It featured a number of innovative concepts including a cockpit mounted on top of the engine, directly behind the propeller, and wing-mounted autocannon that could be adjusted on the ground to fire level or depressed 23° to allow the aircraft to strafe ground targets while remaining in level flight.

[3] As was traditional with Ilyushin's ground-attack aircraft the Il-20 used a load-bearing armored shell to protect the pilot and gunner as well as the engine, fuel, lubrication and cooling systems.

One involved two wing-mounted 23 mm (0.91 in) cannon and two others mounted in the fuselage, fixed downwards at a 23° angle for strafing targets in level flight.

Most studies placed the rear gunner in a dorsal turret separated from the cockpit by the main fuel tank, but one study put him in an armored Il-K8 rear turret, but this required a longer fuselage and moving the wings aft to maintain the CG in the right place.

[5] The obliquely-mounted fuselage cannon were thought to be too difficult to aim and were not included in the prototype; the weight savings allowed the ammunition for the four 23 mm Shpital'nyy Sh-3 wing-mounted guns to be increased to 900 rounds.

[4] The dorsal gunner also fired a Sh-3 gun, which was mounted in a separate, remotely controlled, Il-VU-11 turret that could traverse through 180° and elevated to a maximum of 80°.