In the 1960s, the CH-47A Chinook replaced obsolescent piston-engined helicopters in the medium transport class for the U.S. Army. The CH-47A Chinook has a payload of more than seven tons, and can carry 33 fully equipped troops of 24 litter patients and attendants. The CH-47A cruises at 150 miles an hour (240 km/h) and is powered by two Lycoming T-55 gas-turbine engines. The Chinook has a straight-in rear loading ramp for personnel, vehicles or cargo and can accommodate any component of the Pershing missile system. The first Chinook was delivered to the Army August 9, 1962.