Posts about: "AICU (Air Intake Control Computer)" [Posts: 30 Page: 2 of 2]ΒΆ

M2dude
January 30, 2011, 08:43:00 GMT
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Post: 6212195
Static Ports

CliveL
To further complement the answer, Concorde's static ports are mounted on much bigger plates than usually seen. This is because in supersonic flight the static pressure is peculiarly sensitive to the actual angle of the skin around the 'hole' relative to freestream. Consequently the ports are set in plates that have been machined flat. These plates were then jig-set to accurate angles relative to body datum.
It was found that the relatively miniscule differences in plate alignment produced errors in true Ps measurement and so individual corrections had to be applied to each aircraft. No big deal with a digital ADC of course but not so clever when you are dealing with steam driven analog as we were. (Bearing in mind that any analog ADC is an electro-mechanical device). To give identical Mach 2 cruise readings between ADC 1 & 2 a plug in resistor/diode module was hooked into the respective ADC circuit, and this module stayed with the aircraft always. If we'd ever had to replace a static plate in service (and at BA we never did) we'd have had to have done an in-flight pressure survey in order to calculate the required resistors and altered the module accordingly.
The air intake system, although it used Ps from THREE sources (the side static ports and the static ports built into the nose probe; this being a pressure head and not just a pitot as were the side probes) did not apply any individual aircraft corrections, it just made different corrections between side and nose pressure sources (Ps and Pt). Having a digital processor at it's heart, these corrections were signalled by using 'program pins' at the rear of the AICU rack.
As steam driven as the Concorde ADC was, when it came to RVSM implementation in the late 1990s we found that the air data system was in fact superbly accurate, and no modifications to the computers themselves were required. Such a testament to the original superb design.

Best regards
Dude

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Quax .95
April 06, 2011, 18:43:00 GMT
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Post: 6354590
Hello skyhawkmatthew!

M2dude gave a good answer on your question in post #1085, so I think I may quote this here again.

Originally Posted by M2dude
As far as the MAX SPEED bit goes, Concorde was as we know flown to a maximum of Mach 2.23 on A/C 101, but with the production intake and 'final' AICU N1 limiter law, the maximum achievable Mach number in level flight is about Mach 2.13. (Also theoretically, somewhere between Mach 2.2 and 2.3, the front few intake shocks would be 'pushed' back beyond the lower lip, the resulting flow distortion causing multiple severe and surges).

The maximum altitude EVER achieved in testing was I believe by aircraft 102 which achieved 68,000'.

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consub
March 06, 2014, 18:34:00 GMT
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Post: 8356169
Concorde AICU

I have flitted through the threads, and have a few comments that might be of interest.
There were no classified components in the AICU, however there was company confidential in that we did not want the competition to have our lead, also there was an American embargo on delivering equipment with the 5400 series TTL logic integrated circuits which were milspec and chosen for their environmental screening.
Some of the printed circuit boards were 8-layer.
The program was contained in 512 lines of 24 bit instructions.


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consub
March 08, 2014, 17:15:00 GMT
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Post: 8360094
Concorde AICU

Hi Christian,I was a development engineer at Filton working on the AICU at first but ending up in charge of avionics test.
So as far as your AICU is concerned - I have handled all the boards extensively.
I first worked on the "A" model - the first manufactured box, followed by "A bar" (logically, not "A").
These did not have the doghouse connector on the front, and in order to see what was going on in the program, we made a strobe unit hard wired to the digital boards, this was followed by the connector on the front and an AICU test box.
When first switched on the whole unit rattled at high speed as all the relays chattered.
I spent several days adding decoupling capacitors on all the boards.
The birds nest chassis wiring was chosen to prevent cross- talk.
This was at the start of 1972, but I can still remember a lot of it.
Someone mentioned a prom change at Casablanca, I carried out a prom change there just before the C of A flight.
I am a volunteer at the Bristol Aero Collection, and we have just received a drawing cupboard with the AICS drawings.
We are at the moment documenting archives. One of the volunteers is Ted Talbot who I used to work with, and has been mentioned in posts.
Feel free to ask questions, I may remember the answers!

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ChristiaanJ
March 08, 2014, 17:44:00 GMT
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Post: 8360151
consub,
Slightly amazed about your note re the 5400 series TTL being embargoed.
I pulled a random board from "my" AICU, and all of it is 5400 series, datecodes 71 and 72.
I hope you can tell us some more...
I've been sniffing round the boards, but I haven't found the CPU or the clock... and yes, I know the AICU dates from before the arrival of the microprocessor!

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consub
March 08, 2014, 19:39:00 GMT
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Post: 8360344
Concorde AICU

Hi Christian,I was a development engineer at Filton working on the AICU at first but ending up in charge of avionics test.
So as far as your AICU is concerned - I have handled all the boards extensively.
I first worked on the "A" model - the first manufactured box, followed by "A bar" (logically, not "A").
These did not have the doghouse connector on the front, and in order to see what was going on in the program, we made a strobe unit hard wired to the digital boards, this was followed by the connector on the front and an AICU test box.
When first switched on the whole unit rattled at high speed as all the relays chattered.
I spent several days adding decoupling capacitors on all the boards.
The birds nest chassis wiring was chosen to prevent cross- talk.
This was at the start of 1972, but I can still remember a lot of it.
Someone mentioned a prom change at Casablanca, I carried out a prom change there just before the C of A flight.
I am a volunteer at the Bristol Aero Collection, and we have just received a drawing cupboard with the AICS drawings.
We are at the moment documenting archives. One of the volunteers is Ted Talbot who I used to work with, and has been mentioned in posts.
Feel free to ask questions, I may remember the answers!

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consub
March 19, 2014, 20:54:00 GMT
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Post: 8388573
Hi Christian,
We chose the components for their environmental tests, and all the AICS components were subjected to acceptance testing when received, which was a bit of a problem sometimes because the BAC goods inwards system was so slow that some of the expensive ADC/DACs that were not quite good enough were returned to Harris, but were out of warranty by the time they were returned. The embargo was not just the 5400 TTL I/Cs but all milspec. components.
Its stretching my memory, but AICU1 was the ADC board, 2-5 were the processor, 6-10 were the prom boards. There was a bought in board (AICU 17 I think) that was supplied by ?????, that processed the sensor unit data.
The AICS was filled with redundancy, as well as the obvious 2 AICUs per intake, and 4 sensor units, the program calculated the output data with dummy inputs - twice, and if these were correct, the proper inputs were used and the result was output to the doors. On the analogue bit there were two channels for each output and at the end one output was compared with the other and if different a fail was produced.
We haven't opened the plan chests with the AICS drawings yet.
As well as the 8 AICUs on G-BOAF, we have the prototype AICU that was used on the AICS systems rig.

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grumpyoldman
October 22, 2017, 19:32:00 GMT
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Post: 9933310
Smile AICU its boards and the interconnect wiring

Originally Posted by ChristiaanJ
Mine is one of the 202 development units, and 'knitting' is too kind... 'kludge' describes it better. I'll post a photo, if you like.
That myth was amplified substantially by BA removing those "secret" AICUs from the aircraft after the final delivery flights.
The way I understood the story was that they tried to collect as many reasonably reliable spare AICUs for the last few delivery flights, so as not to have to suddenly cancel a flight.
The AICU was right at the top of the list of "unscheduled removals". IIRC the tea maker was second...
The one I know about is the ADC/DAC board (analog-digital and digital-analog converter board). The supply of either ADCs or DACs ran out literaly worldwide, and the board had to be redesigned, requalified and recertified with more recent components, and a new batch manufactured. The cost, for the replacement of that board alone, came to about 3 million euros.
Somebody passed me a photo taken at Casablanca of a table full of AICUs waiting to be programmed... of course every software mod had to be programmed into all eight computers!
"... 'burning' each individual logic gate with a 9v battery." I believe you, thousands wouldn't... Didn't you have at least some sort of programming unit?
I went through a similar exercise around 1976, but at that time at least we had a programming "suitcase", that let you copy the original in RAM, modifiy bit-by-bit with a keyboard, then 'burn' the PROM (or EPROM, by then) 'automatically'. Still took half the night....

Funny in a way how these things have stuck in our memories... But then, yes, Concorde was unique.
I've said this elsewhere, but I don't mind repeating it... in those days, there were two programmes to be part of. One was Apollo, the other was Concorde. And I've had the chance to be part of one of them.
Well, I can claim some input to this Control Unit. The adc/dac was in fact AICU 1. I designed the PCB at BAC Electronic and Space Systems Div. in Bristol in 1971/72 as I remember. Both the A to D and D to A modules on the board were made by Analogue Devices in the states. There was an array of DG103 FET Switches as i recall. The circuit design engineer and the electronic packaging engineer and I had a few rethinks about component placement on this board. As I recall , AICU1 thru 5 were all control and processing boards. AICU6 thru 9 were memory , harris h512 PROMS mounted on heatsinks which were bonded to the PCBs and all mounted in their own sockets.
The inter board wiring was random, no harness arrangement other than for power supply. Cross talk was even considered by the design engineers then. Wire wrapped in 30awg OFHC single core cables.
I could go on about a lot of things used in the system as it was also my job to keep a record of all the components and which board they were used on. This also applied to the Sensor Unit, The Test Unit, The Management Control Panel. We were busy Bees in the DO for a few years on AICS. Happy Days

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consub
May 17, 2018, 20:23:00 GMT
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Post: 10149658
Originally Posted by MurphyWasRight
( guessing you meant "Cross talk was not even considered"

The inter board (backplane I surmise) random wiring may be what allowed it to work.

"Way back when" I used wire wrap proto boards (socket for each IC) and found out the hard way that neatly bundled routing, Manhattan no direct cross country, greatly increased crosstalk compared to random 'rats nest' routing.

I once made everything start working by dropping a single ferrite bead over the clock driver pin (before adding the wires) to slow edge rate enough to damp reflections.
This was with a 66Mhz clock which is the upper limit for wire wrap.





The reason that "birds nest wiring" was used for the backplane wiring on the AICU was indeed to prevent crosstalk.
I carried out a prom change at Cassablanca just days before the C of A flight, and used a prom blower that I carried out from Filton in my hand baggage together with boxes of proms, i remember the strange reaction by the customs man , until someone rescued me by telling him that I was taking them straight through to air side for Concorde. I programmed the proms by selecting the switches for the 8 bits of the line in the program for that particular prom, and then pressing the "blow" button that destroyed the fusible links in the input circuits of the prom. Of course all 64 lines of program in the prom that was changing had to be blown, even if only one line of program was changing. I carried out the programming on all 8 AICUs in 201, and the prom boards were laid out on a desk in the Air France office. Andre Turcat popped in to see what I was doing.

Last edited by consub; 17th May 2018 at 20:27 . Reason: ommission

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consub
December 17, 2024, 18:27:00 GMT
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Post: 11788941
Hi, for some strange reason I have only just come across this thread, I have looked at some of the early posts and can answer a few questions.
I was a development engineer on the AICU in 1972 and put the first AICU together and got it working.
I am now a volunteer at Aerospace Bristol and we have this box in the archives, it was used on the intake rig by Roger Taplin, half way down the hill at Filton,
There are no secret components used in the AICU, TTL 54 series was used, and these are the milspec version of the 74 series TTL. they are better quality, reliability and better tolerance, and more expesive. They were not available to all countries.
I worked with Ted Talbot at the time and in 1990 he recruited me to be the design manager for aircraft conversions and my first job was to manage the design of the VC10 tankers. There was mention of the leggy girl at Tangiers, that was Liz Pedley, a Cambridge maths graduate systems engineer, she married a GW systems engineer. I worked with her on many a long night sorting out program problems. I was the one who went to Casablanca to do the program program change to the AICUs that someone mentioned being removed from the aircraft and lined up on a desk in the Air France office. While I was there Turcat came in and sat at the table to watch.
I used a prom blower to blow the fusible links not a 9 volt battery, just as Liz would have done at Tangiers (the same prom blower)
Regarding the 1990s modifications to the AICU pcbs for obsolete components, I was requested by John Churchill, who designed the replacement boards, to give him some help. I was amazed that the test specs were still approved by my signature, which meant they had not changed since I moved on around 1978 when I moved to Stevenage. In about 1974ish we bought all the remaining proms as they were stopping being manufactured.
I will try and read the rest of the threads to see if anything else has been asked.

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