Engines of Our Ingenuity

No. 2565
de HAVILLAND DH.9

by John H. Lienhard

Today, swords and plowshares. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Geoffrey de Havilland in 1920 I've talked about the Gargantuan WW-I bombers built by Germany and Britain -- huge slow biplanes, vulnerable to enemy fighters. But the British also had an early light bomber, the de Havilland DH.4 -- a two-seat biplane with a pilot and a rear gunner. It carried 1100 pounds of bombs. Geoffrey de Havilland (actress Olivia de Havilland's cousin) designed it. Here in America, we built our own version of his DH.4 in huge numbers.

Then, on June 13, 1917, the Germans carried out a daylight bombing of London. Suddenly Britain knew she must greatly expand her own bombing raids in Germany. So de Havilland offered the Royal Flying Service his DH.9, an improved version of the DH.4.

It was to fly faster, further, and carry more bombs. Well, I've said before that war is no friend of invention. War's urgencies get in the way of new ideas, and they surely did in this case.

Great Britain liked the new airplane and put it into production. It was sleek and nice-looking, with all kinds of new design features. But it immediately proved to be underpowered, slow, and unable to fly very high. No matter: a war had to be fought so hundreds were flung into combat anyway. And they performed miserably.

A British WW-I DH.9

Necessity does that -- it gets ahead of invention. The British expanded production while they vainly tried new engines and other fixes. By war's end, they were left with thousands of dubious warplanes. What to do with them?

They sold many off to countries fighting enemies with little or no air power. DH.9s flew with White Russian forces in the Russian Revolution. They fought in South Africa and the Middle East. But far more interesting was their civilian use, for they became a kind of laboratory for peacetime flying.

DH.9s were fitted with every kind of engine. A DH.9, modified for racing, won the 1919 Aerial Derby. Some were equipped with floats and flew from water. They served well for aerial reconnaissance and photography. They pioneered air mail service.

In one version, the rear cockpit was removed and replaced with a closed cabin for three passengers, as well as mail. Others carried two passengers on facing seats in large rear cockpit. DH.9s were rigged as air ambulances. They were flown from early aircraft carriers. They made popular trainers. Their wings were equipped with leading edge slots to improve lift. They used propellers with two blades or four. They used both liquid- and air-cooled engines.

Four thousand DH.9s had been made and, only when war ended, did their invention begin in earnest. We hardly remember the DH.9 today, but it was still seeing service in the mid-30s. Some were even resurrected for combat in the Spanish Civil War. The better planes that we do remember benefitted from all that tinkering. What we couldn't finish in war, we did in peace. We made remarkable plowshares indeed from this flawed old sword.

I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


P. Cooksley, de Havilland D.H.9 in Action. (color by Don Greer, Illustrations by Joe Sewell) ( Carrollton, TX: Squadron/Signal Publications, Inc., 1996), No. 164.

See also the Wikipedia articles on the Airco DH.9 and Geoffrey de Havilland.

Images: Above, RAF photo of G. de Havilland, Wikipedia image of a DH.9 in Wartime. Below, Australian DH.9s in war and peace, courtesy of Australian Defense Dept. and Australian National Library, respectively.

Australian military DH.9

Australian DH.9 postwar

The Engines of Our Ingenuity is Copyright © 1988-2009 by John H. Lienhard.