Posts about: "Fuel Burn" [Posts: 24 Page: 1 of 2]¶

Damn, guess I am really that stupid. (Let's just keep that between you, Christiaan and myself ).

M2, the figures you give are incredible (I like stats) so I shall ask for more. Anytime you get tired of answering please just say enough .

How much fuel was used in the taxi. T/O roll. To TOC. Usage in cruise. From TOD?
How long did it take to get to TOC and was it done in one hit or were there stages when fuel burn allowed the climb to resume? What was the ground distance covered to get to TOC? How far out was TOD and what was ROD during the approach?

The amusing trim piece I found quite funny. That requirement must have been designed by several different Government committees; net result, nothing changes.

Had a question on the nose. You mentioned somewhere about a decompression when the nose was lowered to the 5\xb0 stage. This indicates that the nose had more than the Up and Down positions that I always thought. Were there multiple nose positions and when would they have been used. (Obviously nose full down was for T/O and Landing)

Last one for this post. What was the CoG range? I remember when I started flying and finally twigged to what it was all about that the PA28 had something like a 5" from the forward to aft limit and was massively surprised by the small "balance point". Trim tanks on 1 aeroplane I flew would have been most welcome.

I know I have asked a lot so please answer at your convenience.

Many thanks.

Biggles78
Stupid, you? no way!! (Besides, I'm Mr Stupid of the aviation world, that's my title ). The thing is, out here in the world of flying machines, there are almost an infinite number of questions (and hopefully answers too). This applies to just about all aircraft from the Wright Flyer up!!.
Keep asking away, there are so many of us Concorde 'nuts' out here who are more than happy to help out/bore the socks off you.
Fuel burns: The problem was that when flying slow/taxying, Concorde was an extreme gas guzzler, even when idling each engine burnt around 1.1 tonnes/hour (so every 15 minutes after push back meant over a tonne gone). A typical taxi fuel would be around 1.4/1.5 tonnes, depending on the runway in use on the day. I'd have to leave it to some of my pilot/F/E friends to remember some of the specific fuel burns after take off etc, but I can at least give you some interesting consumption figures:
At the beginning of the take off roll, each engine would be burning around 21 tonnes/hour. (Made up of around 12 T/Hr dry fuel (Fe) and 9T/Hr afterburner (reheat to us Brits) fuel (Fr). As Fr was scheduled against Fe, as a function of inlet total temp (T1) by the time V2 was reached (around 220 KTS) the rising T1 has pushed the total fuel flow (Ft) up to a staggering 25 tonnes/hour/engine. As i've pointed out before in previous topics, although the afterburner only gave us a 17% improvement in take off thrust, it was responsible for around an 80% hike in fuel burn. (Hence that is whay it was only used sparingly). However when reheat was used for transonic acceleration, it used a dramatically reduced schedule (roughly a 60% rise in fuel flow) , so it was not quite as scary. The afterburner would be lit at the commencement of the acceleration (0.96 Mach) and cancelled completely at 1.7 Mach. After this time the aircraft would accelerate on dry power only up to mach 2 and beyond. (The cooler the temperature the quicker the time to Mach 2). On an ISA+ day, it sometimes felt that the aircraft was flying through cold porridge, and could take quite a while to get to Mach 2 after reaheat cancellation, where as on a nice ISA - day, she would go like a bat out of hell, and the AFCS would have to jump in to prevent overspeeds.
Before I hit some more numbers, let me say that with Concorde, TOC = TOD!! After reheat cancellation at Mach 1.7, the aircraft would be at FL 430. The aircraft would climb at an IAS of 530 KTS until Mach 2 was reached at fractionally over FL500. From then on the aircraft would cruise/climb as fuel was burnt, up to a maximum of FL600. On warmish days (eg. the North Atlantic) TOD would typically be around FL570-580. On a cool day (the lowes temperatures would of course be reached in the more tropical regions; the LGR-BGI sector encountered this), FL 600 would be reached easily and she would love to climb some more. BUT, the aircaft was only certificated to 60,000' with passengers onboard, for decompression emergency descent time reasons, and so we were stuck with it. The pity is of course, the fuel burn would have been improved, but we never were able to take advantage of this. On test flights however, the aircraft would routinely zoom climb to FL 630. On her maiden flight, aircaft 208 (G-BOAB) reached an altitude of 65000'; the highest recorded Concorde altitude was on one of the French development aircraft, which achieved 68,000'. On a technical point, the analog ADC's were 'only' calibrated to 65,000'.
Anyway, back to some figues; at Mach 2, 50,000', the typical fuel burn per engine would be around 5 tonnes/hour, falling to around 4.2 tonnes/hour at 60,000'.

THE NOSE You are quite correct in your assumption, there were two positions of droop: 5 deg's for taxi/take-off and low speed flight and 12.5 deg's for landing. The glazed visor retracted into the nose and could ONLY be raised once the nose was fully up, and had to be stowed before the nose could move down. There were 2 emergency nose lowering sysyems; one using stby (Yellow) hydraulics and a free-fall system. Free-fall would drop the nose all the way to 12.5 deg's, the visor free falling into the nose also.

Biggles78
I know these fuel flows seem crazy (If take-off fuel flows had been maintained the endurance of the aircraft would have been about 55 minutes!!). But as the majority of the flight was carried out at Mach 2 and above, with the relatively miniscule fuel flows, you can see how we were able to cross the Atlantic with relative ease. It was the subsonic bit that was the pain.
The powerplant was as you say truly amazing. We had an, as yet, unmatched engine/intake combination, with a variable primary and secondary nozzles. The variable intake allowed supersonic operation with maximum pressure recovery, minimum aerodynamic drag, as well as extreme operational stability. (Extreme temperature shears, that would have caused surge/unstarts in military installations) were dealt with as a total non event). It's astonishing to believe, but at Mach 2 cruise, the intake provided approximately 63% of the powerplant thrust. It was controlled by the world's first airborne digital control system. (The system computers were built by the Guided Weapons Division of what was then BAC). The combination of the variable intake, plus the LP and HP compressors gave an overall compression ratio of 80:1.
The engine itself, being supplied with air at an ideal pressure, could run at an almost conststant TET, thanks to the variable primary nozzle. This also allowed N1 and N2 (corrected for total temperature) to be controlled more or less independently and run as close as possible to their separate surge lines throughout the entire flight envelope.
The variable secondary nozzle (wide open above Mach 1.1) allowed the jet efflux to gently expand against a cushion of air that was passed over the rear ramp of the intake, through the engine bay and into the annulus of the nozzle itself. This prevented thrust being wasted by the jet efflux widely splaying as it met ambient air that was at a pressure of as little as 1.04 PSIA.
It was this integrated powerplant that made true supersonic cruise possible
The airframe life issue was sort of like 'how long is a piece of string?'. The airframes are lifed in supersonic cycles, (which had been extended before, with modifications) and studies were always underway as far as further life extensions were concerned. (Basically the airframe was as tough as a brick outhouse in structural terms). 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 A\xe9rospatiale who, it was said, went a bit loopy). When the FAA evaluated the design (in order for the aircraft to be registered in the USA, for Braniff operations out of IAD) they wanted 'crown planking' to be fitted externally, which would have added over a tonne to the weight of the aircraft, as well as producing some not inconsiderable drag. Fortunately a compromise was reached and additional NDT inspections were carried out, as well as more limited structural modifications. There was a long term, cost effective solution being studied, which would have cured the problem altogether. (The changes would have been mandated, over new requirements for ageing aircraft)

Nick Thomas
Nick, the whole expansion issue was one of the biggest issues that had to be addressed. Wiring looms would 'snake' in some underfllor areas to take up expansion, but the biggest difficulty of all were the mulitudes of hydraulic lines. These required sliding expansion joints, with of course seals to prevent leakage. When a seal deteriorated YPU GOT A LEAK!! (Fluid at 4000 PSI tends torun for freedom very quickly ). As far as fittings go, ChristiaanJ is quite right, you tried to anchor at one end only. I seem to remember that the passenger seat rails travelled over a roller afair. Fuel lines wer less of a problem, because their relative lengths were less.
I also agree wholeheartedly with ChristiaansJ's explanation about the 'friction' thing, I never really liked those stories. As a matter of interest, 127 deg's, for Mach 2, that would be at ISA +5 (-51.5 deg's C). Any warmer than that and we could not achieve Mach 2, due to the Tmo limit of 127. I remember one year, for several weeks we had unusually high north Atlantic temperatures; these impacted both the flight time AND the fuel burn. The further away you were from Mach 2, the higher the fuel consumption. (The faster you flew, the less fuel you burnt. How's that for a paradox?).
At ISA (-56.5 deg's C) temperatures, the total temperature was at around 118 deg's C.

ChristiaanJ
I remember the 17.5 degree position on the nose; it always looked as if the aircraft was trying to eat ants to me . I can not recall personally anyone removing the 12.5 deg' stops for access, although this could of course have been done on your side of the 'puddle' I guess.
As far as the APU ducting issue goes (hee, hee, not often we disagree Christiaan ) we are just going to have to agree to disagee about this, although I accept that two 4" diameter pipes (PLUS THERMAL INSULATION) might have done it, BUT I still stand by the other points.

Stlton
Unfortunately not; the keel beam area was extremely thin and there was not anywhere near enough room. Interesting solution on the 727 though, I never knew that one.

Galaxy Flyer
We never had a case of lost pressurisation, ever. The cabin windows had dual laminated panes; an inner pressure pane and an outer thermal pane. We had dual systems that kept the cabin at a max diff' of 10.7 PSI, the engine bleeds pushing about 200lb of air per minute into the cabin. This allowed you to fly the cabin at an altitude of around a 6000' maximum only, right up to TOD. If you HAD to fly subsonically, the ideal was Mach 0.95 at FL290. (Subsonically the aircraft had similar range to normal, but took well over twice as long of course). If however you had to shut down an engine, your range deteriorated quite dramatically, and a diversion was usually sought.

It's great that Bellerophon is posting here again; we need a steely eyed Concorde pilot's input here (not just the boffins/nutters and nerds [that's me ]. To touch more on a couple of his valid points;
Fuel burn: The aircraft would naturally require less fuel as she became lighter and as a consequence gently climbed to maintain cruise Mach number, this is what the engine control system was doing all the time, even though the throttles were wide open it was 'tweaking'.. BUT, the decreasing IAS as you climbed, due of course to the reducing density, just like any other aircraft meant that drag was reducing too, so it was a combination of both of these factors, reducing weight and reducing drag.
Flying controls: It was a slightly weird but wonderful arrangement; pilots inputs would move a servo valve in the hydraulic relay jack, the jack would move in response and drive both a resolver AND mechanical linkages. The resolver ourput was sumed with the flying control position resolvers, and the error signal was fed into an autostab' computer, where it was summed with stabilisation demands (primarily axis rate and acceleration). The autostab computer would the directly drive the surface, and the reducing error signal would reduce the demand etc. While all this was going on, the mechanical linkages would slavishly follow, but as long as you were in FBW (what we used to call 'signalling') mode, these mechanical inputs were de-clutched at the PFCU, so did nothing at all. Only if there was an EXTREMELY unlikely failure of BOTH FBW channels would these inputs be clutched in and the flying control group (rudders, inner elevons or outer and mid' elevons) would then be in Mechanical signalling. The system redundancy was checked after engine start on every flight. But to reinforce what Bellerophon stated, there was no mechanical reversion here; without hydraulics you had nothing. Another aside here; the designers, being paranoid like all good designers (no offence Christiaan ) were worried what would happen if the controls would somehow jam up. A jammed mechanical flying control input run itself would have no effect on FBW operation whatsoever, due to spring boxes being fitted to the runs. A 'Mech Jam' light would be set, together with a separate red light and audio warning, but this was all. But to completely protect against the aircraft was fitted with a Safety Flight Computer (SFC) system. The idea was, if a control axis (pitch or roll only) jammed up, the captain could press down on a switch light set between the two halves of his control wheel, (at the centre of the 'W') and the Emergency Flight Controls would activate. Strain gauges at the front of the control wheel, two sets on each control column for pitch and roll axis, would input into an SFC that would covert the control force into an elevon demand. These commands were then fed into the autostab' computers, and hence directly into the controls. (A little like L-1011 CWS in a way). There was a little test button that was used to test this system, again after engine start. So although the controls were jammed, the aircraft could still be flown. (Never used in anger I'm pleased to report).
But there was a problem; if this system was inadvertantly used, the results could have been catastrophic, as the system was extremely sensitive indeed, and full elevon movement could be enabled with only moderate effort. Because of this hairy prospect some safeguards were obviously put in place. The first safeguard was an interlock in the autostab' engage logic; If the switchlight had been inadvertently selected beforehand (the light was green by the way) you would not be able to engage pitch or roll autostab's (both channels too) so you would not be going flying until that was fixed. The second safeguard was a little more subtle; A plastic, frangible cover was fitted over the switchlight, unless the captain pressed reasonably hard the cover would prevent the switchlight from being pressed. At least that was the theory, in practice this little bit of plastic could be a pain in the ass . It was carefully fashioned, and I seem to remember BAe charging the airlines a few hundred pounds each for these things. If some wally fitted the cover upside down (and unless you were careful it was easy to do) THE THING WOULD NOT BREAK!! I remember at Fairford in 1976, G-BOAD was on pre-delivery flight testing, and the late great test pilot John Cochrane was doing a test of the system. The cover on this occasion HAD been fitted upside down, and of course he could not plunge his thumb through it and engage the EFC button. After trying everything, in the end he removed a shoe, took out his pen, and smashed the plastic cover until it broke. (It's OK, the autopilot was engaged at the time). Unfortunately, his combined shoe/pen emergency device also wrecked the switchlight as well, so the system still could not engage. (There was only a switchlight on the captain's side). After he landed and he confronted us all with his dilemma, he was shaking; not with rage but with laughter. (This was the great John Cochrane, sometimes the dour Scotsman but he was always able to see the lighter side). After that event, careful instructions were issued regarding the fit of the cover, and it was modified and made a little more frangible.

I have yet another couple of questions and I hope all you Concorde experts don't mind me taking up your valuable time.
As regards fuel burn: was there any difference between each indvidual airframe and if so was it significant enough to be considered when calculating the trip fuel? Also did different engines also have slightly different fuel consumption?
Whilst on the subject of engines, I just wondered how many were required to keep the BA Concorde fleet flying? What sort of useful life could be expected from the engines?

In my case, my time is no longer THAT valuable, being retired for several years !
And I enjoy answering those questions, if and whenever I can!
There WERE differences... after its misadventure at Dakar, F-BVFD definitely consumed more fuel, although IIRC he was already reputed as a gas guzzler even before that incident.
It was one reason why, when Air France withdrew an aircraft from service, Fox Delta was the first one to go.
Also, due to the gradual improvements in production methods, and minor redesign, the last British production Concorde, G-BOAF, was about a ton lighter than the first one (G-BOAC). While the differences weren't huge, they were noticeable.
Of course... but there I have no figures at all, and I doubt the differences, evened out over four engines, were really significant.
Interesting question, and I hope somebody will come in and answer it.
According to 'Wikipedia', 67 engines were built, which would mean, in theory , 64 engines for 16 aircraft and 3 spares....
In practice, of course, fewer aircraft flew at any one time, so the statistics are different, but even so, a lot of engine swapping went on over the years.
As to the MTBO, I don't know... it's not my field at all....

Biggles78
This is the minimum Mach number that can be flown with the existing CG. (which would be around 59%). Just as the CG indicator (not shown in this photo) gave minimum and maximum CG for a given Mach number, the Machmeter gave a reciprical indication also). You can also see that as the aircraft is not flying at Vmo any more, being at Mach 2 cruise, that the VSI pointer is now away from the orange and black Vmo bug. At our 'not so coffin corner', now that the aircraft is at maximun alllowable altitude, Vmo would naturaly coincide with Mmo; the orange and black Mmo bug being shown at Mach 2.04. This really superb photo taken by Bellerophon gives a graphic illustration of what the panels looked like at Mach 2. Note that the with the TCAS VSI Concorde retained it's original linear VSI also. (Miust have beeen the only aircraft flying with FOUR VSIs. (The originals had to be retained due to the fact that the autopilot Vert' Speed Mode error was derived from the indicator itself. As far as TCAS goes, R/As werer inhibited above FL300 (on acceleration this would coincide with the aircraft becoming supersonic, and the mfrs would not countenance the aircraft doing extreme manoeuvrs as a result of TCAS RAs at supersonic speeds).
The tail wheel was lowered for all 'normal' gear cycles (not stby lowering of free-fall). It was designed to protect the bottom the nacelles in the case of over-rotation, but in practical terms the thing was a waste of space (and weight) and a simple tail skid (used on the prototypes) would have sufficed. Any time that the tail wheel contacted the ground, it would ALWAYS collapse, damage the tailcone structure and in fact aforded no protection whatsoever. Fortunately these events were EXTREMELY few and far between. The biggest problem with the tail wheel was a major design flaw: On gear retraction the assembly would retract in sequence with the nose and main gear, and as it entered the opening in the tailcone, it would release over-centre locks that were holding the spring-loaded doors open. The doors would then firmly spring shut behind the gear assembly and finish the job. UNFORTUNATELY this was a very poor design; if for any reason one of the two doors had not gone over-centre on the previous gear lowering, it would be struck by the retracting tail wheel gear and cause structural damage to the local skin area, that would have to have a repair done. Unfortunately these events were not quite so rare, and several measures were tried to reduce the chance of this happening. Although not a safety issue, it was an issue that was a total pain. (As a matter of interest, G-BOAC had this happen on one of it's first test flights out of Fairford in 1975).
Nick Thomas
As ChristiaanJ said, the last two BA aircraft WERE lighter than the others, and would be preferred aircraft for certain charters. But that is not to say that any aircraft could not happily do ANY sector. We fortunately had no distorted airframes in the British fleet, so this was never an issue. There was very little spread, regarding fuel consumption between different engines; one of the best parts about the Olympus 593 was that it hade very little performance deterioration with time, it was an amazing piece of kit.
Time on wing for the engines was a real variable. Each engine was built up of modules, each one of these had a seperate life. In the early days of operation, time on wing was quite poor, and MANY engines would be removed on an attrition basis. One of the early failure problem was the fuel vapourisers inside the combustion chamber were failing, taking bits of turbine with it!! A Rolls Royce modification that completely changed the design of the vapouriser not only solved the problem completely, but also increased the performance of the engine. As the engine matured in service time on wing greatly improved, and in service failures became a thing of the past. A 'trend analysis' was done after each protracted supersonic flight, where engine parameters were input into a propiatry RR computer program, that was able to detect step changes in the figures, and if this were the case, more boroscope inspections were carried out. The OLY time on wing was nothing compared to the big fan engines, but the conditions that it operated under bore no comparison. Not really sure about absolute figures on this one Nick, I'll ask one of my Rolls Royce friends and see if I can find a figure.

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

Nick Thomas
This of course is one for one of my pilot friends to answer properly again, but as galaxy flyer says, it's an 'eye to wheel' issue here when compared to other aircraft.
galaxy flyer
Again best answered by learned gentlemen such as my friends EXWOK or Bellerophon, but to the best of my feeble knowledge a resounding NO, at least as far as CRUISE flying was concerned. As the majority of the flight was carried out between FL500 and FL600 there was really no weather as such to avoid during supercruise. (As has been previously posted, at Mach 2 you would invariably be above FL500). Only at extremely low latitudes where the tropopause could theoretically extend up to around 70,000' was there ever any chance of seeing any cloud anywhere near your cruise altitudes. The only turbulence as such you would ever encounter was as the result of a temperature shear, but these never felt to be too much in the way of 'bumps' to me. And again, only at very low latitudes did you encounter severe shears anyway; anything encountered on the North Atlantic was generally very mild and civilised.
A CONCORDE PARADOX
The tropopause issue here is an interesting one, in that the coldest stratospheric temperatures we ever encountered were close to the equator, whereas the WARMEST temperatures possible are over the POLES , where the tropopause can be as low as 22,000'. This is just one of the many paradoxes involving Concorde, and the reason why the aircraft would never be routed over the poles, BECAUSE THE DARNED TEMPERATURES ARE TOO HIGH, in terms of the stratosphere. The result here would be that the aircraft is temperature (Tmo) limited all the time to 127 deg's C. (I previously mentioned in another post in this thread that only 5 deg's C above ISA, -51.5 deg's C, would mean Tmo being reached at Mach 2; any warmer and we HAD to slow down) The relatively high polar temperatures mean that we are unable to fly anywhere near Mach 2. Another paradox would then come into play, the slower your cruise speed, the HIGHER your fuel burn. It was originally proposed in the early 1970's that Concorde would fly from London to Tokyo, and the routing for that needed two things: It could not be polar, and possibly just as important , you required a refuel stop. The Soviet Union amazingly proposed granting a supersonic corridor over Siberia, refuelling at the Siberian city of Novosibirsk. This was hardly an ideal routing (definitely far from a great circle) but was arguably one of the very few that was possible at all. This by the way was not some early iteration of glasnost, but the Soviets fully expected that flying thoroughbred, the TU-144 (bad dude ) to be a success, and could compete side by side with Concorde.
ANOTHER CONCORDE PARADOX
If anyone wonders why when you flew faster you burned less fuel, it was primarily down to drag, actually a thing frighteningly termed as 'pre-entry spill drag'. As most people (???) are aware, the Concorde engine inlet utilised a series of carefully controlled and focused shockwaves to slow the air down entering the engine; in 14 feet of engine intake you lost in the order of 1,000 mph of airspeed! Now most of these different shocks varied with a combination of intake variable surface angle, intake local Mach number and also engine mass flow demand. However the oblique shock coming off the top lip of the intake produced a shock that varied with Mach alone, and would project downwards, just forward of the intake bottom lip. Due to the air downstream of this fairly weak shock still being supersonic, a measured amount of this air spills downwards, away from the intake. If you can possibly picture it, we have this wall of air spilling downwards over the lower lip of all four intakes, the combined effect of this supersonic forespill is a fair amount of drag. The faster we go, the more accute the angle of the shock and therefore the less air is spilled, and in consequence the lower the spill drag. Remembering that cool temperatures could produce a higher Mach number, temperature really could either be our friend or enemy, but cool was COOL
I hope this explanation does not sound like too much gibberish, but it really was a fact that 'More Mach = Less Fuel'. Hope it makes some sense.

Dude

Thanks for those nozzle diagrams Dude, they are very useful to visualise what's happening.

I remember reading Stanley Hookers book "Not Much of an Engineer" (I know the feeling ), in which he explains how at Mach 2 the Olympus is only providing about 8% of the total thrust but then goes on to say that at the low speed end of the take-off run it was 100% of the thrust so his designers were not let off the hook. That falls to 82% in subsonic cruise.

Ah, found the figures for Mach 2, the inlet provides 63% of the total thrust, exhaust nozzles 29%. That certainly explains why the thinning and re-profiling of the inlet lip was so important to improving the fuel burn, and hence range.

Feathers, these are the joys of afterburning; a totally gas guzzling way of extracting some more thrust from an engine. With Concorde, at 15 degrees TAT, you got a 78% increase in take off fuel flow for, as you say, about a 6000lb increase in thrust. Normaly adding an afterburning/reheat system is a fairly complex and heavy affair; you need both the system itself plus a variable exhaust nozzle. Because Concorde already required the primary nozzle for N1 control, the addition of reheat was at least a relatively simple and lightweight afair. The original Olympus 593-22R engine was really a little lacking in terms of dry thrust, and the addition of the reheat system was deemed essential. Concorde only had a single reheat spray ring and flame-holder, military systems often have several, with a corresponding increase in thrust growth as well as a hyper increase in fuel burn.
Further development plans for the Olypus 593 included a large increase in dry thrust; the reheat being retained only for transonic acceleration. It is such a pity that it was not to be.

Dude

Concorde was exactly the same as any other aircraft in that it would be loaded in such a manner that with zero fuel the aircraft's C of G would be within the landing limits.. If this was not possible then ballast fuel has to be loaded[ or any other form of ballast] so as to achieve this C of G. This ballast fuel however must not form part of the fuel burn or diversion fuel

With the above in mind all fuel on Concorde was useable fuel but during some part of the flight prior to being burnt it it would be used for varying inflight regime trimming.

Now prior to landing the F/E would pump a predetermined amount into tank 9 so as to achieve a C of G fwd of 53.5 % for landing. This was only required because there was still fuel on board. If the aircraft was held before landing and the fuel QTY dropped he would pump this fuel out of tank 9 and into the engine feed tanks as it was no longer required for C of G purposes

Therefore yes Concorde could safely land from a C of G point of view with no fuel.

There was nothing magical about 4 Tonnes in tank 9, and in fact it usually was too much for stability reasons, but for simplicity a single big figure was used. In fact if it was not possible to put 4000kgs in tank 9 [due to lack of fuel]then the flight deck crew were instructed to remain on the flight deck until the passengers had got off and the rear hold had been emptied. Now some of us flight deck crew helped more than others in this

For those who wanted to know what the difference in fuel burn between a 737 and Concorde LHR-MAN........I don't know! (Never had the pleasure of flying the 737).

My best guess - at least 200% more. Probably higher.

A comparison:

Typical Concorde taxying fuel burn: 6500kgs/hr

Typical 777-200 cruising fuel burn: 6500kgs/hr

Of course, as we've already discussed earlier, the magic thing about Concorde was that once you'd got to Mach2 its efficiency was outrageously good - better miles per gallon than a 747. An option not available, however, between LHR and MAN.

Edited to add: a slow taxy out at LHR would almost definitely consume more fuel than the 737 would burn for the sector.

I have to admit that some of the subsonic fuel burn figures for Concorde were truly eye watering, and without massive engine and airframe modifications there was precious little in service that could be done to improve things. Paradoxically improvements to the supersonic efficiency of the powerplant were easier to implement, and several modifications were implemented, tried or proposed to improve fuel burn:
Way back in the late 1970's we did a major modification to the intakes that increased capture area by 2.5% and gave us typically a 1.6% improvement in trans-Atlantic fuel burn, and although this was our biggest performance improvement modification, there were more:
The famous elevon and rudder trailing edge extension modifications (that due to poor design, produced in later life the water ingress induced honeycomb failures) together with the re-profiled fin leading edge modification, I never saw the performance gains quantified (anyone have any ideas?).
Can anyone here remember the riblet trial? In the mid 1990's Airbus supplied 'stick on' plastic riblets, applied to various areas on the under-side of the wing on G-BOAG. These riblets had very fine undulations moulded into the surface; the idea being that as the air flowed through and around the riblet patches, boundary layer turbulence, and hence induced drag would be reduced. Now, the performance gains (if any) were never quantified, mainly because the riblet patches either peeled off or the surface deteriorated with the continuous thermal cycle. (I was over in JFK when the aircraft first arrived after having the riblets fitted, and as the crew were trying to proudly show me these amazing aerodynamic devices, they were sadly embarassed, as several had dissapeared in the course of a single flight).
There was one modification, proposed by Rolls Royce in the late 1990's that did have quite a lot of potential; this was to increase the engine N1 by around 1.5%. This would have had the effect of increasing engine mass flow and therefore reducing the drag inducing spill of supersonic air over the lower lip of the intake. Depending on the temperature, the performance gains were in the order of a 1.5% improvement in fuel burn at ISA Plus upper atmosphere temperatures ('normal' LHR-JFK) to none at all at significant ISA Minus temperatures (LHR -BGI). The modifacation had been trialed on G-BBDG before her retirement in the early eighties, and was proven in terms of performance enhancement and engine stability. In order to keep TET at the pre-modification level, there was a small increase in N2 commanded also. (The higher N1 required an increase in primary nozzle area, reducing TET). The main reason for the modification not being implemented was one of cost; The Ultra Electronics Engine Control Units were analog units, and the modification was a simple replacement of two resistors per unit. However because ultimate mass flow limitation was also controll by the digital AICU (built by British Aerospace Guided Weapons Division) the cost of getting a software update for this exremely 'mature' unit was found to be prohibitive.
A certain 'brainy' SEO and myself were working on a modification to improve fuel burn on ISA minus sectors. The idea was to force the autopilot, in Max Cruise at low temperatures only , to fly the aircraft close to Mmo, rather than at Max Cruise speed of Mach 2 - 2.02; this would have given us gains of up to 1%, depending on the temperature. The basic electronics involved for the modification were relatively straightforward, but it was never pursued due to the complexity of dealing with temperature shears and the cost of certification.

Dude

Hi DavvaP, and welcome. As far as ice on the wing goes, I'm sure as any of my pilot friends here will agree that she was treated just like a subsonic in that regard; any ice or snow build up on the surfaces of the wings would not be tolerated and would have to be removed before flight. (She may have had a revolutionary wing design, but still this was a wing nonetheless ). She would also require pre-flight chemical anti-icing/de-icing treatment from a ground truck just like the rest, in shall we say, 'less than tropical conditions'. (Winters in Prestwick during crew base training... such fond memories ). As far as active ice protection on the wings, there was a highly sophisticated Lucas electrical 'spraymat' system fitted, but only the wetted areas of the wing, forward of the engines were 'covered'. Two digitall cyclic timers (CTPUs) would automatically regulate cyclic switching on and off of 115 VAC for various load areas of the wing at a time at pilot pre-selectable intervals (2, 4 or 8 seconds). Also as part of this system, there was continuous de-icing for certain other load areas too, so you had a mix of cyclic and continuous de-icing in operation. The whole idea here was to prevent chunks of ice entering and damaging the engines, the only other areas of this electrical de-icing system were the intake lips and side-walls and also the D Box area above the auxilliary inlet vane, built into the spill door. (This would only operate if the auxilliary inlet door itself was open). The whole shooting match would automatically switch itself off, for obvious reasons, above a TAT of 15\xb0 C. (ie. the vast majority of the flight). The only other de-icing system (apart from the galley drain masts) was on the engine inlet guide vanes, but this was purely pneumatic and again would swith itself off above 15\xb0 C.
I think you will find that precious little of Concorde is now not generally available in the public domain, some control software and laws are still I would expect covered by some sort of patent. (That is why when I publiished here the engine 'E Schedule' graphs I deliberately deleted the equations for the various running lines.
Your efficiency question was a valid one; as IAS and Mach number increase the aerodynamic drag (in all it's forms) will generally increase, but the efficiency OF A WELL DESIGNED powerplant wil also increase, and Concorde was definately no exception here. The real beauty of Concorde was just HOW MUCH the powerplant efficiency increased with increasing speed and more than totally eclipsed the aerodynamic drag rise with this increasing speed. At supersonic speeds, the closer you could fly to Vmo/Mmo the lower the fuel burn was. (Especiall true at Mach 2, although the autopilot would hold you Mach 2 (ish) in Max Cruise mode, flying closer to Mmo, Mach 2.04, would save fuel, assuming the static air temoerature was low enough to sustain this). This fact (along with about a million others) produced what we all like to call 'The Magic of Concorde'

Best Regards
Dude

That's a very 'Concorde' picture, Bellerophon.

Gentle descent in the crz, N1 max, N2 max, similar fuel burn per engine as a 747 (but over double the speed), Airspeed and Mach numbers just shy of the barber's poles, must have been well above FL500 given the Mach number yet the cabin alt is a smidge over 5000'.

Elapsed time 1hr 31, Longitude over 41W. Took me over three hours to get to 40W yesterday.......

PS and it has to be OAD, because for some reason the nose/visor control panel is black. I've no idea why I can remember stuff like that, but not the name of someone I met last week......

I feel that I must pick you up there! As I see the guages each engine is consuming 5.4 tonnes/hour. A B747-400 will consume about 10-11 tonnes/hour and not over 20! So over double the speed but double the fuel consumption.

I have been reading these all night, and find all this information really helpful in learning more about this wonderful aircraft.. I do have a question, what was the fuel burn in Mach 2 cruise?? I did not find anything specific about that, and I was just curious..

Thanks
Mark M

The Concorde and Boeing SST business cases were built on a couple flawed assumptions.

First, jet fuel would remain dirt cheap and the higher fuel burn of supersonic travel not contribute significantly to cost of operation - which was blown out of the water by the first Arab oil embargo.

Second, that the majority of demand for air travel would remain for the 'premium' product - basically that the majority of people would happily pay a premium to get there faster. This assumption applied to most people who flew on jets in the 1960's - either business travelers or well to do people that weren't that worried about what it cost.
Reality was it went the opposite direction - a shift that started with the 747 and other widebodies. The economies of the wide body aircraft lowered the cost of air travel to the 'everybody' level. Suddenly there was a whole new class of air traveler - people for whom an extra $100 airfare meant they just wouldn't go, never mind that they'd get there in half the time. In short, they didn't foresee air travel becoming just another commodity - the low cost trend that continues today.

The reality was, both the Concorde and the SST needed to sell hundreds of copies to even begin to justify the development costs. The evolution of air travel into a low cost commodity, combined with the rising costs of jet fuel, insured that would never happen.

Well, the 2707 project never advanced to the point where such practicalities were considered - but it's certainly the case that part of the Concorde "B" spec was intended to do away with reheat (afterburner) entirely, and be much more fuel-efficient as a result.

Not necessarily - supersonic travel as a "premium" product was always intended to co-exist with subsonic offerings, much as it ended up doing. There's a revisionist narrative that has the USA betting on mass transit with the 747 versus Europe betting on supersonic transit with Concorde - but all the contemporary material I've read indicates no such thing. Even setting aside the protests within the US against the Concorde, the simple fact is that SST was never going to be a viable domestic solution, so that limited the market for the 2707. Whereas a transatlantic SST was very much a viable proposition due to the transoceanic nature of the journey. It could be argued that even with the oil crisis and the subsequent drop in orders, the UK and French governments gave up on the Concorde project too soon.

If that were genuinely the case, then there would have been no Airbus project or consortium. As Clive correctly points out, the A300 project started taking shape while Concorde was undergoing her proving flights. While there's no doubt that the Concorde project was completed for political reasons most of all, the idea that she was a forlorn hope before she went into service is grossly unfair.

Yet, as alluded to before, the R&D gains and technological knowledge coming from the project helped to lay the foundations of a pan-European aircraft maker which would eventually go toe-to-toe with the best the USA had to offer. The sidestick technology which led to an unprecedented level of commonality between short-haul and long-haul types was first tested on a Concorde airframe (Google "concorde minimanche"). Added to which is the fact that in Concorde, for all the project's problems, an airliner was produced which - on a technological level at least - left every competitor in the world in the dust. That is something that can never be taken away.