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Lioré et Olivier LeO 45 Series

Lioré-et-Olivier LeO 45 was a French medium bomber that was used during and after the Second World War.

It had been designed for the new Armée de l’air as a modern medium bomber capable of performing independent strategic operations, unlike the majority of previous French bombers.

The Lioré et Olivier LeO 45 was a twin-engined medium bomber, which had been conceived with the aim of producing a suitably advanced bomber to equip the French Air Force.

In contrast to its predecessors, which had relied on machine guns for self-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 which possessed an unobstructed rear arc of fire thanks to the design of the twin tailfins.

The LeO 45 featured an all-metal construction and a monocoque fuselage; the structure included 60 individual fixed frames attached to longitudinal stringers and was covered by flush-rivetted light alloy panels.

As a consequence of the specified speed requirements of the programme, a lot of effort was spent in reducing parasitic drag.

The fuselage cross-section was reduced via the adoption of not a main fuselage bomb bay paired to smaller bomb bays that were located within the wing roots.

The low cantilever wing, which employed a structure designed and patented by Mercier, was constructed in four separate sections.

Specifically, the inner section was built around two spars equipped with steel booms which had enough room between them to accommodate a 200 kg-class bomb and large self-sealing fuel tanks; the spars did not continue to the wingtip but made way for a box-type structure.

The wings were furnished with large split-type slotted flaps, which were electronically controlled and high aspect-ratio slotted ailerons, the latter of which being depressed during take-off.

The fuselage housed the aircraft’s four-man crew; the bombardier, who was also the commander as per French tradition, was positioned within an almost-fully glazed nose at the front of the aircraft, ahead of the pilot, and performed observation and bombing aiming functions from this location.

Behind the pilot, the radio operator could man a defensive 7.5 mm M.1934 (500 rounds) machine gun from an underbelly retractable “gondola”.

A corridor alongside the main bomb bay led to the dorsal gunner’s position, which featured a powered mounting for the 20 mm cannon Hispano-Suiza HS.404, with 120 rounds; the turret could be retracted.

Another 7.5 mm machine-gun M.1934 was installed in the nose (with 300 rounds).

The Leo 45 had a central bomb bay, within which the majority of the aircraft’s armaments were enclosed.

In total, the aircraft’s armaments comprised: 120 20 mm rounds, 800 7.5 mm rounds, up to seven 200 kg bombs or other combinations (1–2 500 kg bombs in the belly, plus the two 200 kg in the wings).

When flown with the maximum payload, this reduced the corresponding fuel load to only 1,000 litres.

The fuel tanks were also housed within the wings, these comprising a pair of 880 lts tanks within the inner wings), along with a further two pairs of 330 and 410 litres contained in the external wings.

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 aeroplanes of the era, the propellers rotated in opposite directions to eliminate the undesirable effects of propeller torque.

The undercarriage was fully retractable; it featured an unusually complicated mechanism for the main wheels in order to reduce the size of the engine nacelles.

The two horizontal surfaces of the tail unit were constructed in two separate halves and bolted onto a short centre section fixed to the upper fuselage; the twin fins and rudders, which were furnished with trim tabs, were attached at the extreme edges of the tailplane.


LeO 45.01

First prototype, powered by two Hispano-Suiza 14AA-6 / Hispano-Suiza 14AA-7 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 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

LeO 451C

Twelve LeO 451T aircraft were redesignated, used as mail transport aircraft for Air France.

LeO 451E2

Post-war flying laboratory, 11 modified.

LeO 451T

German-captured bombers modified for freight duty with seating for up to 17 troops, roughly 50 aircraft were modified.

LeO 453

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.

LeO 454

Bristol Hercules II engines, one prototype left unfinished.

LeO 455

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.

LeO 455Ph

Post-war photo-reconnaissance variant, powered by two 1,600 hp (1195 kW) SNECMA 14R engines.

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, ten ordered





17.17 m (56 ft 4 in)


22.52 m (73 ft 11 in)


5.24 m (17 ft 2 in)

Wing area

66 m2 (710 sq ft)

Empty weight

7,530 kg (16,601 lb)

Max take-off weight

11,398 kg (25,128 lb)

Fuel capacity

3,235 l (855 US gal; 712 imp gal)


1 × Gnome-Rhône 14N−48,

14-cylinder air-cooled radial piston engine,

790 kW (1,060 hp) LH rotation

(Or −38 or −46)


1 × Gnome-Rhône 14N−49,

14-cylinder air-cooled radial piston engine,

790 kW (1,060 hp) RH rotation

(Or −39 or −47)


3-bladed constant-speed propellers (LH and RH rotation)


Maximum speed

495 km/h (308 mph, 267 kn) at 4,000 m (13,123 ft)

Cruise speed

420 km/h (260 mph, 230 kn)


2,900 km (1,800 mi, 1,600 nmi)

Service ceiling

9,000 m (30,000 ft)



1 × 20 mm Hispano-Suiza HS.404 cannon in dorsal turret, 120 rounds

1 × 7.5 mm (0.295 in) MAC 1934 fixed forward-firing machine gun, 300 rounds

1 × 7.5 mm MAC 1934 in a “dustbin” retractable ventral turret, 500 rounds


Up to 1568 kg (3,457 lb) of bombs in fuselage and wing root bomb bays

7 × 200 kg bombs (actual bomb weight: 224 kg or 494 lb).


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