Posts about: "ADC (Air Data Computer)" [Posts: 11 Page: 1 of 1]¶

I can't be positive about the INS (inertial nav system).
The prototypes used a SAGEM/Ferranti system, replaced by a Litton system on the preprods, then Delco on the production aircraft.
There may have been magnetic core in the prototype INS.

As to the AICS (air intakes) and AFCS (automatic flight control), the answer is a definite NO. The AICUs used PROMs (fuse type, not EPROM) and the AFCS was entirely analog.

Some of the systems were even more 'antique'...

The ADC (air data computer) for instance was still largely electro-mechanical.

And those nifty NAV and COMM frequency selectors, that always stand out on cockpit pictures... no electronics at all, just a set of wafer switches, and about thirty wires linking them to the transmitters/receivers.

CJ

Oh yes Roger, I do agree (and a point well made too). Concorde was very much a 1970's era electronics design (with even a little 1960s thrown in too). It was typical that as long as things were left alone and warm, they more or less were happy.
At Heathrow when the crew arrived to depart the aircraft, she was already fairly well tested and fired up, systems wise, even to the extent that the INSs were usually aligned (but not put into NAV mode). Now this all helped immensely as far as systems reliability went, but a last minute INS or ADC failure could often still occur, and hit you in the 'you know wheres' when you had least time. Such was the nature of the beast. (But we all loved her ).
I hope so Roger, I think we all did our best.

Dude

Kangerlussuaq? Wow, that should have been awesome. Ronivaniemi flights were supersonic? I built and flew a EGLL-EFRO flightplan on the flight simulator once, supersonic along the Norwegian coast, descending and entering continent to reach Ronivaniemi from Northwest. According to my calcs, the difference to a subsonic-only trip using normal airways would be small, so that got me wondering how you actually did that.

Nice! So, by what I already read on this topic, you only worked with Concorde, right? But do you know if Concorde had the same issues as other airliners, or even for you guys "you're not (working) in an airplane, you're in Concorde" quote hold true?

For BA001 and BA003, 2 Concordes were prepared for the same flight, right? Did ever happened some situation that required a ready-for-takeoff Concorde be brought back? How long a cargo and passengers transfer would take? The backup Concorde was fueled?

Please, Landlady, that would an even bigger pleasure! Very interesting to read about Concorde from another point-of-view, much more human than Tons, Kgs, CG %, Celsius degrees, etc.

Hmm. There was, I think, a raft of high-incidence (alpha) protection fitted.

Digging out the old BAe conversion course notes:

The "Anti-Stall" (SFC) 1&2 sytems offered:

Super Stab: Increased authority of pitch autostab as incidence increased above 13.5 degrees - proportional to pitch rate and incidence angle - and a nose down pitch trim with a Vc (CAS) deceleration with incidence > 13.5

Stick "Wobbler": the "unmistakable warning" - when incidence > 19 and Vc<270kts the control columns took a life of their own and tried to fling you into the forward galley. Served you right.

Some other high incidence stuff was fed from the ADC rather than the SFC, like:

The ">13.5d incidence" feed to the SFC

CAS (Vc) feed to the SFC

Incidence from 16 to 19 degrees (rate dependant) to get the SFC to feed in up to 4 degree nose down pitch command and the sticj wobbler trigger.

Increase of authority of yaw autostab as incidence > 13.5d

Autotrim inhibit > 14.5d incidence

Stick shaker >16.5d incidence

AP/FD disconnect > 17.5d incidence

There was loads of other technical stuff which engineers understood, but we had to learn by writing diagrams which made sense to us enough to pass the written exam. The bottom line was an aeroplane which flew beautifully, but which you had to understand well, and which you could not tease beyond its limits. If you ignored a limit or an SOP then you reached an unpleasant place far quicker than with the blunties - it was a challenge which rewarded as quickly and as deeply as it punished.

CliveL
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

Ahah! Got you! Reference my original question about calibrating so many vital analogue systems.

I knew there would have to be something somewhere. However, I have to agree that it only goes to demonstrate yet again, just how good were the original systems and the engineers who designed them.

Nice picture from you too Dude, which raises a couple of questions for me. Why the blind window nearest your wife's camera? And I'm not sure why I've never been aware of it before, but this view shows up some sort of tube mounted atop the fuselage, just in front of the fin. What is that please?

Oh and something that your photograph put in mind. It must be very seldom that even a parked aircraft is actually quiet. Being under AC like that must have been a bit un-nerving for someone so used to being next to Concorde, because she must be virtually silent?

Roger.

gordonroxburgh
It matters not I'm afraid Gordon. I would not have thought that anyone would design ANY flying control system, experimental or otherwise, that does not have full potential authority in all axis. As we do not know what the PROPOSED flight regime was, on the part of SFENA and Aerospatiale,we also can not assume that any particular manoeuvr would not have been considered. (But as I said before, it would be great to find out the whole story).
The limited authority for roll autostabilisation (and hence Emergency Flight Control) was of course a very deliberate piece of design. (You could test the Emergency Pilot on the ground at ADC Test 2 (Which simulated several seperate overspeeds, including Vmo +20) and when you put in a roll demand (against some resistance), only the MIDDLE elevons deflected. It really looked wierd on the ICOVOL as well as outside the aircraft.
(To any chaps or chapesses who are not aware, above Vmo+20 KCAS, a system known as OUTER ELEVON NEUTRALISATION was invoked, where any input demand to the outer elevons was met by an automatic equal and OPPOSITE input, that of course completely neutralised the demand, giving a zero OUTER elevon deflection).

Best regards
Dude

Actually NO CJ. The old steam powered analog electro-mechanical Air Data Computers met RVSM minima quite comfortably when trials were carried out, and that amazed the hell out of most of us. (But a Penny & Giles DADC was still being looked at in the early to mid 90s as a potential ADC replacement).
As far as the expansion joint question goes John, there were several expansion joints all over the aeroplane but I don't recall personally being able to see evidence of thermal expansion anywhere else than the aft flight engineers panel. Perhaps someone else here may know something?.

Best regards
Dude

1) Effectively it was (not the skin, but the TAT probe. The highest temp rise would be at the stagnation point so one can be confident that TAT is a realistic answer for max skin temp).

2) AFAIK pretty standard:

Q from pitots
S from statics
T from temp probe

Modified by ADC for position error. It's possible that ADC used beta inputs and I'm sure it used alpha inputs to achieve this.

Thanks Ex Wok but now I'm even more confused!

1) So there is a direct temp reading, from the TAT probe. But where is TAT probe? Is it in the needle nose probe that also measures pitot/static for the intake computers? And how many TAT sensors are there (failure of a single one if that's all there is would not be good)?

2) Mach comes from dynamic pressure (pitots), from static ports, and from temp. But what temp? OAT perhaps?

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.