Concorde question

[M2dude]

OMG Clive yes, sorry about that. I remeber it well now, I just did a search and posted up my original.

[canuck slf]

Take off reheat selection

I seem to recall from my two take offs in 1978 or 9 that all four reheats were selected in pairs for take off and lit while holding on the brakes, with a preamble/warning over the PA that this was what was going to occur. Is this another indication of my failing "little grey cells" or did the procedure change?
Same PA announcement and lighting in pairs also occurred when going supersonic.

[M2dude]

For take-off reheat was selected (armed) on all 4 engines together, and certainly not in pairs. (As was stated previously, once 81% N1 was reached the reheat light-up sequence was automatically initiated). You would not wind up on the brakes either, the carbon brakes were extremely sensitive to overtorquing. For transonic acceleration however you are quite right about the 'burners in pairs' bit.

[howiehowie93]

Fatigue

I saw some questions earlier about performance but that's pretty well documented. I was wondering more about for how much longer ( if there had been no retirement )??


Was there a Fatigue Index as other aircraft of the same era – I only know of the Tornado in this respect: a long calculation was made per flight taken of flight duration, G readings, TO weight, Landing weight etc leaving a small number of 0.0000x per flight. Then added to the current FI to give a forecast of life left. If anyone remembers the Tornado 25FI Update Program debacle in the 90's ???


So how was the Concorde's airframe life calculated ?? Flying hours or perhaps pressurisation cycles ? Did a higher altitude effect anything since there would be a higher differential pressure??


On the Engine side, I remember an Olympus Service Bulletin describing the calculation of Fatigue Cycles for the Oly 200:- There was a calculation with several parameters but instruction to disregard below a certain figure, 85% to Max RPM & back was a regarded as a cycle and the LP Turbine Disc was the component with the lowest number of cycles before the need for overhaul.Was this still the case with the 593 ??

[CliveL]

So how was the Concorde's airframe life calculated ?? Flying hours or perhaps pressurisation cycles ? Did a higher altitude effect anything since there would be a higher differential pressure??

I can't answer for the engines, but the airframe life was going to be limited by thermal fatigue cycles. There was an on-going programme of testing at RAE Farnborough where, from memory, 21000 cycles had been accumulated by the time it was shut down. The airworthiness authorities were demanding a safety factor of 3 because nobody had flown under that sort of limit before, so the theoretical life would have been 7000 flights.

Not so bad as it sounds in calendar years, as the annual utilisation of any one aircraft was very low, and there would also have been scope for life extension by applying certain modifications to the fuselage.

[Jane-DoH]

M2dude

One of the real beauties of the Concorde intake was that it was completely self-startiing, and so unstarts as such were never heard of.

What does self-starting mean exactly? Does it mean self-stablizing?

I seem to remember that Rolls Royce proposed a solution of their own, whre the right hand pair of engines would rotate ant-clockwise (viewed from the front) rather than the clockwise norm for just about any 'Roller' that I can think of. Although this would have completely solved the vibration problem, and was great business for the folks at RR in Patchway (just about doubling the required number of engines) it was a pretty lousy idea if you were an airline and required a much latger holding of spare engines.

Ironically, that idea worked on piston-driven aircraft. The P-38 actually used a left-hand and right-hand prop; in order to make the prop spin in the desired direction, one of the V-1710's were installed backward.

[M2dude]

Hi again Jane-Doh. Self starting meaning (at least to my non-aerodynamicist avionics infected brain) that the shock system will establish itself perfectly without specific movement of the variable surfaces. Similarly it will not experience the phenomonem (unstart) where the whole shock system will be violently expellled to the extent that it can not tbe safely re-established without changing both the engine power setting and the variable surface position. (This whole thing being the 'train wreck' phenomen ).
That was interesting stuff about the P38, I must admit I'd not heard that one. (Makes sense I suppose though, provided that the engine can be easily be re-positioned in such a way).

[howiehowie93]

I had to look it up on Wikipedia:

Counter-rotation was achieved with the use of "handed" engines, which meant that the crankshaft of each engine turned in the opposite direction of its counterpart. The V-12 engines only required that the spark plug firing order be changed in order for the direction of the crank shaft to be reversed, according to the General Motors Allison V1710 Service School Handbook.

Lockheed P-38 Lightning - Wikipedia, the free encyclopedia

sorry for the thread drift.

regards
Howie

[forget]

Modern day contra-rotating props. (Shacks don't count.)

http://www.pprune.org/military-aircr...ml#post6231665

[M2dude]

CliveL

The airworthiness authorities were demanding a safety factor of 3 because nobody had flown under that sort of limit before, so the theoretical life would have been 7000 flights.

The RELIFE programme had already taken the aircraft to 8,500 cycles, and the escence of RELIFE 2 had already been agreed when the maggots pulled the plug in late 2003. My own personal guess is that we'd now be looking at RELIFE 3 within a few years if we were still operating. It always really was a case of 'how long's a piece of string' as far as how long the aeroplane could be kept flying.

[Shaggy Sheep Driver]

If I may be permitted to tread drift a bit re engine rotation effects: prop-driven aircraft suffer a range of unpleasant effects that jets don't. Not least is the prop slipstream effect; the propwash spirals around the aeroplane and pushes on the fin inducing a turn. This is at its worst at take off, with no slipstream and high power; even our Chipmunk needs a bootful of left rudder to keep straight when full power is applied at the start of the take-off roll. A really powerful aeroplane like a Spitfire cannot use full power until there is sufficient airspeed to make the rudder effective enough to keep straight; one reason why later Spits had contra-rotating props.

Then, for a taildragger like the Chippy, there's the 'assymetric blade effect' or 'p' factor, where with the tail down the down-going prop blade produces more thrust than the up-going one. And the engine torque effect particularly noticable on soft runways with powerful aeroplane where one mainwheel tyre is pushed into the ground with more force than the other, and finally the gyroscopic swing induced in a taildragger as the tail comes up and the prop disc is tilted to the vertical.

All of these effects are cumulative, and it's one reason why tail-wheel prop pilots learn to use their feet! All are obviated by contra-rotating props or, for twins, 'handed' engines which rotate in opoosite directions to each other.

When I had a share in a Yak52 I used to use the 'engine torque effect' to steer the aeroplane on Barton's muddy winter surface; using the conventional method (braking the appropriate mainwheel; the nosewheel was free-castoring) didn't work as the (quite thin) wheel would just lock and slide along, not inducing a change of direction at all. But whack on a fistful of Vendeneyef and 360hp would dig the right main into the ground and she'd turn right. Pull the power off suddenly and the left main would dig in, turning her left. Worked a treat!

[CliveL]

M2dude,

Thanks for that info Dude - you were still working on the beast long after I left it!

Tomorrow is the launch for the 7th edition of Chris Orelbar's book and I hope to meet a few old friends there. Maybe something interesting will emerge

[Mr.Vortex]

Hi all,

I have read through some book and it said that in cold ambient condition [ISA -15C or less], the intake can suffer a supercritical condition and I did look up a picture of intake in supercritical condition and it show that the shock wave seems to get "sucked" in and the shockwave isn't concentrate at lip area. I don't understand that if the aircraft is travelling at M2.0 then the air passing through the engine should have the same mach no and hence the shockwave should be identical to the normal condition but it isn't. Can some explain this for me please.

Best regards

[Brian Abraham]

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.

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,

Jim Zwayer, Lockheed flight-test specialist, and I were evaluating systems on an SR-71 Blackbird test from Edwards. We also were investigating procedures designed to reduce trim drag and improve high-Mach cruise performance. The latter involved flying with the center-of-gravity (CG) located further aft than normal, reducing the Blackbird's longitudinal stability.

On the planned test profile, we entered a programmed 35-deg. bank turn to the right. An immediate unstart occurred on the right engine, forcing the aircraft to roll further right and start to pitch up. I jammed the control stick as far left and forward as it would go.

No response. I instantly knew we were in for a wild ride.

The cumulative effects of system malfunctions, reduced longitudinal stability, increased angle-of-attack in the turn, supersonic speed, high altitude and other factors imposed forces on the airframe that exceeded flight control authority and the Stability Augmentation System's ability to restore control.

The next day, our flight profile was duplicated on the SR-71 flight simulator at Beale AFB, Calif. The outcome was identical. Steps were immediately taken to prevent a recurrence of our accident. Testing at a CG aft of normal limits was discontinued, and trim-drag issues were subsequently resolved via aerodynamic means. The inlet control system was continuously improved and, with subsequent development of the Digital Automatic Flight and Inlet Control System, inlet unstarts became rare.

[steve-de-s]

Concorde G-BOAF heading for the London Eye?

http://heritageconcorde.com/?page_id=7739

[Nardi Riviera]

As a Concorde enthusiast since day one, I'd like to express my sincere gratitude for all the inside info you guys have shared with us outsiders in this thread.

Keep it up, please...

[steve-de-s]

Concorde 202

Was Concorde 202 a production standard Concorde that could have been used as an airliner, or was it nothing more than a development Concorde that could only have been used for flight testing?

[M2dude]

She was a a test airframe only, although in circa 1985/86 we did look at modifications that would bring her up to production aircraft standard. The modifications required to the powerplant alone (mainly engine and intake control logic and management) were truly massive, as well as other things like engine instrumentation and other systems' control management. The total cripler however was the cost of a TOTAL RESKIN of the forward fuselage section (Component 30, made at Brooklands). The production series aircraft had a thicker skin here, and we were told that the CAA insisted on this being done as part of any conversion to airliner standard. Costs of around £30 were being banded about for bringing the entire airframe up to production aircraft standard. Also of course she had an MEPU when flying rather than a HYRAT for emergency power and of course a large flight test observers position.
I worked on 202 personally quite a bit during the mid to late 70's, but she never remotely 'felt' like a real production aircraft. Even aircraft 204 (G-BOAC) in her pre-route proving days was a radically different beast. (The OAC post route-proving modifications although at system level were quite extensive, these were miniscule in comparison to the differences between 202 and what we like to call 'the REAL Concorde'. Don't get me wrong, 202 did some absolutely stirring work in terms of route-proving and certification trials, and the restoration done at Brooklands is most impressive indeed, but she is and always was, nothing other than a test aircraft. She was no more a production airframe in reality than the pre-production aircraft 102, and I'm afraid that anyone thinking that she is anying other than this is truly deluding themselves my friend.
I'm sorry if this reality is dissapointing steve-de-s, but if you want to see a Concorde that is truly representative of what the aircraft was really all about I suggest that you pop up to either Manchester or East Fortune. (The only airliner museums in the UK now open to public viewing). The Manchester exhibit in particular is truly superb and beautifully kept by some great people, and shows you exactly what Concorde, THE AIRLINER was actually like, rather than just seeing a test specimin. (A superb specimin 202 indeed she was, but this is ALL she ever was, a test specimin).

Best regards
Dude

[gordonroxburgh]

agreed Dude...

202 was built as 2nd Production, with a defined role as a test aircraft. Several studies were carried out over the years to see if she could be reused. Initially with the manufacturers, where if Concorde has been a success she could have been refurbished and sold to another airline at a "good" price. Of course here flying outside the certified flight envelope led to a lot of further concerns that really was curtains for any modification.

BA had robbed a lot of parts from her in the 80s, especially to bring G-BOAG back into service, so it was a no brainier in the end to put her in a hangar and rob whatever was required to kept the fleet of 7 in the air.

One little point, in the very late 70s here MEPU was decommissioned and she was fitted with the HYRAT...although the guts of the de-contaminated MEPU is still up in her tail cone.

If you want to see an Concorde as it was in Airline Service go visit MAN or EF, fantastic displays showing an Airline Concorde in the 90s or 00s

If you want to visit a Concorde and want to see the 4 stories in one (Concorde story, the unique story of a development aircraft, the airliner passenger experience and they story of how Concorde pilots were trained).... then visit Brooklands.

We've never been able to prove from a documented drawing perspective at Brooklands that the roof of the forward fuselage was any thiner than that of 204.

[M2dude]

Well in that case you are obviously right I suppose and BA, BAe (as it was) and the CAA were all wrong as far as component 30 goes. And everything that I was told at Fairford was wrong too. I guess it goes to show I suppose that all these bodies can be wrong.
There were several semi-structural and 'heavy' system components that were robbed by BA (I removed some stuff myself in the mid 80's and early 90's), but the fact remains that there were massive system differences that could never be reconciled by simple 'mods'. The fact also remains that she was a 5100 variant aircraft and not a 5101/5102 variant (or a 100 series aircraft either) and was significantly D-I-F-F-E-R-E-N-T to the 'real' aircraft, the airliners. I was THERE and I SAW the differences myself enough times for goodness sake, and the fact remains she was NEVER an airliner and never had any real prospect of being one. (But as I said before, she was a wonderful TEST specimin and did some stirling work). Brooklands really has a lot to offer the visitor as an exhibit I suppose but if you want to see Concorde THE AIRLINER then you really need to go elsewhere. Manchester in the only place where you can now see an intact production series Concorde in the UK and as I said before is NOW lovingly cared for by some brilliant people.

Regards
Dude