BA Concorde Tech stop - Gander

[Shore Guy]

Not the best of explanations, perhaps.... Was he trying to say that the Concorde could not take off with full fuel because of the high temp?


Londoners experienced the hottest day in the city's history when the temperature hit 35.4 degrees C, beating the 35 degrees recorded in 1990. A British Airways Concorde was forced to make an unscheduled stop in Gander, Nfld., during a flight from London to New York to refuel because the hot weather meant it needed to carry more fuel.

The aircraft, which flies at twice the speed of sound, usually takes just three hours and 20 minutes to make the transatlantic crossing. But the detour was expected to add 90 minutes to the flight.

"When it gets this hot, Concorde has to carry more fuel because the air it is travelling through is of a higher pressure," a BA spokesman said. "It is unusual, but . . . not the first time it has happened because of hot weather."

[L337]

oooer... Hot air is less dense. Hot fuel is also less dense so you need more of it to do the same work....If you can't get more of it on, ie the tanks are already full, then a tech stop is on order.

A more technical explanation I am sure is waiting in the wings.

:)

L337

[Dufwer]

While I am not a professional pilot (yet), I'm not convinced by the BA spokesman on this one. I would have thought that if Concorde did take-off with a shortened range capacity then it would have been due to carrying less fuel. The main effect I see of the high temperatures is to increase take-off and landing distances. Higher temp means a longer take-off run for the same aircraft weight. If the temp is high enough to increase the required distance beyond what is available then less fuel (or passangers) can be carried. Anybody know what the take-off distance is for Concorde?

The only logic I see behind the spokesman words is that BA didn't want it reported that the aircraft is taking off with less fuel than normal so a bit of bs is spread around.

D

[MarkD]

Dufwer

careful now.

Remember higher inlet air temperature lowers engine efficiency too, thus lower range for your litre of fuel.

[expedite_climb]

Err, yes, but away from the ground it hasnt been that hot lately.

I don't fly trans atlantic routes, but average temps for flights across europe have been ISA + 8 to 12. Not that unusual for this time of year.

I agree with dufwer.

[Saint-Ex]

Just have a think about fuel S.G at those temperatures and you might come up with the answer.

[SRR99]

Apart from the fact that hotter air has lower density and thus produces less lift on the airframe, I believe that the primary limiting factor is the reduction in thrust from the engines.

The higher temperature and lower density of the air results in a lower mass flow through the engine and into the compressor, and thus a lower thrust. The easy answer, of course, would be to turn up the wick and burn more fuel. Indeed, the engine control system does just this when comparing the difference between a cold day and a warmer day. Eventually on a very hot day, however, this has the effect of making combustion components such as nozzle guide vanes and turbine blades a little more pliable than ideal. So, the engine control limits the amount of fuel, and hence the thrust.

According to an old version of "The Jet Engine" by Rolls-Royce, this can result in a 20% reduction in thrust at 45 deg C. I also believe, although somebody else might like to correct me, that the problem is worse on turbojets (such as the Olympus) and low-bypass engines than the high-bypass engines on many other aircraft. This is due to the relative amount of air going through the engine core and compressor compared with the amount bypassing the core.

With limited thrust, you could go for very long runways to reach take-off velocity, or you could unload passengers and bags to reduce the weight of the aircraft, or you could load less fuel. The relatively easy answer is to load less fuel, but this can necessitate a stop at a service station along the way to top up.

Between the level of science understood by this BA spokesman, and the positive spin required in Britain today, the idea of saying that the aircraft could not get off the ground within safety parameters, and therefore took off with less fuel than was needed for the whole flight, is unthinkable.

One of the main design limitations for aircraft engines is the requirement for "hot and high" take-off capability. Hot days and altitude reduce air density, so there are certain airports which engines are designed to cope with to a certain extent, but not necessarily completely. So, you might expect to see reduced loading of aircraft at airports such as Karachi, Mexico City, Denver etc. in certain conditions.

[PAXboy]

"but away from the ground it hasnt been that hot lately."

Well, on Friday it was! As mentioned in another thread, in Aircrew Notices, I was on BA 0001 on Friday 8th August. The Captain advised us that the external air temp in the FL450 upwards region was 10 degrees C hotter than normal for the time of year. This affected climb and speed. We reached Fl 575 but no higher and M2.0, advised as 1330mph by the flight deck, due to the uncommon heat and the chances of a divert to Gander were very high.

[Capt H Peacock]

Hot weather increases the desity altitude of the airfield and so impinges on the WAT limit of the aircraft.

[expedite_climb]

PAXboy - is that not what I said ?

ISA + 8 to 12. ???? 8 to 12 degrees hotter than standard ?

It appears from your experience that this is a prob for the bird. Interesting.

[norodnik]

Paxboy,

temperature is indeed critical for Concorde as higher temp = lower efficiency of the engines and therefore more fuel required for same distance.

Temperature is also watched carefully as parts of the airframe could start to melt after 130 degrees centigrade is reached. Therefore, on warmer days the mach number is reduced but as the speed of sound is greater in warmer air, there is little difference in flight time.

Finally, on the Westbound Concorde, speed indicated is usually around 1330-1360 mph on the Marilake, and height rarely exceeds 58K, so all in all you had a fairly normal flight.

[PAXboy]

Expedite: Apologies if mis-represented. I was repeating the Captains comments that the external air temp was ten degrees hotter than normal. It may be normal for that time of year but it came across as "more than normal for this time of year".

norodnik: Thanks for that, useful information. As we were approaching the acceleration point, the Captain did say that it would be a long slow climb afterwards. It was. I did not record the time to reach the max cruise height and speed but it must have been close to an hour and a half from the point at which we achieved M1.0

As to temperature on the skin. He advised that the nose cone was at 130 C.

From my point of view the only dissapointing thing about the flight was that we did not get that moment when all the stars turn into streaks of light as we make the leap to ... :8