FighterSweep Fans, breaking the sound barrier was once thought to be an unattainable goal. Several men died while dancing with that particular beast, and it wasn’t until 14 October 1947–when Chuck Yeager strapped into the Bell X-1, that someone punched it in the face and made it heel. What many don’t know is there were other pilots who came close to hitting “the number” in the years before…in a Spitfire!

A handful of flights in Supermarine Spitfires – the single-seat fighter plane that helped win the Battle of Britain – were crucial in helping scientists understand the forces that would have to be overcome if a plane was able to fly faster than sound.

The plane’s superlative performance also made it a natural for test flights, especially for high-speed research. It was on these flights that some Spitfire pilots took the aircraft into previously uncharted territory – encountering the strange aerodynamic forces that occur when the sound barrier is within reach.

According to famed test pilot Eric ‘Winkle’ Brown’s book Wings on My Sleeve, the high-speed trials began in late 1943. During the program, Squadron Leader J R Tobin took a Mark XI Spitfire into a 45-degree dive; the plane reached a top speed of 606mph (975km/h), or Mach 0.89 (Mach 1 being the technical term for the speed of sound).

It was the fastest speed a Spitfire had ever flown – or at least the fastest that a pilot had lived to tell the tale. But a far more dramatic flight was soon to take place.

In April 1944, Squadron Leader Anthony F. Martindale, put the exact same Mark XI Spitfire into a dive. This time, the reduction gear designed to limit its speed failed. The propeller ripped off and the diving aircraft reached more than 620mph (1,000km/h) – Mach 0.92 – as it plunged towards the ground.

Martindale was saved by simple physics. With the heavy propellers wrenched off, the aircraft was now tail-heavy, and this change in the centre of gravity forced it to climb up from the dive at great speed. Martindale was knocked unconscious from the stress of the climb, and woke to find his aircraft flying at 40,000ft (13 kilometers). Somehow he managed to glide the aircraft back to his base, and emerged unscathed. The stress of the plane’s dive had bent the wings, giving them a slightly swept shape – the kind of shape that would eventually help other aircraft travel through the sound barrier.

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(Featured Photo by Jonathan Derden)