Couzinet Arc-en-Ciel
The Couzinet Arc-en-Ciel ('Rainbow') was a family of French wooden trimotor monoplanes built by the Société des Avions René Couzinet to prove that landplanes, rather than flying boats, were the right aircraft for long overwater routes. The first Arc-en-Ciel flew in 1928 and was lost in a crash weeks later; the third, the Couzinet 70, crossed the South Atlantic from Senegal to Brazil under Jean Mermoz in January 1933 and went on to work Air France's South Atlantic mail route as the Couzinet 71. Production orders were cancelled in 1935, and the sole Couzinet 70 was destroyed in 1940; no Arc-en-Ciel survives.
Why It Mattered
René Couzinet held a conviction French officialdom did not share: that the future of long overwater routes belonged to big multi-engined landplanes, not to the heavy, slow flying boats then in favour. His Arc-en-Ciel trimotors were that argument made wood and plywood, and the third of them, the Couzinet 70, proved the point over the South Atlantic in January 1933, when Jean Mermoz flew it from Senegal to Brazil with Couzinet himself aboard. La Poste's official notice for the type's commemorative stamp calls the crossing a triumph that opened a new era for commercial aviation. The flights that followed turned the one-off prototype into an Air France mailplane working the South Atlantic route — yet the official orders the little company needed never came.
Design Notes
The Arc-en-Ciel formula was set by the first aircraft, flown in 1928: a wooden trimotor monoplane whose one-piece wing was 900 mm thick at the root, built around two box spars and covered in plywood. That thickness was functional, since the wing held seven fuel tanks and a corridor 700 mm high through which the crew could reach the engines in flight. The fin rose gradually out of the fuselage, becoming the tapered signature of every Arc-en-Ciel that followed. The Couzinet 70 kept the wooden structure and the in-flight engine access at a larger scale, spanning 30 metres and powered by three Hispano-Suiza 12Nb engines of 650 hp each. Flight tests of the first aircraft had shown it could hold its altitude with the outer engines throttled well back, which Couzinet regarded as a safety margin if an engine failed. After the 1933 proving flights the 70 was rebuilt with a lengthened nose and a strut-braced tailplane, emerging as the Couzinet 71.
Operational History
The first Arc-en-Ciel, the Couzinet 10, flew for the first time on 7 May 1928 from Orly, with Maurice Drouhin at the controls. Re-engined that July as the Couzinet 11 around a single 600 hp central engine, it crashed at Orly on 8 August 1928, killing Drouhin and his mechanic Lanet. A second Arc-en-Ciel was still unfinished when fire gutted the Meudon workshops in February 1930, destroying the aircraft along with Couzinet's plans and archives. The lost drawings were redrawn from memory by the engineer Georges Le Moy, and the third Arc-en-Ciel, the Couzinet 70, flew on 11 February 1932. Aéropostale would acquire the aircraft only if it first completed a Paris–Buenos Aires round trip under line conditions, with company pilot Jean Mermoz in charge. On 16 January 1933 Mermoz crossed from Saint-Louis in Senegal to Natal in Brazil — 14 hours 27 minutes by La Poste's account, with Couzinet among the crew — and the proving flight continued to Buenos Aires. The return reached Le Bourget on 21 May 1933, where the French Wikipedia account records a crowd of 15,000 and a triumphal welcome. As the Couzinet 71 it took up scheduled mail flying to South America, starting on 28 May 1934, and from 24 July the crossing ran monthly. Operated by Air France, it made eight commercial crossings of the South Atlantic in total.
Afterlife
The crossings brought fame but no production order: in 1934 the state ordered three Couzinet 73s — the same aircraft with retractable gear, intended for Air France — then cancelled the order in February 1935 without explanation or compensation. Aeroplanes.fr calls that cancellation the end of the Couzinet company, which never recovered. The Arc-en-Ciel itself was sold in May 1937 and bought back by René Couzinet, who, La Poste records, wanted to save it from the scrapyard. It lasted only until 1940, when it was destroyed in its hangar during the Second World War. With the first Arc-en-Ciel lost in 1928 and the second burned before it was finished, no example of the type survives. In 2000 La Poste honoured the type with a 50-franc airmail stamp devoted to the Couzinet 70.