# Latécoère 631

The Latécoère 631 was a civil transatlantic flying boat built by Latécoère, the largest ever built up to its time. The boat had six piston engines, and was designed for passenger service. Ordered in the late 1930s, its first flight was in 1942; it went on to a limited amount of use up to 1950. However, the type was not a success, being unreliable and uneconomic to operate;it was withdrawn from service after a series of fatal accidents.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.
The all-metal flying boat is remembered as a beautiful and ambitious design, built in the golden age of flying boat airliners, but also marred by tragedy.

## Design and development

The Latécoère 631 was the result of a specification issued in 1936 by the Direction Générale de l'Aviation Civile for a 40-passenger airliner with a range of 4,000 kilometres (2,500 mi). The aircraft was ordered in 1938. It was intended that it would be powered by six Gnome et Rhône P.18 engines of 1,650 horsepower (1,230 kW) each. A competitor for this specification was the SNCASE SE.200 Amphitrite.
Construction of the aircraft was stopped due to the outbreak of World War II and was not resumed until after the signing of the Franco-German Armistice in 1940. The prototype, registered F-BAHG, first flew on 4 November 1942. It 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 Royal Air Force de Havilland Mosquito aircraft on 17 April 1944. SNCASE SE.200 Amphitrite 20+01 was destroyed in the same attack.
In context, the first passenger flight across the Atlantic was in June 1939, by the Dixie Clipper; large flying boats were opening up long distance passenger and mail routes all over the world. However, WW2 would soon intervene;flying boats were turned to military purposes and developments in the war reshaped post-war air travel.

## History

The second aircraft, F-BANT, first flew on 7 March 1945. It was powered by six Wright R-2600 Cyclone engines of 1,600 horsepower (1,200 kW) each. Four aircraft were purchased by Air France, and entered service on the Biscarrosse-Port-Étienne-Fort de France route in July 1947. The aircraft were withdrawn from service in August 1948 following the loss of F-BDRC. SEMAF operated two aircraft until 1950, when the survivor was withdrawn following the loss of F-WANU.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 was not a success due to it being unreliable and uneconomic to operate.

## Accidents and incidents
### 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 3 metres (9.8 ft) 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 USCGC Campbell 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)

Data from World Encyclopedia of Civil Aircraft
General characteristics
* Crew: 5
* Capacity: 46 passengers
* Length: 43.46 m (142 ft 7 in)
* Wingspan: 57.43 m (188 ft 5 in)
* Height: 10.1 m (33 ft 2 in)
* Wing area: 349.4 m$^2$ (3,761 sq ft)
* Empty weight: 32,400 kg (71,430 lb)
* Gross weight: 71,350 kg (157,300 lb)
* Powerplant: 6 × Wright R-2600-C14 Cyclone 14 14-cylinder air-cooled radial piston engines, 1,194 kW (1,601 hp) each
* Propellers: 3-bladed constant-speed propellers
Performance
* Maximum speed: 394 km/h (245 mph, 213 kn)
* Cruise speed: 297 km/h (185 mph, 160 kn)
* Range: 6,035 km (3,750 mi, 3,259 nmi)
* Wing loading: 92.7 kg/m$^2$ (19.0 lb/sq ft)
* Power/mass: 0.10 kW/kg (0.061 hp/lb)

## Operators

* Air France.
* Latécoère.
* SEMAF.
* Société France-Hydro.
* Luftwaffe.