The Voisin 4 was a Voisin 3 adapted to carry a 37mm cannon by lengthening the fuselage and shifting the wings backward.
The gunner was moved to the front seat to operate the cannon. By their arrival at the front in April 1915, they were already to slow
to be a fighter, but they found new life as ground-attack aircraft and they served with one unit all the way through May 1917.
It was also known as the Voisin LB (or LBS when the engine was mounted on an elevated platform).
[5]
A small number of them were built in Russia by Dux.[6]