Although the French had been early pioneers of military aviation and had developed important combat aircraft during World War I, few French designs played important roles in World War II. The most significant French bomber was the Liori et Olivier LeO 451. Introduced in 1937, this medium bomber, crewed by four, was driven by two 1,060-horsepower Gnome-Rhone 14N engines and could achieve a top speed of 298 miles per hour. Service ceiling was 29,530 feet, and range was 1,802 miles. The LeO 451 carried a bomb load of 3,086 pounds and was armed with a single 20-millimeter cannon and five 7.5-millimeter machine guns. Only 373 of these aircraft had been delivered to French forces before the armistice was signed with Germany on June 25, 1940. However, more were delivered to the Vichy French Air Force.
The LeO.451 was France’s best medium-bomber, powered by a pair of Gnome-Rhone 14N 48/49 or 38/39 14-cylinder air-cooled, 1,060-hp radial engines for a maximum speed of 300 mph at 13,125 feet, although its 20-mm Hispano-Suiza HS.404 cannon firing from a dorsal turret, single 7.5 mm MAC 1934 in a “dustbin” retractable ventral turret, and one fixed-forward firing 7.5mm machine-gun comprised inadequate defense. Fuselage and wingroot bays stowed a 3,475-pound payload. As testimony to its general excellence, the LeO 451, a favorite import with Italian Air Force crews, was the last, pre-war French design to leave active French Air Force duty when it was finally retired in September 1957.
LeO 451. Armee de l’Air de Vichy. Aircraft with mine search ring, 1942.
The LeO 451 was the best French bomber of World War II and one of few available in quantity. It fought well during the Battle of France and also flew capably in the hands of Vichy French pilots.
No sooner had the Armee de l’Air become independent in April 1933 than it pressed for immediate expansion and modernization programs. Part of this entailed development of a new four-seat medium bomber capable of day and night operations. The medium strategic bomber LeO 451, designed by engineer Pierre Mercier and manufactured by the SNCASE company, made its first flight in January 1937 and entered service in the French Armée de l’Air in 1938. It was an all-metal, midwing, twin-engine craft with a glazed nose and twin rudders. In contrast to the ungainly aircraft of the early 1930s, the LeO 451 was beautifully streamlined and performed as good as it looked. Operationally, however, the type suffered from technical detriments that were never fully corrected. It had been designed for 1,600- horsepower engines at a time when no such power plants were available. Hence, employing 1,000-horsepower motors, LeO 451s remained significantly underpowered and never fulfilled their design potential. Worse still, when the French government decided to acquire the bomber in quantity, bureaucratic lethargy militated against mass production. By September 1939 only five LeO 451s had been delivered.
The German onslaught in Poland energized French aircraft production, and when the Battle of France commenced in May 1940 around 450 LeO 451s were available. They had been designed for medium-level bombing, but the speed of the German blitzkrieg necessitated their employment in low-level ground attacks. The bomber served well in that capacity, but, exposed to enemy fighters and antiaircraft fire, serious losses ensued. Yet the type remained in production after France’s capitulation, with an additional 150 being acquired. These were actively flown against the Allies in North Africa before Vichy France was occupied by the Germans. They confiscated about 94 LeO 451s; stripped of armament, these were flown as transports. A handful survived into the postwar period as survey aircraft.
The all-metal monocoque had a retractable landing gear, and double fin and rudder. It was operated by a crew of four (pilot, bomb aimer/radio operator/nose gunner, ventral gunner, and dorsal gunner), and had a length of 17.17 m (56 ft 4 in), a span of 22.52 m (73 ft 11 in), and a height of 4.24 m (17 ft 2 in). The two Hispano-Suiza 14 Aa 6/7 radial engines were on later models replaced with two 1,030-hp 14-cylinder, air-cooled Gnome Rhone 14 20/21 radial engines. The aircraft had a maximum speed of 480 km/h (480 mph), a maximum ceiling of 9,000 m (29,530 ft) and a maximum range of 2,900 km (1,800 miles). Although mainly relying on high speed and altitude, the LeO 451 was armed with one 20-mm Hispano-Suiza Hs 404 machine gun placed in dorsal turret, one forward-firing 7.5-mm Mac 34 machine gun mounted in the glazed nose, and one 7.5-mm Mac 34 machine gun placed in a retractable “dustbin” ventral turret. The aircraft could carry a load of 1,500 kg (3,305 lbs) in bombs, stored in fuselage and wing root bays. Produced between 1938 and 1942, 561 LeO 451 were built.
First prototype, powered by two Hispano-Suiza 14AA-6 / Hispano-Suiza 14AA-7 radial piston engines.
The first LeO 45.01 prototype was redesignated, fitted with two Gnome-Rhone 14R engines.
Production version variously fitted with Gnome-Rhône 14N-48 / Gnome-Rhône 14N-49 or Gnome-Rhône 14N-38 / Gnome-Rhône 14N-39 or Gnome & Rhône 14N-46 / Gnome-Rhône 14N-47 engines
Twelve LeO 451T aircraft were redesignated, used as mail transport aircraft for Air France.
Post-war flying laboratory, 11 modified.
German-captured bombers modified for freight duty, seating for up to 17 troops. Around about 50 aircraft were modified.
Post-war conversion to high-speed transports and search-and-rescue aircraft, powered by two 895 kW (1,200 hp) Pratt & Whitney R-1830-67 engines, seating for 6 passengers, range 3,500 km (1,890 nm, 2,175 mi) at 400 km/h (215 knots, 250 mph) cruising speed, 40 modified.
Bristol Hercules II engines, one prototype left unfinished.
High-altitude version with turbo-supercharged Gnome-Rhône 14R engines producing 1,375 hp (1025 kW) each, 400 ordered, one prototype built. The aircraft flew on 12 March 1939 but was later destroyed on the ground.
Post-war photo-reconnaissance variant, powered by two 1,600 hp (1195 kW) SNECMA 14R engines. Five LeO 451s were modified and were used by the Institut Géographique National.
LeO 456 (LeO 451M)
Naval version for the French Navy, 68 ordered. Also known as the LeO 451M.
Wright GR-2600-A5B engines, ten ordered