KG86
Some slight exaggeration of the Belvedere problems, the starter system did use Avpin, but this was also used on the Hunter, and other aircraft with no problems, as an engine fitter on both aircraft, I was well used to handling the stuff, and there was no problem. (unless you accidently drank it, as one of our guys did with no lasting results). The problem was that unlike the Plessey system on the Hunter, the BTH system on the Belvedere , and Wessex 1 was cartridge initiated, ie, the cartridge operated on a piston, to pump the Avpin.
Sometimes the seals leaked, allowing the Avpin into the breach, resulting in an explosion, I don't believe anyone was hurt by this, it happened to me once, as I was sat in the co pilots seat, but it was the rear engine.
There was no jump seat as such, there was a bulkhead behind the pilots seats, then the front engine, then the crew mans seat facing aft, by the door, there was a walkway to the left of the front engine, behind the co pilots seat, alongside the engine. You had to be sat in the seat to operate the controls, as the rotor brake had to be off to operate the starter, and the rotors started turning immediately.
The yaw cables were always a source of worry, as unlike a conventional tail rotor aircraft, where a breakage would only lose you the tail control, on the Belvedere, a cable breakage would lose you all azimuth control of both rotors. This did happen at least once to my knowledge, to a pilot in Aden who was decorated for getting the aircraft safely onto the ground, unfortunately he was killed shortly after when an aircraft disintegrated in the air, the reason for which I don't think an answer was ever found.
People did talk about sync shaft failure, but I don't think there was ever a recorded case of this.
One of the biggest problems was Bristols illogical engine numbering system, the engines were number one at the front, and number Two at the back, but the controls and instruments were lateral, and for some reason, Bristol made number One on the right, and number Two on the left, because the Captain sat on the right. This of course was totally at odds with convention, and was possibly considered the cause of the first fatal accident in Germany, when it was thought that one of the pilots shut down a good engine after a failure of one.
Whatever ones thoughts of the Belvedere, tribute must be given to the work they did in Borneo, during the confrontation with Indonesia, when the poor old indons came across the border, in what they thought was thick jungle hundreds of miles from anywhere, and suddenly came under 105mm artillery fire from a hilltop where a Belvedere had dumped a gun.
For all its faults
What other aircraft in 1959 could cruise at 129 knots , sometimes going up to 140, had an all up weight of 22000 lbs, and could maintain altitude, AUW on one engine.