Powerplants

PW615F TURBOFANS:

  • The aircraft is powered by two Pratt & Whitney Canada PW615F turbofan engines mounted on the aft fuselage. The Pratt & Whitney PW615F is a two-spool, turbofan engine designed specifically for very light jets such as the Cessna Citation Mustang.
  • Each engine produces 1,460 lb (6.49 kN) of thrust at sea-level static conditions and is flat-rated up to 25 °C (77 °F). It has 2.8:1 bypass ratio, twin-spool design with 3 compressor and 2 turbine stages. A forced-mix exhaust improves fuel efficiency and reduces noise.
  • Engine indications and alerts are displayed on the multi-function display (MFD).
  • A continuous-loop fire detection and single-shot extinguishing system protect each engine nacelle.

TURBOFAN ENGINE BASICS:

  • A turbofan engine produces thrust from two main sources: the fan and the high-velocity exhaust. The fan works much like a propeller; drawing air in and accelerating it rearward, while the high-pressure exhaust gases exiting the engine create an equal and opposite reaction that propels the aircraft forward.

MAIN COMPONENTS

IGNITION SYSTEM:

  • Each engine is equipped with two igniters, powered by exciter boxes and governed by the FADEC. These igniters generate the high-energy sparks that ignite the fuel-air mixture inside the combustion chambers.
  • Under normal operation, they remain active only during engine start, ensuring rapid and reliable light-off.

FUEL/OIL HEAT EXCHANGER (FOHE):

  • Integrated into the Fuel Metering Unit (FMU), the FOHE uses hot engine oil to warm the incoming fuel. This dual-purpose system cools the oil, enhancing lubrication efficiency, while heating the fuel to eliminate the risk of ice formation caused by moisture within the fuel system.

STARTER-GENERATORS:

  • Each engine drives a 28-volt DC starter-generator mounted on the accessory gearbox (AGB). During engine start, it functions as a starter motor, drawing electrical power from the aircraft battery, an external ground power unit, or the opposite-side generator.
  • Once the engine accelerates past roughly 40% N₂, the unit automatically transitions to generator mode, supplying electrical power to the aircraft systems.

FADEC - FULL AUTHORITY DIGITAL ENGINE CONTROL

  • Dual-channel Full Authority Digital Engine Controls (FADECs) manage thrust, synchronization, and engine protection automatically. Throttle lever detents: takeoff, climb, cruise, and idle, provide consistent power settings for each flight phase.
  • The FADECs feature automatic relight, time-limited dispatch, and engine synchronization. Electrical power for the FADECs is normally supplied by the aircraft DC system, with engine-driven PMAs maintaining power if DC is lost.

THROTTLES:

  • Each engine is controlled by its own throttle lever located on the cockpit throttle quadrant, labeled “L THROTTLE” and “R THROTTLE.”
  • Each lever drives a dual-coil position sensor that converts throttle movement into precise electronic signals sent directly to the FADEC, allowing exact interpretation of the pilot’s power commands for each engine.
  • Each throttle lever features five distinct detent positions, defining the engine’s primary power settings:
    • TO (Takeoff):
      Delivers maximum rated thrust for takeoff and short-duration use only.
    • CLB (Climb):
      Commands maximum climb power, optimized for climb-out to cruise altitude.
    • CRU (Cruise):
      Sets maximum cruise power, intended for normal cruise operations.
    • IDLE:
      Provides minimum stable power for descent, landing, and ground operation. Idle thrust automatically adjusts based on flight status and anti-ice use.
    • CUTOFF:
      Fully shuts down the engine, closing fuel flow and disabling ignition.
  • Each detent enables the FADEC to interpret throttle position precisely, ensuring consistent and repeatable engine power control across all phases of flight.
  • The pilot may place each throttle in any detent or anywhere between IDLE and CRU. When positioned between detents, the FADEC interprets the exact throttle angle, calculates the corresponding commanded thrust, and precisely adjusts engine power to match the pilot’s intent.
  • A mechanical gate between the IDLE and CUTOFF detents prevents unintended engine shutdown or uncommanded power advance from the cutoff position. To transition a throttle across this gate, the pilot must deliberately lift or override the barrier, ensuring intentional movement only.

  • Each throttle handle’s outboard side houses two key controls:
    • Large slide switch for speedbrake deployment.
    • Small GO AROUND pushbutton that disengages the autopilot and instantly commands the flight director into go-around mode.

L / R IGNITION SWITCHES

Located on the lower instrument panel, left of the pilot’s control wheel, the Left and Right IGNITION switches each feature two positions: NORM and ON.

  • In NORM, ignition is fully FADEC-controlled; the system automatically powers the igniters during engine start or any detected flameout, initiating auto-relight as required.
  • When set to ON, the igniters operate continuously, providing uninterrupted ignition regardless of FADEC commands.

ENGINE STARTER SWITCHES

The ENGINE START controls are located on the tilt panel, to the left of the pilot’s control wheel, and consist of three illuminated, momentary pushbuttons—L ENGINE START, R ENGINE START, and DISENG.

  • L and R ENGINE START switches: When the engines are not running, pressing either switch energizes the corresponding starter motor, initiating engine start. These switches are active only when the respective engine is shut down.
  • DISENG switch: The starter-disengage switch manually opens the starter relay, allowing the pilot to stop starter operation if it remains engaged too long or if the engine accelerates beyond normal starter cutoff speed.

ENGINE SYNC SWITCH

Mounted on the throttle quadrant, just right of the right throttle’s CUTOFF position, the ENGINE SYNC switch controls the FADEC’s automatic engine synchronization feature. It has two positions: NORM and OFF.

  • OFF, engine synchronization is disabled.
  • NORM, the FADECs automatically align engine speeds during flight only when all of the operational conditions are met.

When active, the FADECs precisely match fan speeds between engines, ensuring smooth, synchronized operation.