Posts about: "Sidestick" [Posts: 20 Pages: 1]

Biggles78
Sorry Biggles78, I'd forgotten to answer your CofG query, so here we go: CofG was a really critical parameter on Concorde, being a delta, with no tailplane made it more so at take off speeds, and as we've previously said, was how we trimmed the aircraft for supersonic flight. CG was expressed as a percentage of the aerodynamic chord line. To get indication of CG you needed to know the mass of fuel in each tank; easy, from the FQI system. You needed to know the moment arm of each tank, (fixed of course). You then needed the zero fuel weight (ZFW) and zero fuel CG (ZFCG); these were manually input into the CG computers by the F/E, from load control data. The final parameter you needed was total fuel weight, again easy from the FQI system.
The 'normal' T/O CG was 53.5%, but in order to increase fuel weight (and hence range) an extra 'bump' was enabled to allow a max T/O CG of 54%. (CG was indicated on a linear gauge, with forward and aft limit 'bugs' either side of the needle. These bugs would move as a function of Mach and at the lower end of the speed range, A/C weight also). As the A/C accelerated, the limit bugs would move rearwards (with of course the rearward shifting centre of pressure) and so the fuel would be moved from the two front trim tanks 9 & 10 to the rear tank. 11. Once tank 11 reached it's preset limit (around 10 tonnes), the remainder of the 'front' fuel would automatically over-spill into tanks 5 & 7. (Once the fuel panel was set up, the whole process was controlled with a single switch). At Mach 2, the CG would be around 59%, the whole rearwards shift being in the order of 6'. As we said before, the 'final' CG could be tweaked to give us a 1/2 degree down elevon, for minimum drag.
I really hope this helps Biggles78.

Guys, back to the Airbus thing; My friend ChristiaanJ gave some really accurate insights, (he always does) but there is another legacy that carries on the this day; some of the audio warning tones were COPIED from Concorde into Airbus. (For example, the A/P disconnect audio is identical). I think this is great, and gives 'our' aircraft a lasting everyday legacy.

As far as the fly by wire goes, Concorde had a relatively simple analog system, with little or no envelope protection (Except at extreme angles if attack). As has been previously poted before, production series test aircraft 201, F-WTSB, pioneered the use of a sidestick within a new digital fly by wire Controlled Conviguration Vehicle sytem, with envelope protection and attitude rate feedback. (This evolved into the superb system known and loved by the Airbus community). It is a really bizaar twist of fate that the Concorde FBW system has more mechanical similarities to the system used in the B777 than Airbus. (Mechanically similar at the front end, with an electric backdrive system moving the column in A/P mode; Concorde being backdriven by a hydraulic relay jack).
As a final piece of irony; the Primary Flight Control Computers on the B777 are designed and built by GEC Marconi Avionics in Rochester Kent, now BAe Systems. This is the same plant where Elliot (becoming Marconi and finally GEC Marconi Avionics) developed and built the UK half of the AFCS computers. Isn't this aviation world strange?
Galaxy Flyer
Your inputs here are great, and I'm sure appreciated by all. (I assume from your name that you were a C5A pilot. While I was in the RAF on C-130's, our Lockheed rep' used to supply us all with company magazines, that were full of stuff on this new (it was then) giant of the sky. I fell in love with it there and then).
Anyway, back to Conc': The decel' positions were carefully worked out and adhered to; the aim was to be subsonic to within (I think) 50 nm of the east coast. I'll wait for one of my Concorde pilot friends to confirm that here, but i think I'm correct. I do have a fond memory of one flight out of JFK; we were temporarily 'held' by Boston ATC to Mach 1.6 (and at around FL440) because of an Air France Concorde heading for JFK. We saw this guy above us, at around FL580 on a near reciprical , doing Mach 2, screaming straight over the top of us. We were excited by this amazing spectacle, and so were the AF crew over the VHF ('you never boomed us, did we boom you?'). But the most excited person of all was this guy in Boston ATC. ('I've never seen anything like it guys, your two blips whistled over each other on my my screen like crazy').
Stliton
As far as the F/D noise levels were concerned, once the nose and visor were raised, it was as if someone had switched off the noise . The main source of noise up there was just the equipment cooling, and that was not bad either. It was, in my view, little noisier up than most subsonics. (But not the 744, where you are so far away from all the racket ).
Ozgrade3
You're making us blush here; thanks for your comments, I think we are just trying to share some of our experiences (and 'bit's we've picked up over the years).
From my perspective, I did write some stuff used by our pilots, AF even got a copy or two I think.

EXWOK , more than happy to take a hint........PLEASE! and welcome to this gem of a thread.

With the FBW, was there any feedback built into the yoke? The Airbus with it's "joystick" has, I believe, no feel unlike a Flight Sim force feedback one.
If there was a yoke movement on one side did the other side mirror the movement or like the Airbus did the sidestick play dead?

M2 , it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?

Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?

Landroger
Wow, that's a very interesting question, do you mind if I give it a tiny slant of my own, namely system distribution?
Concorde had an ENORMOUS number of electronic control boxes, for example the powerplant alone used TWENTY SIX rather heavy computers and control units, all of which used conventional 1970's manufacturing technology. (Although the intake box was a work of art; rows and rows of double sided PCBs completely crammed with TTL chips). This whole entourage literally weighed a ton, and could be easily replaced by four modern relatively light units with multiple redundancy built in). Even the AFCS used a total of sixteen heavy boxes, again these could be reduced to three, for a modern triple channel system. The three INUs and two ADCs (Very heavy units all) could be replaced with a single ADIRU and SAARU. To complete the package two FMCs (which would also furnish autothrottle functions) could be added. A massive weight saving could be made on the FBW system, by removing the bulky mechanical components (the feel and relay jacks as well as all the mechanical control runs and the massive mixing unit under the rear floor). Careful design could easily provide a full authority triplex or quadraplex FBW system. The current controls could be replaced with either an Airbus or Boeing type system, using either a sidestick (Airbus) or retain a conventional control column system (B777/787) using electric backdrive. The pilots can decide this one. A modern databus system would also be required for providing communication and redundancy; ARINC 629 would be MY preferred choice). The wholesale replacement of the various control units and computers, not to forget miles of wiring, as well as some bulky mechanical hardware would in my view save around 3 tonnes or more in weight alone. A now far more accurate control of aircraft systems would also bring major efficiency savings. As far as saving space, that possibly free up a couple of seat rows, if it were all done properly.
We can all dream I suppose

Dude

This reallt has to be the best thread I have ever read here.

I have a question also:

201 (I believe) was fitted with a sidestick control on the left, was the aircraft actually flown with this and if so what were the pilots reactions to it?

Was it possibly to have been incorporated on later production aircraft?

Also did it retain the artificial feel system?

Thanks again for the great thread

Tex

You're right, it was 201 (F-WTSB).
After certification the aircraft was retained for several flight test programmes, not all of them Concorde-related.
In this case it was an early trial of the sidestick for the A320.
Concorde was already a fly-by-wire aircraft, so it was "relatively" easy to hook a sidestick into the system.
Unfortunately, I remember only some of the details...
It was only fitted on the left.
The righthand side remained fully conventional, and the RH seat pilot acted as the safety pilot.

Yes, definitely.
The story doesn't tell, I'm afraid. At the time it would have 'confidential', of course.

Not really... as I said it was just an early test for the A320.
At the time the aircraft were already certified, so it would have meant a MAJOR modification of the flying controls, AND recertification.
Also there was no requirement for it... the Concorde flying controls were judged perfectly satisfactory by the pilots.

Yes, that remained connected to the conventional controls (I'm not even sure whether the LH control column was removed).
Of course the sidestick would have its own, totally different artificial feel, since the control laws were different.

CJ

Questions already answered earlier, but I just found this photo on another forum.



The sidestick was located where the LH weather radar display normally is.

CJ

May I ask you guys another question relating to the book I mentioned earlier, in the same book it shows a Concorde with a Airbus sidestick control. I wondered if anymore information is known on this modification I suspect t must have been quite an systems integration exercise.

ITman, nice question.
I haven't seen any of the detailed (block) diagrams, so I'm not sure at all how the sidestick was "hooked into" the AFCS.

Don't forget Concorde already used "electrical flying control signalling" (aka "Fly-By-Wire")., so system integration would have been easier than on some other aircraft.

For those unfamiliar with the story... F-WTSB, very late in its career, was used for some flight trials with a sidestick controller fitted to the left-hand position (the right-hand seat controls still being the normal ones,and with the right-hand seat occupied by a 'safety' pilot).
The flight test data were later "fed" into the A-320 programme.

How much of the "rate" control and other A-320 control logic was already implemented in the test system is unknown, AFAIK ....
Would be interesting to know some more about it, I agree!

CJ

I can't add too much as I was only on the fringes of this.


I think it might have been done by fitting a D/A converter to substitute the digital signals from the sidestick for the normal Concorde stick resolver output. The 'laws' could then be treated as a special case of pitch damper etc. inputs so that the standard Concorde electrical signalling system could be used downstream. I don't know this for sure, it is just a thought - maybe Christiaan could comment on its feasibility.


I think they were looking at at least the rate control but probably not all the envelope protections. Certainly at that time we were having discussions with them about the merits of their FBW laws against the laws we (BAe) were trying out on our BAC1-11 flying test bed. No prizes for guessing who won that argument.


And before anyone asks; no I don't remember (if I ever knew) how we were implementing FBW into the 1-11!


CliveL

My only reasoning for guessing on the Emg flight system was that its would be easy to turn on and off and recover to the normal flying controls.

For a very short test programme, well ahead of any A320 programme which did not come about till 1984, I suspect this was no more than a belt and braces to see if you could fly an aircraft from a side mounted stick.

Gordon,

[quote] My only reasoning for guessing on the Emg flight system was that its would be easy to turn on and off and recover to the normal flying controls. [quote]

I see what you mean, but surely it would be just as easy to insert a kill switch in other systems?

I'm with Landroger on this in that I feel they would want to do a lot more than just find out if aircraft can be flown with a sidestick. I would expect them to want to know about how much stick movement was optimum and this they could not do with the EMG solution (if I have read your remarks correctly that would have been a stick fixed/force signalled system?)

I am also pretty certain that they investigated control laws; with a simple 'can you fly with a sidestick?' system they would surely be effectively in a electronic version of mechanical signalling?, and although you could fly the bird in mechanical it would be making life difficult for yourself, which is the last thing you want to do when investigating something really new.

I personally doubt very much if the Emergency Pilot would be the 'way in' for the sidestick input. EFC ROLL commands were inputed from the SFC computer to the Autostab computers as 'stab demands' and therefore drove the MIDDLE and OUTER elevons only for roll. To make matters worse, if your test flight was really 'exciting' and you found yourself at any time at Vmo + 20 KTS, roll control would be through the middle elevons ONLY. I'm with CliveL in that the most likely scenario would be for the demand would feed via a D/A converter somehow. (It would be great to find out though).
I would have thought that the whole venture was a proof of concept by SFENA for future implementation in the Airbus family. This excersise would have been both costly and highly complex at system level, any other reason would really have been quite daft.

Best Regards
Dude

Thanks for that much better picture Bellerephon.

I have a bit more information now, although my French is very rusty so I may not have it all correct - CJ can probably correct me if necessary.

They did 8 flights over 10 hrs, preceded by about 30 simulator 'flights'. Most of the flight testing was looking at low speed behaviour, since that was where they expected to see most gains on Concorde, and where the most problems might be expected, but they did go up to 2.04M. The primary advantage was seen to be the possibility of using very aft CGs for takeoff to reduce trim drag - they flight tested as far back as 56% at around 0.4M (no consideration of limits from U/C location of course for this sort of testing). In addition they were predicting a weight saving of around half a tonne.

The simulator work sorted out the basic laws, where they tested a pure pitch rate feedback and a C* law with load factor and pitch rate terms. The pilots preferred the latter (which became in time the basis for the A320 laws).
The simulator was also used to establish the best ergonomics (movement and force harmonisation) of the sidestick.

The 'blue' electrical signalling system for elevons was replaced by the digital control and sidestick arrangement, keeping the 'green' signalling as a safety backup. Normal rudder control system was retained, as well as the mechanical backup.

In the general arrangement of the digital control system one can see clearly the genesis of the A320 design - two computers with the software written by separate teams etc.

Pilot reaction seems to have been very favourable, the aircraft being somewhat easier to fly than the basic Concorde (which was already pretty good ....).
In particular the paper suggests that the precision with which the aircraft could be positioned was much improved.
Stick force per 'g' was pretty much the same throughout the speed range at about 7daN/g, whereas on Concorde it varies from 20 to 40 daN/g - but on a sidestick rather than a control column of course.

One problem that did show up, although not peculiar to Concorde, was the sensitivity of these systems to structural response, particularly during ground roll.

Not contained in the report, but in a side letter from Dudley, is a remark that the guy most responsible for the development of the Concorde basic system and later in charge of the Airbus system thought that these Concorde experiments were the key to the success of the A320.

'Nuff said!

CliveL

Never get tired of this thread !


Very interesting about the sidestick, was the installation and testing purely for research / experimentation purposes or was it seriously contemplated for use in production Aircraft ?



If so, why was it decided against ?!

As I recall, they referred to this research project as a CCV (Controlled Configured Vehicle) design study. It would be great if we could get this confirmed, but they talked about subsonic drag reductions of 10 to 15% by flying (not taking off!!) with a far more aft CG than the norm. The 'system' I seem to remember, as a result naturally commanded some down elevon, which increased lift. As the aircraft could then fly with less alpha, I guess this is where the drag reduction comes from. (Clive, I wonder if you could find out through one of your contacts if this was true?).
I'd still personally like to know how the sidestick was integrated into the flying control system, I've been thinking and can not now believe that sidestick inputs could be simply input to the flying control system 'at resolver level'. Remember that the concept of the FBW system on Concorde was that resolvers were utilised as simple 4 wire synchros, and the pitch and roll axis utilised a CX/CDX/CT chain, which produced the error signal to the ESA's in the Autostab computers. Using a sidestick completely breaks up the chain, and my guess is that a seperate digital unit contained the flight rules which were summed against PFCU CT position and sidestick input would have been necessary. It is possible then that an analog output from this 'box' could be fed to the Autostab Computer ESAs and hence drive the elevons. I'm probably completely wrong, but I'd surely still love to know the truth. As you say Clive, ideal stuff for Concorde 2.

Best regards
Dude

Don't need no contacts Dude. The drag reduction came simply from flying at a lower AoA when trimmed at an aft CG. Less 'up' elevon, which is similar but not the same as 'down elevon' in an absolute sense, so less adverse elevon lift and work the wing to a lower AoA in consequence. Just an extension of the basic Concorde certification with a 'point' TO CG really.

They were certainly looking to study control laws that allowed flight at very aft CGs to increase aircraft performance, so yes, this was a CCV exercise, but they were also seeking experience with digital control and system architectures that could be transferred to other active control applications.

The 'sidestick' arrangement was virtually a complete A320 style arrangement using two computers and digital signalling throughout. For just 10 hrs they wouldn't need anything more complicated than a 'panic switch' to return control to the standard Concorde green system that was still there and available.

Clive

Shirley the aft CG research for lower cruise drag could equally be done with conventional Concorde controls? Why is it associated only with sidestick control?

They weren't looking for cruise drag reductions; just takeoff climb improvements which would have required genuine relaxed stability - CGs back at the aerodynamic centre etc.
This entailed introducing artificial stability terms that would have been difficult in a purely analogue system such as the basic Concorde controls, so they decided to go digital.
Sidestick or conventional control column doesn't come into that of course - see Boeing vs AI FBW systems; but no doubt the French government saw the opportunity to get two for the price of one .....

CliveL

Did the Sidestick controller have the same authority as the Conventional Control yoke or were there 'hard limits' a la Airbus 320 and on ?

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

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

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

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