The Weymann 66 was intended to be capable of reconnaissance, including wireless and photographic work; ambulance and troop carrying; and bombing.
Long side windows stretched rearwards from the cockpit almost to the end of the cabin, which was about halfway between the trailing edge and the tail.
At the forward end they merged into the fairings and mountings of the two outer engines, 300 hp (225 kW) Lorraine Algol radials.
The tailplane and elevator was enclosed between two large endplate fins of semicircular shape, which carried horn balanced rectangular rudders.
Two substantial streamlined struts ran diagonally outwards and upwards from the extreme rear of the cabin to the ends of the booms for support.