If only the looks could kill, these flying boats would be the deadliest things over the Atlantic.
In fact, they were obsolete before they could fly and led an unimpressive, even disappointing life. But the looks, oh!
The Saturday Air Mail presents: Breguet 730/731 flying boats. Their story is brought to us by Romantic Technofreak of the Warbird Forum and edited by your humble servant.
On 10 May 1935, the French Navy Command issued the requirement for a large armed flying boat for patrol and reconnaissance to replace the obsolete Breguet Bre-521 Bizerte (see the picture below). The aircraft should have a modern layout, great durability and range to cover the extensive areas of the Atlantic Ocean, and a strong defensive armament mainly consisting of 25mm guns.
Three companies, Breguet, Latécoere, and Potez-CAMS responded with four-engine concepts. The first draft submitted by Breguet had the Bre-710 designation and was using a gull wing. However, by demand of the Navy, in December 1935 Breguet engineers changed the design to straight wing. The modified design, the Bre-730, was accepted by the Navy, and in October 1936 work on the structure of the first prototype started.
Interestingly, the competition showed no winner, and all three designs reached realization. Along with the Bre-730, the Latécoere Laté-611 and the Potez-CAMS 141 were accepted for service.
The Bre-730 was an all-metal cantilever monoplane construction. The extensive two-spar hull had a height of 4.7 m and a width of 3.4 m. The wing consisted of three parts, the rectangular inner section, the outer section in trapeze form and small rounded wing tips. The fuel capacity consisted of 18.000 litres in tanks integrated within the wings, while the wing beam was used as supporting structure. Double vertical tail fins were employed, the tailplane resting on a high single pylone over the fuselage. Two stabilizing floats were placed under the end of the center wing, being equipped with a supporting profile. Four radial engines of type Gnôme-Rhône 14N-2/3 delivering 742 kW (1.010 hp) were placed in nacelles on the forward edge of the center wing, of version N-2 on the right and N-3 on the left side. This installation was chosen to eliminate the torque influence. A special tunnel was placed in the wing so that a mechanic could reach all four engines for minor repairs and adjustments. The crew consisted of 6 to 10 men. The bow section of the fuselage was characterized (like in many other French flying boats) by a subdivided glass-gallery connecting the positions of the pilot and the observer/bombardier.
To answer the Navy demands, the designers planned to install one or two rotating gun turrets on the back of the fuselage, each carrying a single 25mm cannon. Besides this, on each part of the hull gun stations were planned, equipped with Darne 7.5mm machine guns. Five MGs of the same type were installed in a downward shooting position in the rear part of the fuselage, behind the edge. For offensive arming, four 200kg bombs could be carried on external racks under the fuselage. However, none of the actual boats was ever armed.
The first prototype Bre-730-01 was built in two Breguet factories, Le Havre (fuselage, tailplane, floats) and Villacoublay (wing). The assembled prototype started to be tested on 4 February (other source says 4 April) 1938 on the river Seine. Soon the boat was transferred in flight to Cherbourg for extensive tests. On 16 July 1938, the 730-01 was destroyed after running into shallow water during a landing. Two crew members were lost. However, the test results were in a way more than satisfactory and the Navy ordered a batch of three aircraft to be produced in 1939. In September 1939, Breguet was ordered to prepare for producing an unlimited number of the 730s. The problems with the French aircraft industry caused the new batch to be limited to four boats: the production had to be transferred to the old plants of Latécoere in Montaudran near Toulouse, which belonged to the national SNCAN company.
When France surrendered on 25 June 1940, none of the aircraft were finished. Their completion was delayed. It only proceeded in 1941 on order of the Vichy government. The first Bre-730 No. 1 with composite wing and new fuselage was finished in 1942. It employed the Gnôme-Rhône 14N-44 and N-45 for the engines. The Germans delayed the start of the tests in Berre until after the occupation of Southern France in November 1942. The production of eleven 730's slowly continued, but was interrupted when the Allies bombed the factory in Montaudran on 6 April 1944. Only three boats were left.
Meanwhile, after the withdrawal of the Germans from Southern France in August 1944, the testing of the first serial Bre-730 Vega continued in Berre. The tests were finished in December 1944, and in February 1945 the aircraft was transmitted to Escadrille 9FTr Aéronavale. The three other surviving aircraft were finished too, but in Biscarosse. The tests of the second serial-built aircraft, Sirius, started only on 14 June 1946. The two remaining aircraft received a completely redesigned bow and further modified floats. They were equipped with Gnôme-Rhône 14R-24 and R-25 engines. Their designation changed to Bre-731.
The first Bre-731 was tested from 2 September 1947. It was called Bre-731 No.1 Altair, the other one, Bre-731 No.2 - Bellatrix. The Bre-730/731 flying boats were used within the squadron 33S for transport flight between mainland France and her "overseas departments" in Northern Africa.
In December 1948, Vega crashed in Northern Africa, and Sirius met its fate in June 1951 in Morocco. In 1950, Altair was withdrawn from Toulon-Dakar route, Bellatrix continued to serve until 1954. In summer of this year, for these two boats the time of service ultimately ended.