The Heavy Lift Aircraft was designed with the capability to carry an external payload of 37,500 lbs 300 nm from the Sea Base to the Objective, offload its payload, and return to the Sea Base without refueling. Additionally, the Heavy Lift Aircraft was designed to carry an internal load of 20,000 lbs for 300 nm, offload, and return to the Sea Base without refueling. The Heavy Lift Aircraft combat survivability was also addressed in the SEI-3 report. At the time, the primary threat to the troop and material transport aircraft was considered to be shoulder-fired, infrared-guided surface-to-air missiles (SAM) with contact warheads, and small caliber (7.62mm and 12.7mm), armor-piercing, anti-aircraft artillery (AAA) platforms. Based on this, the aircraft was designed to be capable of sustained operations in a threat environment consisting of man-portable SAMs, small caliber AAA, and small arms fire with minimum impact on mission capability.