 Early work by the company included the development of prototype aircraft for other manufacturers; such as the Twin Comanche prototype developed for Piper Aircraft during 1962 and the development of several research helicopters for the Bell Helicopter Company, work which led to the HueyCobra.The company also developed modifications of other designs, an activity Ed Swearingen had been involved in prior to his forming Swearingen Aircraft.These modification programs included the Excalibur 800 conversion of the Beechcraft Twin Bonanza, (because the combined output of its two Lycoming IO-720 engines was 800 horsepower); airframe improvements included modifying the cabin to allow entry via an airstair instead of over the RH wing to a door, and landing gear doors that fully enclosed the wheels when retracted.