Posts about: "Trim" [Posts: 65 Page: 1 of 4]¶

Hi Stilton, that is a question that we all used to ask ourselves; not having an APU was a major pain in the butt for the fleet, particularly at charter destinations, where air start trucks, GPU's and air conditioning trucks would all have to be pre-arranged.
One problem with 'Conc' was always one of weight, (for every extra pound you carried, another pound of fuel was required) so any APU installation would have to have been light, and worth the extra weight. But the main problem was one of 'where to put the darned thing. The only suitable space available for an APU was in the tailcone, aft of the tail wheel. Now a ready supply of fuel would have been available either from the aft trim tank, #11, or from one of the two trim galleries. (For stability reasons, tank 11 was invariably left empty during ground transits). The real crunch however, was how to arrange pneumatic services from an APU: Tank 11 was directly forward of the tailcone, so this would have meant either ducting the pneumatics THROUGH the fuel tank (not a particularly good idea ) or externally around the fuselage, which would have been 'draggy' to say the least.
You could still have had an APU powering hydraulics, and in essence electrics too (the emergency generator was powered from the Green System), but without pneumatics for engine starting and air conditioning, it would really have been a waste of weight. Still, it really is a shame that there was no APU.
Historically, there were 'sort of' aux power units fitted to development aircraft: The prototypes had two GTS's (Gas Turbine Starters), one in each nacelle pair, that could start the engines without an air start truck, but these never saw the light of day in later aircraft. The most unusual unit of all was the MEPU (Monogol Emergency Power Unit), located in the tail cone. This was manufactured by Sundstrand, and was fitted to all of the development aircraft. (A derivation of a unit fitted to the X-15!!). The idea was that if you had a four-engined flameout at Mach 2, this thing would fire up, power Green and Yellow hydraulics (plus the emergency generator, again from the Green system), and give you power and control down to a safe relight altitude. The MEPU was powered by Hydrazine rocket fuel (unbelievably unstable) and I seem to remember that the thing would run for about 8 minutes. There was no way that this monstrosity would ever be acceptable on a commercial aircraft, and so a conventional RAT was developed by Dowty for the production aircraft. (Also, the windmilling engines would give you full electrics down to Mach 1.1, and Hydraulics down to about Mach 0.7, so the thing had little practical use when supersonic anyway).
I hope this extended blurb helps answer your query Stilton.

Galaxy Flyer
Thanks very much for your comments. It's true, that while supersonic, a windmilling Olympus engine would have sufficient N2 to keep all servics on line. (The hydraulic systems on Concorde also operated at 4000 PSI). The RAT itself was 'said' to be good down to approach speeds, fortunately we never had to find out if that was true. (Although the thing was tested routinely using a hydraulic rig to drive it and check the variable pitch speed control). Thr RAT was in fact located and stowed in the fwd part of the R/H inboard elevon Powered Flying Control Unit Fairing. It was an absolute work of art by Dowty, to make the device fit into such a small space.
Yep, an ash cloud would be particularly bad news, particularly at FL600
Stlton
You are most welcome, thank you for posting this topic also. These forums are a wonderful way for all of us out there in the aviation world to share and learn interesting information from each other.
TURIN
I remember reading By the Rivers of Babylon many MANY years ago. The terrorists, I seem to remember, had a bomb fitted inside Tank 11 (the rear trim tank) during construction 'before it was welded shut'. Not sure if the author had researched how aircraft were built, but still I guess it sold a copy or two. (Well at least you and I read it).

10,000kg in a trim tank? No, I am really not that stupid to think it was all used for trim but I am beginning to realise just how little I knew about this technological wonder of the skies. Also wish someone had recorded her being rolled (like the B707 when being displayed). Now that would be something that would stand along side the noise abatement takeoff or maybe not. The T/O is impressive!!

M2dude and ChristiaanJ, please keep posting any anecdotes that you remember about this incredible aeroplane. It really is fascinating learning about the technical side from those who actually knew her.

M2dude,

Re the MEPU at the Le Bourget museum...
The story I just got was that it was taken off F-WTSA or F-WTSB at Roissy for a fault and replaced (both 'SA and 'SB operated out of Roissy around '74 / '75 for things like route proving, etc.).
It got left on a shelf in a store, and was only discovered again in 2003 during the "big clean-out" and was saved 'in extremis' by somebody who recognised it for what it was, stopped it from being 'binned' and took it over to the museum.

Initially of couse it was. It was not until the return to subsonic, towards the end of the flight, that the contents of the n\xb0 11 trim tank were moved forward again to the other tanks.
So yes, you're right, essentially all of it was "useable" fuel, it did not serve only for the trim.

Don't we all....
Jock Lowe seems to have stated there is a photo.... and we all still wonder if there is some footage taken from the Lear Jet during the filming of "Airport 79". But none is publicly known to exist ... we just know it's been done!

Biggles78
I must admit, it seems excessive carrying 10,000kg in a trim tank, but this fuel system really was a study in elegance. Every single drop of fuel carried was usable by the engines, and the Mach Trimming was so good that you could fine-tune the process so as to achieve the minimum drag configuration for the aircraft of 1/2 degree down elevon in supersonic cruise. One rather amusing point about the fuel Mach trimming; the airworthiness authorities insisted that the aircraft also had a conventional Mach trimmer built into the electric pitch trim system. As the aircraft was mostly flown on autopliot, assuming the fuel trimming was being done correctly (it always was), the auto-trim would wind off this Mach trimming as it was applied, the net result of course being no change to the pitch demand. This really was a totally superfluous addition to the electric trim system. (If for any reason the aircraft HAD been hand flown during acceleration, the pilot would have to nudge the trim button nose down all the time as the A/C accelerated, in order to to oppose the nose up electric trim input).
The fuel, apart from 'lighting the fires' and trimming the aircraft was also used as a cooling medium for engine and IDG oil, as well as for the hydraulic system also. Where it was used to massive effect, was as a cooling medium for the air conditioning system. Here, at Mach 2 conditions, we needed air to exit the 'packs' (on Concorde these were called 'groups') at around -25 deg's C. By the time this air had travelled through the wing ducting it had risen to a sweltering 0 deg's C, at which temperature it entered the cabin. The astonishing thing is, that the air used for this, HP compressor delivery air, P3, was at around 550 deg's C as it left the engine. The ram air itself, used to cool the Primary and Secondary heat exchangers, had a total temperature anything up to 127 deg's C, and to complete this story, the fuel itself had an average temperature of around 60 deg's C. And surprisingly enough, it was a more or less conventional air conditioning system, using air/air intercoolers, an air cycle machine, with just the addition of the fuel exchanger (between the outlet of the secondary heat exchanger and the ACM turbine) to make it any different in concept to most other air cond' systems.

Damn, guess I am really that stupid. (Let's just keep that between you, Christiaan and myself ).

M2, the figures you give are incredible (I like stats) so I shall ask for more. Anytime you get tired of answering please just say enough .

How much fuel was used in the taxi. T/O roll. To TOC. Usage in cruise. From TOD?
How long did it take to get to TOC and was it done in one hit or were there stages when fuel burn allowed the climb to resume? What was the ground distance covered to get to TOC? How far out was TOD and what was ROD during the approach?

The amusing trim piece I found quite funny. That requirement must have been designed by several different Government committees; net result, nothing changes.

Had a question on the nose. You mentioned somewhere about a decompression when the nose was lowered to the 5\xb0 stage. This indicates that the nose had more than the Up and Down positions that I always thought. Were there multiple nose positions and when would they have been used. (Obviously nose full down was for T/O and Landing)

Last one for this post. What was the CoG range? I remember when I started flying and finally twigged to what it was all about that the PA28 had something like a 5" from the forward to aft limit and was massively surprised by the small "balance point". Trim tanks on 1 aeroplane I flew would have been most welcome.

I know I have asked a lot so please answer at your convenience.

Many thanks.

I would say not: there wouldn't have been any space in the wheel well.
The gears retracted inwards, and when up, the bogies were right next to each other on each side of the keel. As a matter of fact, the main gear legs had to be "shortened" while they retracted, otherwise they wouldn't even have fitted...
No, because the inside trim wall panels were relatively short (say about 10 ft, don't remember exactly) and each moved with their bit of fuselage (think roof tiles). Same applied to the floor panels, which also were in fairly short sections. The movement was of course hidden by the carpets.
Yes indeed. Flexible sections all over the place.

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.

First, I must apologise to Stilton for hi-jacking his thread. I had inadvertantly asked a question in the wrong thread and have only just realised it, so sorry Stilton. The good part of this is all this delicious Concorde info that were are privileged to be receiving from M2dude and ChristiaanJ is all in the one thread. Unless anyone has any objections maybe the Forum Moderator could merged the other 2 threads into this one.

Thank you for the CoG answer. 6 feet sounds like an awful lot but then I am only able to compare it to the littlies that I fly. The ability to use the trim tanks to only have to use a \xbd\xb0 of elevon must have made a substantial impact on performance and the resulting reduced fuel consumption. To think it was all computer controlled at the time when the PC didn't even exist.

M2, you have said that the fuel system was a work of elegance and the above desciption give me a small insight into this. I know that I am just going to have to find books written about this lady to find out more. I have been lazy when asking about item that I could Google but there was a method behind my laziness. When you and Christiaan share your knowledge there is always a personal anecdote or insight that will never be found in any books that I may be able to find. Gentlemen, for this THANKS seem so insufficient.

The TOC=TOD had me thinking and I believe insomnia may have assisted with some understanding (otherwise the stupid sign for me comes out again ). Gee I hope I have this even partly right. I assume that when accelerating to Mach 2, that it was done while climbing. I was initially stuck with the compression factor of Mach 1 and without thinking the same would happen at Mach 2 (A C Kermode was the hardest book I have read that I didn't understand ). Therefore with that in mind I was stuck trying to figure TOC=TOD. Am I right or even slightly so in thinking that cruise climb and cruise descent was the flight and there was minimal actual level cruise in the "pond" crossing?

I had also forgotten to take into account the speed factor, DUH!! Subsonic climbs, what 35 - 45 mins to FL4xx and then it is in level cruise for the next 6 hours before TOD. The lady took what, about 3.5 hours, and the extra 20,000 feet it had to climb and descend ate up or into any level cruise it had (or didn't have). Am I on the right track or am I making an ass out of me and me.

I was in the jump seat of a B767 on a trans Tasman crossing, CAVOK, when about 2,000 feet lower a dot followed by a straight white cloud approached and passed by. I found that impressive so the 2 supersonics passing at the speed of an SR71 must have been spectacular. Shame radar track isn't available on You Tube. Oh yes, did they boom you?

As you have said, fuel flow was reduced the higher you got. I think it was 5T per powerplant at FL500 down to 4.1T at FL600. Was there any figures for higher the Levels? I am curious to see how much less fuel would have been used at the higher FLs considering it was reduced by 900Kg/hr for just 10K feet. Very interesting what you said about when the temps were ISA+. I would never have thought such a small temperature change could have effected such a signifigant performance result. It also sounds odd, as you said, the faster you go the less fuel you use.

Last greedy question for this post. How much of the descent was carried out while supersonic and how did this affect the fuel flow?

Sorry Bellerophon, a badly worded question from me but you gave a really good analogy. Gonna remember that even though I don't like my Flight Plans have collagen filled lips. I will see if I can reword it to make it comprehensible.

Thank you for the Instrument Panel image that I have now added to my collection. What is the Yellow Arc on the Mach metre that starts at about M1.12?
Do you remember if you had a signifigant headwind at that stage? I notice that the G/S is 1,139kts was this fairly standard for an East-West flight? (DUH me. Just read the fastest crossing was an east-west direction. Winds must have been quite favorable) I am now guessing the displayed G/S would be fairly typical, plus or minus a bit.
The Glide Ratio, even if it is a highly educated guess, is impressive. I would not have expected it to have been about the same as a B747. How many more times is this Lady going to surprise me with her performance.

Also notice the ball is slightly off to the left even though it is still inside the lines. Was this normal or does it need a tad more rudder trim? Can't imagine it is really out of balance.

Was that because of the tight fit on the flight deck or because we really don't like others in our workspace?

ChristiaanJ thanks for the CoG diagram. That I am still getting my head around. There is a large range at the bottom and top of the speed range but fairly narrow in the mid speed range. Seems like 165T was a less complex balancing act than it was at 105T.

The center rear fuselage gear unit, what was that for? I have seen it deployed on many occasions but I can't for the life of me remember if it was during T/O or LDG however it didn't seem to be extended every time the aeroplane flew. Was this used during loading so she didn't accidently "rotate" at the ramp or to avoid a tailstrike during LDG? I can't imagine an over rotate during T/O.

And a big Thank You to Bellerophon for sharing his knowledge with this thread.

This is a wonderful thread about the most superlative aircraft ever built.We were once fortunate enough to be given seats 1 C&D (I would have liked to see a roll-call of their previous occupants) and with regard to the hugely knowledgeable points made about fuel transfer and trim, during boarding and in flight the sound of fuel pumping was often louder than the Olympus music.During a visit to the FD the captain verified that these were the noisiest rows in the cabin despite their often being used by royalty and REAL A-listers. Many thanks for sharing your deep insights into this machine.

Biggles:

Yep, there was feedback. In this respect, the implementation of FBW had a rather different philosophy to FBW Airbus'.

Below 200kts it was basically a spring feedback, above that speed it was achieved throught the feel system, not entirely unlike conventional aircraft.

Of course, the feel was tempered also by the autostab system, which didn't feedback through the yoke, but did make control surface inputs. A basic analogy is to imagine a yaw damper, but on all three axes. (It was of course rather more sophisticated, especially in pitch).

During airtests we would fly portions of the supersonic accel without autostabs and it was then very obvious exactly how much input was being made - great care was needed to remain within sensible bank angles in the low supersonic regime.

Also - watch a video of the control surfaces in the latter stages of the approach and landing - all those rapid deflections are the autostabs overlaid on the pilot's inputs. One has to remember that the aircraft is effectively statically unstable in pitch at approach speeds, so a pilot up-elevator input would soon be followed by a countering autostab elevon-down to contain the tendency to keep pitching up, and vice-versa. Gusts affecting the IAS would also create an input.

All of which means the basic spring feel below 200kts is not as basic as it sounds.....and in normal signalling modes (ie FBW and autostab active) the amazing thing is that the aircraft handled beautifully through an 1100kt speed range.

If you look at a picture of the flightdeck you will see a row of 14 white switches full width of the fwd edge of the overhead panel. These were autostab pitch/roll/yaw, feel pitch/roll/yaw left and right systems and the two pitch trim switches (which played a big part in the low-speed protection).

If any of them dropped out you could be sure that the first thing the nearest pilot would do would be to try to re-engage them, as it made for a vastly more pleasant life.

Well, of course we did have computers in those days, mostly for the really big number-crunching jobs.
But you're right, nearly all of the mundane day-to-day design was with a slide rule, and pencil-and-paper.

I still remember how in about 1972 we had to start calculating the electric trim computer resistor values to 0.1% (rather than +-1%), so I bought my very first pocket calculator.... little red LED display, just the basic 4 functions. Cost \xa342, and those were 1972 pounds (what would the equivalent be today?). Luckily I could put it on my expense account ....

CJ

A great thread and it only goes to show that you can always learn even about a subject that you thought you knew quite a lot about

As M2Dude described the rearwards transfer of fuel during acceleration was meant to be an automated process but in reality there was a lot of manual input. The first requirement of the F/E was to match the rearwards movement of the C of G to that of the ever increasing Mach number. If this was proving to be no problem he would take over the transfer manually by switching off the pumps on one side of tank 9 or 10 so as to pump only to either tank 5 or 7. This was because if you transferred evenly to these tanks due to their different shape size and position the aircraft would go out of trim laterally so the F/E would pump rearward just to one tank so as to keep the C of G going aft whilst maintaining lateral trim.

Being Concorde nothing was straight forward , which meant that when Tanks 5 and 7 ran out and you started using tanks 6 and 8, their size shape and position,was exactly opposite to that of tanks 5 and 7 so it now required the F/E to pump fuel the opposite way across the ship, using various valves and pumps, so as to keep the aircraft in trim laterally.

All the time he had to maintain the trim so as to keep an elevon trim of \xbd deg down, which as fuel was burnt required him to trickle fuel forward from tank 11. On the longer trips such as those to and from BGI the fuel towards the end of cruise became quite low and to stop fuel in the collectors from dropping below 1000kgs each, fuel would be transferred from tank 11 into the collectors until the
C of G had reached it's forward limit at Mach 2.0 of 57.5 %. If then the collectors dropped to 1000kgs the aircraft had to descend to subsonic heights and speed.

Surges

Surges were not an uncommon or common event on Concorde,but when they happened as they usually affected both engines on that side the aircraft would lurch /yaw and everybody on board would know about it as \x93Her In Doors\x94 would testify to that when glasses full and otherwise ended up in her lap during the meal service when a surge occurred.

The drill required all engines to be throttled to a predetermined position and the intake and engine control switches moved to their other position. If this stopped the surge then the throttles were restored to their cruise power a pair at a time and if no surge re-occured then the aircraft would return to cruise / climb

The crews post surge action was normally to have a cup of tea and light up a cigarette.

In the early days on a flight between London and Bahrain when the aircraft was in supersonic cruise the F/E who was a mature and refined gentleman, had to go to the toilet, which was just behind the front galley, and whilst there the engines surged. He was seen running from the toilet to the flight deck with his trousers around his ankles, which was a hell of shock to his refined nature

Enough for now sorry about the length

The PROM board is from an AICU, the other board is from an AFCS computer.
Could be Autostab, Lateral Autopilot or Trim, since they all used exactly the same technology, board size, etc.
Looking at the board, I think it's 'Lat A/P' but I can't be certain.
No excuse needed about missing the "central connector" !
It was really a "one-off" feature, invented by Bendix, and abandoned afterwards. I'm not even sure the early A300B AFCS computers, that used much of the Concorde technology, still had them.

See my post on the subject. I doubt there was any core memory at all in the production aircraft.

CJ

It was determined in a very early stage, that an engine surge or engine failure at supersonic speed would produce a very abrupt, inacceptable, and possibly dangerous, amount of yaw.

So the prototypes were equipped with "autorudder" computers. They used pressure sensors in the engines to detect engine failures, and they would then kick in a "pre-dosed" amount of rudder, that would then be "washed-out" gradually while the pilot dealt with the issue and added rudder trim.

They were manufactured by SFENA, and since I was their flight test support at Fairford, they became automatically my "babies".

The computers (analog, big boxes, the same size as the autopilots or air intake computers) were extremely reliable (we had only two passive faults during the entire flying career of 002).
Unfortunately the same could not be said of the pressure sensors, and since it was always easier to "pull" a computer than a pressure sensor, we found a computer on the bench every few weeks, which then had to be taken through a full test spec and sent back with "no fault found", before anybody was willing to look at the sensors.

Luckily a better solution was found, using a lateral accelerometer, and from the preprod aircraft onwards, each big separate autorudder computer was replaced by a single board tucked away in the autostab computer.

Since the function was always "on", there was no separate autorudder engage switch. Many years later, I discovered that several airline Concorde pilots did not even know the function existed....

CJ

Thanks for your comment M2dude, am just SLF with an interest in design, due to being a member of the profession accused by the Prince of Wales "of doing more damage to this country than the Luftwaffe"!
This may seem a trival question but on the ITVV video Capt Rowlands is checking the pitch trim and the sound made is as he says "rather like a french bicycle bell" and he suggests that it may indeed be made by such a bell. I rather like that idea; but was it so?
I remember in the early eighties loading programmes into my ZX81 using cassettes; and not having much success! Mind you a cassette tape would be far better than an 8 track as an 8 track would keep reloading the route and you would end up flying in circles!
There is a serious point here and that is if you are designing such a complex machine as Concorde, if you can use proven technology in some areas then do so. It appears that all the people involved did so and didn't waste time on "reinventing the wheel" or complicating things just for the sake of it. Good design is about finding the most appropiate solution and Concorde is a fine example of that.
Once again thanks
Nick

Nick Thomas
SLF keep the rest of us in business, your input is so very welcome here. Nick, the 'French Bike Bell' is exactly what it was, as the electric pitch trim wheen ran up or down a striker would impact this tiny bell and make the sound that you describe. 'Pitch Trim' sounds like a strange term, after all the aircraft had no trim tabs or tailplane as we all know. What varying the pitch trim used to do was to alter the neutral setting of the artificial feel unit, the control column following this neautral datum.
ZX81, takes me back here. The tape loading that was used on the INS took around 45 minutes per navigation unit, that's two and a quarter hours total for the system. (There was no cross-loading). If Concorde had remained in service, new legislation meant that a more accurate primary navigation system would have been required. One of the systems under consideration was a Litton 82 laser INS with GPS refinement. (As well as DME updating also).

Dude

M2dude I have another question concerning "debow" You very clearly answered my original question on another thread. I just wondered how the engine was kept at a sub idle 30% N2? Was it done by careful metering of the fuel? and if not how was it done? I ask because the throttles would be closed during start up.
The whole engine installation with the ramps, spill doors, reheats and noozles must have been a nightmare to "fine tune" through all the different phases of flight.
Thanks for the explanation of how the pitch was "trimmed" Due to Concorde having elevrons instead of ailerons; was the aileron trim dealt with in a similar way? I guess the rudder trim could be applied normally.
Thanks again
Nick

DozyWannabe
Good point I suppose, but you could say that the six Concorde prototypes, Pre-Production and Production Series Test aircraft were also development aircraft, and yet more or less worked just as it said on the tin', where the TU144, in spite of all the facilities of Andrei Tupolev's design bureaux, not to mention more or less unlimited Soviet state funds produced a machine that in my opinion really BELONGED in a tin can. (I know this is all off topic, honest guys, I won't mention this stuff again ).
In reality the Soviets really lacked both propulsion technology as well as the systems expertise required to build an aircraft with even a remote hope of Mach 2 cruise, let alone safe and comfortable enough for fare paying passengers. The original aircraft had all for engines in one giant nacelle, and the landing gear retracted into the engine inlet duct itself, great for an undistorted flow path to the engines . The variable inlets were manually operated by the flight engineer as well, no automatics here. In the mid 1970's the Russians even approached PLESSEY to build a digital engine control unit for the TU144. A similar PLESSEY unit had been VERY successfully flight trialled on production series aircraft 202 (G-BBDG) and only lack of funds prevented it being used on the production aircraft. As this unit could obviously be used for Soviet military applications, there was objection from the UK government, and more than just a little trans-Atlantic pressure applied, and so this venture never happened.
Until the advent of the Mig-29 and Sukhoi SU-27 this really was not the case. I'm afraid I'm with galaxy flyer on this; If you look at the air war over Vietnam, when an F4 met a MIG 19 or MIG 21 in an even air-to-air combat, the MIG was going down. (OK this could be partially down to superior US pilot traing etc, but if you look at the handful of skirmishes where the 1960's/1970's Soviet aircraft were engaged in Combat against US or French built fighters, the MIGs never really did very well at all). However, the aircraft that the Russians have been producing from the Mig 29 onwards seem to be in a completely different class now; hope they really are the good guys now.
ANYWAY, back on topic
Lurking SLF
No problem at all Darragh, please keep visiting us and post here also anytime.
Nick Thomas
I'm not sure that I can describe the DEBOW process remotely as eloquently as my friend Bellerophon did, I particularly loved the 'out of balance tumble-drier' bit, but starting a hot or even warm engine, even at DEBOW, you could certainly 'feel' the noise on the flight deck, until the shaft distortions evened out.
Now for the PFM bit, equally eloquently alluded to by Bellerophon:
DEBOW itself was maintained by a special sub-idle datum in the electronic Engine Control Unit, and once the engine was accelerated towards normal idle (61-65% N2, depending on the temperature of the day) even if the switch described by Bellerophon was accidently re-selected, an electronic inhibit gate in the ECU prevented this sub-idle datum from being used again that engine cycle.
You're welcome Nick, actually the roll and yaw trims operated in a similar manner to the pitch, although of course these was applied by a manual trim wheel only. (No French bike bell either ). Rotation of either wheel (more a giant knob actually) merely shifted the neutral datum of the relevant artificial feel unit, which in turn shifted the rudder pedals or control yoke; the resolvers for the FBW system would in consequence demand this 'trimmed' control surface movement.

Dude