The first American designed and built turboprop powered commercial aircraft, the Lockheed Electra, will go into airline use in 1958 with the Allison ‘power package’. This consists of the 3750 horsepower 501-D13 turboprop engine and the Aeroproducts ‘606’ turbo-propeller. The changes from the military T56-A-l engine are reviewed and the propeller features, such as the hollow steel ribbed blades and self-contained hydraulic system and regulator, described in some detail.
It is disclosed for the first time that the propeller and engine reduction gear and other units as initially delivered will handle a higher rated power section, the -Dl5. In addition the -D13 power sections can be brought up to later ratings at fixed cost during overhaul when the new model goes into production.
Control and safety features of the power package insure normal functioning of both engine and propeller in case of complete electrical system failure. Provisions are made for multiple hydro-mechanical and additional electrical protection against overspeeding and high negative thrust.
How the turbo-prop powerplant contributes importantly to an advanced aircraft is discussed with reference to improved passenger comfort, reduced noise around the airport, higher nacelle efficiency and a major reduction in weight. The nacelle weight saving alone is over 5 tons on the Electra, compared to the latest reciprocating engine type, while takeoff and altitude powers are increased and nacelle drag reduced, due to the very light weight and efficiency of the Allison ‘501’ engine.