The Il-40 had wings set low on the fuselage, swept back at an angle of 35°, and a tricycle undercarriage. The two AM-5 engines were in pods adjacent to the fuselage. As was traditional for Ilyushin ground-attack aircraft, the core of Il-40's structure was a load-bearing armored shell that protected both crew positions, six fuel tanks and part of the radio and electrical equipment. The thickness of the shell ranged from in thickness. The armored bulkhead protecting the pilot from the front was thick. The cockpit glazing was also bulletproof and the pilot was given an armored headrest to protect him against shells fired from above and behind. The gunner was protected by armor thick. The total weight of the armored shell and the bulletproof glass was . Ejection seats were provided for both crewmembers. Three perforated airbrakes were fitted on the rear fuselage, one on each side and one underneath, to enhance the aircraft's maneuverability during a dive.