[1][3][4] There were three proposed variants; each had fuel capacity for only two target runs, after which the pilot would have been required to glide without power to a landing on underbelly skids.

All these proposals exploited the Luftwaffe's concept of "gaining a tactical advantage by placing excessive stress on the man in the cockpit (the German pilot)".

[5] The g-forces envisioned in these proposals were feasible for aircraft structures but exceeded human capabilities in a normal sitting position.

The designers attempted to alleviate this constraint by placing the pilot in the prone position, which increased the sustainable g-force limit.

[5] The E.381 began in a proposal from Arado Flugzeugwerke to the Air Ministry for a parasite fighter, carried underneath another aircraft, to destroy Allied bombers.

[5] None of the designs were ever completed due to its cancellation, though some wooden airframes and a single mockup were constructed in 1944 to provide prone-position training for pilots.

In the dorsal area (at the wing mounts), the fuselage humped to accommodate a blister for a single MK 108 30 mm (1.2 in) cannon and 60 (other writers say 45) rounds.

[5][6] The Walter HWK 109-509A[5] single-chamber rocket engine was mounted beneath the aft fuselage, which also carried a twin-fin empennage and the drogue parachute housing.