1934 KLEMM L25 - Oldest flyable German aircraft

However, as peace set in and aeronautical development progressed at a very rapid pace in Europe, BMW got back to making engines for aircraft. It had made loads of liquid-cooled motors for aircraft but while reliable these were heavy, a complete contrast to the lighter air-cooled radial engines preferred by the Americans and the Brits. 

BMW was well on its way to developing its own radial engines but due to development time to market being of prime consequence, the German firm tied up with none other than American engine maker Pratt & Whitney in 1929 to make its Wasp and Hornet radials under license in Germany. What was amazing was the fact that Pratt & Whitney itself had been established just four years earlier in 1925 but it was already making waves in the aero world.

One of the engines made from this partnership was the BMW-miniaturised Pratt & Whitney Hornet radial designated the Xa. It featured a magnesium crankcase and just so that BMW didn’t fell foul of the rules prohibiting it from making specialized fighter aircraft motors, this engine got the same cylinders, displacement and top end as the firm’s small 250cc single cylinder motorcycle engines! This commonality of parts stood it in good stead as the firm’s engineers got to speed learning about radial aero engine technology.

The earliest application of this BMW radial was the Klemm L25 light aerobatic trainer. Only 44 units of this wooden-framed aircraft were made from 1932 onwards till around 1935 but it was the mainstay for a good many budding German pilots wanting to get a feel for the larger more powerful stuff.

This particular aircraft, owned by BMW, is the oldest fully flyable German aircraft in existence in the world! The wooden frame is draped with aluminium sheeting and this might seem pretty flimsy (and it certainly was!) but the fuselage held together by dint of good design.

The BMW version of the downsized 5-cylinder Pratt & Whitney Hornet was supposed to develop 68bhp but in actuality it was good for just 63bhp but then the light (600kg) construction of the aircraft meant there was a good balance of power-to-weight. This rare aircraft is fully certified for flight and does fly on occasion when the event demands. 

It was on the lush lawns of the Villa Erba during the Concorso d’Eleganza Villa d’Este and every hour its specialized crew would fire up the engine which I must say had a very distinctive beat so reminiscent of the piston-engined era. Every bit on the Klemm was original and accurate to the nth degree barring for the special propeller, which incorporated LEDs to spin out the BMW logo whenever the motor was fired!

No harm in letting any and everyone know where the firm’s roots sprang from!