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Old 12th Jan 2011, 19:45
  #1081 (permalink)  
 
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Wow, what a great thread! I started reading it yesterday and am up to page 19 so far! I flew on the wonderful white bird once, in 1999, a Manchester - round the bay at Mach 2 - Paris flight in G-BOAD. And the wonderful thing was I did the entire flight, push back at Manchester to parking at Paris, in the jump seat! What a fabulous experience - thank you Roger!

Here's a picture I took as the aircraft turne left towards the French coast:



One memory is climbing through 50,000 feet over South Wales before turning down the Bristol Channel. It was glorious August day and I had a great view forward past the captain and particularly out of the left window. The speed over the ground at Mach 0.95 seemed noticably faster than a subsonic jet, and that view was breathtaking! The Bristol Channel was edged in golden yellow beaches, and I could see right across south west England to the English Channel. In my headset the controller called another aircraft; "Speedbird 123 if you look up now you will see you are about to be overflown by Concorde". I leaned towards my side window and there was Speedbird 123, a tiny scurrying beetle miles below us. From this height the fair-weather cu looked as if they were on the ground - like small white splodges from some celestial artist's paint brush.

We cruised at Mach 2 and 60,000' over the Bay for a while and the pax came forward to view the flightdeck. I was amazed how patient was the supernumery captain who was answering the same questions over and over again was (the flight crew were too busy to chat).

The approach to CDG looked far steeper than other airliner approaches I had witnessed from the flight deck; more like one of my glide approaches in the Chipmunk! But it wasn't, of course, as we were following the 3 degree glideslope. I guess it was an illusion brought about by the steep pitch angle.

I remember the captain resting his hands on the throttles as they shuttled back and forth under autothrottle control, the smooth touchdown, the 'landing' of the nosewheel followed by full forward stick, and thinking "we'll never make that turn off". Then on came the powerful reverse and the brakes, I was thrust foreward in my harness, the speed disappeared, and we made the turnoff easily!

Oh, and that stange bouncy ride in the flight deck on the ground as the long nose forward of the nosewheel flexed over every joint in the taxyway. So bad at times it was difficult to take a photograph!

What an experience!

I have a question which I hope hasn't been answered in the pages (20 to this one) that I've yet to read.

From an earlier post I understand that the anti-skid used a rotational reference from the unbraked nosewheels to compare to the rotation of the mains, and that with gear down in the air a substiute nose-wheel referance is supplied which, because the mains are not yet rotating, allows the anti-skid to keep the brakes off.

But what happens when the mains touch down with the nosewheels still high in the air? What (if anything) inhibits wheel braking until the nosewhels are on the ground (and therefore rotating)?

Also, this thread started with a question about the lack of an APU. When Concorde was parked could the aircon and cabin lighting be powered by external electrical power, or did the cabin aircon without engine power require an external 'aircon unit' to be connected? Or was aircon simply not available without at least one engine running?

And one for Landlady or any other CC. If a table top was set up between the cabins during service, how did the 'front' crew service the first 2 rows of the rear cabin?

Being 'up front' for my entire flight, I missed out on the cabin service. But superb though I'm sure that was, under the circumstances it's not something I regret!

Last edited by Shaggy Sheep Driver; 12th Jan 2011 at 21:07.
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Old 13th Jan 2011, 08:45
  #1082 (permalink)  
 
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atakacs
Just wondering was that the maximum speed "in" the design ? I understand that "the higher & the colder = the faster" was the key to the performance and that the Mach +/- 2.0 cruise was implied by limiting altitude to FL 600 in order to mitigate cabin depressurization consequences. I guess there where also thermal issues but was, say, Mach 2.2 @ FL700 "warmer" than Mach 2.0 @ FL600 ?

Really an answer for CliveL, but I'll have a go. The short answer to your question is 'oh yeah, big time'. Total temperature varies with the SQUARE of Mach number and static temperature. Depending on the height of the tropopause itself as well as other local factors, there can be little or no significant variation of static temperature between FL600 and FL700. The 400°K (127°C) Tmo limit was imposed for reasons of thermal fatigue life, and equates to Mach 2.0 at ISA +5. (Most of the time the lower than ISA +5 static air temperatures kept us well away from Tmo). In a nutshell, flying higher in the stratosphere gains you very little as far as temperature goes. (Even taking into account the very small positive lapse above FL 650 in a standard atmosphere). As far as the MAX SPEED bit goes, Concorde was as we know flown to a maximum of Mach 2.23 on A/C 101, but with the production intake and 'final' AICU N1 limiter law, the maximum achievable Mach number in level flight is about Mach 2.13. (Also theoretically, somewhere between Mach 2.2 and 2.3, the front few intake shocks would be 'pushed' back beyond the lower lip, the resulting flow distortion causing multiple severe and surges).
On C of A renewal test flights (what I always called the 'fun flights') we DID used to do a 'flat' acceleration to Mach 2.1 quite regularly, as part of the test regime, and the aircraft used to take things in her stride beautifully. (And the intakes themselves were totally un-phased by the zero G pushover that we did at FL630). This to me was an absolute TESTAMENT to the designers achievement with this totally astounding aeroplane , and always made me feel quite in awe of chaps such as CliveL.
Also wondering what was the max altitude ? Was high altitude stall (for the lack of a better word) ever experimented during tests or training ?
Well the maximum altitude EVER achieved in testing was I believe by aircraft 102 which achieved 68,000'. As far as the second part of your question goes, not to my knowledge (gulp!!) but perhaps CliveL can confirm.

Shaggy Sheep Driver
So glad you are enjoying the thread, and absolutely loved the description of your flight in OAD and your photo is superb. I don't think it is possible to name a single other arcraft in the world that could be happily flown hands off like this, in a turn with 20° of bank at Mach 2. (One for you ChristiaanJ; The more observant will notice that we are in MAX CLIMB/MAX CRUISE with the autothrottle cutting in in MACH HOLD. Oh, we are in HDG HOLD too ).
Now for your question
I understand that the anti-skid used a rotational reference from the unbraked nosewheels to compare to the rotation of the mains, and that with gear down in the air a substiute nose-wheel referance is supplied which, because the mains are not yet rotating, allows the anti-skid to keep the brakes off. But what happens when the mains touch down with the nose wheels still high in the air? What (if anything) inhibits wheel braking until the nosewhels are on the ground (and therefore rotating)?
A very good question. The anti-skid system used a fixed simulated nose wheel rolling speed Vo signal as soon as the undercarriage was down and locked, this was confirmed by the illumination of the 8 'R' lights on the anti-skid panel. The illumination of these lights confirmed that there was full ant-skid release from the relevant wheel, due to there being of course zero output initially from the main gear tachos but this simulated Vo output from the nose gear tacho. The Vo signal therefore ensured that the aircraft could not be landed 'brakes on' (all the main wheels think they are on full skid) and that there was anti-skid control pending lowering of the nose-wheel. As the main wheels spin up on landing, their tacho outputs now start to back off the Vo signal, and braking can commence. As the nose leg compresses, the Vo signal is removed and the Nose-wheel tachos(their were 2 wired in parallel) spin up, their output will now replace the Vo signal, and full precise anti skid operates.
As far as your air conditioning question goes, you needed an external air conditioning truck to supply cabin air on the ground. Not needed in the hangars of course, but come departure time if these trucks were not working, then the cabin could become very warm/hot place indeed (depending on the time of year). Oh for an APU
Best regards

Dude
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Old 13th Jan 2011, 10:10
  #1083 (permalink)  
 
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Originally Posted by M2Dude
Really an answer for CliveL, but I'll have a go. The short answer to your question is 'oh yeah, big time'. Total temperature varies with the SQUARE of Mach number and static temperature. Depending on the height of the tropopause itself as well as other local factors, there can be little or no significant variation of static temperature between FL600 and FL700. The 400°K (127°C) Tmo limit was imposed for reasons of thermal fatigue life, and equates to Mach 2.0 at ISA +5. (Most of the time the lower than ISA +5 static air temperatures kept us well away from Tmo). In a nutshell, flying higher in the stratosphere gains you very little as far as temperature goes. (Even taking into account the very small positive lapse above FL 650 in a standard atmosphere). As far as the MAX SPEED bit goes, Concorde was as we know flown to a maximum of Mach 2.23 on A/C 101, but with the production intake and 'final' AICU N1 limiter law, the maximum achievable Mach number in level flight is about Mach 2.13. (Also theoretically, somewhere between Mach 2.2 and 2.3, the front few intake shocks would be 'pushed' back beyond the lower lip, the resulting flow distortion causing multiple severe and surges).
On C of A renewal test flights (what I always called the 'fun flights') we DID used to do a 'flat' acceleration to Mach 2.1 quite regularly, as part of the test regime, and the aircraft used to take things in her stride beautifully. (And the intakes themselves were totally un-phased by the zero G pushover that we did at FL630)


As usual Dude you beat me to it! I really must give up having another life


As Dude says, the 'cruise' condition was set by the aircraft specification for transatlantic range on an 85% (ISA +5) day and the chosen mach Number was 2.0 (of which more anon). This gives a Total Temperature of 400.1 deg K. [Dude, I know your pipe-smoking thermodynamicist and he was having you on - he is quite capable of memorising the square/square root of 407.6 or whatever!]
To give margins for sudden changes in ambient temperature (we had to cater for a 21 deg change in one mile) the Mmo was set at 2.04 which matches 400 degK at ISA +1. In theory then we could have flown faster than our chose Mmo at anything colder than this, but there are two limits:

1) The object is not to fly as fast as you can but to fly with minimum miles/gallon. If you have a nice cold day and enough thrust to go either faster or higher which do you choose? For best specific range you go higher every time.
2) The thing that everyone forgets is that civil aircraft have to have margins around their authorised envelope. In Concorde's case these were set principally by the intake limits and engine surge.

Dude also says quite correctly that 101 flew to 2.23M but the production aircraft was limited to 2.13M. Now you may not believe this, but 101 could fly faster than the production aircraft because she (101) leaked like a sieve!.

I doubt I will get away with that without some explanation

Once you get past a certain Mach Number the airflow into the intake is fixed. The performance (intake pressure recovery and engine face flow distortion) then depends on how this air is shared between the engine and the throat 'bleed'. This bleed was ducted over the engine as cooling air and then exhausted (in principle) throught the annulus formed between the expanding primary jet and the fixed walls of the con-di nozzle. But if you took, or tried to take, more bleed air the intake pressure recovery went up and the primary jet pipe pressure went up with it. This meant that the primary jet expanded more and squeezed the available annulus area which restricted the amount of bleed air one could take.

Obviously if there are alternative exit paths between intake and final nozzle then you can take more bleed air off and the engine face flow distortions will benefit along with the surge margin. 101 was fairly 'leaky' in this respect, particularly around the thrust reverser buckets on the original nozzle design. This meant that 101's intake distortions were lower than the production aircraft so she could fly faster without surge - at least with the first attempt at intake control 'laws'. We managed to tweak most of the margin back eventually. Engine bay leaks were good for surge margin but VERY bad news for m.p.g.!

Here are a couple of diagrams to show what I mean. the first shows the surge lines for the various aircraft variants and also the N1 limiter Dude was talking about. NB: the X-axis is LOCAL Mach Number not freestream. The difference comes from the compression of the underwing flow by the bit of the wing ahead of the intake. Mmo + 0.2 is shown

">The next shows the surge free boundaries in sideslip and normal acceleration. You can see the zero 'g' capability Dude was enthusing over.">

As for 'high speed stall', I don't think we ever contemplated trying it! Our requirements in 'g' capability were defined and that was it. Besides, the aircraft would fly like the proverbial stone-built outbuilding at those sorts of conditions so I don't think one would have been able to get anywhere near a stall in the conventional sense. Stall as commonly defined for subsonics (deterrent buffet) might have been another matter, but I don't remember anything.

Cheers

Last edited by CliveL; 13th Jan 2011 at 10:17. Reason: additional explanation
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Old 13th Jan 2011, 16:44
  #1084 (permalink)  
 
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Now you may not believe this, but 101 could fly faster than the production aircraft because she (101) leaked like a sieve!
Just love this thread - thanks CliveL and all involved
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Old 13th Jan 2011, 17:56
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What was the reason for the kink in the leading edge, shown in the photograph in post #1065? It couldn't have made the wing easier to fabricate or maintain.
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Old 13th Jan 2011, 19:12
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What was the reason for the kink in the leading edge, shown in the photograph in post #1065? It couldn't have made the wing easier to fabricate or maintain.
Basically we had to recamber the wing to optimise cruise drag. By the time that was discovered metal had been cut on early production aircraft and the only bits that could be altered in time were the wing apex, leading edges and the wing tip. There is a production joint just where the 'kink' appears so it did not affect build difficulty all that much. similarly the detachable leading edges were easy to alter.
There really isn't any significant maintenance on the LE apart from de-icing mats ahead of the intake and they are all inboard of the kink
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Old 13th Jan 2011, 19:23
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If you look at it from straight ahead it's not really a 'kink'.



From the angle the 'kinky' photo was taken the outer sweep of the ogee wing is towards the camera before sweeping aft to the drooped and washed-out tips and it looks like a kink in the LE sweep. The actual shape is seen better in the picture above. I've spent hours studying our G-BOAC at Manchester and to me the wing is a complex and lovely blend of curves and slopes, with no sudden changes such as a kink would require. Standing under the wing and observing it closely, no kink is apparent.

The wash-out on the tips shows particularly well in the above photo (washout is a forward twist of the wing at the tips to reduce the angle of attack of the tips compared to the rest of the wing, to prevent tip-stalling).

A question I have, relating to the photo above, is about the LE. The LE definately 'droops' in the area ahead of the intakes (it doesn't do so nearer the roots or tips). Is this to provoke a clean flow-breakaway in this area at high angles of attack to encourage the votices to form at this point as the wing transitions to vortex lift?

M2Dude Thanks for the kind words and careful explanations. I take it from your description of the anti-skid that once the mains start to rotate the brakes can be used, as the anti-skid comes 'off' (mains no longer think they are skidding).

I thought there was protection to prevent brake use until the nose wheels have landed, else brake application with the nose high would cause a rapid nose-down pitch, slamming the nosewheels on! Is there any such protection?

Last edited by Shaggy Sheep Driver; 13th Jan 2011 at 20:41.
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Old 13th Jan 2011, 23:06
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A really wonderful photo.
As you say, as the main gear tachos spin up the brakes no longer they think that they are in full skid and can be applied. The only electronic 'protection' as such is the anti-skid itself via that Vo signal in the anti-skid unit (known as the S.P.A.D. box). This would still help control and limit main wheel braking. However the professionalism of my friends such as EXWOK, NW1 and Bellerophon was the REAL protection here. I will let one of them explain the normal braking procedure on landing.
Best regards

Dude

Last edited by M2dude; 13th Jan 2011 at 23:31.
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Old 14th Jan 2011, 03:41
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Such an amazing sight when viewing Concorde head-on....beauty indeed.....
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Old 14th Jan 2011, 06:10
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He's right!!

Did ever a more beautiful aircraft fly??

Wow, an engineer like me moved by such beauty - what's the world coming to???

She is simply a supremely elegant design, something almost every engineer worthy of the profession can admire and love.

Keep posting you who know, please!!
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Old 14th Jan 2011, 07:00
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Devil Wet start

OK, here is a more unusual photo, but it's not as bad as it looks. It's a photo I took of OAD in 1994 during pushback in IAD. Occasionally if there was an excess of fuel lying in the bottom of the combustion chamber you used to get about 3 or 4 seconds of rather scary looking flames coming out of the jet pipe. It was never a problem, but looked quite spectacular (especially at night )





Best regards

Dude
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Old 14th Jan 2011, 07:29
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A question I have, relating to the photo above, is about the LE. The LE definately 'droops' in the area ahead of the intakes (it doesn't do so nearer the roots or tips). Is this to provoke a clean flow-breakaway in this area at high angles of attack to encourage the votices to form at this point as the wing transitions to vortex lift?
No, it is just the opposite. It delays the formation of vortices so that one can develop some leading edge suction on forward facing surfaces and keep the drag down in subsonic cruise. It is there inboard and not outboard because inboard there is some wing thickness which allows one to get some decent forward facing area whereas out board the wing is too thin to make it worthwhile.

The prototype had even more 'droop' in front of the intakes, but that produced a vortex at low incidence (near zero 'g') that went down the intakes and provoked surge.

The wash-out on the tips shows particularly well in the above photo (washout is a forward twist of the wing at the tips to reduce the angle of attack of the tips compared to the rest of the wing, to prevent tip-stalling).
Normally in subsonic aircraft yes, but in this case the reason is that since the tips are well behind the CG the washout makes the tips give an effective nose-up pitch which helps trim the aft movement of lift as you go supersonic.

Cheers

Clive

PS: Everyone seems to be adding their favourite Concorde photograph so I thought I would be different and add my LEAST favourite

">

Last edited by CliveL; 14th Jan 2011 at 07:43. Reason: adding a photo and additional remarks
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Old 14th Jan 2011, 07:37
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Happy New Year!

Hello again, chaps and chapesses, and a belated HNY to all.

I was prompted to post again by a fellow forumite..... I haven't really been in the mood to write after I fell over on the ice (well, that's my story and I'm sticking to it...) damaging a few bones, and then caught 'flu (woman 'flu, not man 'flu,) so I'm hoping that after a shaky start, 2011 will brighten up a bit now!

This is the year I will retire ..... I really don't know how I feel about that....but if anyone knows a kindly book publisher, perhaps it's time I thought about how to subsidise the pension, and keep Mr LL (or the Landlord, as he likes to be known), in gin and golf balls.

In reply to Shaggy's question with regard to the table top which was put into place after take-off at D2R, it didn't divide the cabins .... it was put accross the actual doorway to make an extra work-space during service. (Rather like a side-board in your dining room. Posh or what!) The fwd crew would take everything that could be needed during service from the front to the mid...wine, fizz, ice, lemon, water, etc., which would help the cabin crew (as opposed to the galley crew) to quickly replenish anything they needed without having to return to the galleys and more importantly, disturb the smooth running of the service...trolleys may be in the cabin and no-one wants to ask the crew on the trolleys to get more wine/water/whatever when they were busy. Of course, you could never second-guess what would be needed, and most probably someone would ask for a drink which you wouldn't have at the mid, but the things we needed all the time were there. The table top remained in place until the seat-belt sign came on for landing, and it was really handy. (Probably designed by a woman!) It was also a place for a couple of pax to stand and have a drink and a chat after the meal service was completed, if they fancied stretching their legs or were waiting for the loo.

Dude, your pic of pushback in IAD is fabulous! Just look what we were missing by being on-board!

With warm regards,
LL x
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Old 14th Jan 2011, 08:25
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Many thanks CliveL and LL! Most informative!
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Old 14th Jan 2011, 21:57
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CliveL

PS: Everyone seems to be adding their favourite Concorde photograph so I thought I would be different and add my LEAST favourite
Ohh yuk!! What is that Clive? It looks photoshopped to me, because why would anyone want Concorde to look like that?

Roger.
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Old 14th Jan 2011, 23:27
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The dreaded Pepsi scheme? Not on for long; it didn't help with skin temps for one thing. Even worse... it was hideous!

Serious question now. At 60,000 feet outside and 6,000 feet inside, what was the PSI pressure the cabin was subjected to? If I was clever I could probably work it out, but I'm not.
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Old 15th Jan 2011, 06:59
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Ohh yuk!! What is that Clive? It looks photoshopped to me, because why would anyone want Concorde to look like that?
Not photshopped I assure you. That's 201 in the dress she wore for the celebrations of Concorde's first flight in Toulouse. 'orrible isn't it? I don't think she ever flew like that. As Shaggy said it would completely screw up the skin temperatures.

Shaggy - your serious question - the pressure at 60,000 ft is 1.04 psi and at 6000 ft it is 11.78 psi so 10.74 psi differential.

Clive
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Old 15th Jan 2011, 07:20
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I personally agree about that photo, YUCH!!

Now about the cabin pressure thing: The pressurisation system would control to a MAXIMUM differential of 10.7 PSIG. Now at 60,000' the static pressure is 1.04 PSIA and at that altitude we would not QUITE be able to hold a cabin altitude of 6000', more like 6,200-6,300'. This is because 6000' altitude corresponds to a static pressure of 11.78 PSIA, giving us a diff' of 10.76 PSIG. Still as near as dammit mind, and for the MAJORITY of Atlantic crossings 6000' was fine. Such a 'civilised' cabin pressure was just one of the 1000 reasons that you never 'felt' as if you'd just flown over 3000 miles in Concorde.
Here is a diagram of the pressurisation panel.



The idea was that you selected a desired cabin altitude and the system would control to maintain that altitude all the way up to max diff. You could control the rate of presurisation too, to minimise popping ears etc. (Personally I always found Concorde particualarly good in that respect). There is one minor goof in the diagram, in that the discharge valve position indicator show both systems in operation. You only ever had one of the two systems in operation (via the SYS1/SYS2 selector switches). The only exception to this was on the ground when both systems were powered (and both sets of valves fully open).
Best regards

Dude

Last edited by M2dude; 15th Jan 2011 at 07:31. Reason: kerrektions
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Old 15th Jan 2011, 08:17
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Many thanks CliveL and Dude!
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Old 15th Jan 2011, 09:59
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A Journey Back In Time !!

OK, here is a photo that I took at Fairford in November 1976. I'd just had my very first Concorde flight on a brand new G-BOAD, and took this flight deck photo in the hangar later that afternoon (the doors are open hence the late afternoon Cotswold sky. The point of this rather poor (sorry guys, I was young for goodness sake) photo is to look at just how subtly different the 1976 flight deck WAS.



The first thing I know EXWOK and BELLEROPHON will (maybe) notice is that originally OAD had a 'normal colour' electroluminescent light plate on the visor indication panel. (If I remember rightly (it was a million years ago chaps) when this one 'stopped lighting' we could not get a replacement and had to rob 202 (G-BBDG) at Filton; this one being the same black development aircraft colour that OAD has to this day.
The OTHER first thing that you may notice is the Triple Temperature Indicator on the captains dash panel. (The first officer had his in in similar position). These got moved around (twice in the end) when TCAS was installed in the mid-90's. It was amazing just how much equipment got moved around over the years, in order to 'shoe-horn in' various bits of extra equimpent.
The cabin altimeter here fitted just above the #1 INS CDU also got moved (to the centre consul) when the FAA 'Branniff' modifications were embodied later in the 70's. It's spot got occupied by a standy altimeter mandated by the FAA but this was removed after Branniff ceased flying Concorde; the cabin altimeter returning to it's former home. The REALLY observant will notice that there is neither an Autoland Ca3/Cat2 identifier on the AFCS panel (glued on by BA at LHR) or the famous and precision built 'Reheat Capabilty Indicator' flip down plate fitted to the centre dash panel a few years later by BA.
Also not shown here, as they were buyer furnished equipment also fitted at on delivery LHR, are the two ADEUs (Automatic Data Entry Units, or INS Card readers). These were located immediatel aft of the CDU's and were used for bulk waypoint loading ('bulk' being 9, the most that the poor old Delco INU memory could handle). These were removed in the mid 90's when the Navigation Database was fitted to Concorde INUs, and bulk loading then was achieved by simply tapping in a 2 digit code. (Hardly the elegence of FMS, but still very elegent in comparison with the ADEU's, and worked superbly). A little note about these ADEU things; You inserted this rather large optically read paper data card into the thing and the motor would suck the unsuspecting card in. As often as not the ADEU would chew the card up and spit the remnants out, without reading any data, or not even bother spitting out the remnants at all. Removing these things FINALLY when the INUs were modified was absolute joy!!
ps. When G-BOAG (then G-BFKW) was delivered in 1980 it had neither any of the Branniff mods or ADEUs fitted. (Also the INS was not wired for DME updating). This meant that obviously she could not fly IAD-DFW with Branniff but also she could not do LHR-BAH either, because of the lack ADEUs. (You could not manually insert waypoints quick enough over the 'Med', or so the guys told me. So for the first few years good old FKW/OAG just used to plod between LHR and JFK. And plod she did, superbly. She never did get the ADEUs (not necessary thank goodness when the INUs got modified) but we wired in DME updating and so she could navigate around with the best of them.
My gosh I do prattle on, sorry guys.
Best regards

Dude

PS Welcome back Landlady, hope you've recovered from your fall XXXX

Last edited by M2dude; 15th Jan 2011 at 10:29.
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