SYSTEMS OVERVIEW
POWER PLANT
The power plant comprises the engines and related installation, fire
detection and extinguishing system.
Engines
The helicopter is powered by two PT6C-67C turboshaft engines. Each
engine is installed in a separated fireproof area above the cabin roof and
supplies power to the drive system by means of a rotating shaft. The
engines are connected to the airframe by means of two attachment points on
the engine body and to the main gearbox by means of a tube and a gimbal
joint.
Air is supplied to the engine via individual, side facing air inlets. The engines
are started by a DC starter-generator.
Engine control is achieved via a control panel located in the cockpit and
manual back-up of the engine control via push-pull cables.
The engines are provided with torque sensing and matching.
Fire detection and extinguishing
The fire detection system consists of a continuous wire detector installed in
the powerplant fire zones, routed in a way that allows coverage of all critical
areas.
The fire extinguishing system consists of directional flow valves which allow
discharging the contents of one bottle while sealing the connection to the
other bottle and the subsequent discharge of the second bottle in the same
bay if required.
DRIVE SYSTEM
The drive system consists of the Main Rotor Drive System and the Tail Rotor
Drive System.
Main Rotor Drive System
The Main Rotor Drive System mainly consists of the Main Gearbox (MGB)
that is mounted on the roof of the cabin by means of four struts and an antitorque
device.
The MGB has three stages of reduction and includes a duplicated oil
lubrication system. It provides the attachment points for the rotor brake
coaxial with the tail rotor drive output.
The MGB drives three hydraulic pumps and other accessories.
Tail Rotor Drive System
The tail rotor drive system consists of three drive shaft driven by the MGB:
the Intermediate Gearbox IGB and the Tail Gearbox TGB, both oil splash
lubricated.
ROTORS
The rotor system consists of a Main Rotor (MR) and a tail Rotor (TR).
The main rotor is a five blades, fully articulated rotor.
The tail rotor is a four blades, fully articulated rotor.
HYDRAULIC POWER
The hydraulic power system consists of two independent circuits that supply
hydraulic fluid at a nominal working pressure of 3000 psi (207 bar). Both
hydraulic power system circuits supply the hydraulic power necessary to
operate the flight control servo-actuators and the landing gear.
For ground test and malfunction condition, a shut-off valve allows to shut-off
the flight controls circuits.
For safety reasons, another shut-off valve allows to shut the landing gear
circuits off, increasing the survivability of the flight control functions.
Hydraulic power to the landing gear actuators is used to extend and retract
the main and the nose landing gears.
The main and nose landing gear are maintained in UP position by the
hydraulic pressure (no mechanical uplocks are provided). The extended
DOWN position is maintained with a mechanical locks in the main and nose
gear actuators.
LANDING GEAR
The AW139 helicopter is provided with a fully retractable, nose tricycle
landing gear equipped with shock absorbers.