A little diversion for the festive season for anyone interested in old military electronics.
Earlier this year I visited the Newark Air Museum just outside Newark-on-Trent in the UK. It has an excellent collection of planes, with the jewel in the crown being an Avro Vulcan. On some days, it is possible to do a cockpit tour, and as a result of that I later decided to buy an Air Indicator Unit (AIU) from a surplus supplier.
I had no idea it was still possible to obtain equipment like that, as the last RAF Vulcan was scrapped in the mid-eighties. The Vulcan was the UK's Cold War nuclear bomber with a quite remarkable specification for an aircraft designed in the late 40s to early 50s. It could fly at over600 mph, and sometimes exceeded Mach 1 in a dive. Its range was around 4000 miles, with a ceiling of 55 - 65,000 feet.
What initially surprised me was the weight of the AIU - around 10kg (22lb). No wonder the aircraft weighed not far short of 100 tons! When I opened the bottom of the unit the first things I saw were what appeared to be two sealed-unit transformers (although one wasn't a transformer, just a choke). The other was a standard 200v 400Hz transformer, and I wondered why that supply was needed. In my ignorance I expected to find transistors in the AIU, but all I could see at a quick glance was a valve (just over the capacitor above the choke)!
When I took the top cover off I was even more amazed - the whole unit was full of valves! These were all CV types (some subminiature) - CV465,468, 469, and 4501.
I had a look at a few capacitors to see if there was a date on them, but unfortunately there wasn't. There were some rectifiers (such as CV2384 and CV7030), but as far as I could see those were the only semiconductors. The data sheets for CV numbers can be found at
There were no PCBs of course, just paxolin boards. This is the underside of the valve board:
On the internet, I found that the AIU was part of a "Green Satin" Doppler radar unit, which provided the navigator with true groundspeed and drift. Anyone interested should search on "Green Satin" and "radar" for more info.
It seems surprising that electronic equipment in an aircraft still flying in the 80s used valves instead of transistors, despite the equipment being constantly upgraded and improved. Maybe the valve-based equipment was considered less likely to be affected by an EMP from a nuclear explosion. But the equipment was reliable - the last Vulcan flew only a year ago in an air display. Maybe because the equipment was of such old design it was that reliable - I was told by the pilot on my cockpit tour that aircrew from the WWII Avro Lancaster bomber would have found much of the Vulcan cockpit instrumentation familiar!