Posts about: "Reverse Thrust" [Posts: 8 Page: 1 of 1]¶

Nick Thomas

... I think am right to assume there were no spoilers...

Correct.

...so on landing did the act of bring the nose down spoil the lift...

Yes, as with most conventional aircraft, reducing the aircraft pitch attitude (once the main wheels were on the runway) would reduce the angle-of-attack and therefore reduce the amount of lift being generated by the wing. Modern aircraft wings are very efficient and will still be generating a considerable amount of lift during the landing roll, even as the aircraft slows down.

Put simply, spoilers and/or lift dump systems are required to destroy this lift, in order to get as much of the aircraft weight as possible on the main landing gear, which, in turn, allows greater pressure to be applied to the wheel brakes before the wheels start to lock-up and the anti-skid units activate to release the applied brake pressure.

Concorde\x92s wing however developed very little lift at zero pitch attitude, so, once you had landed the nose wheel, there was no need for spoilers.


...is that the reason why the non flying pilot pushed the yolk forward once she was down?...

No.

The reason was that using reverse thrust on the ground on Concorde caused a nose-up pitch tendency, strong enough to lift the nose. The procedure was the handling pilot would call Stick Forward as soon as she had landed the nose wheel and the NHP would apply forward pressure on the control column to make sure the nose didn\x92t rise.

If the handling pilot applied reverse thrust before the nose wheel was on the ground, things could get very awkward very quickly.

Firstly, the nose would probably rise, quite possibly beyond the power of the control column to lower it. Secondly, the wing would still be generating (some) lift and so only reduced wheel braking would be available before the anti-skids kicked in, and the amount of runway left would be diminishing faster than normal.

The solution was to reduce to Reverse Idle power until the nose wheel was back on the runway, however, in the heat of the moment it was very easy to go through Reverse Idle and on into Forward Idle. Not only would this again hinder the deceleration of the aircraft, but it would also run the risk of scraping the reverser buckets on the runway (as the buckets moved from the reverse thrust position to the forward thrust position) so tight were the clearances between the buckets and the runway on landing.


Best Regards

Bellerophon

Great thread which I am thoroughly enjoying.

I seem to recall that Concorde was certified for the use of reverse thrust in the air. I also recall that it was "problematic".

Would any of the contributors like to expand?

I did experience reverse thrust (in flight) once and, as I recall, we needed to get down somewhat quicker than normal.

From my usual seat (25A) the airframe vibrated a good deal and you could feel that the descent was more rapid than usual.

However, after getting down we had to go twice (or maybe 3 times) round in the hold before lining up.

I always looked forward to holding as it was a little bit like being in a race car with the aircraft being powered round the loops all the time much like you would throw a go-kart round the track with full throttle and opposite lock. Normally I was out of luck as we usually went straight in.

This thread deserves an award...

I'm not a professional pilot, just a humble owner of a PPL with a very strong interest in aviation and a long time reader here (esp. in the Tech Log board). I've never posted here, because I prefer to read and learn from those who know it better, but this thread has finally managed to lure me out of lurking mode
Like in this video?
YouTube - Concorde late 32 landing at Leeds/Bradford Airport

There is a strange high pitch sound that kicks in for about a second in the same moment the nose wheel makes contact with the ground and before the actual reverse thrust sound can be heard.

Thanks to all for sharing all this information about one of the most fascinating machines ever created by human mankind.

Each engine had associated with it a set of lights , Blue, Amber, and Green

BLUE reverse light --- this reflected the correct operation of the
reverse thrust.

Flashing, rev selected but buckets in transit
On steady reverse selected and achieved

Amber Configuration
[CON] light----------- ON if reheat fails with no loss of engine RPM
On if reverse selected and primary nozzle greater
than 15%

Green Go light---------- This light monitored the engine for correct power
for take-off in that

Fuel flow and P7 had to match or exceed a pre
calculated figures, which were preset on their
individual gauges prior to take off.

The secondary nozzles had to within their
take-off limits

The CON light is off

In the case of No 4 engine the N1 limiter has
returned to normal position

Now normally there was a call of 100kts and at that point there had to be 4 green GO lights illuminated otherwise the t/off would be aborted. There was a concession to this in that if runway/ conditions /weight allowed the takeoff could continue with only 3 green lights illuminated at 100 kts as long as the
affected basic engine was OK[ this covered the loss of one reheat]

The green lights were considered necessary if the aircraft was using a rough runway and nose nodding could interfer with correct engine instruement monitoring and were also handy as the pilots could at a glance check whether they had at least minimum eng power for t/off.

To keep things simply their use was standard on all T/offs rough or otherwise

Fuel Saving Landing

Requirements :

• Manual landing, at V REF , only
• Minimum of one autothrottle operative at start of approach
• Contingency power available
• Specific fuel distribution achieved
• Record in Maintenance Log

Not permitted with :

• Slippery runway
• Precipitation covered runway
• 3-engine ferry
• 2-engine approach and landing
• Reduced noise approach
• Fuelled with wide-cut fuel
• Secondary nozzle locked out
• Brake unit isolated
• Total loss of Electric Trim
• Total loss of Pitch Stab
• Total loss of Electrical Signalling
• Suspected tyre failure

Notes

3-engine landings were permitted. For all landings the landing gear would be lowered earlier than normal to ensure the brakes were stone cold to start with, maximum reverse thrust would be used on landing, and braking modulated so as to use (nearly) all of the full length of the runway. Landing performance figures at 130,000 kgs were in the performance manual for most runways. Any runway for which this procedure had not been pre-authorised required some rather tedious calculations, using the generalised basic data and graphs found in the performance manual.

If manual performance calculations were necessary, the F/E and I usually seemed to find that another problem that required our urgent and undivided attention had come up, and we would reluctantly be compelled to hand over all the manuals, charts and graphs for the F/O to perform the calculations!

If the aircraft had an AFT ZFW CG (perhaps loaded with a lot of heavy bags in the rear hold), and given the specific fuel distribution requirements for a fuel saving landing, it was possible that the landing weight might have to be reduced below 130,000 kgs, in order to achieve a landing CG of 53.5%.

After landing, record the actual landing weight in the Maintenance Log using code 2899XXOO, sign it, and then leg it swiftly, to avoid M2Dude and the boys, who somehow always managed to imply that you were responsible for anything that had gone wrong with their pride and joy since they last handed her over to you!

Reasons

The clue is in the name! A possible saving of roughly 5,200 gallons of fuel, nearly 19,000 kgs, which need not be jettisoned, thus reducing the time spent in the air before re-landing, fuel costs and pollution.


Best Regards

Bellerophon

Reverse Thrust in the air - Limitations

• Inboard engines (either or both) only
• Idle power only
• Between 30,000 ft - 3,000 ft AGL only
• Subsonic only
• Max speed 370 kts over most of the allowable range
• Min speed 250 kts above 15,000 ft
• Min speed 225 kts below 15,000 ft
• 4 minutes only

The descent profile was planned without the use of reverse thrust, but it was available, and used, when required.

The principal benefit of reverse thrust in the air, in my view, was the ability to reduce speed quickly in a shallow descent, whilst keeping the aircraft attitude (and so the cabin floor) substantially level. Passengers found this more comfortable than using reverse thrust, at a constant IAS, to achieve a very high rate of descent, with the consequent steep nose down attitude.

If a runaway bar trolley, dragging a stewardess behind it, thumped into the back of the flight deck door, you had probably overdone the nose down attitude!

4 min limitation, of my memory serves, is because reverse thrust blocks off the cooling air flowing over the engine mounted accessories. The limitation is then to stop them cooking up.

Regarding an earlier question, you really need a flight crew member to answer, but looking at the RHS panel on the Concorde Heritage site it looks to me that the symbol is the landing gear indication - nose, two mains and a tailwheel. Haven't a clue what the other indication might be.