Concorde question
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On the ITVV Concorde DVD the Captain explains that during the cruise climb at mach 2 the auto throttles were armed and would be used as required. Then during descent the throttles were gradually pulled back whilst the autopilot was given an IAS of I think 350 knots. Therefore the plane would have to descend to maintain that speed. He explained that the power settings were chosen to ensure that there was sufficent cooling etc.
My query is if an autoland was to be undertaken was the auto throttle system able to maintain the required landing speed or would the pilot have to manage the throttles? I guess that decreasing or increasing the pitch to control speed when on the glide slope would not be a good idea.
Thanks again
Nick
My query is if an autoland was to be undertaken was the auto throttle system able to maintain the required landing speed or would the pilot have to manage the throttles? I guess that decreasing or increasing the pitch to control speed when on the glide slope would not be a good idea.
Thanks again
Nick
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Approach handling was an interesting exercise - being so far down the back of the drag curve (over 100kts below best L/D) very accurate thrust handling was required.
The autothrottle was always used for approach if servicable, except for a two-engined approach, and was absolutely excellent. There were two, operating in parallel, and if the speed was more than a couple of knots out for more than a few seconds it was unusual. In IAS ACQ mode there was an active input from the INS which tracked grounspeed and so enabled anticipatory throttle movements during wind changes - if an autoland runway was available the preferred method of dealing with an approach likely to experience windshear was to carry out an autoland. (I think I speak for everyone, though, if I express a preference for the just going somewhere else option).
In Supercruise one autothrottle only was rearmed if the associated autopilot was engaged - it wasn't active but was available to cater for sudden drops in temperature which could cause unpleasant sudden high rates of climb if the temp shear was sufficient.
The rest of the flight - basically manual thrust, usually with the throttles fully forward.
Maybe one day we'll start making aeroplanes with such sophisticated systems again...........there's still lots that hasn't been hinted at on this thread
The autothrottle was always used for approach if servicable, except for a two-engined approach, and was absolutely excellent. There were two, operating in parallel, and if the speed was more than a couple of knots out for more than a few seconds it was unusual. In IAS ACQ mode there was an active input from the INS which tracked grounspeed and so enabled anticipatory throttle movements during wind changes - if an autoland runway was available the preferred method of dealing with an approach likely to experience windshear was to carry out an autoland. (I think I speak for everyone, though, if I express a preference for the just going somewhere else option).
In Supercruise one autothrottle only was rearmed if the associated autopilot was engaged - it wasn't active but was available to cater for sudden drops in temperature which could cause unpleasant sudden high rates of climb if the temp shear was sufficient.
The rest of the flight - basically manual thrust, usually with the throttles fully forward.
Maybe one day we'll start making aeroplanes with such sophisticated systems again...........there's still lots that hasn't been hinted at on this thread
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Originally Posted by EXWOK
there's still lots that hasn't been hinted at on this thread
With the FBW, was there any feedback built into the yoke? The Airbus with it's "joystick" has, I believe, no feel unlike a Flight Sim force feedback one.
If there was a yoke movement on one side did the other side mirror the movement or like the Airbus did the sidestick play dead?
M2, it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?
Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?
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This is a wonderful thread about the most superlative aircraft ever built.We were once fortunate enough to be given seats 1 C&D (I would have liked to see a roll-call of their previous occupants) and with regard to the hugely knowledgeable points made about fuel transfer and trim, during boarding and in flight the sound of fuel pumping was often louder than the Olympus music.During a visit to the FD the captain verified that these were the noisiest rows in the cabin despite their often being used by royalty and REAL A-listers. Many thanks for sharing your deep insights into this machine.
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yoke feedback
Biggles:
Yep, there was feedback. In this respect, the implementation of FBW had a rather different philosophy to FBW Airbus'.
Below 200kts it was basically a spring feedback, above that speed it was achieved throught the feel system, not entirely unlike conventional aircraft.
Of course, the feel was tempered also by the autostab system, which didn't feedback through the yoke, but did make control surface inputs. A basic analogy is to imagine a yaw damper, but on all three axes. (It was of course rather more sophisticated, especially in pitch).
During airtests we would fly portions of the supersonic accel without autostabs and it was then very obvious exactly how much input was being made - great care was needed to remain within sensible bank angles in the low supersonic regime.
Also - watch a video of the control surfaces in the latter stages of the approach and landing - all those rapid deflections are the autostabs overlaid on the pilot's inputs. 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. Gusts affecting the IAS would also create an input.
All of which means the basic spring feel below 200kts is not as basic as it sounds.....and in normal signalling modes (ie FBW and autostab active) the amazing thing is that the aircraft handled beautifully through an 1100kt speed range.
If you look at a picture of the flightdeck you will see a row of 14 white switches full width of the fwd edge of the overhead panel. These were autostab pitch/roll/yaw, feel pitch/roll/yaw left and right systems and the two pitch trim switches (which played a big part in the low-speed protection).
If any of them dropped out you could be sure that the first thing the nearest pilot would do would be to try to re-engage them, as it made for a vastly more pleasant life.
Yep, there was feedback. In this respect, the implementation of FBW had a rather different philosophy to FBW Airbus'.
Below 200kts it was basically a spring feedback, above that speed it was achieved throught the feel system, not entirely unlike conventional aircraft.
Of course, the feel was tempered also by the autostab system, which didn't feedback through the yoke, but did make control surface inputs. A basic analogy is to imagine a yaw damper, but on all three axes. (It was of course rather more sophisticated, especially in pitch).
During airtests we would fly portions of the supersonic accel without autostabs and it was then very obvious exactly how much input was being made - great care was needed to remain within sensible bank angles in the low supersonic regime.
Also - watch a video of the control surfaces in the latter stages of the approach and landing - all those rapid deflections are the autostabs overlaid on the pilot's inputs. 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. Gusts affecting the IAS would also create an input.
All of which means the basic spring feel below 200kts is not as basic as it sounds.....and in normal signalling modes (ie FBW and autostab active) the amazing thing is that the aircraft handled beautifully through an 1100kt speed range.
If you look at a picture of the flightdeck you will see a row of 14 white switches full width of the fwd edge of the overhead panel. These were autostab pitch/roll/yaw, feel pitch/roll/yaw left and right systems and the two pitch trim switches (which played a big part in the low-speed protection).
If any of them dropped out you could be sure that the first thing the nearest pilot would do would be to try to re-engage them, as it made for a vastly more pleasant life.
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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.
If you want to fly supersonic, frontal area is everything so 4000psi also has the benefit of keeping the PFCU cross-section down.
I'm sure M2Dude will be able to give a better explanation of this aspect - it's nearly seven years since I flew the beast (that's depressing) and it's hard enough to remember detail of the flying bits, let alone the complex engineering aspects.
If you want to fly supersonic, frontal area is everything so 4000psi also has the benefit of keeping the PFCU cross-section down.
I'm sure M2Dude will be able to give a better explanation of this aspect - it's nearly seven years since I flew the beast (that's depressing) and it's hard enough to remember detail of the flying bits, let alone the complex engineering aspects.
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Oh yeah - finally:
As for my allusion to other interesting areas of this aeroplane, we've all got our favourite examples - but I for one will see how the thread progresses naturally before I start proselytising about my favourite bits.
As for my allusion to other interesting areas of this aeroplane, we've all got our favourite examples - but I for one will see how the thread progresses naturally before I start proselytising about my favourite bits.
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Biggles78
The tailwheel design really was the one exception in poor design terms, but I'm sure that if the aircraft was doing what she should be doing right now, (you know routinely flying across the Atlantic and beyond, instead of languishing in museums), modifications would have finally put this particular malady to bed). In design terms, the rest of the aircraft was nothing short of a flying work of art, a masterpiece. Having said that though, personally I would rather that four rather than three hydraulic systems had been used. Originally there were four systems in the design, but the RED system was deleted, as it was felt to be superfluous. My own view is that this particular decision was total poppycock. Oh, and Green, Blue and Yellow hydraulic systems was something else that Airbus copied from Concorde.... although we ourselves pinched that idea off of the Comet 
).
As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset
EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you.
(for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).
The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).
To all, I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.
Dude
M2, it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?
Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?
Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?
). As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset
EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you.
(for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).
To all, I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.
Dude
I'm just an interested non-pilot bystander, & hope it's OK to post here.
Thank you all for this truly fascinating information. I've a question arising from watching the ITVV DVDs:
Having two pilots obviously gives some options if one becomes ill or incapacitated, but how were things handled if the FE became unable to perform his duties? Did the FO take over, & how familiar were the pilots with the FE's duties - could either pilot do the FE's job in full, or was it limited to some subset such as required for a diversion/landing etc. I assume this kind of thing was practised in the simulator regularly?
I note (unless I've misunderstood) that there was some presetting of the load limit fuel transfer system, so that the pilots could initiate a CofG movement for descent if required.
Thanks!
Thank you all for this truly fascinating information. I've a question arising from watching the ITVV DVDs:
Having two pilots obviously gives some options if one becomes ill or incapacitated, but how were things handled if the FE became unable to perform his duties? Did the FO take over, & how familiar were the pilots with the FE's duties - could either pilot do the FE's job in full, or was it limited to some subset such as required for a diversion/landing etc. I assume this kind of thing was practised in the simulator regularly?
I note (unless I've misunderstood) that there was some presetting of the load limit fuel transfer system, so that the pilots could initiate a CofG movement for descent if required.
Thanks!
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MEMORIES
Like so many in the Concorde family, I have millions, I'd like to share a couple here. I remember at Fairford in mid 1974, a CAA test pilot (I honestly forget the gentleman's name) was taking the British pre-production A/C 101 (G-AXDN) for a special test flight. The reason that this flight was so special was that for the first time, the CAA were going to do an acceptance flight trial of the brand new digital air intake system. This revolutionary system had been retro fitted to 101 barely a year earlier, and being a brand new (and totally unique, in electronics terms) system had been plagued with teething troubles. It was quite reasonable for any airworthiness authority to have serious misgivings about any system that was going to wave great big metal lumps around in front of the engine compressor face, and that if only a few degrees out from the commanded position out could cause the engine to 'backfire' etc.
So anyway, 101 took off and disappeared into the very blue sky and we waited, and waited, AND WAITED. (I'd only left the RAF and joined the project a few months previously, and did not want my new association with this amazing aircraft to end). I was biting my nails, drinking coffee, losing my hair... (without the help of M2V). Anyway after about 2 1/2 hours the aircraft returned to Fairford, and everybody crowds around the crew for the debrief. A very stern faced CAA pilot looked at us all, broke into a grin and said "as far as I'm concerned gentlemen, you've got yourselves an airliner". At that point the room was a study of total happiness, blessed relief, and a need to go to the loo..... But from my point of view, I will remember those words forever.
101, which now resides at the Imperial War Museum Duxford was the fastest Concorde ever. She achieved Mach 2.23, which was an incredible irony, as Concorde can trace a large part of it's developement history back to the BAC 223, proposed SST.
As far as flying memories go, I just don't know where to start; My first ever Concorde flight was in November 1976, out of Fairford on a pre-delivery test flight on G-BOAD. (Now sadly bobbing up and down on the Hudson, next to the USS Intrepid). I was staggered how fast and high we flew (Mach 2.08, FL580). Most of my flying up to that date had been in C-130's in the RAF, at around 340 KTS and FL300; Concorde also being infinately quiter in flight than the good old Herc'. I remember a BA QA guy showing me how I could touch the skin of the aircraft at Mach 2 (You reached behind a door busstle flap, moved your hand through some insulation until you felt bare metal). OUCH!! it was hot, very hot.
But I think one of my most memorable flight memories was aboard G-BOAG, (now residing in the Boeing Museum of Flight in Seattle) returning from BKK, having stopped off to refuel in BAH. We were forced to fly subsonic over Saudi, and got caught in this amazing electrical storm, There was St Elmo's fire cracking and bubbling all over the visor panels, but just as incredible was the long blue electrical discharge coming off of the nose probe; it seemed to extend about 50' in front of the aircraft. The crime was, none of us on the F/D had a camera. Every time I bump into the captain on that day (are you reading this Ian?), we go back to remonissing about that incredible flight. Also, later on the same sector, after we had decelerated to subsonic cruise again, this time flying up the Adriatic, we had another fascinating sight: It was getting quite dark now, and here we were, travelling at Mach 0.95 at FL290, when above us was all this Mach 0.8 ish traffic at around FL330-350. All we could see were all these navigation and ant-coll' lights above us, seemingly travelling backwards. It was quite a sight. On the original BAH-BKK sector a week earlier, we flew through some of the coldest air I'd ever seen; The air was at ISA -25, and at Mach 2 our TAT was only about 85 deg's C. (You could feel the difference too; the cabin windows felt only warm-ish to the touch). The upside also of all this was that your fuel burn was much lower than usual. (The only downside of course is that your TAS is a little lower). Rolls Royce did some analysis on the flight, and were amazed at how well the propulsion systems coped with some of the temperature sheers that we encountered, sometimes 4 to 5 deg's/second. They said that the prototype AFCS had been defeated by rises of only 0.25 deg's/second ).
Not meaning to go off onto a (yet another) tangent; Negative temperature shears, very common at lower lattidudes, always plagued the development aircraft; you would suddenly accelerate, and in the case of a severe shear, would accelerate and accelerate!! (Your Mach number, quite naturaly, suddenly increased with the falling temperature of course, but because of the powerplant suddenly hitting an area of hyper-efficiencey, the A/C would physically accelerate rapidly, way beyond Mmo). Many modifications were tried to mitigate the effects of severe shears, in the end a clever change to the intake control unit software fixed it. (Thanks to this change the production series A/C would not be capable of level flight Mach numbers of any more than Mach 2.13, remembering that Mmo was set at 2.04).
There was one lovely story, involving the Shah of Iran, having one of MANY flights in a developmment aircraft. The aircraft encounterd quite a hefty series of temperature shears that plagued havoc with some Iranian F4's that were attempting to close on the Concorde, to act as an escort for the Shah. (or so the strory goes). I'm still trying to picture these F4's, on full afterburner trying to get close to a Concorde cruising away on dry power). It is said that the F4's were having such difficulties, due to their relatively crude powerplant, coping with the temperature changes, that the Concorde was ordered to slow down, 'so the escorting F4's could catch up'!! True or not, it is part of Concorde folklore.
Dude
Like so many in the Concorde family, I have millions, I'd like to share a couple here. I remember at Fairford in mid 1974, a CAA test pilot (I honestly forget the gentleman's name) was taking the British pre-production A/C 101 (G-AXDN) for a special test flight. The reason that this flight was so special was that for the first time, the CAA were going to do an acceptance flight trial of the brand new digital air intake system. This revolutionary system had been retro fitted to 101 barely a year earlier, and being a brand new (and totally unique, in electronics terms) system had been plagued with teething troubles. It was quite reasonable for any airworthiness authority to have serious misgivings about any system that was going to wave great big metal lumps around in front of the engine compressor face, and that if only a few degrees out from the commanded position out could cause the engine to 'backfire' etc.
So anyway, 101 took off and disappeared into the very blue sky and we waited, and waited, AND WAITED. (I'd only left the RAF and joined the project a few months previously, and did not want my new association with this amazing aircraft to end). I was biting my nails, drinking coffee, losing my hair... (without the help of M2V
). Anyway after about 2 1/2 hours the aircraft returned to Fairford, and everybody crowds around the crew for the debrief. A very stern faced CAA pilot looked at us all, broke into a grin and said "as far as I'm concerned gentlemen, you've got yourselves an airliner". At that point the room was a study of total happiness, blessed relief, and a need to go to the loo..... But from my point of view, I will remember those words forever.101, which now resides at the Imperial War Museum Duxford was the fastest Concorde ever. She achieved Mach 2.23, which was an incredible irony, as Concorde can trace a large part of it's developement history back to the BAC 223, proposed SST.
As far as flying memories go, I just don't know where to start; My first ever Concorde flight was in November 1976, out of Fairford on a pre-delivery test flight on G-BOAD. (Now sadly bobbing up and down on the Hudson, next to the USS Intrepid). I was staggered how fast and high we flew (Mach 2.08, FL580). Most of my flying up to that date had been in C-130's in the RAF, at around 340 KTS and FL300; Concorde also being infinately quiter in flight than the good old Herc'. I remember a BA QA guy showing me how I could touch the skin of the aircraft at Mach 2 (You reached behind a door busstle flap, moved your hand through some insulation until you felt bare metal). OUCH!! it was hot, very hot.
But I think one of my most memorable flight memories was aboard G-BOAG, (now residing in the Boeing Museum of Flight in Seattle) returning from BKK, having stopped off to refuel in BAH. We were forced to fly subsonic over Saudi, and got caught in this amazing electrical storm, There was St Elmo's fire cracking and bubbling all over the visor panels, but just as incredible was the long blue electrical discharge coming off of the nose probe; it seemed to extend about 50' in front of the aircraft. The crime was, none of us on the F/D had a camera. Every time I bump into the captain on that day (are you reading this Ian?), we go back to remonissing about that incredible flight. Also, later on the same sector, after we had decelerated to subsonic cruise again, this time flying up the Adriatic, we had another fascinating sight: It was getting quite dark now, and here we were, travelling at Mach 0.95 at FL290, when above us was all this Mach 0.8 ish traffic at around FL330-350. All we could see were all these navigation and ant-coll' lights above us, seemingly travelling backwards. It was quite a sight. On the original BAH-BKK sector a week earlier, we flew through some of the coldest air I'd ever seen; The air was at ISA -25, and at Mach 2 our TAT was only about 85 deg's C. (You could feel the difference too; the cabin windows felt only warm-ish to the touch). The upside also of all this was that your fuel burn was much lower than usual. (The only downside of course is that your TAS is a little lower). Rolls Royce did some analysis on the flight, and were amazed at how well the propulsion systems coped with some of the temperature sheers that we encountered, sometimes 4 to 5 deg's/second. They said that the prototype AFCS had been defeated by rises of only 0.25 deg's/second ).
Not meaning to go off onto a (yet another) tangent; Negative temperature shears, very common at lower lattidudes, always plagued the development aircraft; you would suddenly accelerate, and in the case of a severe shear, would accelerate and accelerate!! (Your Mach number, quite naturaly, suddenly increased with the falling temperature of course, but because of the powerplant suddenly hitting an area of hyper-efficiencey, the A/C would physically accelerate rapidly, way beyond Mmo). Many modifications were tried to mitigate the effects of severe shears, in the end a clever change to the intake control unit software fixed it. (Thanks to this change the production series A/C would not be capable of level flight Mach numbers of any more than Mach 2.13, remembering that Mmo was set at 2.04).
There was one lovely story, involving the Shah of Iran, having one of MANY flights in a developmment aircraft. The aircraft encounterd quite a hefty series of temperature shears that plagued havoc with some Iranian F4's that were attempting to close on the Concorde, to act as an escort for the Shah. (or so the strory goes). I'm still trying to picture these F4's, on full afterburner trying to get close to a Concorde cruising away on dry power). It is said that the F4's were having such difficulties, due to their relatively crude powerplant, coping with the temperature changes, that the Concorde was ordered to slow down, 'so the escorting F4's could catch up'!! True or not, it is part of Concorde folklore.
Dude
Last edited by M2dude; 24th Aug 2010 at 14:31. Reason: spelling (again) :-(
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Hi M2Dude - keep it coming! I missed all this stuff from the early days......
Tim00 - good question, and very relevant.
It takes a lot to incapacitate a Flight Engineer - beer, cigars and scary women were no issue - they were definitely the most relaible part of the operation. (And arguably the least attractive.....)
If the unthinkable happened the First Officer would find himself on the FE's seat. We practised it less often than you might think, but thought about it a great deal. Especially the fuel system management.
Which brings me to your second point - yes, there was a preset for the 'automatic' fuel transfer system, although that wasn't the mechanism used for the pilots to 'take control' of the CG. The critical thing was to be able to get the CG forward if a rapid decel had to be made - for this reason there was an override switch above the First Officer which used various pumps and valves to txfr fwds - primarily by txfring from tank 11. It would be used in various recall checklists (supersonic 4-engine flameout and Continuous Ssurge at M>1.3 seem to register from the dim past) until the FE was able to take over the txfr system himself.
I didn't ever need it - in the surges I encountered the FE was always ready to manage the txfr before we needed the override.
Oooooooh!!!! There's a new topic for someone: Surges.
Theoretically the correct checklist to call for was the "Continuous Engine surge above M 1.3 Conditional Procedure, please". In reality the call was always much more succinct.
Monosyllabic, in fact................
I'm off to the pub, but I bet Bellerophon can speak with erudition on the operational aspects, and if M2Dude is who I suspect he is, I KNOW he'll be able to cover the technical aspects in great depth!
WOK
Tim00 - good question, and very relevant.
It takes a lot to incapacitate a Flight Engineer - beer, cigars and scary women were no issue - they were definitely the most relaible part of the operation. (And arguably the least attractive.....)
If the unthinkable happened the First Officer would find himself on the FE's seat. We practised it less often than you might think, but thought about it a great deal. Especially the fuel system management.
Which brings me to your second point - yes, there was a preset for the 'automatic' fuel transfer system, although that wasn't the mechanism used for the pilots to 'take control' of the CG. The critical thing was to be able to get the CG forward if a rapid decel had to be made - for this reason there was an override switch above the First Officer which used various pumps and valves to txfr fwds - primarily by txfring from tank 11. It would be used in various recall checklists (supersonic 4-engine flameout and Continuous Ssurge at M>1.3 seem to register from the dim past) until the FE was able to take over the txfr system himself.
I didn't ever need it - in the surges I encountered the FE was always ready to manage the txfr before we needed the override.
Oooooooh!!!! There's a new topic for someone: Surges.
Theoretically the correct checklist to call for was the "Continuous Engine surge above M 1.3 Conditional Procedure, please". In reality the call was always much more succinct.
Monosyllabic, in fact................
I'm off to the pub, but I bet Bellerophon can speak with erudition on the operational aspects, and if M2Dude is who I suspect he is, I KNOW he'll be able to cover the technical aspects in great depth!
WOK
Last edited by EXWOK; 26th Aug 2010 at 22:50.
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Fascinating thread. Please keep it going.
I see from photo in post 66 that pitch attitude at Mach 2 was about 4 nu. Could you say what attitudes were normal at other stages of flight?
I think I read that initial rotation was to a pre-computed attitude which allowed for simultaneous climb and acceleration. What was the speed typically when re-heat was cancelled at I assume 1000 agl?
Jo
I see from photo in post 66 that pitch attitude at Mach 2 was about 4 nu. Could you say what attitudes were normal at other stages of flight?
I think I read that initial rotation was to a pre-computed attitude which allowed for simultaneous climb and acceleration. What was the speed typically when re-heat was cancelled at I assume 1000 agl?
Jo
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M2dude,
Thanks for bringing up the story of the temperature shears at low latitudes, saves me some explaining !
The phenomenon was not really "discovered" until the route proving started.
As you say, it meant abrupt changes in Mach and Tt.
Since the pitch autopilot in, say, 'Mach Hold', had only one way to cope with those changes : pitching up or pitching down, this resulted in abrupt climb and descent manoeuvres that were totally inacceptable.
It was not only fixed by modifiying the intake controls.... !
It also led to a fairly major mod in the AFCS, by bringing the auto-throttle into the loop.
Instead of letting the pitch A/P take the aircraft into a zoom climb to try and stay within the "speed limits", it woold be the autothrottle pulling the throttles back.
After a fair amount of flight tests, this became the final form of the 'Max Cruise' mode.
I know... I should have kept a diary.
All this happened 35 years ago, so I can't put exact dates, or even specific aircraft, into the story. At least I still have some Concorde doc, that at times allows me to refresh my memory.
But one thing stayed in my memory over the years ...
The initial A/P+A/T 'Max Cruise' mod meant a major modification of the autothrottle computers. One of the circuit boards in particular was totally "butchered" on-site (Fairford), with well over a hundred track cuts and new wire links, not to mention the number of component changes (to give an idea to the 'experts', these were double-sided PCBs of about 15x20cm).
We got the job done (4 boards : 2 boards per computer, 2 computers), got the computers tested and on the aircraft. Knowing full well how easy it was to introduce faults and problems during such a modification (a dud solder joint could be enough), we expected to see them back within days, or at least within a few flights.
Well..... those computers left the lab with each about a thousand hours "on the clock" (they have little elapsed-time counters that indicated hours under power, NOT flight hours).
The first time we saw them back (for a minor mod, not a fault), both clocks showed over 10,000 hours !
Ah, those were the days
CJ
Thanks for bringing up the story of the temperature shears at low latitudes, saves me some explaining !
The phenomenon was not really "discovered" until the route proving started.
As you say, it meant abrupt changes in Mach and Tt.
Since the pitch autopilot in, say, 'Mach Hold', had only one way to cope with those changes : pitching up or pitching down, this resulted in abrupt climb and descent manoeuvres that were totally inacceptable.
It was not only fixed by modifiying the intake controls.... !
It also led to a fairly major mod in the AFCS, by bringing the auto-throttle into the loop.
Instead of letting the pitch A/P take the aircraft into a zoom climb to try and stay within the "speed limits", it woold be the autothrottle pulling the throttles back.
After a fair amount of flight tests, this became the final form of the 'Max Cruise' mode.
I know... I should have kept a diary.
All this happened 35 years ago, so I can't put exact dates, or even specific aircraft, into the story. At least I still have some Concorde doc, that at times allows me to refresh my memory.
But one thing stayed in my memory over the years ...
The initial A/P+A/T 'Max Cruise' mod meant a major modification of the autothrottle computers. One of the circuit boards in particular was totally "butchered" on-site (Fairford), with well over a hundred track cuts and new wire links, not to mention the number of component changes (to give an idea to the 'experts', these were double-sided PCBs of about 15x20cm).
We got the job done (4 boards : 2 boards per computer, 2 computers), got the computers tested and on the aircraft. Knowing full well how easy it was to introduce faults and problems during such a modification (a dud solder joint could be enough), we expected to see them back within days, or at least within a few flights.
Well..... those computers left the lab with each about a thousand hours "on the clock" (they have little elapsed-time counters that indicated hours under power, NOT flight hours).
The first time we saw them back (for a minor mod, not a fault), both clocks showed over 10,000 hours !
Ah, those were the days
CJ
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There were questions about the JFK 31L take-off.
I think this is it....
YouTube - Concorde British Airways take-off
CJ
PS The YouTube legend says last t/o from Heathrow, obviously wrong.
I think this is it....
YouTube - Concorde British Airways take-off
CJ
PS The YouTube legend says last t/o from Heathrow, obviously wrong.
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As Concorde was in reality the first and only successful SST; a lot of useful information must have been gained during the flight testing phase. Were there any plans to incorporate any updates/modifications based on leasons learnt into later production models(if there of course had been more orders)?
Whilst typing the above I was reminded of something I read many years ago; that MI6 managed to pass slightly doctored "blueprints" to the Russians and that was the reason that "Concordski" was such a failure. I have always assumed that this was an "urban myth".
Regards
Nick
Whilst typing the above I was reminded of something I read many years ago; that MI6 managed to pass slightly doctored "blueprints" to the Russians and that was the reason that "Concordski" was such a failure. I have always assumed that this was an "urban myth".
Regards
Nick
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Attitudes
Always more nose up than a conventional a/c.
As you note, about 4 in the CRZ. About 10.5 degs on approach.
As part of the performance calcs we calculated a 'theta 2' value of pitch. This was bugged on the ADI with a little bug controlled from a thumbwheel on the yoke - at all speeds very accurate pitch control was required, hance this device and the ADI being calibrated in 1 degree increments.
Theta 2 was attitude reqd to obtain V2 in the first segment with one engine out, i.e. the target attitude if an engine failed after V1. Once the gear was up (second segment) one would pitch up a little to hold V2 until 600ft then start initial accel.
On all engines, one held it until 250kts then pitched up to maintain that speed. You'd typically reach it before passing over the M25 departing LHR to the West.
In all cases, as soon as SID altitude or noise abatement limits had been reached you went to the barber's pole asap (400kts initially) as this was where best performance lay.
As you note, about 4 in the CRZ. About 10.5 degs on approach.
As part of the performance calcs we calculated a 'theta 2' value of pitch. This was bugged on the ADI with a little bug controlled from a thumbwheel on the yoke - at all speeds very accurate pitch control was required, hance this device and the ADI being calibrated in 1 degree increments.
Theta 2 was attitude reqd to obtain V2 in the first segment with one engine out, i.e. the target attitude if an engine failed after V1. Once the gear was up (second segment) one would pitch up a little to hold V2 until 600ft then start initial accel.
On all engines, one held it until 250kts then pitched up to maintain that speed. You'd typically reach it before passing over the M25 departing LHR to the West.
In all cases, as soon as SID altitude or noise abatement limits had been reached you went to the barber's pole asap (400kts initially) as this was where best performance lay.
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Sorry, haven't worked out how to embed videos. Stunning departure!
YouTube - Concorde: Last Takeoff From JFK Airport With Live Commentary
YouTube - Concorde: Last Takeoff From JFK Airport With Live Commentary
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Modern LSI surface mounted, multi layer electronics.
First of all, many, many thanks to our four main sources of Concorde 'nectar'; M2Dude, ChristiaanJ, Bellerophon and Exwok. Their input, each from a slightly different viewpoint, is absolutely captivating. As fascinating as the lady herself.
Christiaan rang an awful lot of bells with his description of some of the electronics - it was very, very similar to the stuff I used to work on, back in the early days of production CT Scanners. Cut tracks and wire links were the 'staff of life' and the stuff of nightmare. 
Our first minicomputers - to reconstruct the CT image - had 32 kilobytes of memory on four boards, each about 17" square!! My phone has about 2 Gigabytes of memory! Now this was in the late seventies, when Concorde had been flying for a good number of years.
My question, which is a bit of a tilt at windmills, is this; If you had to build Concorde all over again with the same airframe and engines, how much more room, how much lighter and how much more capable would the electronics be if they were made using the latest surface mount, Extremely High Density integrated circuits and microprocessors?
Thanks again everyone, for the best thread I have read on PPRuNe for two years (and there have been some superb ones in that time)
Roger.
The initial A/P+A/T 'Max Cruise' mod meant a major modification of the autothrottle computers. One of the circuit boards in particular was totally "butchered" on-site (Fairford), with well over a hundred track cuts and new wire links, not to mention the number of component changes (to give an idea to the 'experts', these were double-sided PCBs of about 15x20cm).
Our first minicomputers - to reconstruct the CT image - had 32 kilobytes of memory on four boards, each about 17" square!! My phone has about 2 Gigabytes of memory! Now this was in the late seventies, when Concorde had been flying for a good number of years.My question, which is a bit of a tilt at windmills, is this; If you had to build Concorde all over again with the same airframe and engines, how much more room, how much lighter and how much more capable would the electronics be if they were made using the latest surface mount, Extremely High Density integrated circuits and microprocessors?
Thanks again everyone, for the best thread I have read on PPRuNe for two years (and there have been some superb ones in that time
)Roger.
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As Concorde was in reality the first and only successful SST; a lot of useful information must have been gained during the flight testing phase. Were there any plans to incorporate any updates/modifications based on leasons learnt into later production models(if there of course had been more orders)?
Concorde "B"
Concorde '217' would have been the 'prototype' for the 'B' version. Sadly it never happened.
Whilst typing the above I was reminded of something I read many years ago; that MI6 managed to pass slightly doctored "blueprints" to the Russians and that was the reason that "Concordski" was such a failure. I have always assumed that this was an "urban myth".
Yes, there was some industrial espionage, and a Russian or two was arrested with microfilms of blueprints and a few components, in the best James Bond style (this was in France, BTW...).
Some "duff gen" may have been passed as well... although the main reason the Concordski failed was that they didn't really get some of the vital stuff sorted, with the subtlety of the wing shape and the intake controls being only a few of the examples.
To my mind, the best story (urban legend or not) was that a Russian got caught scraping tyre deposits off the runway after a few accelerate/stop tests. The sample was duly sent to Russia, mixed with chewing gum and a few other ingredients, and a certain amount of time is reputed to have been wasted tryng to reproduce the 'formula".....
Legend also has it, that the Russians at one point quite seriously inquired if they could buy the license to the intake control system.
Since at the time it would still have had quite significant military use as well, the answer was a very firm "njet" !
CJ
