Imagine a fighter aircraft that cannot take off. It has no way to move under its own power on the runway, no way to build up speed, no way to leave the ground at all. To fly it, you must bolt it to the roof of an airliner, haul it up to altitude, and drop it — and only then, as the air rushes through its hollow body, does the engine come alive.

This was the Leduc, one of the strangest flying machines France ever built, and one of the first aircraft in the world to fly on the raw power of a ramjet alone. Stranger still was the seating arrangement: the pilot lay flat on his stomach, sealed inside a glass nose cone in the very centre of the engine’s air intake, staring out as the airflow howled past him toward the flame.

It was the obsession of one stubborn engineer, René Leduc — and for a brief moment in the 1950s, it looked like the future of flight.

A stovepipe with wings

The ramjet is the simplest jet engine imaginable: no compressor, no turbine, barely any moving parts. It is little more than a shaped tube that uses its own forward speed to ram air inside, where fuel is added and burned. The idea was patented by another Frenchman, René Lorin, back in 1913 — but it had a fatal catch. A ramjet only produces thrust once it is already moving fast through the air. Sitting still on a runway, it does precisely nothing.

René Leduc spent decades wrestling with that paradox. He secured a small government grant in 1933, demonstrated a working ramjet by 1936, and won a contract to build an actual aircraft around it — only for the Second World War to intervene. His prototype was hidden from the occupying Germans, nearly destroyed in a bombing raid, and not flown until years after the war.

The plane that had to be dropped to fly

Since the Leduc 0.10 could not take off, Leduc simply mounted it on a gantry above a four-engined Languedoc airliner. The composite machine would climb together; the little ramjet aircraft would then be released to glide until it was fast enough to light its engine. On 21 April 1949, over Toulouse, the ramjet was ignited in flight for the first time and the Leduc climbed and manoeuvred entirely under its own power, reaching some 680 km/h on half throttle. The principle had been proven in the most audacious way possible.

Flying from inside the engine

Because the entire fuselage was the ramjet, there was nowhere ordinary to put a cockpit. Leduc’s solution was as bold as the aircraft: the pilot reclined face-down inside a double-walled nose, sealed in a glazed pod at the centre of the intake, with the incoming air flowing around him in a ring. Forward visibility was almost nil, and bailing out was a nightmare no one wished to contemplate — but it flew.

Chasing Mach 2

The experiments grew more ambitious. The Leduc 0.21 flew more than 250 times and approached Mach 0.95. Then came Leduc’s masterpiece, the 0.22: a swept-wing interceptor that finally solved the take-off problem by adding a SNECMA Atar turbojet for the runway, keeping the ramjet for high speed. A jettisonable nose gave the pilot an escape pod at last. In December 1957 it reached Mach 1.15, and it flew more than 140 times — until it was gutted by a fire while taxiing.

The future France walked away from

The Leduc did not fail on its merits. France was pouring money into the wars in Indochina and Algeria, and a far more conventional aircraft had appeared: the Dassault Mirage, which reached beyond Mach 2 on an ordinary afterburning turbojet, with none of the ramjet’s awkwardness. In February 1958 the government cancelled the Leduc programme, and René Leduc never designed another aircraft. His flying stovepipes went to museums — a brilliant dead end from a man history has been too quick to forget.

Sources: PlaneHistoria (Vegim Krelani); Wikipedia (Leduc 0.10; Leduc 0.21; Leduc 022); Musée de l’air et de l’espace. Dates and speeds are given as reported; sources differ slightly on some details.