Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Concorde question

Tech Log The very best in practical technical discussion on the web

Concorde question

Old 8th Sep 2010, 16:40
  #281 (permalink)  
 
Join Date: Mar 2007
Location: Cardiff UK
Age: 65
Posts: 118
Hi Exwok, am interested in the fact that Concorde proudced very little lift before rotation. As am SLF I may be mistaken but I can understand that on landing she was pitched up about 10 degrees and obviously on take off this was not the case so there would be little lift. So I presume the high angle of attack is how lift was maintained at slow speed. Therefore on rotation how were the forces that lifted the nose wheel generated?
Regards
Nick
Nick Thomas is offline  
Old 8th Sep 2010, 18:05
  #282 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
Another IPhone answer, so apologies for rubbish post. On rotation the process was about as subtle as a coffee grinder. As the elevons were raised the downforce against them caused the aircraft to rotate about the mainwheels, raising the nose, increasing angle of attack and finally allowing the wing to generate some lift. Apologies again to all

Dude
M2dude is offline  
Old 8th Sep 2010, 19:52
  #283 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,319
Nick Thomas,
I think M2dude has already answered your question.

Anyway, herewith a few very crude scribbles to further illustrate your question and his answers.



Simplistically, an "old-fashioned" airplane has an asymmetric wing profile (at take-off even more so because of the flaps). Such a profile will start producing lift as soon as you start moving, and if you had enough take-off space, the aircraft would fly off the ground even without rotating it - in practice you rotate to get a more optimum angle of attack, more lift and a better climb speed to "get over the fence".



The Concorde wing, in the same circumstances, is little better than a big flat plank, and will not produce any lift at all, or at least far too little to carry the aircraft.



As M2dude already said, raising the elevons produces enough of a downforce at the trailing edge to lift the nose, and from there on the wing does start producing lift.
Not quite conventional lift, but "vortex lift" (a different subject), but lift just the same.

CJ

Last edited by ChristiaanJ; 8th Sep 2010 at 20:42. Reason: Resizing a picture, typos
ChristiaanJ is offline  
Old 8th Sep 2010, 21:47
  #284 (permalink)  
 
Join Date: Sep 2007
Location: UK
Age: 53
Posts: 124
And just to round this off.......you will see from the above that the final insult to a Concorde tyre comes at rotate when (owing to the download caused by the up-elevon input) the download on it is actually increased until the rotation passes 7 degrees or so, and vortex lift starts properly.
EXWOK is offline  
Old 8th Sep 2010, 21:53
  #285 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,319
Re the Concorde disaster and bizdev's question, I've opened a separate thread on the subject.

Concorde Paris crash, questions, facts, opinions

Can we post any specific questions and discussions on that specific subject over there, please ???

CJ
ChristiaanJ is offline  
Old 8th Sep 2010, 23:09
  #286 (permalink)  
 
Join Date: Jun 2001
Location: at the edge of the alps
Posts: 329
I cannot think of a civil airliner where the nose gear retracts backwards - they all retract forwards.
Well, the deHavilland Dash 7 has one, and I will take exception to anyone denying it airliner status. A small handpump is used to ensure downlock after freefall extension. (The Dash 8 and Fokker 50 have - much larger and draggier - backwards retracting main gear, assisted by handpump and springloading respectively for downlock after emergency freefall extension.)

Thanks to all Concorde experts for this truly wonderful thread. The ingenuity of design and the complexity of design that enabled the technological marvel that is Concorde never cease to amaze this humble airline driver. Having missed the opportunity to fly on Concorde is high on my list of aviatic regrets as well, and I'll have to make do with the memories of watching Air France Concordes taking off from CDG during our turnarounds there.

I could (and actually have) spent hours following this thread.

Is it true that Concorde was always flown by the highest seniority BA captains, copilots and flight engineers? Would Concorde usually be the last rung on the ladder before retirement for Captains/FEs or was it usual to return to slower equipment after a stint on Concorde?

And, sorry if I missed this, would Concorde thrust levers move during autothrottle operation?

Lastly, Concorde was originally to have had a large moving map system. Any insights into why and how that got scrapped along the way?

Thanks!
Alpine Flyer is offline  
Old 9th Sep 2010, 04:27
  #287 (permalink)  
Thread Starter
 
Join Date: Apr 2004
Location: Planet Earth
Posts: 1,805
Thank you Exwok and M2Dude for your continuing information.


The Concorde tyres were obviously under enormous stress. The only other Aircraft that I can think off whose Tyres have such a hard life (on landing only of course!) are those installed on the Space Shuttle.


I would imagine, however these are replaced after each flight. How long would the Concorde Tyres last in normal service ?
stilton is offline  
Old 9th Sep 2010, 05:03
  #288 (permalink)  
 
Join Date: Aug 2005
Location: Albuquerque USA
Posts: 166
SR-71 tires had a hard life

The Concorde tyres were obviously under enormous stress. The only other Aircraft that I can think off whose Tyres have such a hard life (on landing only of course!) are those installed on the Space Shuttle.
Not sure how the landing and takeoff speeds compare, but the SR-71 tires had the additional disadvantage of a prolonged heat soak to far higher temperature than any large Concorde component, I think. Sources say the tires were good for 15 cycles, other say 6, and attribute two early hull losses (64-17950 and 64-17954 in 1967 and 1969) to tire failures progressing to magnesium wheel fires propagating into the rest of the airframe.

Last edited by archae86; 9th Sep 2010 at 12:41. Reason: fix "the the" typo
archae86 is offline  
Old 9th Sep 2010, 06:51
  #289 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
Alpine Flyer
Well, the deHavilland Dash 7 has one, and I will take exception to anyone denying it airliner status.
And a darned good airplane too
Is it true that Concorde was always flown by the highest seniority BA captains, copilots and flight engineers? Would Concorde usually be the last rung on the ladder before retirement for Captains/FEs or was it usual to return to slower equipment after a stint on Concorde?
One for my 'winged' friends really, but with BA it was an issue of seniority, with a long waiting list for selection. As far as I recall there were only ever a couple of cases when a captain left the fleet for another aircraft, most would very happily fly Concorde until retirement at 55. The senior first officers generally had to (reluctantly) change fleets when they got their commands, however there was as far as I remember two exceptions here, where an SFO was able to 'jump seats' to captain. SEOs would stay on Concorde until retirement. (In all the years that I can remember there was only one case of an SEO switching fleets from Concorde). A pilot friend once put it to me that if your passion in life was as a flyer of aeroplanes, then there was really nowhere to go after Concorde.
And, sorry if I missed this, would Concorde thrust levers move during autothrottle operation?
Oh yes, Concorde had a 'real' full flight flight regime autothrottle. The autothrottle actuator would drive all four levers together via individual isolation clutches and the computer used the sum of all four lever angles. In the unlikely event of an engine being shut down in flight, the A/T could still be used. There was an isolation switch on the roof panel that would enable the affected engine's thrust lever to be isolated and closed to idle, the computer using the sigmals from the other three engines, demanding a now higher lever angle to compensate for the failed engine.
Lastly, Concorde was originally to have had a large moving map system. Any insights into why and how that got scrapped along the way?
The prototypes I recall had a DECCA moving map, but with the availability of INS (and the decline and finally shutting down of the DECCA chains) made the system a waste of time (not to mention space).

Dude
M2dude is offline  
Old 9th Sep 2010, 07:03
  #290 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
stilton and archae86
I seem to remember that the average tyre life prior to the NZG tyre was roughly between 12 and 20 landings. One of the main concerns of prolonged high altitude flight was the deterioration of the tyre rubber by atmospheric ozone (above 50,000'). For this reason a small amount of cabin air was bled into the undercarriage bays and expelled through vents in the doors. And archae86, my friend you will find nothing but respect for the SR71A and her crews from the Concorde 'family'.

Dude
M2dude is offline  
Old 9th Sep 2010, 07:29
  #291 (permalink)  
 
Join Date: Mar 2004
Location: schermoney and left front seat
Age: 53
Posts: 2,312
What a fascinating read, thanks to all guys contributing to it.

The fact that the Conc still fascinates so many people after so many years is the best prove of its uniqueness. Never flown on one, but having brought clients to it I remember a time where we parked right under the nose of an AF example at CDG with our tiny Cheyenne. The Pax was lead from our airplane up the stairs and off they went. (1989ish, I was a wet as a fish F/O then) Queing in Heathrow a few years later I couldn't hear my KingAirs engines for quite a while when the guys opened up and fired the cans. Fond memories and still the most graceful airplane I saw in my life.
I still use the opportunity to see the 2 examples at the museum at Le Bourget when there. Having seen a documentary on the first flights in Toulouse and Filton I had a trip to Filton a few days later and sitting in the air field ops Landrover was sort of a time travel.

We had the pleasure to have ex FEs and an ex Capt. as trainers at FlightSafety in Farnborough. Very nice blokes and I should add, very capable and knowledgable guys. One can see why they were on the sharp end.

Sorry that I cant ask a good question right now, just had to get my thanks off my chest!
His dudeness is offline  
Old 9th Sep 2010, 09:22
  #292 (permalink)  
 
Join Date: Dec 2007
Location: Pasadena
Posts: 633
Shuttle Tires/Tyres

I don't know whether the shuttle tyres are actually reused or not, but if a remember right, the side wall printing says good for 12 uses.

Here's a link to michelin's description of loading and lightweighting:
Michelin Air: The very best in aviation tires.
awblain is offline  
Old 9th Sep 2010, 10:58
  #293 (permalink)  
 
Join Date: May 2002
Location: UK
Posts: 136
ALPINE FLYER

Is it true that Concorde was always flown by the highest seniority BA captains, copilots and flight engineers? Would Concorde usually be the last rung on the ladder before retirement for Captains/FEs or was it usual to return to slower equipment after a stint on Concorde?



To answer your question fully the fleets history has to be broken into two halves, that is the first 10 years and then all the time after that

The first ten years

When the fleet was very new 1976 and crews were bidding for it you have to remember that it was a BOAC aircraft and only BOAC crews could bid onto it. Very few people saw a long future for the aircraft and so were reluctant to go through the long training if it was only going to last for a few years

Also because it always had a limited route net work then there was far more money to be made on say the B747 with it's large route network

Anyway this all opened up the fleet to the younger members of the flight crew fraternity, and indeed the youngest Captain on Concorde at that time was only 32 years old with the youngest F/E being 29 years old. Indeed most of the crews on joining the fleet were in their 30's or early 40's and nowhere near being the most senior. With the exception of the F/Os most of these crews stayed with the aircraft until retirement so in the end it became a senior fleet. Indeed 20 years and even up to 24 years was the term that some stayed on the fleet for.

After 1985 when cross bidding was allowed between the old BEA and BOAC
and Concorde started recruiting crews again then people had to be fairly senior to get onto the fleet as people could see a future for the aircraft and realized it looked exciting.

It was never really a fleet for the most senior as you could as a Captain or F/E only bid for the fleet if you had at least 7 years to go to retirement and the F/Os had to be willing to forgo their oppurtunity for cammand for at least 5 years although this was sometimes ignored

F/O had to leave the fleet to get their command, but many came back as soon as their new Captains seniority allowed them to

Some Captains and 2 F/Es did leave the fleet for another aircraft prior to retirement

Therefore you can see with crew numbers hovering around 20 sets and this was reduced near the end it was no wonder that Concorde was known as the Boys club and Barbara was one of the boys too

On Circuit training tyres were always our problem, especially when we could not have the spare hubs /tyres made up locally by a man from the tyre workshop. Instead we had to bring ready made up wheels with us and the rest delivered by truck. This was no real problem when we did our circuit training in the UK ,but when we moved it to France then the logistics became more difficult.
If I remember correctly you would be lucky to get more than 20 landings out of a tyre, with the rear mains taking the biggest hammering and often being changed quite a bit before 20 landings. With up to 6 details a day and each detail consisting of up to 10 landings you can see that tyre usage on training was heavy

Fingers tired now
Brit312 is offline  
Old 9th Sep 2010, 10:58
  #294 (permalink)  
Tabs please !
 
Join Date: Jun 2004
Location: Biffins Bridge
Posts: 705
I cannot think of a civil airliner where the nose gear retracts backwards - they all retract forwards
The Trident did it sideways
B Fraser is offline  
Old 9th Sep 2010, 11:44
  #295 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
Talking "Wheel Meet Again" - More on the rotating stuff

More on wheels and brakes
Concorde was without doubt the first ever aircraft to have a fully automatic, active braking system, with NO mechanical linkages to the brakes whatsoever: Firstly there was the 'normal' anti-skid, but the Concorde system was far from normal. Instead of the universally used anti-skid concept that monitors main wheel deceleration, we of course did it differently. Main wheel rotational velocity was compared with (un-braked of course) nose wheel rotational velocity. With zero skid the RELATIVE velocities would of course be the same, any difference would relate to the % skid value. That was the the real advantage of 'our' system; the percentage of main wheel skid could be calculated by the SNECMA (Hispano) SPAD Box, maximum runway 'stopping power' being achieved at around 20% skid. (I always thought that it was strange, the maximum runway adhesion being achieved while the wheel was skidding, but that's what it said on the tin). When the aircraft initially touched down, and the braking/anti-skid system was enabled, a fixed nose wheel speed Vo was used until the nose wheel touched down. (Can't quite remember what equivilant ground speed this related to though).
As well as anti-skid there was also torque modulation also, due to the use of carbon fibre brakes and the enormous amount of rotational torque involved. (A maximum figure of 8.5 MILLION ft./lbs. of torque springs to mind!!!). When a brake demand was input into the BRAKE ADAPTOR BOX (this also manufactured by SNECMA /Hispano) it was compared with a reference torque. As this brake demand input was applied to the 'box', the torque feedback from a torque link connected at one end to the brake would feedback the actual applied torque, where it was compared to reference torque, and the demand was modulated to suit.
The beauty of it all was that the anti-skid, basic brake demand as well as brake torque limits could all be superimposed on one another, giving a wonderfully flexible system that the pilots could have and did had an enormous amount of faith in.

Dude
M2dude is offline  
Old 9th Sep 2010, 12:07
  #296 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
Cool And more.....

Just to round up the braking issuue....
A fully laden Concorde had a V1 significantly higher than a fully laden 747. (A figure of about 50 MPH springs to mind; perhaps one of the 'flyers' will confirm this). Although the Jumbo is twice the take-off weight, the amount of kinetic energy present in Concorde was significantly higher, due to energy = Mass x the SQUARE of the velocity. Added to this, Concorde had only eight braked wheels compared to the Jumbo's SIXTEEN. This really is further testament to the Concorde braking system, that had to have an enormous amount of stopping power, particularly in the case of a near V1 RTO. And all of this achieved with just eight compact, extremely reliable and relatively light brake units.

Dude
M2dude is offline  
Old 9th Sep 2010, 12:42
  #297 (permalink)  
 
Join Date: Jan 2008
Location: UK
Posts: 41
Thanks For The Memories

I have spent the early afternoon reading this wonderful thread. Thank you to all you guys, it has brought back so much that I had forgotten.

I was a stewardess on The Beautiful Bird for a few years, and I know first-hand the love that we all had for our beloved 'Connie'.

I started my flying carreer with Freddie Laker in the early 70's, and was on the inaugral SkyTrain to JFK on July 4th 1976.

I am still flying for BA,and over the years I have been honoured to fly with some amazing crew, and like others on here, I count myself truely lucky to have been part of the Concorde Family.

Thank you again for sharing your amazing knowledge.

LL
landlady is offline  
Old 9th Sep 2010, 15:00
  #298 (permalink)  
 
Join Date: Jun 2001
Location: at the edge of the alps
Posts: 329
I don't know whether the shuttle tyres are actually reused or not, but if a remember right, the side wall printing says good for 12 uses.
Given the frequency of Shuttle sorties 12 landings would mean a lifetime longer than most airline tires, at least if expressed in years.
Alpine Flyer is offline  
Old 9th Sep 2010, 15:06
  #299 (permalink)  
 
Join Date: Sep 2007
Location: UK
Age: 53
Posts: 124
M2Dude.....

In response to your query: V1 was typically about 160kts on a transatlantic sector, with a Vr of about 190 and a V2 approx 220.

a fixed nose wheel speed Vo was used until the nose wheel touched down. (Can't quite remember what equivilant ground speed this related to though).
It wasn't in the flight manual but I seem to recall that the standing signal prior to nosewheel spinup was 100m/s. Presumably this also prevented brake application until the nose was down, being much higher than touchdown speed.

Anyone who travelled in the beast will know that we didn't use the brakes gently - they worked far better if you stood on them firmly and also seemed to wear less; certainly there seemed to be a lot more dust on the wheels if you used them gently.

Taxying out one had to be careful, it was easy to get a brake temp light on (was it 200degs? 220?) which meant waiting ages for it to cool. The watchword was minimum number of brake applications and make them firm, not feathery. And be careful on the lightweight departures as you needed them more.
EXWOK is offline  
Old 9th Sep 2010, 15:44
  #300 (permalink)  
 
Join Date: Jan 2008
Location: FL 600. West of Mongolia
Posts: 462
EXWOK
Mate I know the Concorde V Speeds, my query relates to the comparison with the 744.
It wasn't in the flight manual but I seem to recall that the standing signal prior to nosewheel spinup was 100m/s. Presumably this also prevented brake application until the nose was down, being much higher than touchdown speed.
Yeah that figure sounds familier, and you are correct on the presumption also. (That's why you got the eight 'R' lights illuminated on the anti-skid panel with the gear down on approach). With the fixed Vo signal and no output from the main wheel tacho's, the system sensed full skid and gave a FULL anti-skid release. The brakes were electronically held off by this, nomatter what, prior to landing.
Regards as ever EXWOK

Dude

Last edited by M2dude; 9th Sep 2010 at 21:47.
M2dude is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.