In 1934, the Service Technique issued an outline specification for a new single-seat fighter, all the contenders but one having all-metal stressed-skin monocoque structures with enclosed cockpits and retractable undercarriages. The structural exception was the MS 405.
The Loire 250 was powered by a 1000hp Hispano-Suiza 14Ha-79 two-row radial and was first flown on 27 September 1935 temporarily with a fixed-pitch two-bladed wooden propeller. Intended armament comprised two synchronised 20mm cannon and two 7.5mm machine guns, but trials with the Loire 250 proved disappointing from the outset, the prototype suffering serious drag problems. Various methods were applied to reduce drag, the vertical tail was redesigned to rectify a stability problem and a three-bladed variable-pitch propeller was fitted. Regardless the fighter proved incapable of attaining the max speed of "at least 485km/h" called for by the specification, and was eliminated from the contest at an early stage.
Engine: 1 x 1000hp Hispano-Suiza 14Ha-79 two-row radial
Max take off weight: 2200 kg / 4850 lb
Empty weight: 1500 kg
Wingspan: 10.80 m / 35 ft 5 in
Length: 7.81 m / 25 ft 7 in
Height: 3.72 m / 12 ft 2 in
Wing area: 16.30 sq.m / 175.45 sq ft
Max. speed: 480 km/h / 298 mph
Range: 875 km / 544 miles