The McDonnell Douglas DC-9 is a twin engine turbofan, short to medium range jetliner. It is capable of serving smaller communities with shorter runways and a minimum of ground equipment for short 20 to 30 minute turnaround times.
Control surfaces for roll and pitch are operated by mechanical linkage from the cockpit control wheels to the respective control tabs which in turn deflect the ailerons and elevator. Hydraulic power augments the elevator down force when the aircraft is at high angles of attack to assure a nose down capability. The rudder is hydraulically powered but with manual reversion using a control tab similar to the ailerons and elevators. Hydraulic spoilers on top of the wings assist the ailerons for roll control and are also used as speed brakes in flight and as ground spoilers to reduce lift during landing roll. Hydraulically powered wing leading edge slats and trailing edge flaps shorten takeoff and landing distance.
The aircraft is air-conditioned and pressurized for comfort up to 35,000 feet. A passenger forward entrance retractable stair is provided along with an onboard auxiliary power unit (APU) gas turbine engine for standalone electrical power, air-conditioning and engine start on the ground as well as backup electrical power in-flight. This, along with capability to manually load baggage into the cargo compartments without any equipment, makes this aircraft ideal for smaller station operations and charters.