Posts by user "ChristiaanJ" [Posts: 266 Total up-votes: 0 Page: 13 of 14]¶

As I said, haven't been to the museum for years.... So my judgment may be outdated.
Which had no real relation with Concorde. Unless you're confusing the SC-1 with the HP-115 (which is also at Yeovilton).

CJ

mfaff ,
Point taken.

In a way, Apollo is relevant.... At the time, there were two "prestige" programs to be on : Concorde and Apollo. I've been lucky, I was part of one of those !

CJ

Shaggy ,
I doubt South Ken would want to get rid of their 593 (BTW, I'm still curious where that one came from, and what model it is).

I thought Alpha Charlie arrived with all its four engines....
Without wanting to go into the current squabbles, couldn't the museum drop one of the engines for display? They're pretty well invisible from the outside, so taking one out (and replacing it with a couple of plywood panels inside the nacelle, to avoid the horrible hollow-tooth effect we saw on Alpha-Delta in NY), would not do any damage to the display, but it would add another attraction to the museum.

CJ

I couldn't even afford those.... but my family paid for one of the last "Bay of Biscay" trips, and yes, I did keep the salt and pepper shakers.

CJ

I was curious as well, and hoping somebody with practical experience would post an answer.
The engines were interchangeable among the airframes. Just as well, really, otherwise it would have meant keeping a stock of spare engines for each aircraft !

A more practical issue was that the engines were "handed", so that if a "left-handed" engine failed and you had only "right-handed" engines in stock, you had a problem.....
There is a nice interesting chapter in the Olympus 593 manual on how to convert a "left-handed" engine into a "right-handed" one (it mostly involved moving auxiliaries and other connections from one side to the other), but it was work, and took time. More time than a 'simple' engine change .....

CJ

Does anybody still have notes about how much the Olympuses at Dovebid went for at the time?

Shaggy , I doubt anybody would buy it to "use" it. I would bet that surplus military engines of the same kind of thrust rating could be had much cheaper. Not to mention that parts, ancillaries, etc., would be far easier to procure....

CJ

Sorry to have caused some confusion....

BN2A is right : some of the pipes, pumps, generators, ancillariy gearboxes, connectors and suchlike on the outside of the 'round peg' are installed either on the left or the right side of the engine, so that they fit inside the 'square hole' while remaining accessible for inspection/maintenance.

911slf , all engines rotate in the same direction. However, the vortices rolling off the leading edges of the wings into the air intakes rotate in opposite directions.
Now if you look at a photo or a model, you'll see that the intakes of the outboard engines (#1 and #4) are quite close to the leading edges.
No problem for engine #1, because the rotation of the air entering the intake is the same as that of the engine itself, but for engine #4 there is a conflict between the senses of rotoation, leading to vibration at low speed.
Engine #3 is further back from the wing leading edge, so the airflow into the intake has already been 'straightened out' more, hence the problem doesn't occur there.
Maybe M2dude has some more details?

CJ

CliveL ,
Many thanks for chipping in.... I gave the explanation to the best of my knowledge, but as you know I'm not an aerodynamicist, nor an engine expert, so I was actually hoping either M2dude or you would add the corrections.

What caused the actual vibration? Incipient stall of the first compressor stages, or some separate phenomenon?

CJ

She was pretty well 'state-of-the-art', really.
And through the long proto-preprod-prod developent cycle, I would say she was as near 'perfect' as we could make her at the time she went into service.

Maybe I should mention that in 'my field' (automatic flight control systems) the 'state-of-the-art' was changing significantly almost from year to year.

I'd be interested too.

LOL.....
Being Dutch, I had to convert my school French to engineering French on the one hand, and 'argot' on the other hand, while at the same time getting familiar with the way 'my' firm was implementing the latest developments in electronics.

Has anybody here read "The Soul of a New Machine", by Tracy Kidder?
It's a pity no book quite like that has ever been written about Concorde... and I can't imagine it could be written today. Too many of the 'actors' have retired, or are not there anymore....

Maybe somebody ambitious could use this thread as a base, and do some interviews, and write "Concorde, From Then to Now" ?

CJ

I just looked at the one cockpit item I possess, and indeed I would call it dark gray, without a bluish tint. Unfortunately I don't have the color/paint reference....
I suspect the bluish tint is the result of lighting and camera settings.
If you're really interested, I can ask my wife to dig out her "Munseill Book of Color" (standard color chips) and try to match it up.

CJ

LOL.... OK.
Anyway, for modelers (not your case, I take it) a Munsell chip ref wouldn't be much use..... they'd need a Humbrol paint number !

"Matching colors" is a Concorde problem to this day....
A small group of enthusiasts is trying to re-paint F-WTSA (the French preprod Concorde, now at a small museum south of the Paris Orly airport) in the same paint scheme as in the olden days... ancient BA livery on one side, ancient AF livery on the other side.
Getting hold of all the paint color references is not obvious!

CJ

IIRC (somebody else can confirm?) that's right.
It was a JFK-LHR BA Concorde which landed at Cardiff (in Wales) with some kind of tech problem. The paxs were ferried to LHR and the repairs were done at Cardiff.
Then the a/c was flown back to LHR. Since the take-off was over the sea (so no noise abatement needed), and the plane was empty, with only little fuel, she went "like a scalded cat" and hit Mach 1 in about 6 minutes.

Mr Hoppy ,
I am aware it doesn't quite answer your question... I hope one of the pilots can answer that. But I doubt they would normally have kept specific records.

CJ

Nope.
IIRC you had to push/pull the HDG/TRK SET button in or out to set either heading or track which would then show on the HSI.
This from memory only... I may well be wrong.

CJ

I doubt the "scalded cat" went all the way to 60,000 ft on that particular trip....

CJ

Sorry all, this is now forty years back, literally....
So no, I don't have all the block diagrams and circuit diagrams in my head any more... I'll have to look through what I still have in the way of documentation.
i'll try to give some quick answers.

Da-20 monkey ,
Yes, Concorde had "artifcial damping", or "autostabilsation" as we called it, on all three axes (pitch, roll and yaw), even if it could be flown without it.
On the prototypes there were three separate computers (one per axis).
On the preprod and production aircraft the A/S function was 'compressed' into a single unit (I still have one).

CliveL has given the basic answer.
Don't confuse the Concorde FBW (which we referred to as "electrical signalling") with the current "Airbus" digital FBW.

One, rather than in previous-generation aircraft, the pilot no longer pushed and pulled on cables and rods to move the control surfaces. Instead, when he moved the controls, those movements were translated into electrical signals that were sent to the electro-hydraulic control surface actuators (even if in the Concorde days there still was a mechanical back-up).

Two, the entire system was "analogue". A concept difficult to explain in these days, where nearly everything is digital.....
Very briefly, you can convert 'physical' data, like control positions, or altitude, or pitch or roll rate, or Mach number, into 'analogue' electrical signals. You can then perform all kinds of 'computations' on those signals, like filtering them, or add or subtract them, or even multiply them, using electronic circuits based on 'operational amplifiers'.

In digital systems you go one step further.... you convert all those data into digital values, and use a digital computer to perform all your calculations, in accordance with the 'system software', then convert all the results back into physical data, such as control surface commands.

In analogue systems there is no "software". The entire system is defined by 'control laws ' (not the same thing at all as in the Airbus FBW aircraft) that are fixed in terms of 'transfer functions' of the various control loops.
Those in turn are determined by the values of the components in the various electronic circuits (resistors and capacitors mostly). So in those golden days.... we didn't re-write and re-program software.... we changed resistor and capacitors, and re-wired logic circuits.

I admit, you almost have to have been there to understand it....

I'm not sure whether it's worth starting an entire new thread on 'analogue computing' (maybe there's something on wikipedia, I haven't looked)....

CJ

Thanks MathFox, for looking up the link to the Wiki article.
I just read it, and I wasn't impressed... it's more historical than a clear explanation of what analogue computing really is and does. I wouldn't advise it to somebody who's trying to get his head around the basic concept.

CJ

I really like this question..... and I admit to still being baffled....

A Mirage 2000, a Rafale or a Mirage F1 is only about 15m (50ft) long.
Yet the booms we get locally (see above re returns from exercises over the Med), are still the same double boom - "whah-boom" (N-wave).

Of course, when it comes to judging the exact duration of a sonic boom, things get very subjective.... I wouldn't trust my own judgment, since it's as much based on the rattling of the window/door as the actual sound.

CliveL, are there any documented records of the trials in "Boom Alley" we could use to settle some of the issue?

CJ

johnjosh43 ,
You're quite right about the cable 'problem'.
It's not even typical to Concorde.... airframes are aluminium, while the control cables are steel, so the expansion factor is not the same, and the same problems exist even in subsonic aircraft.

The problem is solved with 'cable tensioners'.

Unfortunately I have no drawing instantly to hand. Maybe some other reader here does, and can post it.... if not I'll try and do a sketch from memory and post it.

As said, the problem is/was much older than Concorde, and we just 'borrowed' from existing technology.

And of course, the expansion differential, and the length and flexibility of the airframe, were some of the reasons why Concorde went for 'fly-by-wire', or - as we called it at the time - 'electrical signalling'.

CJ

PS And yes, there was deliberate 'slack' in the electrical wiring, and also various arrangments of expansion joints in the fuel and hydraulic systems.

I'm not sure to what extent you intend to model the mechanism... but I wouldn't call it simple.

It's not Rube Goldberg, but it's still a pretty complex mechanism, with rails, hydraulic cylinders, uplocks (both hydraulic and manual), intermediate stops for the 5\xb0 and 12.5\xb0 positions, etc.
And you'll discover that (even on the production aircraft) the nose can still be lowered to 17.5\xb0 by removing a set of mechanical stops (IIRC the reason for that is already mentioned earlier in the thread).

Wishing you luck and courage with your venture, and I will be curious to see the final result!

CJ

Shanewhite , define "components"....
If you count every rivet, every bolt, every resistor in the electronics... you'l easily get to a few million....
I don't think YearoftheTiger is going to quite that level of detail.

CJ