The Concorde laid the ground work for the scientific basis of some of our airworthiness assessments today.

To say it another way, since the airplane was so different in its enviroment, some extra thought went into how to make it safe.

Today when we look at supersonci high altitude flight, we also have to look at potential decompressions and how to get the plane down quick enough to save the passengers. No real harm in a few healthy passengers passing out, but we would like them to wake up for the landing. Thus the size of the hole that lets the air out has to be considered vs the probability of the hole being made.

So a consideration is made of uncontained engine failures as well as a window out, etc. Because of this a limitation had to be placed on the size of the engines in diameter, simply due to the size of an engine disk being ejected.

I suppose that other what ifs could enter into this but they would all be veted by the historical probability of them occurring.

That of course brings one back to the arguments was the Concorde really safe enough?

In my view it was considered a leader in safety for its design period, not withstanding a couple of surprises to us in its service life. It simply had less surprises.

Decompression is already discussed in the other Concorde thread.

Have a look here :
Concorde question, post #68
and the few posts before and after that.

And yes, decompression was definitely taken into account!

The critical case was considered to be the loss of a cabin window with only three of the four air conditioning / pressurisation packs operating.
With a near-immediate emergency descent, cabin altitude would have reached 40,000 ft for about two minutes, which is survivable with pure oxygen without pressure breathing.

I wasn't personally involved, but obviously tests were performed to measure the air loss with the appropriate pressure differential.
And yes, that's why the windows are so small. They are slightly bigger on the prototypes, either because the tests hadn't been done before the construction of the prototypes started, or because the certification requirements were narrowed afterwards.

I don't know about the uncontained engine failure case (never happened either), but I suspect it was considered the resulting shrapnel would have resulted in several smaller holes, with a total area not bigger than that of a cabin window.

lomapaseo is right, in that many of the existing certification and airworthiness requirements for subsonic aircraft were either inapplicable or inadequate, and in the end a huge document, the TSS (Transport SuperSonique) Standards was written specially for Concorde.

CJ

RJTRT -

Yes, the flight crew had pressure breathing apparatus.

I believe the EROS masks we're all so familiar with were developed for Concorde??? Anyway - that's what we had, with the addition of a couple of supplementary 'pull' straps to ensure the mask remained firmly attached in pressure-breathing mode. The system was automatic - if the pressure altitude was above 42000' you were px breathing, below that you weren't.

Every other year we'd go on a rig during SEP to practice it, and it was really not that big a deal. A bit odd and a bit harder to speak but no issues.

There would have to have been a pretty serious event to the cabin to >42000', mind.

As for uncontained failures, don't forget the Olympus' were in pretty substantial housings - I know of one fairly severe fire which burned for a few minutes, resulting in huge damage inside the nacelle but none out of it.

Wasn't 202's divider robbed to go on AB after the latter had a fairly big failure of an engine? Again - no question of airfram damage outside the cowlings.

In this respect I reckon the Conc was more robust than many conventional designs.

When Intakes Go Wrong Part 1
 

When intakes go wrong
We've talked quite a bit here about surges and such, so I thought it might be useful to look at what was involved with Concorde 'when things went wrong', in that direction as well as a few other intake horror stories.
The variable air intake control system on any supersonic aircraft is fraught with pitfalls, and downright dangers, the main areas of concern are those of surge and unstart.
A surge, resulting from the breakdown of stable compressor flow, can occur in just about any type of gas turbine engine, however with a supersonic aircraft the effect are really dramatic; The typical characteristics can be really quite disturbing. We get a loss of thrust, an increase in turbine entry temperature and most alarmingly of all a short sharp inlet overpressure, followed by a fairly small longer duration under-pressure. The problem is with any such surge is that unless the cause of that surge is corrected, then the whole process can repeat again and again.
Unstart is far more serious than a simple surge; the inlet shock system is expelled forward of the inlet, with severe 'surge like' effects. Unless changes are made to the intake geometry itself AND ALSO engine demand is reduced, the inlet and engine will not recover and very severe cyclic yawing forces will continue to act on the airframe.
In the case of a Mach 2 surge on Concorde, the most commonly occurring event would be due to a control system malfunction. (The malfunction itself could be an intake ramp going slightly off schedule, a mis-matched engine N1 and N2 at a given temperature or even wing-induced flow distortions. Above Mach 1.6, a surging engine would always cause it's neighbour to surge also. The dynamics of all this, 'a typical surge' are as follows (again quoting from 'The Concorde AICS':
The surge drill used by Concorde crews involved reducing power on the affected engines, until the surging stopped, and when the power was re-applied this was done quite gingerly. (I will leave it to the guys to tell you all how not easy this wa, but the thing was that this well rehearsed drill did in fact work well, and normal service was normally resumed afterwards.
As far as unstart went on Concorde, well I#m pleased to say that there was no such thing :). The intake was designed from the outset to completely self-starting, and so unstarts were fortunately completely unheard of.
I'll continue the surging saga and things that went bang in the night in my next post.

Oh, and ps:
EXWOK
It was OAF, and you are quite right. (OAF's damaged titanium centre wall was removed, 202's was first modified to airline standard and fitted to OAF, the centre wall from the retired French pre-production aircraft 102 was fitted to 202 (to enable the aircraft to remain airworthy) and finally the damaged OAF centre wall fas fitted to 102 in the museum SO THAT THE ENGINE DOORS COULD AGAIN BE CLOSED. (A neat game of musical centre walls). I may have repeated in another thread that when this event happened (as the result of a first stage LP compressor blade loss in 1982 that an FAA inspector was quoted as saying the no other commercial aircraft could have survived the same titanium fire that OAF did.
EXWOK, as far as your statements regarding the safety of our aircraft go, I'm with you 1000%.



Dude :O

M2dude

I know this is the CONCORDE thread, and Blackbird was a twin that operated at 3+, so I'll not stay long, but only share what her pilots have shared with me.

Bird burns a one-off fuel, I think J-8. It will not light on start up without a hypergolic chemical reaction with injected ethyl Borate. I am unfamiliar with airstart, but believe it to be impossible following an unstart. If one engine unstarts, the Yaw is nearly 90 degrees, and instantaneous. Rather than wanting to be in dense air, the only hope is to be at thin air, and hope the a/c does not tumble. I have heard estimates that after unstart, the event is 50% fatal. There is a "club" where one's trophy is the helmet, worn at loss of sym thrust. The helmet strikes the side glass and folds in two. I think it is the "crease club".

Her pilots, (there are but two seats) are well trained for all possibilities, and have an edge over CONCORDE in that they have weighed the odds. The commercial ship is engineered to closer risk taking, and her limits also dance at the "edge".

One last SR-71's Size. Don't get the impression she is dainty, she has the shadow of a 727 classic. The Blackbird may have wider limits, but the Concorde put money in the Bank. The Blackbird "stole" two or three Banks per mission.

I was always impressed with the groundschool's instructors comment that the a/c could maintain (*maintain*!) a cabin altitude of 15,000' with the a/c at FL600 and 2 windows blown out (all 4 airgroups working). Would've been a bit breezy I should imagine.

NW1,
It's not impossible that your instructors were wrong....

http://img.photobucket.com/albums/v3...ompression.gif

This graph is from Chris Orlebar's book "The Concorde Story" (redrawn by me, because the original was too pale to scan properly).

It tells a very different story... after a window blowout you very quickly started an emergency descent, and in the worst case (only 3 airgroups working), the cabin altitude would still peak at about 40,000 ft for about 2 minutes.

I think we'll have to look at our flying manuals to setlle the question!

CJ

Christiaan - possibly. But even Chris's book's (4-groups working) graph shows the cabin peaking only at just above F220: and that's with the engines at idle with the resultant low bleed pressures. At full dry power, FL600, I could believe the manufacturer's claims on this one. It doesn't really matter - the point is they designed the aircraft not to be exposed to rapid depress to FL600 as that wouldn't be survivable - the small windows and over-engineered air groups meant that the only way the cabin would "pop" to zero diff at ceiling would be following a structural failure the like of which would make what happened next moot...

bearfoil
Thanks for you interesting post regarding the 'HABU', just like Concorde the SR-71 deserves and has it's own truly unique place in the realms of aviation history. (It really IS my second favourite aircraft of all time). We were always told that the 'I survived an unstart' club was called the Split Helmet Club; any S-R71 guys around can maybe clear this one up. I think that you will find that the fuel was JP-7; your points regarding igniting the stuff are I think correct, at least that's what I read.
The first really good look that I got of an SR-71 was at the Smithsonian hanger at IAD, before it was opened to the general public, and I have to admit that I was surprised what a big beasty she is. (But an absolutely awesome one too).
Please feel free to chip in here anything that you'd like to about the SR-71, I'm sure readers of this particular thread will find it as fascinating as I do.

Dude :O

NW1
It always amazed me just how 'tight' the airframe was in this regard. I remember that during construcion we used to do a pressure sustained leak check at 15 PSIG!!! (No one on board of course). She was totally amazing structurally , and if you were lucky enough to do any C of A renewal test flights you'll remember just how long that cabin altitude could be maintained at a fairly comfortable level with ALL air groups (packs to the rest of the world) shut down.
For pressure control, instead of using the 'traditional' motorised Boeing type outflow valve, she used four (I know, we only used two at a time) wonderfully designed pneumatically operated Normalair Garret (now part of the American Honeywell Group) discharge valves. These were not only lighter and far more elegant than the 'modern' units, they were INFINATELY more reliable than the units fitted to the 744 and 777. (As a 777 driver I'm sure you agree). But the real beauty with these things is in the deatail; for example if for some God-forsaken and unknown reason the entire 'guts' of the valve blew out at 60,000', the cabin altitude would be limited to no more than 15,000', due to the design of the frame of the outlet nozzle. (The flow of air through the divergent nozzle section produced. yes you've guessed it, a normal SHOCKWAVE across the divergent neck, choking down the flow).
Yes, they really DID think of everything with our wonderful aeroplane.

Dude :O

Re the SR-71 JP-7 fuel I cheated, and copied Wikipedia, but it explains an issue mentioned earlier about relights.

"When the engines of the aircraft were started, puffs of triethylborane (TEB), which ignites on contact with air, were injected into the engines to produce temperatures high enough to ignite the JP-7 initially. The TEB produced a characteristic puff of greenish flame that could often be seen as the engines were ignited. TEB was also used to ignite the afterburners. The aircraft had only 20 fluid ounces (600 ml) of TEB on board for each engine, enough for at least 16 injections (a counter advised the pilot of the number of TEB injections remaining), but this was more than enough for the requirements of any missions it was likely to carry out."

She's 107.5 feet long, just over half a Concorde....
But yes, dainty she isn't.
And for my UK friends (or rather the few who may not know this yet), the only SR-71 in a museum outside the US is at Duxford in the American Air Museum.
And very much worth a visit.

CJ

When Intakes Go Wrong Part 2
 

There were many concerns regarding the design integrity of the system, where performance and stability had to be both predictable and safe. The designers at British Aerospace (and to an extent Rolls Royce also) had hundreds and HUNDREDS of flight test hours ahead of them; remembering also that a digital control system had to be 'invented' and flight testing begun in less than two and a half years; the original analog system being totally discarded as far as development went.
The biggest worry for the intake design team was however the STRUCURAL integrity of the intake itself, in the event of engine surging, and this was a worry that was well justified by events. In 1971, the French prototype 001 was undergoing tests when on cancelling reheat (At Mach 1.9, not 1.7 as was the eventual 'norm') the associated engine suffered an N1 overspeed and surged, along with it's neighbour. (001 like it's British sister 002 used the original Ultra Electronics constructed analog intake control system; the digital system being still two years away from taking to the air). Unfortunately in the case of this surge, the intake design was found to be seriously under engineered and the surge over-pressure spike caused the failure of the entire forward ramp attachment assembly. A large section of the forward ramp was blown forward and over the top of the wing (we are doing Mach 1.9 remember) and pieces of the rear ramp were swallowed by the engine, which was already in deep surge. The engine was seriously damaged and flamed out, but miraculously was re-lit at Mach 1.5, of course only to surge again, and was then shut down manually.
After the above event the structure was substantially improved mechanically, in order to prevent any such surges causing failures within the linkages and hinges. The biggest surge fear was always the over-fuelling surge which produced the highest overpressures of all, and it was always a concern that the structure could suffer terribly from such an event. Although the electronic engine control system was carefully designed to avoid such a thing, in normal airline operation it was hoped that this would never happen; IT DID!!:
In early 1977 a Concorde (NOT British Airways) was flying at Mach 2 when the crew noticed a mismatch on engine parameters; the fuel flow of one of the engines was depressed compared to the other three. Unfortunately it was decided instead of following normal procedures that a little 'experimentation' would be tried, and the F/E pulled the N1 overspeed protection system circuit breaker. There was a loud bang, and the aircraft was buffeted by some quite severe yawing forces, the autostabilisation system working flat out to prevent violent yawing of the aircraft. The engine was subsequently shut down as a precautionary measure and luckily the aircraft landed safely. Although there was a little damage to the frame of the intake, generally the structure had stood up well to a very serious event brought about quite honestly by abject stupidity. (There was a malfunction of the overspeed system, causing the system's own 'butterfly’ valve' to partially close off from it's normal wide open position in order to limit the fuel flow. In response the 'normal' engine control system's butterfly progressively opened to attempt to keep N2 on schedule. The overall effect was a wide open normal fuel valve and the overspeed one, in 'series' with the other guy partially closed off. When the F/E tripped the C/B the overspeed valve, that for obvious reasons was not rate limited in any way, to fly back to it's normal wide open position in about 150 milliseconds. So we have two valves, and both of them are wide open, and before the 'normal' valve has a chance to react, MAXIMUM fuel flow is fed to the engine, hence the violent surge.
There was another violent event that was in many ways far more serious: In late 1977 another NOT BA aircraft was undergoing maintenance at CDG, and part of this maintenance input was to replace an intake hydraulic actuator. Now this rather substantial unit lived high in the roof of the intake, just above the forward ramp and drove two screw jacks, winding in and out at ether side. The two screw jacks were coupled to the twin torque tubes (that rotated and subsequently moved the ramps up and down) with a pair of trunnion blocks, these being secured to the screw jacks with a large nut and bolt. The trunnion blocks were very substantial, being designed to absorb any shock loads that an engine surge could provide. Unfortunately the engineers in Paris forgot to fit, yes THEY LEFT OUT the two trunnion blocks, and the only thing attaching the two torque tubed to the actuator were the nut and bolt. (In this condition the thing would have rattled around like crazy, it's a 'surprise' that no one spotted it. (Or even not to mention followed the maintenance manual). The aircraft departed from CDG for JFK, and miraculously attained Mach 2 cruise without incident, that is until there was a system defect on the adjacent intake; this defect was a failure of the servo valve that operated the spill door that was located in the floor of the intake. (There were several servo valve failures in the early years of operation until modifications remedied the problem). The spill door would normally only ever open at top of descent when the throttles were reduced for decelleration, or in the event of an engine shutting down. Now the control system had quite adequate and sophisticated protection for such an falure event, and, due to the same spill door servo being mechanically common to both control channels, (but with independent control windings) froze the intake as both channels failed, preventing any further movement of the surfaces. I seem to remember that the crew drills just allowed a single reset attempt; every time you did a reset, all failure were over-ridden for just over 100 milliseconds, to give the system a chance to get online. While this time delay is in effect, the door was allowed to drive open, before the protection system freezing things up again. Unfortunately, the F/E performed a completely unauthorised rapid series of multiple resets, ech time the door travelling downwards, each time pushing the terminal shock system further aft in the intake, until the inevitable happened and the engine surged. Quite naturally this induced a 'sympathy' surge into it's neighbour intake, the one with the trunnion blocks missing. The surge loads hit the ramps, and without the two vital trunnion blocks in place, the two attachment bolts (which were never designed to absorb such punishment) sheared. The two ramps then freely fell downwards, the front ramp hitting the floor of the intake violently, shattering the honeycomb structure as well as seriously damaging the intake lower lip. Pieces of intake went straight into the compressor, taking out the engine and it's associated temperature probe. (Which unfortunately at the time was being used by the adjacent engine). Fortunately the aircraft, although with serious intake damage, was close enough to JFK to make an emergency descent, and land safely. The intake itself was so badly damaged that is had to be returned to Filton for repair. (Where all Concorde intakes for both countries were built on a separate production line, and fortunately in this case that line was still making intakes). It was highly fortunate that the intakes were still being constructed in late 1977; the wrecked assembly spent several weeks back in the assembly jigs. But things could have been far worse; it was lucky in this event that this pattern of poor maintenance and airmanship did not cause more serious damage.
The intake things that went bang in the night story IS TO BE CONTINUED

Dude :O

When Intakes Go Wrong Part 3
 

BA themselves had a serious incident, but unlike the OTHER airline this was not as a result of pathetically poor maintenance or airmanship, but of a strange defect coupled with a design anomaly. In the early 1990’s the ramp actuator brake assembly of #2 intake of G-BOAD detached in flight and travelled rearwards, seriously damaging the engine itself, which of course had to be shut down. This defect had never happened before and was attributed to a random failure, until three weeks later the same thing happened again. The aircraft was of course grounded until a fix was found (we could not even find out why this happened). It was known that a feature of the system called ‘HOLD’ would freeze the intake for a brief period (400 milliseconds) in the case of certain failures, inhibiting failure indications and control lane switching at the same time and it was postulated that maybe here maybe lay a clue. (just a theory at this point). Although no static failures could be detected (using specific electronic test equipment) we tried it during an engine run, and found that with a little vibration there was a high frequency repetitive failure of the spill door position resolver, which was replaced. The subsequent engine run proved good, with no further failure indications, and a test flight carried out with the same test equipment fitted, again with without any further failure indications. (It was a great flight too, just me, the three crew and my very large yellow test box at the rear of the aircraft). The aircraft was now allowed safely back into service, and when the offending spill door resolver pack was inspected in the overhaul workshop, a dry soldered joint was confirmed. Analysis showed that the failures were at just the right frequency to allow the ramp actuator brake to be applied, but after the HOLD time delay period expired the failure had cleared, and so the brake was released again, with no other indications, but a fraction of a second later the process would repeat itself. It was estimated that in the three week period between failures over a quarter of a million brake applications had been made, eventually the attachment bolts of the brake assembly failed as a result of metal fatigue. It was a horrible coincidence that this one little soldered joint could fail at just the right frequency to cause such mayhem; eventually stronger bolts were fitted to all aircraft and regular bolt replacements were routinely implemented.
During the first couple of years of Concorde airline operation there was a serious structural issue regarding the intake assemblies. Serious cracking was discovered at the ramp hinge area, and the cause was found to be an aerodynamic resonance issue in the Mach 1.4 to 1.8 flight regime. A short term fix was to strengthen the structure, coupled with a change to the control laws in this speed band. (The change to the intake software did have a performance penalty however). The long term fix was a profiled rear ramp leading edge, and more software changes coupled with a performance enhancing modification to fit a lower, thinned bottom lip to the intake.
The intake was nothing more than an aerodynamic balancing act, where you not only knew and controlled the position of the terminal shock system to within fractions of an inch you also hat to ensure that maintaining critical operation (the normal shock being at the narrowest part of the intake convergent/divergent duct) did not compromise other factors such as ramp angle and control schedule limits variable limits that could result in flow distortion and surge. The system always controlled everything to give you maximum performance, but would move slightly away from this point when necessary to preserve engine flow stability and safety; as was said before, a surge was always the result of something going slightly off 'tune' and was never just ‘one of those things’.
To find the root cause of a surge required a fair bit of forensic analysis; unlike AF, BA had a superb Plessey PVs1580 digital flight data acquisition and recorder (AIDS) system that monitored all the intake parameters; this enabled us to find the cause most of the time, by reading data from the Quick Access Recorder after the flight. (A fair bit of Midnight oil burned though; I still have bags under my eyes ). I remember that originally the singular most important parameter, inlet void pressure, was only sampled once every four seconds by the AIDS system, but once we showed that this was like an ETERNITY when you were trying to track down an engine 'hiccup', we got the sampling rate increased to once per second. Although even this was not ideal, it generally did prove to be sufficient for us.
One small drawback of the thinned and lowered bottom lip was a susceptibility to small pop surges at top of descent, when the throttles were retarded. You just had to be a little careful, and I seem to recall that the initial 'throttle back' minimum limit was 18 degrees throttle angle; zero being max throttle. These surges were very mild and did no damage, but as with all surges post flight engine and intake inspections were required, (no problems werer ever found) together with the usual forensic investigations, ‘just in case’.

Dude :O

Just found this thread after a pointer in another Conc thread.

In all the 40 years I've been reading about Concorde, I've never found any of this sort of information before.

Seriously this all needs to be copied over to one of the specialist Concorde sites and tidied up for permanent display. It's a complete treasure trove and it needs preserving.

Amazing information about the SR-71 too, I've been a 'Sled' fan for a very long time too....

Thanks Feathers, glad you enjoyed the thread. The 'black art' of Concorde always was a fascinating subject. I always found ithe idea numbing that this more or less 'set it and forget it' system could achieve so much and contribute so much to the performance of Concorde. Never in the world both before or since could a variable intake give such a large amount of stability and efficiency, time after time. A tribute to the twelve British and two French designers; well done lads and lass. (The two Aerospatiale guys were responsible for the intake/wing aerodynamic interface, true masters of their craft).

Dude :O

I suppose that with the exception of the the SR-71 engine installation, no other aircraft had need of an intake control system that maintained performance in such a tight set of constraints. But yes, truly an impressive piece of engineering and all done with a tiny fraction of the computing power available to the modern designer.

M2dude
 

Magnificent stuff. Thanks.

Yes and no.
Yes, in the sense that just about any aircraft going up to Mach 2 and beyond needs some type of variable intake system.
No, in the sense that most of them have a far less sophisticated intake control system than Concorde or SR-71, with only Mach number and throttle setting as inputs.

The Tornado was originally designed for Mach 2+ and used variable intakes. Legend had it that the Tornado AICS had a family relation with the system on Concorde, but since it was developped by a German firm (Nord Micro), that's unlikely.
Also, most of the later Tornados were limited to Mach 1.3, so the AICS and the ramp actuators were removed.

CJ

Ditto the production B-1B, vs the pre-production B-1A.

And here lies a very true tale: When the Tornado airframe and systems 'carve up' was done in the early 1970's,the aerodynamic responsibility for the variable intake went to MBB in Germany. Now the last time that this particular company was involved with air inlets was in World War 2, so some ideas for problem solutions were required here. The only real place for MBB to go in Europe for help was good old BAC in Filton. The method of aerodynamic shockwave control and feedback used for the Concorde 'two stream' intake was totally unique, and BAC were only too happy to help out their German brethren (kinda dumb really as we shall soon see). After the Tornado intake was (finally) developed in the mid 1970's MBB realised that there was no existing patents on their (copycat) design, and so they applied for and obtained these necessary patents. The next part is pure comic opera; MBB then approach BAC for financial compensation with regard to this copyright infringement, (yep!! BAC design and develop the Concorde intake, give all the necessary knowledge and 'know how' to MBB for the Tornado and then are required to PAY THEM for the pleasure??). No money in fact ever changed hands, there was of course no justifiable case here, but there is a bit of poetic justice; the final Tornado intake was a very poor design, with excessive levels of fuselage boundary layer ingestion and shockwave control. The RB199 engine (a totally 'political' design, with a never to be repeated, for a supersonic engine that is, 3 shaft layout) was already down on thrust, but now had even worse Mach 2 performance due to a wholly inadequate intake design. (MBB had the design principles thanks to BAC, but were totally out of their depth when it came to applying these principles into a practical intake). The eventual 'locking out' of the Tornado intake ended up being no big deal.
(Not sure if this was done with the F3 though).
Fortunately for the western world, the Tornado was (and still is) a superb low level performer, but would have been a so much better Mach 2 aircraft if the powerplant (including the intake) was left to expertise and not politics.

Dude :O

M2dude,

Thanks for a very interesting story, that puts it all into context !

You may want to glance at this old PPRuNe thread re the Tornado :
Is the Tornado GR4 still supersonic? [Archive] - PPRuNe Forums

It would seem your guess about the F3 was right.

CJ

Thanks ChristiaanJ, that Tornado thread was absolutely fascinating to read. The poor old Tornado was so down on thrust; a little more thought and effort in the powerplant design would have resulted in an otherwise good aeroplane becoming a GREAT aeroplane. (I stll remember the case of an F3 being left standing by Concorde during transonic acceleration).

Dude :O

As Feathers said...

"In all the 40 years I've been reading about Concorde, I've never found any of this sort of information before.

Seriously this all needs to be copied over to one of the specialist Concorde sites and tidied up for permanent display. It's a complete treasure trove and it needs preserving."

Totally agree. If only we could get Dude, Christiaan, Exwok, Bellapheron and all the Concordians to somehow have their stories documented and thus preserved. So many stories and names I have never heard of - could keep on reading till the cows come home. But seriously....as Feathers said....its a complete treasure trove and it needs preserving......

Thanks speedbirconcorde, possibly food for thought indeed. This particular thread I think deals with one of the most mystical and definately most 'clever' of all of the various 'Concorde Magic' aspects; that is how a 14' long box can end up providing 63% of the 'welly' pushing you through the air at Mach 2. After nearly 37 years of my own personal involvement in the project, it still fascinates the hell out of me. :ok:

Best Regards
Dude :O

Another great 'dollop' of my favourite 'indulgence'. Reading these two Concorde threads, especially this one - even though it makes my brain ache and my eyes wobble. :uhoh:

Dude wrote;
This raises a couple of observations, one is really a question and is this; The Plessey Data Logger you coveted Dude, was surely only as good as the thermocouples, strain gauges and pressure transducers to which it was connected? Also the quality - or validity - of the data acquired from them was really only as good as the locations decided upon by the engine/intake group? Does it then follow that the production Concorde (BA and AF?) was routinely fitted with a whole outfit of sensors that were not normally monitored unless you and your mates needed to know something specific? (I've just realised there are about four questions there, but you probably know what I'm getting at?:))

The observation is; a picture is beginning to emerge of one airline who cherished and took care of an extraordinary asset, while another, broadly speaking, did not. :( Yet another remarkable aspect of Concorde, that the same aeroplane should have been held in such diametrically opposed regard. :confused:

Dude also wrote;
This highlights yet another example of how British Industry/ government have habitually managed to snatch defeat from the very jaws of victory, especially in aviation. I am currently re-reading Genesis of the Jet - the story of Sir Frank Whittle and the struggle he had to bring his revolutionary creation to life - and although one is very proud that Sir Frank was one of the good guys ( a Brit :D) the story is ultimately quite depressing. The attitude of the government of the day, British Thompson - Houston's reluctance and Rover's deviousness all conspiring to delay what should have been a war winner. :ugh:

One thinks of the TSR2 which, on the limited amount of flight data acquired by the single flying airframe, appears to have been an aeroplane in the same astonishing mould as Concorde. With later digital electronics the TSR2 would have made an unbeatable bomber, allowing the money and effort 'squandered' (?) on MRCA to be spent on an agile interceptor replacement for the 'Electrifying' Lightning. :{

One also thinks of the P1154 and later, the offer of joint development on a supersonic AV8B succesor. All of these and many more until even reading about them becomes too depressing and frustrating. :ugh: :ugh:

Finally, Dude wrote;
I completely agree and what is more, your fascination mirrors my own with my day job. Although MRI scanners are my day job, I still - after more than twenty years - look at some of the images it can produce and think; " That is bl00dy clever!" :) I still haven't got over the 'novelty'.

Thanks once more to all the Concorde respondents - amazing stuff. :ok:

Roger.

Landroger
Actually Roger the Plessey PVS1580 system generally used 'spare' outputs from existing system sensors as far as the powerplant went, the one exception to this being T3 (HP compressor delivery temperature) which had it's own dedicated thermocouple. An engine surge would be 'indicated' on the recorder playback as a spike in EGT (Exhaust Gas Temperature), Pv (Inlet Void Pressure - a static absolute pressure measurement above the fwd intake ramp) as well as a collapse in P7 (Exhaust gas total pressure). The surge itself might only be evident for one to three recorded frames, before the engine recovered. The E/O would usually give you a head start by pressing an 'event' button on the system control panel, which put a marker on the recording. You then needed to decide (by looking at the frames immediately BEFORE the surge) whether the engine or the intake caused the surge in the first place. (Not always easy and straightforward). The recorded frames were generally one second samples, so there could often be quite a bit of 'searching' involved.
I see your point Roger, but personally I found that it was more a case of one airline not taking matters (and the aeroplane) for granted and approaching everyday Concorde 'life' in a disciplined and professional manner and the other, very clearly, not. I remember one visit to CDG where I was horrified by the state of the aeroplanes there: The airframes were generally filthy and festooned with repair 'patches' (one large one over the main passenger entry door looked absolutely awful) and the flight deck panels had at least one broken switch and a couple of cracked instrument glasses. (I thought 'surely they don't actually FLY the aircraft like this?' .... they did!!). When I witnessed with my own eyes how aircraft defects were being investigated I could only wonder if 'they' had any clue how the aeroplane really worked. It was blessed relief when I returned to LHR that evening, and could see two gleaming Concorde aircraft in the hangar.
I can only agree with you here Roger, the story is one of complete political and industrial madness; the designer and manufacturer of the finest quality and most capable aircraft in all of Europe being relegated to a producer of mere sub-assemblies and spare parts for certain European 'partners' :ugh:
(Who must now be rubbing their hands together in glee at this short sighted British stupidity). As has been said here before; 'WHAT A WASTE'
Oh I can echo that 1000%. After having an MRI done last year (a very sick Dude indeed) I was absolutely AMAZED at the quality and detail of the resulting images. (Being a true engineer of course I drove everybody at the hospital nuts, wanting to know all the ins and outs of this incredible (but rather LOUD) machine). Truly amazing stuff Roger, I can see your attraction here.

Regards
Dude :O

Intake Thrust is Due to Impulse
 

I realize this thread is two years old...but I just came across it and would like to clear up some of the misconceptions here about what causes the high amount of thrust produced by the Concorde inlet duct...

The reason is very simple and it has to do with the fluid impulse principle...the air entering the inlet duct has a very high momentum (mass flow times velocity)...but it slows down inside the duct from about M2 to ~M0.5...as a result there is a large decrease in fluid momentum...

Since momentum must be conserved...the aircraft gains that much forward momentum...which is thrust...

This momentum change happens in every stage of the engine...the inlet...the compressor...the combustor...and the nozzle...the total thrust of the engine can be computed by computing the impulse (the change in momentum) at each station in the engine...

Even in subsonic flight a diffusing inlet that slows down the flow will produce a thrust impulse...the compressor also...and the burner...the turbine produces a net drag force...and so will the nozzle...

The basic math is that the net Force (in the longitudinal x axis) produced on the engine inside wall is equal to the (mass flow times velocity at the inlet...plus the pressure times area at the inlet)...MINUS... (the mass flow times velocity at the outlet...plus pressure times area of the outlet)...

Fx = (mdot * V1 + P1 * A1) - (mdot * V2 + P2 * A2)

Looking at the right hand side of that equation we have the intake duct opening as the first term..and the fan face as the second term...in order to make thrust in the forward direction we need Fx to end up with a negative value...which means the second term must be bigger...

The mass flow-velocity product decreases as the flow slows down in the duct...but the pressure-area product ends up much bigger so we end up with the second term being bigger than the first term...and we have a change of momentum to the left (ie negative impulse) and we get thrust...

So while it is true that flying at M2 we can greatly increase the static pressure going into our engine by converting dynamic pressure to static pressure...that does not tell us why this causes thrust...the reason is the change of momentum...or impulse...

By itself an increase in pressure ratio will result in somewhat more thrust...and a six-fold increase in static pressure would result in about a 40 percent increase in thrust...compared to an engine that is at atmospheric pressure...but that does not tell us which components of the engine are actually making thrust and which ones are making drag...only a component-by-component breakdown of the impulse will give us the answer...

I’ve also just come across this thread after two years, and although I for sure don’t want to repeat any of the millions of electron-volts expended in the excellent discussions I thought it might be of interest to have some additional comments ‘from the inside’.
The first thing I would like to say is that we always thought of the total system as “powerplant”. As in any aircraft powerplant (engine) the forces on the various components vary – some produce drag, others thrust. Part of the intake had a thrust component, part had drag. Similarly with the engine itself and the propelling nozzle. It is really a bit misleading to say that “the intake produced thrust”. For us it was just one component of the powerplant that gave a thrust .- and we weren't particularly bothered whether that came from pressures on the diffuser walls or momentum changes, What mattered for us was that the intake efficiency (pressure recovery and intake external drag) was as high as possible. (not intake drag as high as possible of course). I can't stress too highly that the powerplant had to be considered as a whole!



Dude’s remark:


was absolutely on the mark. Other things I found interesting:


Post #15 B377
Not a lot!
Post #31 Landroger
Very definitely played for !
Yup!
Post # 33 M2Dude
The analogue system wasn’t thrown away exactly – we retained the inner ‘analogue’ system that did the closed loop dynamic control of ramps etc. and wrapped a digital system around it to define the control ‘laws’ to which the intake operated.

Post #39 Mr Optimistic

Actually Concorde was the first civil aircraft to be certificated using this 10^-9 approach, although the rules were of course contained in TSS Standards not enshrined in FARs. Also we adopted a far more pragmatic ‘engineering’ way of working than the almost blind faith in numbers that seems to be the case today!
Post #56 M”Dude
Post #66 Pugilistic Animus
Ain’t that the truth!
Post #56 again
Also true, but only two of the team smoked (mind you they made up for the others)
Post #67 M2 Dude
True, but we also did the ‘Hi-tech’ bit. I thought people might be interested in the actual flow visualisation results we got from the lamp black and diesel fuel trick:


http://i1080.photobucket.com/albums/...1/scan0031.jpg

Post #100 M2Dude
In fairness to MBB, one should say that the Tornado had conflicting design requirements in that there was a need for efficient subsonic performance to give loiter (CAP) endurance, so they were forced to compromise a bit on the purely supersonic efficiency.


Hope I haven’t hogged too much space!

Interesting Stuff
 

Clive...thanks for chipping in with some very interesting info...


Always good to hear from one of the design team members...just curious about a couple of things...what was the mass flow per engine at M2 cruise...?...and what about the jet velocity out the tailpipe...?...my rough estimate puts it at ~300 lb/s and ~ 1,100 ft/s over and above the freestream velocity...


That would put propulsive efficiency at ~80 percent...which means engine thermal efficiency would be just over 50 percent...


Some other interesting figures...total flight power at M2 would be over 140,000 thrust hp...nearly three times the flight power of a triple seven...fuel burn would have been most impressive at over 13 lb per second...compared to 5 for the triple seven...


The triple seven's GE90 engine is good for a TE of ~50 percent...and propulsive efficiency of ~0.8...really quite amazing that a Mach 2 transport could still be the high water mark after all these decades...


Regards,


Gordon.

Bloodhound SSC
 

I'm fascinated by this thread too chaps, addicted to is a better way of putting it.

I know it's not Concorde but how will Bloodhound SSC be addressing these problems do we think?

1,000 mph at 0 agl must be some challenge too and not exactly "off the shelf"....

CW

Tupolev Tu144
 

It was mentioned earlier that the Tu144 did not supercruise...and that Soviet designers never did solve the technical challenges in creating an efficient engine inlet...

In the spirit of fairness and accuracy...this is not correct...it is true that the initial version of the airplane was not ale to supercruise...due to using inefficient Kuznetsov turbofan engines... instead of more efficient turbojets which are better suited to supersonic cruise...the Russian designers were aware of this but there was not a suitable turbojet engine available at the time...


The D model of the airplane switched to Kolesov RD36 turbojets when those became available...and was able to cruise at M2 without reheat...SFC of the Kolsesov engine was comparable to the Olympus at ~1.2...although the Kolesov was a bigger more powerful engine with `12,000 pounds of cruise thrust compared to the Olympus's 10,000...


The more efficient engines greatly increased the range of the airplane to 3,500 nm...largely closing the gap with Concorde's 3,900 nm range...an extended range model was in the works that would have exceeded Concorde...when the program was cancelled in 1983...


The original intake ducts were not as efficient as Concorde...but this was rectified with subsequent models...starting with the S model that preceded the D...


In the 1990s Nasa obtained a Tu144LL which was a D model retrofitted with Kuznetsov fan enngines due to the fact that the more efficient Kolesov jets were no longer in production...a comprehensive flight test report is available from Nasa...


http://dcb.larc.nasa.gov/DCBStaff/ebj/Papers/TM-2000-209850.pdf


The report notes that "the engine inlets appeared insensitive to sideslips (up to 4.5 degrees) or to pitching moments..."...this points to good inlet design...something that is not always present in supersonic aircraft...for instance the F14 which was known to have compressor stalls at high yaw angle...



Overall the Tu144 is a bigger and heavier aircraft than Concorde and was able to reach a higher speed...M2.4...although cruise was at M2...the prototype used a lot of titanium although this was cut down on production models...unfortunately...


Regards,


Gordon.

Interesting stuff
 

Gordon,

Without doing a lot of sums (which I have probably forgotten how to do), the best I can offer is:

58000 ft, M 2.0, Ambient temperature - 52 deg C, Ambient pressure 1.2 lb/sq.in
Engine intake conditions
Total pressure 8.5 lb/sq.in, Total Temperature 127 deg C, Mass flow 189 lb/sec.
Fuel burn 9700 lb/hr
Jet pipe exit (not final nozzle) Total pressure 16 lb/sq.in, Total Temperature 687 deg C
Engine thrust 8050 lb.

The jet pipe nozzle was choked of course and the petal angle was 10 deg, but I don't have the value of the actual area handy.

Clive

Thanks for those numbers, Clive...
 

I had estimated the compressor inlet area at ~1 m^2...based on the engine static mass flow of ~450 lb/s...and an assumed inlet Mach of 0.5...


Seeing as cruise mass flow is a lot less...perhaps some of my assumptions were off the mark...


Also surprised to hear a cruise thrust figure of just 8,000 lb...a Concorde website with lots of info gives 10,000 lb per engine...Wikipedia gives a Lift to Drag ratio of ~7 at M2 cruise...which would imply that ~50,000 lb of total thrust would be needed...since maximum weight is ~400,000 lb...fuel weight is ~200,000 lb...and fuel flow with max power and reheat is ~50,000 lb/hr...


This means even if it takes a full hour at the maximum fuel flow the airplane would still weigh at least 350,000 lbby the time it reached cruise speed and altitude...since thrust must equal drag in straight and level unaccelerated flight...it means 50,000 lb of thrust would be required...


Looks to me like there is a fair bit of confusing information floating around...hope you can clear some of that up...would like to do a full cycle analysis on the engine at cruise power...that SFC figure of 1.2 is very impressive...


Regards,


Gordon.

First, thanks for resurrecting this most interesting thread. At one point I thought I was getting this, but clearly I wasn't.

Gornaut states that momentum is being transferred from the supersonic incoming air flow to the engine (and hence to the aircraft). I can't visualize it. Isn't the momentum already in the aircraft?? (It is the aircraft that is moving through the air, not the other way round.)

As I read the discussion, it seems we are getting the ultimate free lunch (which I know isn't right). I'm sure that if we turn off the fuel flow, the net thrust must drop to zero. So how can we say that 63% (or whatever) of the thrust is coming from the inlet duct.

I'm really trying to understand this.

Crabman,

Perhaps post #5 explains:

Gornaut states that momentum is being transferred from the supersonic incoming air flow to the engine

That would be drag as something has to slow the air down. This thread caused endless discussions a while back. The way it was originally phrased you would think you had the basis for a perpetual motion machine, ie just bend metal into a sophisticated shape and off it would fly ! Need to take a holistic view of the whole power plant to really get the picture, hence the quotes above. My view was that it was really about the efficient recovery of pressure for the intake but what do I know: certainly the intake on its own isn't a prime mover or the active source of any thrust.

Trying to Post A Sketch ut It Won't Let Me...
 

The math is quite straightforward and can be found in any good engine text or fluid mechanics text...but that does not help us understand the physical principles behind it...


I have already given the momentum equation involved which is a statement of Newton's Second Law of Motion...which we mostly know as F = mass times acceleration...


In fact the Second Law tells us that a force results from a change of momentum...In differential form F = m * a becomes...F = m * dV / dt...which means a mass that experiences a velocity change (differential of V with respect to time) is experiencing a momentum change...


Of course momentum must be conserved...just as mass or energy must be conserved...if a car collides with another car it loses its momentum as it stops...but the other car gains momentum as it is shoved forward...


Same thing with a flowing fluid... if it goes into a control volume such as an engine intake with a certain amount of momentum...and then loses a good part of that momentum...what happens to it...?...it is transferred to the control volume...ie the engine...which is attached to the airplane...


An impulse is simply a change of momentum...when we accelerate a hot gas stream out the tailpipe we impart a change of momentum to that mass flow...the result is reacted by the engine which is attached to either an airplane or a test stand...in either case a change of momentum in the forward direction means thrust...

If we were to take an engine inlet duct (a diffusing duct that has a smaller hole at the front than at the back) and bolt it to the floor inside a wind tunnel... and then blow air at 500 mph through that duct...what do you think would happen...?


If we allowed the mount to slide back and forth...which way would it slide...forward or backward...?


What if we turned the duct around and now had the big hole at the front and the little hole at the back...?...which way would it move now...?...isn't this how a wind sock works...?...which way does it want to go...?...back of course...


And have you ever seen a wind sock where the wind is blowing into the little hole...?...and coming out the big hole in the back...?...of course not...


So why would that intake duct that is shaped just like a wind sock that is turned around front to rear want to move back...?...of course it is going to move forward...


The reason is that the impulse (change of momentum) gets bigger as we go from front to back...

Now we can work out an example like the illustration...we have an airplane flying at 250 m/s...and the inlet opening is 1 m^2...the mass flow is 100 kg/s...let's say the opening at the aft end of the duct is 1.25 m^2...which has the effect of slowing down the flow and increasing static pressure...at the same time the flow loses momentum as it slows down...


We recall that Force = mass flow * velocity...so the force at the front of the duct is 250 m/s * 100 kg/s = 25,000 newtons...a little over 5,000 lb of force...


If the flow slows down to 125 m/s at the aft end...its total force will now be 125 m/s * 100 kg/s = 12,500 N...(mass flow does not change of course...owing to conservation of mass)...


So the fluid flow has lost 12,500 lb of force...but we need to account for all the forces acting on that control volume...we see that there is pressure from the wall pushing on the fluid that is equal and opposite to the pressure of the fluid that is pressing on the wall...since pressure acts exactly perpendicular to any wall...we see that a lot of the arrows are canted in the forward (thrust) direction...this gives us a clue that the sum total of all those little arrows is going to end up as a net forward force...


We can integrate all the pressure forces across that surface and expend a lot of math...or we can just do a simple multiplication of the pressure times the area of the inlet and outlet respectively...that will give us the answer...


So we see that our static pressure at FL350 is 22,500 N/m^2 (22.5 kPa)...and our intake area is 1 m^2...so the total pressure force pushing back is 22,500 N...


At the aft end our pressure is 1.5 times higher...this is a subsonic plane and slowing down the flow from ~M0.8 to ~M0.4 will result in a static pressure increase of that amount...


Our duct exit is 1.25 m^2...so our total force at the back is 22,500 N * 1.5 * 1.25 m^2 = ~42,000 N...So we have gained nearly 20,000 N from the pressure on the engine duct inside surface...!...


We subtract the 12,500 we lost from the flow slowing down...and we are still ahead y more than 7,000 N...an engine of that mass flow would make perhaps 30,000 N total thrust so that would be a good part of it right there...nearly ¼... of total thrust...


So yes the engine inlet is making thrust...that is very real...it is just that we are used to thinking purely about thrust as mass flow times velocity coming out of the tailpipe...and that is the simplest way to account for the sum total of all the physical forces going on in the engine...


However...if you want to do a more thorough line-by-line accounting...then we must start at the tip of the engine and do this impulse analysis for each component...we would then go on and do this for the compressor...the burner...the turbine...and the jet nozzle...and we would find that the net thrust still remains the same...but it is the physical forces of pressure and momentum and impulse that do their work at each point along the way...


Regards,


Gordon.

Source/Site

Power/Work

I think unpacking any aeronautical question leaves room for almost absurd conjecture. Of course the nacelle does not provide power. It is the site, instead, of the Work. Or at least most of it, in modern Turbofan engines. Powered aircraft need, well, power. This happens well aft of the Work.

The Wrights used unducted fans. The power came from a combustion engine that provided mechanical energy to the fans.

Given extreme latitude in architecture, how is the Concorde different from the Wright Flyer? Distance from power to work?

I am still trying to suss the Wright's accomplishments. There were few shoulders to stand on, they made their own engine, for goodness sake.

The idea is to move mass, energetically enough to gain useful work, after all. It is an attempt at lazy magic that pulls people into heated discussion that requires a suspension of the basic Laws.

Mr. Optimistic has busted out the thread, imho.

Here is the Sketch Hope It Works
 

Perhaps it helps, just for a moment, to view the engine as a flow inducer. This is the term used by 'Kelly' Johnson to needle P&W J58 engineers. This merry banter should be seen for what I'm sure it was, just that.

However there is merit in viewing the engine as such since another angle on any issue can only help to get a better picture.

This particular view imo helps to come to terms with the ever-increasing relative contribution of the intake to the total thrust.

At the same time though the engine is producing ever more gross thrust from an ever-increasing release rate in its engine and jetpipe combustors. Everything can be traced back to the fuel. The burning fuel induced the flow which, by virtue of its finer details, must produce forces in some direction or other.

Imagining what's going on in the combustors should help prevent downplaying the loser in the relative stakes.

On a slightly different tack:

Would the inlet momentum drag be zero when the flight speed is the same as the engine entry speed, say M0.5, assuming, of course, that the intake design flow was matched to the engine flow at that flight speed?
After all, if I watch a plane go right to left at M0.5 the compressor face is going left at M0.5 and the air is going right at the same speed, ie is stationary like it was before the plane appeared.

Alternatively, if I'm sitting on the Rosemount probe and looking ahead I see air approaching at 0.5 and if I look behind I see it going away from me into the compressor at 0.5, again no speed change.