Concorde question
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"I haven't worked out how to reply to postings and quote the relevant remarks yet - cut and paste doesn't seem to work, sorry."
Can someone with greater skill than I have please post some instructions for Clive and myself on how to include quotes from others posts in replies?
Can someone with greater skill than I have please post some instructions for Clive and myself on how to include quotes from others posts in replies?
Alternatively, to just reply with quote to one post, click the "reply" button, and then look at the address bar (where you type website addresses) in the browser. The address will end with: "&noquote=1". Click in the address bar, and replace that last "1" with a "0", press enter and the page will refresh with the post you are replying to already quoted.
[Edited: swapped the last 1 and 0 to the right way round - oops... thanks ChristiaanJ for spotting]
Hope this helps.
Last edited by infrequentflyer789; 20th Dec 2010 at 23:47.
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Point CG for Take off Performance - Post 890
Having found this superb thread back when it was at its page 8. It is a daily 'must check' for me, and is about to get more interesting because 'CliveL' is joining. Welcome Clive.
As the CAA surveyor/flight test engineer referred to in Clive's Post 890, I am happy to confirm that the discussion took place and we had a good result for the aeroplane. My logbook suggests it was March 1975 at Torrejon with G-BBDG.
I will try to dig back into 35 years ago memory banks and find a few more anecdotes of a fascinating development and certification programme.
Compliments of the season to all readers.
Andrew
As the CAA surveyor/flight test engineer referred to in Clive's Post 890, I am happy to confirm that the discussion took place and we had a good result for the aeroplane. My logbook suggests it was March 1975 at Torrejon with G-BBDG.
I will try to dig back into 35 years ago memory banks and find a few more anecdotes of a fascinating development and certification programme.
Compliments of the season to all readers.
Andrew
Last edited by asmccuk; 28th Mar 2020 at 12:13. Reason: Correction to Title
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Minor correction (typo) about quoting from a post.
As, said, the address will end with "&noquote=1" (meaning 'noquote' is "on").
Either replace that last "1" with a "0" or just delete the "1", then press enter.
CJ
...click the "reply" button, and then look at the address bar (where you type website addresses) in the browser. The address will end with: "&noquote=1". Click in the address bar, and replace that last "0" with a "1", press enter and the page will refresh with the post you are replying to already quoted.
Either replace that last "1" with a "0" or just delete the "1", then press enter.
CJ
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Why the switches for climb and cruise ratings. What was being accomplished that modulation of the throttles couldn't
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Once you know how the rating selections work, enabling the throttles to be left fully forward throughout normal flight, you can draw a line to the Airbus FBW thrust lever arrangement - the detents equating to different ratings.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
BTW I was told in the conversion course that during the design phase the idea was mooted to only have one thrust lever for all four engines. This would probably have worked - even non-normal engine shutdown drills didn't require the engine's throttle to be closed, the first thing you did was pull the shutdown handle.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
BTW I was told in the conversion course that during the design phase the idea was mooted to only have one thrust lever for all four engines. This would probably have worked - even non-normal engine shutdown drills didn't require the engine's throttle to be closed, the first thing you did was pull the shutdown handle.
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CliveL
First of all a hearty welcome from myself also to the thread, speaking as a fellow old Filtonian/Fairfordian. (I'm sure I must have bumped into you during my years at BAC Clive).
It is thanks to the tremendous skill and dedication of 'designer chaps', such as yourself and ChristiaanJ, that Concorde became this breathtakingly amazing aeroplane that she was. I can't wait to read some more of your informative posts; you obviously have one hell of a story to tell, and can obviously teach us all (especially me) a thing or three.
It was thanks to this superb system for sealing off the engine bay (as well as actuating closed the nacelle ground running flap) when the ESDH (fire handle) was pulled, that generally limited the damage caused by the engine bay fire you mentioned on G-BOAF in 1980 to the affected engine only. (Save as you say, those small holes in the centre wall). Also worth mentioning is the fact that extinguisher pressure would also trip a 'fire flap', that would isolate the ram airflow into the air conditioning heat exchangers, that were mounted directly above the engines.. In the case of the aforementioned incident, this was just as well, as both heat exchangers were seriously damaged by the fire, and another potential source of oxygen was fortunately removed. Yet another truly brilliant piece of design.
Best Regards
Dude
First of all a hearty welcome from myself also to the thread, speaking as a fellow old Filtonian/Fairfordian. (I'm sure I must have bumped into you during my years at BAC Clive).
It is thanks to the tremendous skill and dedication of 'designer chaps', such as yourself and ChristiaanJ, that Concorde became this breathtakingly amazing aeroplane that she was. I can't wait to read some more of your informative posts; you obviously have one hell of a story to tell, and can obviously teach us all (especially me) a thing or three.
Anyway, after that 1980 engine fire incident we did find a couple of small holes in the centrewall and as a result we fitted some ceramic coated steel plates in the vulnerable areas.
But as stated, the fire precautions built in did a good job. In this connection though it is worth saying that the cooling air passing over the engine comes from the ramp bleed in the intake and that it is controlled by 'secondary air doors' in the corners left between the circular engine and the square nacelle. These are there to stop air flowing back from the engine bay into the intake during takeoff and are opened once the pressure diferential between intake and engine bay is favourable. Part of the fire drill was to close these doors so the engine fire was deprived of oxygen, which helps a lot
But as stated, the fire precautions built in did a good job. In this connection though it is worth saying that the cooling air passing over the engine comes from the ramp bleed in the intake and that it is controlled by 'secondary air doors' in the corners left between the circular engine and the square nacelle. These are there to stop air flowing back from the engine bay into the intake during takeoff and are opened once the pressure diferential between intake and engine bay is favourable. Part of the fire drill was to close these doors so the engine fire was deprived of oxygen, which helps a lot
Best Regards
Dude
Last edited by M2dude; 21st Dec 2010 at 08:37.
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ChristiaanJ
Not quite right I'm afraid here my friend. The superb Vulcan used self-contained electro-hydraulic PFCUs, similar in concept to the VC10. The pilot signalling from the fighter type joystick to the PFCUs however was still mechanical, no FBW here.
EXWOK
Oh Amen to that. Although quite complex in its concept, at least 'our' system was logical and intuitive, with full pilot control throughout.
Best Regards
Dude
Originally Posted by CliveL 
Sure, Concorde was the first aircraft to fly with FBW flight controls...
I thought it was the first civil aircraft, and that the Vulcan had already been there and done that...
Sure, Concorde was the first aircraft to fly with FBW flight controls...
I thought it was the first civil aircraft, and that the Vulcan had already been there and done that...
EXWOK
Once you know how the rating selections work, enabling the throttles to be left fully forward throughout normal flight, you can draw a line to the Airbus FBW thrust lever arrangement - the detents equating to different ratings.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
Best Regards
Dude
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Originally Posted by EXWOK
Once you know how the rating selections work, enabling the throttles to be left fully forward throughout normal flight, you can draw a line to the Airbus FBW thrust lever arrangement - the detents equating to different ratings.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
Mercifully no-one had thought of that when Concorde was being designed; I still think it's a diabolical system.
Originally Posted by M2Dude
Oh Amen to that. Although quite complex in its concept, at least 'our' system was logical and intuitive, with full pilot control throughout.
PBL
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It's entirely possible;, in fact there's a probability of at least some crossover since one idea, as I suggested, is to some extent an extension of its predecessor.
My views on their relative merits aren't affected by that, however.
My views on their relative merits aren't affected by that, however.
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PBL
As far as the Autothrottle side of things (you know, the throttles actually MOVING in response to autothrottle action, how novel 
), that was designed by the Elliot part of the Anglo-French AFCS consortium. (This then became Marconi-Elliot, and then GEC-Marconi, and finally part of BAe Systems). I doubt very much if this is in anyway connected with Airbus at all. (I know,...Duh!!).
As far as the Concorde engine power control philosophy, well this was Rolls-Royce, through and through, with some BAe input, so again I think you can rule that out too.
Basically PBL, I would say that in answer to your question, we can say that they were definately not, thank goodness
... (Naughty boy, Dude 
). Bearing in mind of course that the current Airbus philosophy can be traced back to the early A320s.... not a Roller in sight there.
Best Regards
Dude
And how do we know they weren't designed by the very same people?
), that was designed by the Elliot part of the Anglo-French AFCS consortium. (This then became Marconi-Elliot, and then GEC-Marconi, and finally part of BAe Systems). I doubt very much if this is in anyway connected with Airbus at all. (I know,...Duh!!).As far as the Concorde engine power control philosophy, well this was Rolls-Royce, through and through, with some BAe input, so again I think you can rule that out too.
Basically PBL, I would say that in answer to your question, we can say that they were definately not, thank goodness
... (Naughty boy, Dude ). Bearing in mind of course that the current Airbus philosophy can be traced back to the early A320s.... not a Roller in sight there. Best Regards
Dude
Last edited by M2dude; 21st Dec 2010 at 10:36. Reason: My crap spelling
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quote:Re the autotrim, tell us some more?unquote
It is a little complicated, but let me go back half a step.
Concorde was not certificated to FARs or BCAR (the French code was essentially a straight translation of FAR) but to completely new set of requirements known as TSS (Transport Supersonique Standards). The old UK ARB had initiated discussions about these even before cooperation negotiations had started. The result was that young, junior engineers got to debate the basics of airworthiness rules with older, experienced airworthiness specialists. In hindsight it was wonderful training!
But to get to the point, it was this thinking that allowed us to ignore some of the older rules which, although great for the aircraft flying at the time they were written, had little or no relevance to SSTs. We could interpret that as trying to find out what the pilots really wanted the aircraft to do and then to try and provide it.
In the particular case of trim/speed stability it was quite clear that what they wanted was an aircraft that could be flown with minimal trim changes and which once trimmed would not go wandering off all over the place. We also knew that in some cases the 'elevator angle per 'g' ' could get as low as one degree/g in some cases and that the pilot could not tell exactly where his hands were positioned to that precision, although he would always know if he was pushing or pulling. So we could abandon the old rules for stick movement and instead supply classic stick force stability for deviations from the trimmed state.
All this had to be matched to the varying aerodynamics through the transonic region (where everything varies rapidly) and the fuel transfer system characteristics. The resulting Mach trim laws were quite complex and were not, in fact just Mach Number sensitive. We also had two airspeed (Vcas) terms, one of which had a variable gain which was itself Mach dependent and kicked in above Vmo = 5kts and the other was a straight nose up elevator command as a function of Vcas. The Mach trim itself was highly nonlinear. The best way to illustrate this is probably a diagram but now I've run into another gap in my knowledge of this thread - how do I do that?
Anyway, the result was that the fuel transfer held the trim setting variation down to between 2 deg down to 1.5 deg up through the acceleration from 0.95M up to 0.5 deg down at Mach 2.0. Without fuel transfer the trim at Mach 2 would have been closer to 10 deg. The trim between say 0.95 and 1.2 varies in a nonlinear fashion and the Mach trim law shows roughly similar variations.
But the best measure of our success is the comments we are getting here from the guys who actually had to fly it.
Clive
[IMG]file:///C:/Users/Clive/AppData/Local/Temp/moz-screenshot.png[/IMG][IMG]file:///C:/Users/Clive/AppData/Local/Temp/moz-screenshot-1.png[/IMG]
It is a little complicated, but let me go back half a step.
Concorde was not certificated to FARs or BCAR (the French code was essentially a straight translation of FAR) but to completely new set of requirements known as TSS (Transport Supersonique Standards). The old UK ARB had initiated discussions about these even before cooperation negotiations had started. The result was that young, junior engineers got to debate the basics of airworthiness rules with older, experienced airworthiness specialists. In hindsight it was wonderful training!
But to get to the point, it was this thinking that allowed us to ignore some of the older rules which, although great for the aircraft flying at the time they were written, had little or no relevance to SSTs. We could interpret that as trying to find out what the pilots really wanted the aircraft to do and then to try and provide it.
In the particular case of trim/speed stability it was quite clear that what they wanted was an aircraft that could be flown with minimal trim changes and which once trimmed would not go wandering off all over the place. We also knew that in some cases the 'elevator angle per 'g' ' could get as low as one degree/g in some cases and that the pilot could not tell exactly where his hands were positioned to that precision, although he would always know if he was pushing or pulling. So we could abandon the old rules for stick movement and instead supply classic stick force stability for deviations from the trimmed state.
All this had to be matched to the varying aerodynamics through the transonic region (where everything varies rapidly) and the fuel transfer system characteristics. The resulting Mach trim laws were quite complex and were not, in fact just Mach Number sensitive. We also had two airspeed (Vcas) terms, one of which had a variable gain which was itself Mach dependent and kicked in above Vmo = 5kts and the other was a straight nose up elevator command as a function of Vcas. The Mach trim itself was highly nonlinear. The best way to illustrate this is probably a diagram but now I've run into another gap in my knowledge of this thread - how do I do that?
Anyway, the result was that the fuel transfer held the trim setting variation down to between 2 deg down to 1.5 deg up through the acceleration from 0.95M up to 0.5 deg down at Mach 2.0. Without fuel transfer the trim at Mach 2 would have been closer to 10 deg. The trim between say 0.95 and 1.2 varies in a nonlinear fashion and the Mach trim law shows roughly similar variations.
But the best measure of our success is the comments we are getting here from the guys who actually had to fly it.
Clive
[IMG]file:///C:/Users/Clive/AppData/Local/Temp/moz-screenshot.png[/IMG][IMG]file:///C:/Users/Clive/AppData/Local/Temp/moz-screenshot-1.png[/IMG]
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quote:The only real area of concern was the crown area (the roof 
). There was a design flaw here in that the structure had not been designed fail-safe (allegedly by designed a Korean designer at Aérospatiale who, it was said, went a bit loopy) unquote
I think he was Vietnamese actually, cerainly there was a guy of that nationality working in the Sud Aviation Stress Office, but he wasn't loopy - just cussed!
Clive
). There was a design flaw here in that the structure had not been designed fail-safe (allegedly by designed a Korean designer at Aérospatiale who, it was said, went a bit loopy) unquoteI think he was Vietnamese actually, cerainly there was a guy of that nationality working in the Sud Aviation Stress Office, but he wasn't loopy - just cussed!
Clive
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quote:You then needed the zero fuel weight (ZFW) and zero fuel CG (ZFCG);unquote
So you need to know where the payload is going to be. Sud did flirt wit a 'bumsonseatometer' but eventually settled for allocated seating and simple preflight calculations (by the dispatcher I think, but ex-pilots would be able to help out on that)
Clive
So you need to know where the payload is going to be. Sud did flirt wit a 'bumsonseatometer' but eventually settled for allocated seating and simple preflight calculations (by the dispatcher I think, but ex-pilots would be able to help out on that)
Clive
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CliveL
At BA the ZFW & ZFCG were sent to the aircraft from Load Control via NOCARS. Only joking folks, with no third VHF ACARS never happened, it was VHF verbal. On charters a despatcher would usually either fly with the aircraft or be positioned at the charter destination in order to make the load control calculations. My pilot buddies will confirm this I'm sure
(I seem to remember that in the early 90s we were looking to fit Concorde with ACARS, but when informally approached, Filton pleaded 'please, not another aerial position
'.... we had only just got over the TCAS installation issues you see).
... Oh, he was Vietnamese eh? And not LOOPY??????
tee hee, We are certainly living and learning here thanks Clive, keep on posting
.
Best Regards
Dude
At BA the ZFW & ZFCG were sent to the aircraft from Load Control via NOCARS
. Only joking folks, with no third VHF ACARS never happened, it was VHF verbal. On charters a despatcher would usually either fly with the aircraft or be positioned at the charter destination in order to make the load control calculations. My pilot buddies will confirm this I'm sure (I seem to remember that in the early 90s we were looking to fit Concorde with ACARS, but when informally approached, Filton pleaded 'please, not another aerial position
'.... we had only just got over the TCAS installation issues you see).... Oh, he was Vietnamese eh? And not LOOPY??????
tee hee, We are certainly living and learning here thanks Clive, keep on posting
.Best Regards
Dude
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quote:I don't know why this popped into my head but what was her glide ratio if all the engines stopped? Maybe because I remember from my early training being told the a B707 had a better glide ratio than the PA28-140 I was learning in. Now that was an eye opener at the time.unquote
A lot depends on how fast you were flying. You can get pretty good values of Lift/Drag ratio (that defines the potential glide slope with all engines operating, if that is not a contradiction in terms) from the Concorde B pages of the Concorde SST site. The actual glide slope with engines out would have been a lot worse than those numbers because of windmilling and (supersonically) intake spillage drag.
Nowhere near any subsonic values!
Clive
A lot depends on how fast you were flying. You can get pretty good values of Lift/Drag ratio (that defines the potential glide slope with all engines operating, if that is not a contradiction in terms) from the Concorde B pages of the Concorde SST site. The actual glide slope with engines out would have been a lot worse than those numbers because of windmilling and (supersonically) intake spillage drag.
Nowhere near any subsonic values!
Clive
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On charters a despatcher would usually either fly with the aircraft or be positioned at the charter destination
L&B was done by the flt crew on charters; if the flight had a PR flt crew member on board it was his job, otherwise it was the NHP's. (Unless the Captain was the NHP when it became the SFO's job.....)
At some BA stations arrangements might be made to get a L&B through company, but generally for charter flights we operated the way charter companies did!
Edit: Actually, I now recall we did sometimes get a dispatcher sent to UK stations occasionally. No big deal, either way - you just got on with it.
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Thanks EXWOK, as always I humbly stand corrected. We DID take one with us when we took OAG to BKK, and I do remember a few other occasions when a 'cap' got positioned. But this worn out brain does remember you guys doing L&B stuff when away.
Best Regards (And I hope you're not working over Christmas... I am)
Dude
Best Regards (And I hope you're not working over Christmas... I am
)Dude
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quote: One has to remember that the aircraft is effectively statically unstable in pitch at approach speeds, so a pilot up-elevator input would soon be followed by a countering autostab elevon-down to contain the tendency to keep pitching up, and vice-versa.unquote
Sorry EXWOK, but I just don't agree that the aircraft was statically unstable in pitch at approach. When I think of the hours we put in trying to straighten that damned pitch curve!
It WAS designed to operate with low CG margins on approach, and that meant that the elevator (elevon) deflection needed to trim any desired incremental 'g' was quite small. On the other hand the pitch inertia was high and the elevon moment arm low, so if you just applied the elevon needed for the final state the pitch response would have been pathetic. This meant that the elevon needed to be 'overdriven' to get the aircraft moving and then backed off to hold it to the desired final state. Maybe the apparent reversals you are seeing in the video come from this source.
CliveL
Sorry EXWOK, but I just don't agree that the aircraft was statically unstable in pitch at approach. When I think of the hours we put in trying to straighten that damned pitch curve!
It WAS designed to operate with low CG margins on approach, and that meant that the elevator (elevon) deflection needed to trim any desired incremental 'g' was quite small. On the other hand the pitch inertia was high and the elevon moment arm low, so if you just applied the elevon needed for the final state the pitch response would have been pathetic. This meant that the elevon needed to be 'overdriven' to get the aircraft moving and then backed off to hold it to the desired final state. Maybe the apparent reversals you are seeing in the video come from this source.
CliveL
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quote:Also, regarding the 4000psi pressure adopted - the control surfaces most definitely did need powerful actuators; as you now know they were very active, especially on approach and transonic, and as well as IASs of up to 530kts you have all the lever arm changes brought by shifting centres of pressure over the surfaces caused by shockwave movements.unquote
Yup, I agree with that. I did the original control hinge moment calculations before we joined up with Sud, and the static hinge moments generated are quite impressive!
In fact the most critical zone is the transonic region and some (most) of the CG boundaries in the 'transonic corridor' are defined by hinge moment capability to provide the necessary manoeuvre 'g', especially with one system inoperative. The control rates aren't all that demanding, but the static hinge moment definitely was critical, and as you say, frontal area is everything and the jacks lie outside the wing section profile.
CliveL
Yup, I agree with that. I did the original control hinge moment calculations before we joined up with Sud, and the static hinge moments generated are quite impressive!
In fact the most critical zone is the transonic region and some (most) of the CG boundaries in the 'transonic corridor' are defined by hinge moment capability to provide the necessary manoeuvre 'g', especially with one system inoperative. The control rates aren't all that demanding, but the static hinge moment definitely was critical, and as you say, frontal area is everything and the jacks lie outside the wing section profile.
CliveL