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Concorde question

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Concorde question

Old 6th Sep 2010, 23:05
  #241 (permalink)  
 
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Mykul10
Mach No is a percentage value of the speed of sound ie 0.85 = 85% speed of sound. Unfortunately the speed of sound changes with pressure but at sea level is around 760 mph and decreases as pressure decreases.
Small correction

....sound. Unfortunately the speed of sound changes with (Abs) temperature but at sea level is around 760 mph and decreases as temperature decreases.
M (dry air within reasonable temperature limits) = Sq.Rt (Gamma x R* x Tabs)

R* is a combined gas molecular value
Gamma is 1.4 (truly adiabiatic compression wave)
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Old 6th Sep 2010, 23:15
  #242 (permalink)  
 
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I have two recollections which I treasure. The first is of a sales demo ride for a VIP party I had to organise from Abu Dhabi on 29th August 1974; one by one we went to the flight deck to look around, which is when I first saw the gap by the F/E panel as the skin stretched. The flight took us overhead Dubai and then halfway to Bombay with a level turn at M2 and back along the outward track. The contrail was close by the RH side and gave a tremendous impression of what the speed really meant.

Some 13 or 14 years later I had the privilege of a jump seat ride from Exeter for the whole of one of the round-the-bay flights. We flew North to join the westbound route to the acceleration point at minimum separation behind the schedule Concorde to New York (or perhaps Washington?). The display as the other aircraft's nose lifted and the aircraft accelerated was awesome.

Then on landing, handflown by the FO (currency requirement?), we seemed to be heading for a touchdown halfway down the runway. It was truly terrifying to a simple PPL, and just as I was about to let out a strangled sob the mainwheels touched down precisely on the markers, well below and behind. Apart from the terror, what impressed me was that as far as I could see the FO was flying the aircraft exactly as you would a Tiger Moth; stick, throttle and rudder. I know that there was far more to it than that, but that's how it appeared.

What a gorgeous aircraft. My model, in its original Gulf Air colours as presented in 1974, flies in the ceiling of my office.
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Old 6th Sep 2010, 23:32
  #243 (permalink)  
 
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Once again thanks to everyone who has patiently answered my questions. I have certainly learnt a lot about Concorde over the last couple of weeks.
I also agree with many other people who have said that the valuable information provided on this thread should be recorded for posterity. Not an easy task as she is such a wonderful and complex machine. Mind you I think that such a project would be worthy of a Heritage Lottery grant, I say that as in my "real life" I have had experience of how Lottery grants are awarded.
Regards
Nick
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Old 7th Sep 2010, 06:12
  #244 (permalink)  
 
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Hi guys, here is a schedule showing CG against Mach number (It's very old just like the author here). I hope that it now completes our collection of flight envelope diagrams. (Bellerophon, by the way, your diagram is precisely the one that I was scouring around for). Great explanations by everybody on the Mach/TAS/IAS etc issue, mostly all clear and concise ( a couple of minor goofs that were subsequently corrected, otherwise very good) .
If I were in the LEAST bit pedantic (and any here that know me would say that the b****d certainly IS pedantic), I would merely add that Concorde (like virtually all complex aircraft) relied on CALIBRATED airspeed (Vc) and not IAS, taking into acount plate and probe errors. Just as well I'm not pedantic .

Dude

Last edited by M2dude; 7th Oct 2010 at 17:12.
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Old 7th Sep 2010, 06:24
  #245 (permalink)  
 
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Main Landing Gear Shortening.

I believe that the main landing gear was shortened to fit into the wheel wells during the retraction sequence.
As I see it, as the gear started to retract, the oleo`s were compressed to something like when the weight was on the wheels. Then a latch would have been applied before the gear reached the full up position to hold the gear strut compressed.
I would like to find out more how this was accomplished.
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Old 7th Sep 2010, 06:29
  #246 (permalink)  
 
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ChristiaanJ
....... in a way, that illustrates that for flying the aircraft things like TAS and GS are not really that important... that's why there are no big instruments indicating TAS or GS..
It was one of the strange little differences between the BA and Air France aircraft that the French had a small digital TAS indicator (on the lower F/O's instrument panel) and BA had none.
As you rightly say, as an indicator TAS is not that much use to you, BUT TAS is vital for calculating wind speed/direction within an INS/IRS system, hence that is why any air data computer gives a TAS output to the INS or IRS.
dumb question from a techie... the 373 miles is presumably just the distance to the next INS waypoint?
Nothing dumb about the question (I wonder if you are even capable of such a thing ChristiaanJ ). Yes, the distance window on the HSI related to the next INS waypoint.

Dude
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Old 7th Sep 2010, 06:34
  #247 (permalink)  
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M2Dude,


You mention a minor instrumentation difference between the AF and BA Concordes.


Were there any other technical differences between the two Airlines respective Concorde Fleets that come to mind ?
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Old 7th Sep 2010, 06:45
  #248 (permalink)  
 
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Stilton
Hi again my friend. There were a few; BA used a Delco Carousel 4AC INS, where AF used a Litton system. BA updated the radar to a Bendix sytem, where I believe that AF retained the original RCA fit. (The RCA radar was awfully unreliable (rubbish actually, and very expensive to fix) , although most of the guys would agree that it gave a superbly detailed picture, better for mapping than the Bendix.
BA used quite a sophisticated Plessey integrated flight data system, where the AF recording system was a little simpler.
There were various other minor differences, but I think that's just about it.

Dude
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Old 7th Sep 2010, 06:52
  #249 (permalink)  
 
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Runaround Valve
I believe that the main landing gear was shortened to fit into the wheel wells during the retraction sequence. As I see it, as the gear started to retract, the oleo`s were compressed to something like when the weight was on the wheels. Then a latch would have been applied before the gear reached the full up position to hold the gear strut compressed. I would like to find out more how this was accomplished.
This was quite a neat system, as the gear was retracted, a SHORTENING LOCK valve was signalled, allowing a relatively tiny jack to pull the entire shock absorber body into the body of the oleo progressively as the gear retracted. So the shock absorber itself never compressed on retraction, more like the whole shooting match was pulled inside the body of the oleo. On the ground the shortening lock was disabled, and also isolated by a geometric lock, the weight of the aircraft on the leg holding the shortening mechanism over centre.centre. Hope this helps.

Dude

Last edited by M2dude; 7th Sep 2010 at 07:42.
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Old 7th Sep 2010, 07:39
  #250 (permalink)  
 
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I hope this one is interesting; it's a Rolls Royce diagram illustrating what the wildly varying differences were in terms of the engine between take off and supersonic cruise. The primary nozzle can be seen at the rear of the engine, together with the reheat assembly and the secondary nozzle (reverser buckets).
Yes ChristaanJ, I FINALLY managed to upload stuff here.
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Old 7th Sep 2010, 08:06
  #251 (permalink)  
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About 15 years ago I visited a friend living in a rented farmhouse in southern England. It had a huge fireplace (large enough to stand in) that had been retrofitted for a small log-burning stove. Looking up, I noticed the chimney had been blanked off by what appeared to be aluminum sheeting bearing Concorde diagrams: white anodized aluminium with deep blue ink. I wonder if they are still there, and how they got there.
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Old 7th Sep 2010, 08:44
  #252 (permalink)  
 
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Stilton, M2dude -

Did the French aircraft not have a slightly different DC system a la OAG?

If so, it primarily related to NiCd batteries and chargers to suit same, and the lack of main DC bus tie split IIRC.

Oh, and I believe the French flt crews' seat cushions were grey, not blue!
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Old 7th Sep 2010, 08:59
  #253 (permalink)  
 
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Makes me wonder... In the event of a complete loss of thrust at Mach 2 (say fuel contamination) would the deceleration be significant ? If so I guess the fuel redistribution / pumping to maintain acceptable CG would become interesting...

Concorde did actually have a four engine failure drill, which covered it's complete speed rsnge including Mach 2.0. There was one assumption made in this drill and that the engines would continue to windmill which would allow them to give you full hydraulic pressure

As you could imagine, If all 4 engines cut at Mach 2.0 the F/E would be quite busy and so the the non flying pilot would use his fuel transfer switch to start the fuel moving forward. This was a pretty basic selection where fuel would be pumped out of Tank 11 using all 4 pumps [2 electrical and 2 hydraulic driven] and into the very forward tank which was no 9.

As a rule of thumb transferring 1000kgs from tank 11 to tank 9 moved the Cof G forward by 1%. Now with all 4 pumps in tank 11 running the tansfer forward was so quick that the pilot had to keep switching the transfer off and then on to stop the Cof G moving forward too quickly. It was usually to everybody's relief when the F/E could find the time to take over the fuel transfer as he had the selections to allow him to be more selective as to where the fuel went and so slow the rate down
---------------------------------------

This was quite a neat system, as the gear was retracted, a SHORTENING LOCK valve was signalled, allowing a relatively tiny jack to pull the entire shock absorber body into the body of the oleo progressively as the gear retracted. So the shock

Forther to M2dude's explanation Concorde's main landing gear consisted of 3 seperate metal castings . there was the normal two for the oleo and these two were fitted inside the outer casting, which was the one you could see.
As the gear retracted a mechanical linkage , which was driven by the gear's retraction movement, would lift the oleo assembly up into the outer casing, so shortening the length of the leg . If I remember the shortening jack was just to assist in breking the geometric lock of the linkage
------------------------------------------

The other difference between AF and BA aircraft was the DC electrical system

AF had Nickel cadmium batteries with an automatic charging system

BA had the good old lead acid battery sysytem, well except for AG where the DC system was one of the systems they never changed when AG was incorporated into the BA fleet
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Old 7th Sep 2010, 09:02
  #254 (permalink)  
 
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for atakacs:

Makes me wonder... In the event of a complete loss of thrust at Mach 2 (say fuel contamination) would the deceleration be significant ? If so I guess the fuel redistribution / pumping to maintain acceptable CG would become interesting...
The deceleration would be like very hard braking after landing, so - yes.

The drag incurred flying supersonic was once described to me as like flying through wood, not air. The only times I ever closed all 4 throttles at M2 was dealing with surges (see earlier posts on the subject). While not quite like flying into teak, the decel was very impressive - it more than once resulted in a member of cabin crew appearing in the flt deck in a semi-seated position, grimly trying to stop a fully loaded galley cart.......

As for four-engine flameouts - perish the thought. The checklists, like many, depended on flight phase;

Above M1.2 it was expected that windmilling would provide adequate eletric and hydraulic power so the c/list aimed to start a fuel txfr forward, use the spare hydraulic system to drive half the PFCUs, ensure a fuel supply to the engs and ensure cooling to equipment.

Below M1.2 the RAT would be deployed, it was less likely that the standard means of fuel txfr would work so valves were overridden and the hydraulic fuel pumps brought into use, and the Mach fell further the PFCUs were put on half-body use only, using the stby hydraulic system.

You weren't far from the ground, in time, at this stage so it was a good time to get an engine relit!

Given the Olympus' auto-relight capability a four engine loss was going to be caused by something fairly drastic.
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Old 7th Sep 2010, 10:41
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Brit312
Concorde's main landing gear consisted of 3 seperate metal castings . there was the normal two for the oleo and these two were fitted inside the outer casting, which was the one you could see.
As the gear retracted a mechanical linkage , which was driven by the gear's retraction movement, would lift the oleo assembly up into the outer casing, so shortening the length of the leg . If I remember the shortening jack was just to assist in breking the geometric lock of the linkage
Right on the button as usual Brit312, the shortening jack DID just assit breaking of the geometric lock, it was the process of retraction alone that did the actual shortening. Humble aplologies to all for this age induced goof.
And as both yourself and EXWOK pointed out, Air France had a ni-cad based DC power system, the same as G-BOAG.

Dude
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Old 7th Sep 2010, 11:45
  #256 (permalink)  
 
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it was the process of retraction alone that did the actual shortening.
Is this another item that Airbus used for the A330/340? I can't remember the exact arrangement for Concorde, but the 330 uses a clever lever arrangement at the top of the leg. Requires regular lubrication too or.

As we're on landing gear.
Why was the sidestay a telescopic affair? Most aircraft use a hinged geometric lock arrangement. More weight saving or down to available space in the landing gear bay?
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Old 7th Sep 2010, 12:07
  #257 (permalink)  
 
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TURIN
Is this another item that Airbus used for the A330/340? I can't remember the exact arrangement for Concorde, but the 330 uses a clever lever arrangement at the top of the leg. Requires regular lubrication too or.
I was not even aware of this A33/340 similarity, sounds yet another case of Airbus using Concorde technology. (Immitation still is the greatest form of flattery I guess). As far as I am aware Concorde had none of the lubrication issues that you describe.
Why was the sidestay a telescopic affair? Most aircraft use a hinged geometric lock arrangement. More weight saving or down to available space in the landing gear bay?[/
I think it's a space saving issue TURIN, I'm not even sure if 'our' telescopic strut arrangement was any lighter. (The Concorde solution was also somewhat more elegant don't you think)?

Dude
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Old 7th Sep 2010, 12:27
  #258 (permalink)  
 
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Re the CG limits, here is the diagram from the 01 (preprod a/c) flying manual.



The production a/c diagram is slightly different, but it shows the same kind of "corridor".

Edit : here is the production a/c diagram.
Sorry for the distortion during the scan....



For the full A4 page, use this link :

Prod CG enevlope A4 format

CJ

Last edited by ChristiaanJ; 7th Sep 2010 at 14:16.
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Old 7th Sep 2010, 12:55
  #259 (permalink)  
 
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Trident

A bit of thread drift - but the Trident had a main undercarriage with four wheels aligned laterally with the a/c - two on one axle and two on the other. This obviously would not retract into the fuselage so had to be swivelled through 90 degrees in the retraction process.

I think this was achieved by the oleo assy being driven down an outer barell with a helix in it. I think it had an A-frame mechanism on top of the gear which was fixed to the wing structure (rib 5?). As the gear went up the wheels rotated into the bay. PFM
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Old 7th Sep 2010, 13:07
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M2dude----- you might be correct in saying that the side strut was for space saving considerations. However in the design office old habits die hard and you will find that the support stay on the Bristol Britannia was very similar to Concordes main gear side strut, with locking fingers etc.and even looked similar

In fact quite a bit was transferred from previous aircraft designs to Concorde , such as the 4 fwd cabin door are very similar to that of the VC-10 as is the oxygen system.
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