Lioré et Olivier LeO 451

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Lioré et Olivier LeO 451
Type	Medium bomber
Manufacturer	SNCASE, SNCAO
Designed by	Pierre Mercier
Maiden flight	1937-01-16
Retired	1957
Primary user	French Air Force
Produced	1938-1942
Number built	561

Lioré-et-Olivier LeO 45 was a French medium bomber used during World War II.

Contents 1 Development 2 Operational history 3 Variants 4 Operators 5 Specifications (LeO 451) 6 References 7 External links 8 Related content

[edit] Development

LeO 451 was conceived as a second-generation strategic bomber for the new French Air Force. In contrast to its predecessors which relied on machine guns for protection, the emphasis was placed on high-speed high-altitude cruise. The expectation was that high speed would force enemy fighters into tail-chase attacks and to that effect the aircraft was designed with a rear-firing cannon with an unobstructed rear arc of fire thanks to the twin rudders.

Service Technique Aeronautique released the initial requirements on 1934-11-17, specifying a 5-seat bomber with a top speed of 400 km/h (215 knots, 250 mph) at 4000 m (13,125 m), and a payload of 1500 kg (3,300 lb) carried for 900 km (485 nm, 560 mi). In September 1936, the requirements were revised to account for development of 1,000 hp (746 kW)-class engines, with cruise speed raised to 470 km/h (255 knots, 290 mph) and crew reduced to four. The Air Force's Plan II called for 984 of the resulting B4-class bombers.

The LeO 45-01 prototype powered by a pair of Hispano-Suiza 14Aa 6/7 radial engines producing 1,120 hp (835 kW) each flew for the first time on 1937-01-16. Despite problems with longitudinal instability, and engine reliability and overheating, the aircraft demonstrated excellent performance, reaching 480 km/h (260 knots, 300 mph) at 4000 m, and attaining 624 km/h (337 knots, 388 mph) in a dive. In July 1938, the prototype fitted with new Mercier-type engine cowlings reached 500 km/h (270 knots, 311 mph). Subsequently, the troublesome Hispano-Suiza engines were replaced with Gnome-Rhone 14N 20/21 producing 1,030 hp (768 kW) each, and the aircraft was redesignated LeO 451-01.

The aircraft was of all-metal construction with a monocoque fuselage fitted with a retractable ventral machine gun turret. Wings were equipped with slotted flaps and small bomb bays in the wing roots in addition to the main fuselage bomb bay. On production aircraft, propellers rotated in the opposite directions to eliminate the undesirable effects of propeller torque.

[edit] Operational history

The first production LeO 451 was built in 1938. The decision to abandon Hispano-Suiza engines and a shortage of propellers resulted in production delays. The latter also caused most aircraft to be fitted with slower Ratier propellers which reduced the top speed from 500 to 480 km/h. As the result, although 749 LeO 451 had been ordered, only 22 were delivered by the start of World War II. Of these, only 10 were formally accepted by the Air Force.

At the start of the Battle of France on 1940-05-10, only 54 of the 222 LeO 451 were considered ready for combat, the remainder being used for training, spares, or undergoing modifications and repairs. The first combat sortie was flown by 10 aircraft from GB I/12 and GB II/12 on 1940-05-11. Flying at low altitude, the bombers suffered from heavy ground fire with one aircraft shot down and 8 heavily damaged. By the 1940-06-25 Armistice, LeO 451 of the Groupement 6 flew approximately 400 combat missions, dropping 320 tons of bombs at the expense of 31 aircraft shot down by enemy fire, 40 written off due to damage, and 5 lost in accidents. A total of 452 aircraft had then been built, 373 accepted into service (including 13 for the Aéronautique navale), and around 130 lost in action in Europe.

Following the Armistice, LeO 451 continued to fly, now under the Vichy government. The aircraft were fitted with larger rudders and two additional 7.5 mm machine guns in the rear turret, and an additional 109 aircraft were manufactured under the Vichy regime. The most notable of these was LeO 451-359 which was fitted with a large degaussing coil for remotely detonating naval mines (some British Vickers Wellingtons and German Junkers Ju 52s also carried a similar device).

After Operation Torch which began on 1942-11-08, surviving French LeO 451 in North Africa were used primarily for freight duties, although they flew a few bombing missions against Axis forces during the Tunisia Campaign. They were ultimately replaced in active service by Handley-Page Halifax and B-26 Marauder bombers. Aircraft captured by Germans in occupied France were also primarily used as transports, although a small number saw action with the Italian Regia Aeronautica.

Following the war, the 67 surviving aircraft were used primarily as trainers and transports. LeO 451 was finally retired in September 1957, making it the last pre-war French design to leave active duty.

[edit] Variants

LeO 45

First prototype, Hispano-Suiza 14Aa engines

LeO 451

Production version with Gnome-Rhone 14N engines

LeO 451E

Post-war flying laboratory, 11 modified

LeO 451T

German-captured bombers modified for freight duty, seating for up to 17 troops.

LeO 453

Post-war conversion to high-speed transports and search-and-rescue aircraft, Pratt & Whitney R-1830-67 engines, seating for 6 passengers, range 3500 km (1,890 nm, 2,175 mi) at 400 km/h (215 knots, 250 mph) cruising speed, 40 modified.

LeO 454

Bristol Hercules II engines, one prototype left unfinished.

LeO 455

High-altitude version with turbosupercharged Gnome-Rhone 14R engines producing 1,375 hp (1025 kW) each, 400 ordered, one prototype built. The aircraft flew on 1939-03-12 but was later destroyed on the ground.

LeO 455Ph

Post-war photoreconnaissance variant, SNECMA 14R engines with 1,600 hp (1195 kW) each, 5 modified.

LeO 456 (LeO 451M)

For French Navy, 68 ordered

LeO 458

Wright GR-2600-A5B engines, 10 ordered

[edit] Operators

•  France
• Germany: Luftwaffe (captured)
• Italy: Italian Air Force
•  United States: USAAF (used as unit hacks)

[edit] Specifications (LeO 451)

Data from Aircraft Profile 173^[1]

General characteristics

• Crew: 4
• Length: 17.17 m (56 ft 4 in)
• Wingspan: 22.52 m (73 ft 11 in)
• Height: 5.24 m (17 ft 2 in)
• Wing area: 66 m² (710 ft²)
• Empty weight: 7530 kg (16,600 lb)
• Max takeoff weight: 11398 kg (25,130 lb)
• Powerplant: 2× Gnome-Rhone 14N 48/49 or 38/39 14-cylinder air-cooled two-row radial engine, 790 kW (1,060 hp) each
• Fuel capacity: 3,235 l (855 US gal)

Performance

• Maximum speed: 480 km/h (260 knots, 300 mph) at 4000 m (13,125 ft)
• Cruise speed: 420 km/h (225 knots, 260 mph)
• Range: 2900 km (1,565 nm, 1,800 mi)
• Service ceiling: 9000 m (29,530 ft)

Armament

• 1x 20 mm Hispano-Suiza HS.404 cannon in dorsal turret, 120 rounds
• 1x 7.5 mm (0.295 in) MAC 1934 fixed forward-firing machine gun, 300 rounds
• 1x 7.5 mm MAC 1934 in "dustbin" retractable ventral turret, 500 rounds
• Up to 1500 kg (3,305 lb) of bombs in fuselage and wing root bomb bays

[edit] References

[edit] External links

[edit] Related content

 

Comparable aircraft

Bristol Blenheim - Dornier Do 217 - Douglas DB-7 - Heinkel He 111 - Junkers Ju 88

 

Related lists

List of aircraft of the Armée de l'Air, World War II