Posts about: "SR-71" [Posts: 29 Pages: 2]

I didn't read all 45 pages only the first 30 and the last page so my question about how much thrust was acquired from the front of the engine because of the pressure differential may have been answered. Also the question may not pertain to the Concorde like it was to the SR-71, but a large quantity of the SR-71 thrust was acquired at the front of the varible nose cone because of the huge pressure differential of the engine. This issue was relayed to me by a Lockheed test pilot who tested both the A-12 and SR-71.This test pilot also said the limiting speed factor of the SR-71 was the wing leading edge temperature of 734 degrees which was 3.2 mach although the plane could go faster. Above FL600 there is no wind so the flight times were always the same either way for the SR-71 and I assume that was true for the Concorde although the SR-71 normally flew at FL800+ except when they came down for a quick drink from a tanker.I really appreciate the ex Concorde drivers and engineers sharing their experiences and time. It should be interesting reading by our great-grandchildren in 100 years.

As with any aircraft the 71 was subject to any number of limitations, but airframe temperature was not one of them. The crew had no info on skin temp in any event. However compressor inlet temperature was the major limiting item (427\xb0C).

Thread on the Concorde inlets here Concorde engine intake "Thrust"

I think Dude's above statement more or less characterises the Concorde design and therefore this entire thread - which I have read, avidly, since post #1. However, since Dude made the statement most specifically about the synergy of the whole intake, engine and nozzles, it is worth reiterating that Concorde's only real peer in her occupation of the very highest and fastest regimes of wing borne flight - the SR71 - initially at least, had a lethal gene. Asymmetric 'Unstart' caused by intake instability.

This quote is from a much longer article quoted in this thread, about a test flight by Bill Weaver, a Lockheed development pilot, in which Weaver was, quite literally torn out of the aeroplane at Mach 3.2, as was his back seater who, sadly, did not survive the incident.

Basically, a relatively small failure within the intake/spike structure of the SR71 engine, was enough to simply tear the airframe apart within seconds of onset. The scale of forces within these structures therefore, must be almost beyond imagination and yet the Concorde design was such that she did not suffer such destructive failures.

My admiration for everyone who worked on her is endless.

Not quite the case, although the potential for a very rough ride was always there. Bill Weavers accident was the only one that involved an unstart, and was due in no small part to the test nature of the flight - CG out the back door. In Bills own words,

I was in Seattle for a wedding this weekend, and got to see BOAG at the Museum of Flight.

It was gratifying, but I can't say she's in stellar condition. I'd give her a solid "B" grade. For one thing, it drives me nuts that all the literature and display placards all say "the Concorde." I far prefer Concorde to stand on her own. Her paint was dull and oxidized, and the exhibit sort of stands alone, without much in the way of history or surrounding material. It pained me a bit to see her outside in the Seattle weather, too. The interior is nice, being cordoned off by plexiglass that could stand a replacement sometime soon. I didn't see peeling paint.

That said, it was a spectacularly more enjoyable experience than the last time I saw Concorde F-BVFA at the Udvar Hazy museum in DC, thanks completely to this thread. I noticed things I'd never seen before, and took a much more profound appreciation of things like the curve and droop of the wing leading edge and the complexity of the engine intakes... and I loved seeing the difference in fuel consumption numbers between Concorde and the SR-71 also on display. My wife thinks I'm a genius because I knew why #4 engine was N1 limited below 60kt and what the little 3/4 tag to the left of the engine EGT gauges was for.

Thanks again to all the knowledgeable individuals on this thread.

I suspect that, given the Concorde's rather unusual fuel consumption figures, the most efficient climb profile was also the fastest one, since pretty much anything other than the M2.0 cruise-climb was fairly inefficient. From way back in the thread ( here ) the minimum time to hit M1.0 was about six minutes, and M2.0 came at 9 minutes (although a few posts later someone mentions that these figures may be wrong as the fuel transfer rate wouldn't allow such a fast climb).

Some questions from me, after reading through the thread:

- Someone mentioned that, as a result of Concorde's sustained supercruising across the Atlantic, the twenty-odd Concordes have more supersonic flight hours than all other aircraft combined. Does anyone know what the figures are?

- What was the minimum range for supersonic travel to be worthwhile? Obviously if you were only going a few hundred kilometres it'd make more sense to cruise at 29000ft an M0.95 rather than climbing all the way up to 40000ft+ and M2.0.

- What other aircraft are/were more efficient supersonic than subsonic? The modern supercruising fighter jets (eg. the F-22) are still more efficient at subsonic speeds. The original Tu-144 would certainly have been much more efficient subsonic (since it couldn't supercruise); I'm not sure about the later models. The SR-71 was more efficient at high supersonic speeds than at low supersonic speeds, but I can't find anything about subsonic fuel consumption. And that leaves the XB-70, which is just a big unknown.

Hi all, slowly working my way through this thread, 3 days and up to page 15! Should be finished by Christmas. Hehe Absolutely fascinating reading, so good to have memories of the people who made, flew and maintained this incredible aircraft. My only reminiscence is trying to persuade my parents that they could not hear Concorde go supersonic when living in Bournemouth, OK they could and once being held at Filton, whilst she landed. Has anyone seen the BBC items reflecting 10 years since last flights. Which includes something from page 5 or 6 of this thread. The SR71 asked to wait for Concorde to proceed! I am sure these pages are far more interesting than the books, as one can ask questions, I just hope it is being saved somewhere for reference or for sale to help maintain this very informative site. Thanks to all the professionals who give their time and all the questioners for such interesting questions. http://www.pprune.org/forums/images/.../eusa_clap.gif

It's over two hours long... Probably best downloading it!!

Then look around the site, similar on the SR-71 and U-2 as well as the space shuttle..

After about a week of 3-hour nights (not much on the telly) I have finally got to the end of this thread. Let me echo others in praising the patience and technical openness of the main engineering contributors, along with the excellent recollections of the pilots, cabin staff and many others.

I am afraid I have only been on Concorde around a dozen times, and as I live a few miles from Duxford, you'll probably guess that's 101 now in Hangar 1. Standing in the cabin I can only imagine the experience of actually flying in her, but you guys have certainly bought her back to life in my mind at least.

While reading the thread I came up with many questions (around ten or so) and these have been answered in later exchanges on the thread, however I do have a few left over:

1. The speed freak in me always wants to know "how fast"? Notwithstanding the principles outlined on p.55 by CliveL and M2Dude, if the intake system were somehow made "more leaky" and reheat were applied, in theory at least, how much more thrust could the 4 engines produce, in "ideal" conditions (I saw somewhere that -80C had been encountered)? If you then extrapolate the drag, what sort of peak Mach number might be attainable in short bursts (ignoring for now the detrimental effect on the airframe?)

2. There was a discussion or two of the (highly theoretical, expensive and unlikely) prospect of restoring one of the airframes back to flight around p22. However I don't think I saw 101 or 102 mentioned in any of these discussions, are these even further 'gone' (101 having sat outside for 20 years)? On the other hand, would the lack of sponge-like insulation mean less corrosion might have set in?

3. Again on p.55 there is mention of (naff) paint schemes and their bad effect on skin temperature. Was the paint on Concorde specifically chosen to radiate infrared (for example) to help cooling? The SR-71 (which I also visit at Duxford regularly - how lucky am I!) of course is matt black, which presumably radiates even better? When the airframe attained thermal equilibrium at the top of the cruise, what were the relative contributions to cooling of: radiation, cold uncompressed air passing over parts of the skin, the internal aircon (cooling from the inside), etc?

4. M2Dude referred a couple of times to robbing spares from other airframes. Spares that may have been 5-8 years old? What sort of testing regime must these spare parts go through to ensure they are still fit for flight? Is it labour-intensive?


If I can opine (at the risk of having M2Dude chastise me if he still reads this - as I am not staff) the computer he mentioned on page 37 sounds to me very much like a "bit slice" computer. These were typically constructed from discrete logic and quite often had very long words - 64 or 128 bits. I only ever saw one of these in my 30-year career in computing, a rare beast indeed. And yes I remember that Mil Spec TTL - back in the day I used to pop the lid off the ceramic packages and you can look at the gates, and even watch the silicon glow if you apply a bit too much Vcc! But I digress.

Thanks again for a fascinating thread.