FSX Boulton Paul P.111A 'Yellow Peril' British experimental high-speed tailless delta-wing research and test aircraft. Modified from the P.111 after an earlier landing accident, the P111A first flight was on 2nd July 1953 and the last flight was on 20th June 1958. It reached Mach 0.93 at 35,000 ft and Mach 0.96 in a shallow dive. Boulton Paul Chief Test Pilot A.E. 'Ben' Gunn described the P111 as 'touchy' and 'like flying a razor's edge'. Also, when the undercarriage was raised or lowered there was a large trim change of 4 degrees or more and the landing speeds were high. By Tyler Gladman.