North American P-51 Mustang XP-51G

The XP-51G shares the airframe of the lightweight Mustang programme in full: the redesign of the P-51D as model NA-105 that North American proposed in 1943 and the USAAF accepted, with a modified cowling, a simplified undercarriage with smaller wheels and disc brakes, a larger canopy and armament cut to four .50 in Brownings. Working to British load factors, lower than the American ones, the design came out some 730 kg below the P-51D.

What sets this designation apart is the powerplant: where the XP-51F used V-1650 series engines, the XP-51G received Merlin RM 14 SM units supplied under reverse lend-lease, driving a five-bladed propeller that distinguishes it at a glance from every other Mustang. The wing was the common lightweight one, with NACA 66,2-(1.8)15.5 a=.6 airfoils at the root and NACA 66,2-(1.8)12 a=.6 at the tip and a trapezoidal planform without leading-edge extension. NA-105 testing recorded 790 km/h at 6,400 m.

Two aircraft were built. Like the rest of the experimental lightweights the XP-51G never went into series production, but the experience gained with it and with the XP-51F went into the production P-51H. The reference material gives no flight dates, no performance figures specific to the G and no output for the RM 14 SM, and this text does not invent them.