited by a spark in a situation
> where it's pouring out of a fuel tank.
I'm sure it wasn't. But remember, when the sequence started there were
a couple of afterburner exhausts out there. They would be more than
capable of igniting the fuel, and once burning it would be self
sustaining.
RT
"JB" <jb.3...@gmail.com> wrote in message
news:e6691183-86d7-488b...@y12g2000prb.googlegroups.com...
>> I'm sceptical about kerosene being ignited by a spark in a situation
>> where it's pouring out of a fuel tank.
>
> I'm sure it wasn't. But remember, when the sequence started there were
> a couple of afterburner exhausts out there. They would be more than
> capable of igniting the fuel, and once burning it would be self
> sustaining.
Yes, the kerosene was pouring out of a tank. But into a high speed
airstream. The resultant cloud of vapour could have been ignited by rubbing
two boy scouts together, let alone a red hot afterburner exhaust!
David Varidel
> A couple of comments that were made, then not followed up.
Page 50 onwards of the Jul-Aug (issue 75) copy of the crash comix has a good
debrief.
David Varidel
Oz...@crackerbox-palace.com
Mag.
Or if you're a licernced pilot, it should be on you desk or coffee
table.
http://www.casa.gov.au/scripts/nc.dll?WCMS:STANDARD::pc=PC_91346
OzOne of the three twins
I welcome you to Crackerbox Palace.
who where
wrote:
>Sylvia Else wrote:
>> One was that the aircraft was 1.5 tonnes (or perhaps tons), overweight
>> when it started the takeoff roll, partly because of a 500kg unaccounted
>> for baggage load, and partly due to less fuel being used during taxying
>> than expected. However, there was talk of the flight engineer moving
>> fuel to compensate. It wasn't clear to me whether what they really meant
>> was that the aircraft was above the weight originally anticipated, or
>> whether it was actually above its certified takeoff weight.
>
>The aircraft was over the performance limited weight for the
>conditions. If I recall the original report correctly, they basically
>should have gone to the other end of the runway. In practical terms
>though, it most likely made little difference to the performance.
It was my understanding - and I stand to be corrected - that it was
over its MTOW (by that 1/2 tonne plus unburnt fuel), had a slight
tailwind, and had a CofG aft of the envelope. The fuel transfer was
to mitigate that last.
>>
>> The other was that it left the ground while travelling too slowly. The
>> latter could I suppose be the crew's response to the aircraft drifting
>> off the runway.
>
>Early rotation in a delta is especially dangerous, as it puts you into
>a very high drag area. If you don't have enough power to accelerate
>out of it, then, well you know the results.
The early rotate has been attributed in some arenas to the track
deviation to the left and the 747 at the hold point - which it just
cleared by some 30ft if the report is accurate. In turn, the track
deviation has been attributed by some to the missing undercarriage
spacer. The French bureau's investigations seemed to be somewhat
dismissive of the importance of the missing spacer.
In the doco, the views of the French lawyer were "interesting", as
were the observations that the fire was evident some 700ft before the
Continental debris was reached.
In the FDR plots, there is a "wheel/tyre warning" which activates when
the airspeed has dropped to zero .... One wonder what it takes to
activate that alarm.
who where
<syl...@not.here.invalid> wrote:
(snip)
>The other was that it left the ground while travelling too slowly. The
>latter could I suppose be the crew's response to the aircraft drifting
>off the runway.
According to the FDR plots, computed airspeed was a tad over 200kts at
liftoff about 202 AFAICT. It averaged 200kts for the 30 seconds after
liftoff. The highest it reached was ~ 212kts about 45 seconds after
liftoff.
who where
D:
"When Marty pulled back on the control column to raise the nose and
take to the air - the process pilots call 'rotation' - the plane's
airspeed was only 188 knots, 11 knots below the minimum recommended
velocity (VR) required for this manoeuvre.
But he had no choice: the plane was about to leave the tarmac
altogether and plough into the soft and bumpy grass at its side. That
might have ripped off the landing gear, leaving Concorde to overturn
and blow up on its own. If not, the 747 lay straight ahead. So he took
to the air, although he knew he was travelling too slowly, which would
impair the damaged plane's chances of survival."
(Source: Guardian Unlimited)
matt weber
<syl...@not.here.invalid> wrote:
>Thanks to Graham for the heads up - I've posted this anew with a more
>specific subject.
>
>The program was more interesting than I expected. The fact that BA
>discovered that it was charging less for tickets than its passengers
>thought they were paying was quite surprising.
>
>A couple of comments that were made, then not followed up.
>
>One was that the aircraft was 1.5 tonnes (or perhaps tons), overweight
>when it started the takeoff roll, partly because of a 500kg unaccounted
>for baggage load, and partly due to less fuel being used during taxying
>than expected. However, there was talk of the flight engineer moving
>fuel to compensate. It wasn't clear to me whether what they really meant
>was that the aircraft was above the weight originally anticipated, or
>whether it was actually above its certified takeoff weight.
The rate of fuel consumption is so high (13+ pounds per second) with
the re-heat on, and 100% power that while the aircraft may have
exceeded MGTOW, it would in fact fall below MGTOW in less 3 minutes at
full re-heat.
I would argue that given that the aircraft weight is rarely known to
better than 1%, a 1.5t error is in fact within the margin of error
(almost 2t). So while it is interesting, is is also very unlikely to
have had a measurable impact on aircraft performance, or the accident.
>
>The other was that it left the ground while travelling too slowly. The
>latter could I suppose be the crew's response to the aircraft drifting
>off the runway.
This is especially problematic for delta wing aircraft. L/D detiorates
rapidly with reduced airspeed and increased angle of attack. At
takeoff at nominal Vr, it is actually miserable, reducing Vr means a
higher angle of attack, and even worse L/D.
Consider this for a moment.
747-400 at MGTOW 875,000 pounds, thrust 232,000 pounds.
Thrust to weight .265
L/D for a large widebody 'clean' is about 17.
Concorde at MGTOW 408,000 pounds, thrust 162,000 pounds
thrust to weight .397
The fact that the aircraft cannot even maintain altitude on 2 engines
even with emergency thrust augmentation at Vr implies an L/D of less
than 5!
It is a sufficently nasty problem that the flight management system is
designed to run the engines well past 100% for brief periods in the
event of an engine failure. A BA Concorde driver told me that in the
event of a single engine failure on takeoff, the first priority is to
get the airspeed above 285kt, and then worry about gaining altitude.
The higher speed means you can survive another engine failure, and
also gives you a better L/D to climb with.
>
>It was mentioned that the gear wouldn't retract, but again there was no
>further discussion.
>
>So could the Concorde have gained height on two engines if it had been
>1.5 tonnes lighter, and rotated at the correct speed, even with gear
>that wouldn't retract?
The answer is NO. Minimum safe speed on 2 engines at MGTOW is
approximately 285kt. This is well above Vr.
Concorde's minimum drag speed at MGTOW is about 400kt!! (From
Aviation Week and Space Technology)
If you have only two engines, you either find a way to get above
285kt, or you YOU WILL CRASH. Twin engine failue below 285kt airspeed
is a black hole in the flight envelope!
>
>I'm sceptical about kerosene being ignited by a spark in a situation
>where it's pouring out of a fuel tank.
It was a warm day, and the high speed airflow is probably pretty good
at making the leaking Jet A into a very fine mist, which is far more
likely to ignite than a pool of Jet A on the ground.
>
>Sylvia.
AA
we were given a list of their restrictions. They included:
Depart from 33 unless downwind component was greater than 20KT - This
was due to the left turn from RWY 15 at departure end of runway onto
heading 030 as against departing RWY33 straight ahead for a couple of
miles and then a more gentle right turn.
An engine failure on departure 15 would require them to continue
straight ahead down the valley for approx 20NM until they had enough
height/speed for a left turn and return for a landing.
Unrestricted climb to high level (above F500) cruise climb - any lower
level off would probably result in a return to departure airport.
AA
Sylvia Else
[Sylvia Else wrote]
>> So could the Concorde have gained height on two engines if it had been
>> 1.5 tonnes lighter, and rotated at the correct speed, even with gear
>> that wouldn't retract?
>>
>
> No. And even if the gear did retract, I'd expect it still would have
> crashed. But, it may have done so a little later.
>
I've been going back over the original accident report. Back of the
envelope calculations suggest that being 1.5 tonnes lighter would have
reduced the zero rate of climb speed by 1 knot - not enough to notice.
If the gear had retracted, they'd have had some abililty to accelerate,
though given the relatively short time before the second engine failed,
it does seem unlikely they'd have reached the ZRC speed for two engines.
It appears that gear retraction is an all or nothing thing. The damage
to left gear mechanism (whatever it was exactly) prevented the nose and
right gear from being retracted as well. While it probably made no
difference in this case, one can imagine scenarios where getting half
the gear up would reduce the drag enough to change the outcome.
All a bit theoretical now, of course. It looks like it will be a long
time before we see another four engined delta-winged airliner in the
skies. Not in my lifetime, I suspect.
Sylvia.
JB
> The rate of fuel consumption is so high (13+ pounds per second) with
> the re-heat on, and 100% power that while the aircraft may have
> exceeded MGTOW, it would in fact fall below MGTOW in less 3 minutes at
> full re-heat.
Totally irrelevant. Firstly taking off above the limiting weight is a
bit of a no no anyway. Secondly, I expect it was the performance
limited TOW, not, the Max TOW. In that case, the most likely limit
would have been second segment. That extends from a few seconds after
lift off, to about a minute...so, having the weight come good after
you depart the most limiting segment isn't all that helpful.
The limits are based on the start of the take off roll, not the end,
or the point at which you start a segment.
Sylvia Else
without losing speed, but then seemed to get stuck on a knife edge,
unable to climb further, nor accelerate.
The radio altitude varied somewhat, but was above 150 feet for most of
the time.
Given a wingspan of 84 feet, I'd have thought the aircraft would have
been well out of the ground effect.
http://www.bea-fr.org/docspa/2000/f-sc000725a/pdf/appendix4p.pdf
Sylvia.
RMK
"Sylvia Else" <syl...@not.here.invalid> wrote in message
news:8crgb9...@mid.individual.net...
> I'm somewhat puzzled by the fact that it was able to climb to 200 feet
> without losing speed, but then seemed to get stuck on a knife edge, unable
> to climb further, nor accelerate.
All four engines were producing thrust after takeoff.
Then they shut down an engine!
With the gear stuck down, they just got stuck at the back of the drag curve.
Sylvia Else
>
> "Sylvia Else" <syl...@not.here.invalid> wrote in message
> news:8crgb9...@mid.individual.net...
>
>> I'm somewhat puzzled by the fact that it was able to climb to 200 feet
>> without losing speed, but then seemed to get stuck on a knife edge,
>> unable to climb further, nor accelerate.
>
> All four engines were producing thrust after takeoff.
>
> Then they shut down an engine!
I think it's clear that one engine failed before Vr. They didn't shut it
down at that point, of course, but it wasn't producing thrust.
Sylvia.
RMK
> I think it's clear that one engine failed before Vr. They didn't shut it
> down at that point, of course, but it wasn't producing thrust.
>
> Sylvia.
The engine didn't fail! It suffered a severe loss of thrust.
An engine fire in itself does not preclude a engine from producing thrust.
The only varible is how much thrust is available and how long it will last.
What we do know is once the Fire Switch is activated, the engine will shut
down.
Summary
During takeoff from runway 26 right at Roissy Charles de Gaulle Airport,
shortly before rotation, the front right tyre (tyre No 2) of the left
landing gear ran over a strip of metal, which had fallen from another
aircraft, and was damaged.
Debris was thrown against the wing structure leading to a rupture of tank 5.
A major fire, fuelled by the leak, broke out almost immediately under the
left wing. Problems appeared shortly afterwards on engine 2 and for a brief
period on engine 1. The aircraft took off. The crew shut down engine 2, then
only operating at near idle power, following an engine fire alarm.
They noticed that the landing gear would not retract. The aircraft flew for
around a minute at a speed of 200 kt and at a radio altitude of 200 feet,
but was unable to gain height or speed. Engine 1 then lost thrust, the
aircraft泅 angle of attack and bank increased sharply. The thrust on engines
3 and 4 fell suddenly.
Sylvia Else
The FDR whose link I posted seems to indicate that the aircraft
continued to climb at constant speed long after the engine had stopped
producing thrust.
Sylvia.
gregg
Gregg 35 A/B