Exploring Turn Of The Century RAF Avionics

The second hand market is a wonderful thing; you never know what you might find selling for pennies on the dollar simply because it’s a few years behind the curve. You might even be able to scrounge up some electronics pulled out of a military aircraft during its last refit. That seems to be how [Adrian Smith] got his hands on a Control Display Unit (CDU) originally installed in a Royal Air Force AgustaWestland AW101 “Merlin” helicopter. Not content to just toss it up on a shelf, he decided to take a look inside of the heavy-duty cockpit module and see if he couldn’t make some sense out of how it works.

Unsurprisingly, [Adrian] wasn’t able to find much information on this device on the public Internet. The military are kind of funny like that. But a close look at the burn-in on the CDU’s orange-on-black plasma display seems to indicate it had something to do with the helicopter’s communication systems. Interestingly, even if the device isn’t strictly functional when outside of the aircraft, it does have a pretty comprehensive self-test and diagnostic system on-board. As you can see in the video after the break, there were several menus and test functions he was able to mess around with once it was powered up on the bench.

With the case cracked open, [Adrian] found three separate PCBs in addition to the display and keyboard panel on the face of the CDU. The first board is likely responsible for communicating with the helicopter’s internal systems, as it features a MIL-STD-1553B interface module, UART chips, and several RS-232/RS-485 transceivers. The second PCB has a 32-bit AMD microcontroller and appears to serve as the keyboard and display controller, possibly also providing the on-board user interface. The last board looks to be the brains of the operation, with a 25 MHz Motorola 68EC020 CPU and 1Mb of flash.

All of the hardware inside the CDU is pretty generic, but that’s probably the point. [Adrian] theorizes that the device serves as something of a generic pilot interface module, and when installed in the Merlin, could take on various functions based on whatever software was loaded onto it. He’s found pictures online that seem to show as many as three identical CDUs in the cockpit, all presumably running a different system.

[Adrian] has uncovered some interesting diagnostic information being dumped to the CDU’s rear connectors, but he’s still a long way off from actually putting the device to any sort of practical use. If any Hackaday readers have some inside information on this sort of hardware, we’re sure like to hear about it.

25 thoughts on “Exploring Turn Of The Century RAF Avionics

  1. haven’t worked on that system but from experience of mil efis systems of that era on the other side of the pond you would need a few more boxes to get it to full action. typical boxes might be a air data computer and autopilok module and others that feed into a master display generator. Really depends on whose system. That itself might be the master display as the air data computer from 90’s Honeywell has a Z-80 as the mcu compared to what you found.

  2. I’m just finding it amusing that I pass Leonardo, [ formally Westlands], on a fairly regular basis. Yeovil isn’t the nicest place to live but it has a few plus points. II only live about a half mile from the site. It’s been a while since I had a wander around. As you can imagine, we get a lot of low flying helicopter traffic around here.
    Many years ago now I got a chance to play with one of their flight simulators, it took eleven computer towers to run the thing, consisting of essentially the instrument panel from a helicopter, sat on some hydraulic rams, in front of three large projection screens, it played just like a life sized videogame but I was aware they were not showing me half of what it could do. Not that far down the road you’ve got Yeovilton, there are some pretty interesting things in there too. Yeovil collage actually had a project in which they built a helicopter from scratch, including building the jet engine, quite a lot of work. Sadly it was a few years after I escaped the public education system.

    1. Love it. I used to pester my parents to drive the little dog-leg of road through the lynx industrial estate so I could get a close up look at the new helicopters being tested. Was also lucky enough to do my 15 year old work experience placement at Yeovilton and got a ride in a Lynx. It was a sad day when the Sea Harriers left though, helicopters just aren’t quite the same.

      1. I grew up near Yeovil and dreamed of working at Westland but by the time I had graduated the jobs just weren’t there and I ended up North instead. I miss Somerset though…would move back if I had the chance!

    2. I am always irritated when people say nonsense along the lines of “….Yeovil isn’t the nicest of places to live…”!!! It’s surely no different to any other provincial town in a predominantly rural county. What does set Yeovil apart from other town is that it has a world class engineering facility which employs world class engineers who do more than merely drive through it.

  3. Neat to see it working. The display is very similar to the plasma displays that Planar makes. Great for high light environments.

    I have a Honeywell CD-815 and a CD-820 front panel that I am trying to bing back to life. Its just the keyboard and found some 5.6″ lcds that fir perfectly. Got the keyboard matrix figured out and made PCBs to tie in with a teensy,

    1. Upon further inspection I noticed the manufacturer of the panel was partially obscured by a label. Removing this shows it is indeed made by Planar and although it is a custom display it has the same resolution and pinout as their EL320.256-F6 TFEL display and I’ve found the datasheet. Now to see if it can be driven from an arduino or pi.

      1. Ah, nice. I have or had a bunch of their displays lying around. You should be able to write to them but you will have to probably make a driver to do it since it does not talk any standard flat panel interfaces. I have a demo unit that runs off WinCE that does connect to the flat panel connector though. Also have a couple demo boards that drive them with a microcontroller.

      2. So, funny thing. I went and looked through to see what planar displays I have left and I actually have what is basically the same display as you have, a EL320.256.FD7 SEI. The difference seems to be instead of the two headers for the connections mine has flying leads which terminate in a MicroD connector. Ill be curious to see what you come up with. Planar is in the same town as me and I have gotten some of their surplus from time to time

  4. Oddly enough the specifications behind the MIL-STD-1553B interface module used there, are indeed available from sources online. It’s the hardware that talks to them that becomes hard to find. Our friend would need to find the other end to it before continuing. But so far I am impressed. Very impressed in fact.

    1. Yes, I think that any critical data exchange would be via the MIL-STD-1553B bus and the serial interfaces are for diagnostics and less critical systems or optional add ons. It’s probably waiting for a handshaking signal from the CCS and it would reply. It does have a remote power on which if left floating defaults to powering on; if pulled low it will switch off so I guess once the main computer system starts it will switch on the aux devices like the CDU and start handshaking.

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