Lioré et Olivier LeO 45

Infobox Aircraft
name=Lioré et Olivier LeO 451


caption=
type= Medium bomber
manufacturer = SNCASE, SNCAO
designer =
first flight = 15 January 1937
introduced = 1938
retired = 1957
status =
primary user=French Air Force
more users =
produced= 1938-1942
number built= 561
unit cost=
variants with their own articles=tooshort

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

Development

The 1934 B4 bomber programme

The 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.

The "Service Technique Aéronautique" 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. Numerous manufacturers submitted a proposal, including Latécoère, Amiot with its Amiot 351, and Lioré et Olivier, which was to be soon nationalized as part of the SNCASE.

LeO 45 project

Lioré et Olivier was a long-time purveyor to the "Armée de l'air" with its LeO 20 and other lesser-known biplane bombers, that had earned a reputation for reliability, but were very traditional in design. The 1934 programme required modern solutions, and consequently the company management put a younger engineer called Pierre Mercier, who had expertise in cantilever airframes, at the helm of the design team.

Mercier's work resulted in a design, christened LeO 45, of a twin-engined aircraft of all-metal construction with a monocoque fuselage. Because of the speed requirements of the programme, a lot of effort was spent in reducing parasitic drag. Wings were equipped with slotted flaps and small bomb bays in the wing roots in addition to the main fuselage bomb bay, so as to limit fuselage's cross-section. A specific wing structure was designed and patented by Mercier, where the inner part used two spars, with enough room between them for a 200 kg-class bomb and large self-sealing fuel tanks. However the spars didn't go all the way to the wing-tip, but made way for box-type structure.

Mercier also used his patented type of fairing for the LeO 45's radial engines. Unlike typical NACA cowlings, flow adjustment was not provided by flaps, but by a frontal ring that moved back and forth to respectively reduce or increase flow, without change in drag. Like many other French twin-engine planes of the era, propellers rotated in the opposite directions to eliminate the undesirable effects of propeller torque. Undercarriage was fully retractable, with an unusually complicated mechanism for the main wheels in order to reduce the size of the engine nacelles.

The fuselage hosted the four-man crew in the following order: the bombardier, who was also the commander as per French tradition, sat in the glazed nose ahead of the pilot. Immediately behind the pilot, the radio operator could man a defensive machine gun from an underbelly retractable "gondola". A corridor alongside the main bomb bay led to the rear gunner position, that featured a powered mounting for the required 20 mm cannon.

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 the new Mercier 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.

As the international situation was worsening, the Armée de l'Air ordered the LeO 451, explicitly asking SNCASE not to delay production with further improvements, even though teething troubles were far from cleared.

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. They were issued to a frontline unit tasked with experimenting the new type in the field, and flew a few reconnaissance flights over Germany, which resulted in the type's first combat loss.

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 of the campaign 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. Within the next 8 days many of them were shot down, like the one driven by sergent-chef Hervé Bougault near Floyon during a bombing mission over German troops. 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 451s continued to fly, now under the Vichy government, that used them during the Syria-Lebanon Campaign. The aircraft were fitted with larger rudders and, later, two additional 7.5 mm machine guns in the rear turret. These extra weapons were added because of the limited capacity of the cannon magazines, and the fact that changing them in flight was extremely difficult. Aircraft production had totally stopped with the German occupation, but a 1941 agreement authorized Vichy authorities to have a limited number of military aircraft built. As a result, 109 additional LeOs were manufactured in 1942. The most notable of these was LeO 451-359 which was fitted with an experimental 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 used as transports after being specifically modified for this role. A small number was reportedly used by the Italian Regia Aeronautica.

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

Variants

;LeO 45.01:First prototype, powered by two Hispano-Suiza 14Aa radial piston engines.;LeO 451.01:The first LeO 45.01 prototype was redesignated, fitted with two Gnome-Rhone 14R engines.;LeO 451:Production version with Gnome-Rhone 14N engines;LeO 451C:Twelve LeO 451T aircraft were redesignated, used as mail transport aircraft for Air France.;LeO 451E:Post-war flying laboratory, 11 modified.;LeO 451T:German-captured bombers modified for freight duty, seating for up to 17 troops. Around about 50 aircraft were modified.;LeO 453:Post-war conversion to high-speed transports and search-and-rescue aircraft, powered by two 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, powered by two 1,600 hp (1195 kW) SNECMA 14R engines. Five LeO 451s were modified and were used by the Institut Geographique National.;LeO 456 (LeO 451M):Naval version for the French Navy, 68 ordered. Also known as the LeO 451M.;LeO 458:Wright GR-2600-A5B engines, 10 ordered

Operators

;FRA
*French Air Force
*Aviation Navale
*Air France;flagicon|France|vichy Vichy France
*Vichy French Air Force;flag|Germany|Nazi
*Luftwaffe operated several captured aircraft.;flag|Italy|1861-state
*Regia Aeronautica;flag|United States|1912
*United States Army Air Force operated several captured aircraft as unit hacks.

pecifications (LeO 451)

aircraft specifications

plane or copter?=plane
jet or prop?=prop

ref=Aircraft Profile 173 [cite book
author=Danel, Raymond
title=The Liore Et Olivier LeO 45 Series - Profile Number 173
publisher=Profile Publications
year=1967]
crew=4
capacity=
length main=17.17 m
length alt=56 ft 4 in
span main=22.52 m
span alt=73 ft 11 in
height main=5.24 m
height alt=17 ft 2 in
area main=66 m²
area alt=710 ft²
airfoil=
empty weight main=7,530 kg
empty weight alt=16,600 lb
loaded weight main=
loaded weight alt=
useful load main=
useful load alt=
max takeoff weight main=11,398 kg
max takeoff weight alt=25,130 lb
more general=
*Fuel capacity: 3,235 l (855 US gal)
engine (prop)=Gnome-Rhône 14N 48/49 or 38/39
type of prop=14-cylinder air-cooled two-row radial engine
number of props=2
power main=790 kW
power alt=1,060 hp
power original=
max speed main=480 km/h
max speed alt=260 knots, 300 mph
max speed more=at 4,000 m (13,125 ft)
cruise speed main=420 km/h
cruise speed alt=225 knots, 260 mph
stall speed main=
stall speed alt=
never exceed speed main=
never exceed speed alt=
range main=2900 km
range alt=1,565 nm, 1,800 mi
ceiling main=9000 m
ceiling alt=29,530 ft
climb rate main=
climb rate alt=
loading main=
loading alt=
thrust/weight=
power/mass main=
power/mass alt=
more performance=
guns=
**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
bombs=Up to 1500 kg (3,305 lb) of bombs in fuselage and wing root bomb bays
avionics=

ee also

aircontent
related=
similar aircraft=
*Bristol Blenheim
*Dornier Do 217
*Douglas DB-7
*Heinkel He 111
*Junkers Ju 88
sequence=
lists=
*List of aircraft of the Armée de l'Air, World War II
see also=

References

Notes

Bibliography

* Danel, Raymond. "The Lioré et Olivier LeO 45 Series (Aircraft in Profile 173)". Leatherhead, Surrey, UK: Profile Publications Ltd., 1967.
* Danel, Raymond and Cuny, Jean "LeO 45, Amiot 350 et autre B4 (Docavia n°23)" (in French). Editions Larivière.
* Danel, Raymond and Cuny, Jean "L'aviation française de bombardement et de renseignement 1918-1940 (Docavia n°12)" (in French). Editions Larivière.
* Ehrengardt, Christian-Jacques "Le bombardement français, tome I: 1939/1940". "Aéro-Journal Hors-Série N°5" (in French)
* Marchand, Patrick and Takamori, Junko. "Loiré et Olivier LeO 45" (in French). Le Muy, France: Editions d'Along, 2004. ISBN 2-914403-21-6.
* "Notice descriptive et d'utilisation de l'avion LeO. 451 à moteurs Gnome et Rhône 14N", SNCASE, 1939