Latécoère 631

The Latécoère 631 was a civil transatlantic flying boat designed and produced by the French aircraft manufacturer Latécoère. At the time of its maiden flight, it was the largest flying boat to have ever been built.

The Latécoère 631 was designed in response to a specification for a transatlantic passenger aircraft to be operated by flag carrier Air France; it was the largest and heaviest of three flying boats (the others being the SE.200 Amphitrite and the Potez-CAMS 161) that were designed to fulfil this requirement. Along with all-metal construction and an unconventional V-tail, the Latécoère 631 was originally intended to be powered by six Gnome-Rhône 18P radial engines; however, the type was typically powered by six Wright GR-2600-A5B Twin Cyclone 14-cylinder radial engines instead.

While the Latécoère 631 was ordered in 1938, its construction was disrupted by the outbreak of World War II one year later. The prototype made its fight flight on 4 November 1942; having demonstrated strong performance, decision makers were convinced to put the Latécoère 631 into production in 1944. Accordingly, in July 1947, the type started flying transatlantic routes for Air France, as had been originally intended for the type. However, the Latécoère 631 was not typically regarded as a success, proving to be both unreliable and uneconomic to operate. It was withdrawn from service after a series of fatal accidents. Five of the eleven aircraft built were written off in accidents and one was lost during World War II.

Design and development

The origins of the Latécoère 631 can be traced back to 1936 and the issuing of a specification by the French Air Ministry that sought a new transatlantic airliner to be operated by the national flag carrier Air France; the prospective aircraft was to possess a range of as well as a capacity for up to 20 passengers and 500 kg of cargo.Hartmann 2000, p. 4. This high-profile specification quickly attracted the attention of various French aircraft manufacturers, including Lioré et Olivier and Potez-CAMS (which would submit their SE.200 Amphitrite and the Potez-CAMS 161 respectively); Latécoère was another firm that opted to produce a response.Flight 1 December 1938, p. 506. Designated as the Latécoère 631, it was both the largest and heaviest of the three flying boats designed to meet the specification.Nicolaou 1998, p. 152. It featured all metal construction, an unorthodox V-tail arrangement, and stabilising floats that retracted into the nacelles of the outboard engines as to minimise drag, akin to the earlier Latécoère 611.

The Latécoère 631 was ordered in 1938, at which point it was intended for the flying boat to be powered by six Gnome-Rhône 18P radial engines, each capable of producing up to . During the following year, the first passenger flight across the Atlantic was flown by a competing flying boat, the Dixie Clipper; around this time, large flying boats were opening up long distance passenger and mail routes all over the world.

The outbreak of World War II would prove decisive to the future of the Latécoère 631; flying boats were turned to military purposes while developments made during the conflict substantially reshaped post-war air travel. Specifically, construction of the Latécoère 631 was temporarily halted shortly after the conflict broke out, but it was resumed shortly after the signing of the Franco-German Armistice in 1940. Final assembly of the first prototype was undertaken in a hangar at Marignane.

On 4 November 1942, the prototype, registered F-BAHG, performed its maiden flight. During its test flights, the flying boat reportedly exhibited favourable flight and seaworthiness characteristics in addition to the fulfilment of the specification's performance stipulations. One issue observed was an occasional vibration in the outermost portion of the wings. The prototype was subsequently confiscated by the Germans, and passed to the Luftwaffe, who allocated the codes 61+11 to it. The aircraft was flown to Lake Constance, where it was destroyed in an attack by two RAF Mosquito aircraft on 17 April 1944. One month later, France's provisional government, then based in Algiers, decided to pursue serial production of the Latécoère 631 once conditions were right to do so.Nicolaou 1998, p. 151.Green and Pollinger 1956, p. 114. Latécoère allegedly worked with the French Resistance to conceal components for a second aircraft from the German occupation forces.

Operational history

The second aircraft, F-BANT, first flew on 7 March 1945. It was powered by six Wright R-2600 Cyclone engines of each. Four aircraft were purchased by Air France, and entered service on the Biscarrosse-Port-Étienne-Fort de France route in July 1947.Taylor and Mondey 1982, p. 129 The aircraft were withdrawn from service in August 1948 following the loss of F-BDRC. SEMAF operated two aircraft until 1950, when the survivor was withdrawn following the loss of F-WANU. The Société France Hydro operated one aircraft until it was lost on 10 September 1955. This was the last flying aircraft, with the remaining four survivors being scrapped. The Latécoère 631 had quickly become undesirable to operators, largely as a result of it being both unreliable and uneconomic to operate.

Operators Data from Aeroplane Monthly 2014 Air France. Latécoère. SEMAF. Société France-Hydro. Luftwaffe.

Accidents and incidents 17 April 1944 The Latécoère 631 prototype (F-BAHG; 61+11) was destroyed in an attack by two RAF Mosquito aircraft. SNCASE SE.200 Amphitrite 20+01 was destroyed in the same attack.

31 October 1945 An Air France Latécoère 631 (F-BANT) was operating a flight from Rio de Janeiro, Brazil, to Montevideo, Uruguay, and Buenos Aires, Argentina, when the propeller of No. 3 engine separated in flight and debris struck the No. 2 engine. A propeller blade sliced a hole in the cabin, killing two passengers. A small fire started and an emergency landing was made in the Laguna de Rocha, Uruguay. The aircraft was subsequently repaired and returned to service. The poet, diplomat and composer Vinicius de Moraes and writer Rubem Braga, both Brazilians, were on board. 21 February 1948 A Latécoère 631 (F-BDRD) was on a delivery flight from Le Havre, Seine-Maritime, to Biscarrosse, Landes when it crashed into the English Channel off Saint-Marcouf, Manche, in a snowstorm with the loss of all nineteen people on board. The aircraft lacked any ice protection system.

1 August 1948 Air France Flight 072 (F-BDRC) ditched in the Atlantic Ocean for reasons unknown with the loss of all 52 people on board. The aircraft was operating a flight from Fort-de-France, Martinique, to Port-Étienne (now Nouadhibou), Mauritania. Following this loss, the Latécoère 631 was withdrawn from service by Air France. The United States Coast Guard ship reported finding debris on August 4 but no sign of survivors. 28 March 1950 A SEMAF Latécoère 631 (F-WANU) crashed into the Atlantic Ocean off Cap Ferret, Gironde, after the aileron control couplings failed due to severe vibration in one of the engines' gearboxes with the loss of all twelve people on board. The aircraft was on a test flight from Biscarrosse to determine the cause of the crash of Air France Flight 072. 10 September 1955 A France-Hydro Latécoère 631 (F-BDRE) suffered wing separation (probably due to wind shear) after flying into a tropical storm, and crashed 38 mi north of Banyo, French Cameroon, killing all 16 on board. The aircraft was on a flight from Lac Lérè, Chad, to Douala, French Cameroon (now Cameroon), en route to Biscarrosse for maintenance.

Specifications (Latécoère 631)

Latécoère 631

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