 Like the L 76, the L 77v had a fabric-covered welded-steel fuselage and wooden dual-spar wings with plywood skins supported by N-type struts.It was armed with twin 7.92 mm (.312 in) machine guns in fixed forward-firing positions and a third on a ring mounting in the rear cockpit.Three of the aircraft saw service performing armament trials in Lipetsk in the Soviet Union; these included one aircraft testing a free-mounted 20 mm cannon.