Beech 90 Series

  TTP B1-L3 ATA 76 Beech 90 Series B2-L1 Engine Control ENGINE CONTROLS - DESCRIPTION AND OPERATION 1. General  The engines incorporate a propeller reversing system comprising a single-acting, hydraulically operated propeller controlled by a propeller governor, and with overspeed governor back-up. The propeller governor combines the functions of a normal propeller governor (CSU), a reversing (Beta) valve and a power turbine governor (Nf) into a single unit. Note that terminology used in this section is of a general nature and may thus differ slightly from that used in specific airframe manufacturer’s manuals. Likewise, the percentages stated are generalized, and specific airframe installations may require different settings.  2. Description  B. Propeller Governor   The propeller governor (Ref. 61-20-00) performs three functions: Under normal flight conditions, the governor acts as a constant spe...

  TTP B1-L3 ATA 76 Beech 90 Series B2-L1 Engine Controls ENGINE CONTROLS - DESCRIPTION AND OPERATION 1. General  The engines incorporate a propeller reversing system comprising a single-acting, hydraulically operated propeller controlled by a propeller governor, and with overspeed governor back-up. The propeller governor combines the functions of a normal propeller governor (CSU), a reversing (Beta) valve and a power turbine governor (Nf) into a single unit. Note that terminology used in this section is of a general nature and may thus differ slightly from that used in specific airframe manufacturer’s manuals. Likewise, the percentages stated are generalized, and specific airframe installations may require different settings. 2. Description   A. Propeller  The engine is normally equipped with a three-bladed metal propeller (refer to Propeller Manufacturer’s Handbook), which is dowelled and bolted to ...

TTP B1-L3 ATA 75 Beech 90 Series B2-L1 Air Engine Air System 00  General 10 Engine Anti-icing 20 Accessory Cooling 30 Comp r essor Cont r ol 40    Indicating AIR SYSTEMS - DESCRIPTION AND OPERATION 1. General Three separate air systems are provided for the engine; one system for bearing compartment sealing, the second for cooling air, and the third for the compressor bleed valve and airframe services. 2. Description and Operation A. General Air pressure is utilized to seal the Nos. 1, 2 and 3 bearing compartments and to cool the compressor and power turbine disks and compressor turbine guide vanes. Pressure air is used in conjunction with labyrinth seals which consist of two separate parts. One part is in the form of a plain rotating surface, sometimes vented; the other part consists of a stationary circular seal with deep annular grooves in the bore. These parts together form an air seal when matched. The running clearance between each pair of rotating ...

TTP B1-L3 ATA 73 Beech 90 Series B2-L1 Engine Fuel and Control ENGINE FUEL AND CONTROL - DESCRIPTION AND OPERATION Description A. PT6A-21 Engines The fuel control system consists of an oil-to-fuel heater, fuel pump, fuel control unit, flow divider and dump or purge valve, dual fuel manifold with 14 simplex nozzles, fuel drain valves and interconnecting pneumatic sense lines. For purposes of description, the system also includes the power turbine governor. The fuel pump delivers fuel to the fuel control unit (FCU), which determines the correct fuel schedule for engine steady-state operation and acceleration. The flow divider supplies the metered fuel flow to the primary and secondary manifolds as required. Full propeller control during normal operation is provided by a governor which incorporates a propeller governor (CSU) section and a power turbine governor (Nf) section. The Nf governor section provides powe...

  TTP B1-L3 ATA 72 Beech 90 Series B2-L1 Engine Turbo Prop Engine T urbine/ T urbop r op 00     General 10     Reduction Gear and Shaft Section 20     Air Inlet Section 30     Comp r essor Section 40     Combustion Section 50     T urbine Section 60     Accessory Drives 70    Bypass Section The engine on the King Air C90A/B/GT aircraft is the PT6A-21 and is rated at 550-shaft horsep o w er (SHP). The engine on the C90GT/G T i aircraft is a PT6A-135A and is also rated to 550.   The nomenclature stands for: P—Propeller   T— T urbine   6—6th design series   A— T w o-stage reduction gearb o x   21 or 135A—The sequence number in the design series   The PT6 w as d e v eloped in 1958 for use in fi x ed- and rota r y-wing aircraft. The first ce r tificated engine ...