In 1979, this Chipmunk Mk.22A (G-ARWB c/n C1/0621) was modified to act as test bed and demonstrator for the 200 hp Aero Bonner Super Sapphire V6 aero engine, liquid-cooled by a ventrally mounted radiator. G-ARWB was flown for the first time with its new engine on July 2, 1979 and was subsequently displayed at the SBAC Show at Farnborough. The aircraft is also referred to as the Aero Bonner Chipmunk 200
Bill flew it at the 1980 Farnborough Airshow, when the RAF put in a request to re-equip their fleet of Chipmunks with the Sapphire engine, and Rolls-Royce announced their desire to take over and manufacture the engine in quantity.
At the Farnborough exhibitor’s dinner, guest of honour, Margaret Thatcher, said her govt. was happy to be a first customer for the kit on show, but we should also look to make our profits from the wider world. Fair enough; so Bill wrote to the PM, saying that the RAF wished to purchase the Bonner V6 aero engine for their Chipmunks, and could the MOD kindly put in a purchase order. Unfortunately, there was a moratorium on defence spending, came the reply from No 10, and the govt. could not afford it. Furthermore, by the end of 1980, R-R told Bill that they thought that the Bonner engine was pointing the way to the future of light piston aero engines, but nevertheless they were going through a divorce from Continental Motors and pulling out of light aviation altogether, and reluctantly could not remain in the sector for this engine alone.
All Aero 