Lioré et Olivier LeO 451
Encyclopedia
Lioré-et-Olivier LeO 45 was a French medium bomber used during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. It was a low-wing monoplane, all metal in construction, equipped with a retractable undercarriage and powered by two 1,100 hp Hispano-Suiza engines. It was a very effective bomber, but it appeared too late to give any substantial contribution to the war effort. Although designed before World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, it remained in service until September 1957.
The 1934 B4 bomber programme
The LeO 451 was conceived as a second-generation strategic bomber for the new French Air ForceFrench Air Force
The French Air Force , literally Army of the Air) is the air force of the French Armed Forces. It was formed in 1909 as the Service Aéronautique, a service arm of the French Army, then was made an independent military arm in 1933...
. 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 17 November 1934, specifying a 5-seat bomber with a top speed of 400 km/h (215 knots, 250 mph) at 4,000 m (13,125 ft), and a combat radius of 700 km (435 mi) carrying a payload of 1,200 kg (2,650 lb). 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 cantileverCantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
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
Monocoque
Monocoque is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork...
fuselage. Because of the speed requirements of the programme, a lot of effort was spent in reducing parasitic drag
Parasitic drag
Parasitic drag is drag caused by moving a solid object through a fluid medium . Parasitic drag is made up of many components, the most prominent being form drag...
. Wings were equipped with slotted flaps
Flap (aircraft)
Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed an aircraft can be safely flown at and to increase the angle of descent for landing without increasing air speed. They shorten takeoff and landing distances as well as...
and small bomb bays in the wing roots in addition to the main fuselage bomb bay, so as to limit the 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 cowling
NACA cowling
The NACA cowling is a type of aerodynamic fairing used to streamline radial engines for use on airplanes and developed by the National Advisory Committee for Aeronautics in 1927...
s, 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
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
. 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 7.5 mm M.1934 (500 rounds) 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. This was a really powerful one, the Hispano-Suiza HS.404
Hispano-Suiza HS.404
The Hispano-Suiza HS.404 was an autocannon widely used as both an aircraft and land weapon in the 20th century by British, American, French, and numerous other military services. The cannon is also referred to as Birkigt type 404, after its designer. Firing a 20 mm caliber projectile, it delivered...
, with 120 rounds, and excellent ballistic proprierties (over 800 m/s), well over MG FF and other Oerlikon guns. The turret was retraclable when not needed. The armament was completed with another 7.5 mm machine-gun M.1934/39, this time fixed in the nose (300 rds). Overall, the Leo's armament was: 120 20 mm rounds, 800 7.5 mm rounds, up to seven 200 kg bombs, or other combinations (up to 1-2 500 kg bombs in the belly, plus the two 200 kg in the wings). The maximum load penalized the fuel, that was reduced to only 1,000 lts. The fuel tanks were: two 880 lts (inner wings), two 330 and two 410 lts (all in the external wings).
The LeO 45-01 prototype, powered by a pair of Hispano-Suiza 14AA-6 / Hispano-Suiza 14AA-7 radial engines producing 1,120 hp (835 kW) each flew for the first time on 16 January 1937. 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 shallow 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
Gnome-Rhône 14N
|-See also:* Pratt & Whitney R-1830 a comparable engine sometimes fitted as an alternative to the 14N on French designs* BMW 801* Bristol Hercules* Wright R-2600* Fiat A.74* Mitsubishi Kinsei* Nakajima Sakae* Shvetsov ASh-82-References:...
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 a 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
Battle of France
In the Second World War, the Battle of France was the German invasion of France and the Low Countries, beginning on 10 May 1940, which ended the Phoney War. The battle consisted of two main operations. In the first, Fall Gelb , German armoured units pushed through the Ardennes, to cut off and...
on 10 May 1940, only 54 of the 222 LeO 451 that had been delivered were considered ready for combat, the remainder being used for training, spares, undergoing modifications and repairs or having been lost. The first combat sortie of the campaign was flown by 10 aircraft from GB I/12 and GB II/12 on 11 May. 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 piloted by sergent-chef Hervé Bougault near Floyon during a bombing mission over German troops. By the Armistice
Armistice with France (Second Compiègne)
The Second Armistice at Compiègne was signed at 18:50 on 22 June 1940 near Compiègne, in the department of Oise, between Nazi Germany and France...
of 25 June 1940, LeO 451 of the Groupement 6 had flown 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. There are other numbers, stating about 47 bombers lost (26 to fighters, 21 to flak). Although the LeO's were faster than many 1940's fighters and faster than almost all other types of bombers, unfortunately for them the Luftwaffe was equipped with fighters that were even faster (Bf-109 and 110). The cruise speed, up to 420 km/h (7 km/min), was one of the strengths in the LeO's performances and would make them difficult to track down. The diving and climbing speed were very good as well (the Italian SM.79 took 17 minutes to reach 5,000 m, compared to 14 for the LeO), even if not that useful for a bomber. Leo's were optimized for medium-altitude operations (5,000 m), but were forced to go far lower to search and destroy tactical targets, but seldom had an even basic fighter escort (P-75, D.520). The LeO's were not unarmed however and German fighters had to keep a look out for their dorsal turret: on 6 June 1940, a single LeO (gunner Stg. Grandchamp, GBU.II/11) shot down two Bf-110C's with the Hispano gun. German fighters came to avoid this danger by attacking from below, forcing the Leo's to deploy they retractable turret, which slowed them appreciably (not known how much).
Another problem had been the German's initial strike. The 6th Groupement had 50 Leo's, but they were not dispersed and even lacked AA defence on their airfields. When the Luftwaffe attacked them, they destroyed 40 bombers. In spite of this, 6th Groupement continued the fight, since the LeO's were produced on a fast pace (around 4-5/day, over 200 built within 45 days) allowing them to re-equip. Losses still remained high though, in a single mission 13 LeO's were intercepted and four shot down by Luftwaffe fighters. 6th Groupement totalled around 70 losses both in air and ground, but still continued to fight until the end. Meanwhile, with Italy joining the war on the axis side, LeO's attacked Livorno, Novi Ligure, Vado, and even Palermo in a 4-ship morning mission. Against Italy the LeO's operated without much difficulty. Turin (Fiat plants) was near the fronteer and thus easy to reach, if needed. Furthermore Italy did not possess an operative radar system and radios were not commonly used on the Italian fighters. On the other theatre however, Flak and Luftwaffe took a heavy toll.
A total of 452 aircraft had then been built, 373 accepted into service (including 13 for the Aéronautique navale
Aviation Navale
French Naval Aviation of the French Navy includes 206 aircraft and 6,800 men, both civilians and military personnel. They operate from six airbases, five of them in Metropolitan France and one overseas....
), and around 130 lost in action in Europe.
Following the Armistice, LeO 451s continued to fly, now under the Vichy government
Vichy France
Vichy France, Vichy Regime, or Vichy Government, are common terms used to describe the government of France that collaborated with the Axis powers from July 1940 to August 1944. This government succeeded the Third Republic and preceded the Provisional Government of the French Republic...
. 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
Degaussing
Degaussing is the process of decreasing or eliminating an unwanted magnetic field. It is named after Carl Friedrich Gauss, an early researcher in the field of magnetism...
coil for remotely detonating naval mine
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...
s (some British Vickers Wellington
Vickers Wellington
The Vickers Wellington was a British twin-engine, long range medium bomber designed in the mid-1930s at Brooklands in Weybridge, Surrey, by Vickers-Armstrongs' Chief Designer, R. K. Pierson. It was widely used as a night bomber in the early years of the Second World War, before being displaced as a...
s and German Junkers Ju 52
Junkers Ju 52
The Junkers Ju 52 was a German transport aircraft manufactured from 1932 to 1945. It saw both civilian and military service during the 1930s and 1940s. In a civilian role, it flew with over 12 air carriers including Swissair and Deutsche Luft Hansa as an airliner and freight hauler...
s also carried a similar device).
Two bomber units equipped with LeO 451s, GB I/12 and GB I/31 were based in Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
when Allied forces invaded on 8 June 1941, at the start of the Syria-Lebanon Campaign
Syria-Lebanon campaign
The Syria–Lebanon campaign, also known as Operation Exporter, was the Allied invasion of Vichy French-controlled Syria and Lebanon, in June–July 1941, during World War II. Time Magazine referred to the fighting as a "mixed show" while it was taking place and the campaign remains little known, even...
. These were supplemented by GB I/25, which was dispatched from Tunisia
Tunisia
Tunisia , officially the Tunisian RepublicThe long name of Tunisia in other languages used in the country is: , is the northernmost country in Africa. It is a Maghreb country and is bordered by Algeria to the west, Libya to the southeast, and the Mediterranean Sea to the north and east. Its area...
. During this campaign, the LeO 451s flew a total of 855 sortie
Sortie
Sortie is a term for deployment or dispatch of one military unit, be it an aircraft, ship, or troops from a strongpoint. The sortie, whether by one or more aircraft or vessels, usually has a specific mission....
s, losing 29 LeO 451s in the process.
After Operation Torch
Operation Torch
Operation Torch was the British-American invasion of French North Africa in World War II during the North African Campaign, started on 8 November 1942....
which began on 8 November 1942, 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
Tunisia Campaign
The Tunisia Campaign was a series of battles that took place in Tunisia during the North African Campaign of the Second World War, between Axis and Allied forces. The Allies consisted of British Imperial Forces, including Polish and Greek contingents, with American and French corps...
. They were ultimately replaced in active service by Handley-Page Halifax and B-26 Marauder
B-26 Marauder
The Martin B-26 Marauder was a World War II twin-engine medium bomber built by the Glenn L. Martin Company. First used in the Pacific Theater in early 1942, it was also used in the Mediterranean Theater and in Western Europe....
bombers.
The Germans were not especially interested in this airplane, but on 21 May 1943, Luftwaffe requested Regia Aeronautica to hand over 39 Lioré et Olivier LeO 451
Lioré et Olivier LeO 451
Lioré-et-Olivier LeO 45 was a French medium bomber used during World War II. It was a low-wing monoplane, all metal in construction, equipped with a retractable undercarriage and powered by two 1,100 hp Hispano-Suiza engines. It was a very effective bomber, but it appeared too late to give any...
, captured by Italians troops in SNCASE factory in Ambérieu-en-Bugey
Ambérieu-en-Bugey
Ambérieu-en-Bugey is a commune in the department of Ain in eastern France.It is the largest town in the arrondissement of Belley and the seat of the Ambérieu-en-Bugey canton, as well as the capital of the historic region of Bugey.-Geography:...
(Lyon
Lyon
Lyon , is a city in east-central France in the Rhône-Alpes region, situated between Paris and Marseille. Lyon is located at from Paris, from Marseille, from Geneva, from Turin, and from Barcelona. The residents of the city are called Lyonnais....
). The Luftwaffe - that claimed to have previously bought the Lioré - gave in exchange a stock of 30 Dewoitine D.520. Subsequently, the 451s were converted into trasport aircraft for fuel and troops. Other Lioré were delivered to the Regia Aeronautica
Regia Aeronautica
The Italian Royal Air Force was the name of the air force of the Kingdom of Italy. It was established as a service independent of the Royal Italian Army from 1923 until 1946...
and 12 were put in service with a ground attack unit, although they saw almost no active service.
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-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 FranceAir FranceAir France , stylised as AIRFRANCE, is the French flag carrier headquartered in Tremblay-en-France, , and is one of the world's largest airlines. It is a subsidiary of the Air France-KLM Group and a founding member of the SkyTeam global airline alliance...
.
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 895 kW (1,200 hp) 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-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 photoreconnaissance 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 NavyFrench NavyThe French Navy, officially the Marine nationale and often called La Royale is the maritime arm of the French military. It includes a full range of fighting vessels, from patrol boats to a nuclear powered aircraft carrier and 10 nuclear-powered submarines, four of which are capable of launching...
, 68 ordered. Also known as the LeO 451M.
LeO 458
- Wright GR-2600-A5Bengines, 10 ordered
Operators
- French Air ForceFrench Air ForceThe French Air Force , literally Army of the Air) is the air force of the French Armed Forces. It was formed in 1909 as the Service Aéronautique, a service arm of the French Army, then was made an independent military arm in 1933...
- Aviation NavaleAviation NavaleFrench Naval Aviation of the French Navy includes 206 aircraft and 6,800 men, both civilians and military personnel. They operate from six airbases, five of them in Metropolitan France and one overseas....
- Air FranceAir FranceAir France , stylised as AIRFRANCE, is the French flag carrier headquartered in Tremblay-en-France, , and is one of the world's largest airlines. It is a subsidiary of the Air France-KLM Group and a founding member of the SkyTeam global airline alliance...
Vichy FranceVichy France
Vichy France, Vichy Regime, or Vichy Government, are common terms used to describe the government of France that collaborated with the Axis powers from July 1940 to August 1944. This government succeeded the Third Republic and preceded the Provisional Government of the French Republic...
- Vichy French Air ForceVichy French Air ForceThe Vichy French Air Force was the aerial branch of the armed forces of Vichy France - the government of France that collaborated with the Axis powers following the defeat of France by Germany in 1940....
Nazi Germany
- LuftwaffeLuftwaffeLuftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
operated several captured aircraft.
Kingdom of Italy (Napoleonic)
- Regia AeronauticaRegia AeronauticaThe Italian Royal Air Force was the name of the air force of the Kingdom of Italy. It was established as a service independent of the Royal Italian Army from 1923 until 1946...
United States
- United States Army Air Force operated several captured aircraft as unit hacks.