There’s more to this weird box-frame aeroplane than you would imagine. Over 1500 were produced by the Caudron brothers, René and Gaston, in their factory at Le Crotoy on the eastern side of the Somme estuary, from 1913 onward. And it proved to be, despite appearances, tough, reliable and popular with the pilots who flew it. It was mostly used by the French and British as a trainer, but also for reconnaissance, artillery observation, and ground attack.

The whole thing, cockpit plus engine, wings and tail, were held together in a box-frame of spars, skids and tension wires. Elevators and rudders for pitch and yaw, were conventional, but it used wing-warping instead of ailerons for roll. Its 100hp engine gave it a maximum speed of 108kph (67 mph).

Despite its unusual build, it was the first biplane* to fly a loop. It was the first to fly off a French warship on 7th May 1914, and it was the first (& only) aircraft to be landed – by the adventurous French aviator Jules Védrines – on the roof of the Galeries Lafayette department store in Paris (28m x 12m), on 19 January 1919.

It was also flown by Caudron’s extraordinary Test & Delivery pilot, Adrienne Bolland (it was her who flew the first loop) over the Andes between Chile and Argentina on 1st April 1921.

This (feature image above) is a G.3 built in 1913 and now on static display in the RAF Museum in London. The Airspace Museum in Rio de Janeiro also has one.

The Amicale Jean-Baptiste Salis built an airworthy replica from the original plans in 1991.

It is on display at the Salis Flying Museum just south of Paris, where it sometimes takes to the air.

And if you visit the Air Space Museum at Le Bourget on the outskirts of Paris, you can see an example of the Caudron G.4 twin-engine version suspended from the ceiling.

The G.4 was developed in 1915 and was the world’s first twin-engine aircraft to be widely used.

* Technically the G.3 was a “Sesquiplane” – a biplane with one wing less than half the area of the other.