The power plant converts chemical potential energy (fuel) to kinetic mechanical energy necessary to operate the helicopter.
It consists of the systems and the components that follow:
Engine
Cowlings
Mounts
Fire seals
Air intake
Engine drains
Engine
The engine is a ARRIUS 2R is a free turbine turbo-shaft engine which is rated to provide 505.56 shaft horsepower (shp) (377 kW) for takeoff and 460 shp (343 kW) for maximum continuous operations. To respect main transmission limits, the maximum allowed shaft horsepower input to the main transmission is 475 shp (354 kW) for takeoff power and 428 shp (319 kW) for maximum continuous operations. The engine incorporates a Dual Channel Full Authority Digital Engine Control (FADEC) with an Auxiliary Control Unit (ACU) back-up system.
Cowlings
The cowlings provide inspection and maintenance access, protect the engine compartment from the environment, and help to reduce aerodynamic drag by their streamline design with the surrounding aircraft structure. They consist of the forward engine cowling and the aft engine cowling.
Forward engine cowling
The forward engine cowling is constructed out of aluminum alloy. Captive fasteners around its periphery serve to secure it to the surrounding structure. When removed, it provides access to the forward section of the engine as well as the forward section of the freewheel unit, Reduction Gearbox (RGB), rotor brake disc and calipers (optional kit), Kaflex driveshaft and starter generator. The cowling incorporates a hinged access door on the right side as well as venting to allow air movement through the engine compartment. The hinged access door is secured with quarter turn wing nut fasteners.
Aft engine cowling
The aft engine cowling is constructed out of aluminum alloy. Captive fasteners around its periphery serve to secure it to the surrounding structure. When removed, it provides access to the aft section of the engine, as well as the aft section of the freewheel unit, the # 1 tail rotor driveshaft and the air conditioning compressor (optional kit). The cowling incorporates a hinged access door on the right side as well as venting to allow air movement through the engine compartment. The hinged access door is secured with quarter turn wing nut fasteners.
Mounts
The mounts secure the engine to the helicopter structure, hold the engine secure to allow transmission of power to the drivetrain, and prevent deflection that can cause damage to the drivetrain. They consist of the components that follow:
Forward left mount
The forward left mount consists of an assembly of a monopod link and a bipod link machined from steel. The monopod link is bolted into the outboard aft leg of the bipod link. A spherical bearing located in the vertex of the bipod link serves as the attach point through which the mount is bolted to the left engine trunnion. The three legs of the monopod and bipod assembly are secured on top of the horizontal firewall via welded tabs on the aircraft structural truss assembly. It is designed to be the fixed point of the engine and to support loads from all directions.
Forward right mount
The forward right mount is a bipod link machined from steel. It has three spherical bearings that serve as attachment points. One of the three spherical bearings is in the vertex of the bipod link, and is where the link is bolted to the right engine trunnion. There is spherical bearing at the bottom of each of the two legs of the bipod link, and is where the link is secured on top of the horizontal firewall via welded tabs on the aircraft structural truss assembly.
Aft mount
The aft mount consists of an assembly of a monopod link and a bipod link machined from steel. The clevis end of the monopod link is bolted to the vertex of the bipod link. The other end of the monopod link with the spherical bearing is bolted to a clevis designed on the aft hot section of the engine. There are spherical bearings at each end of the bipod link where it is secured on top of the horizontal firewall via welded tabs on the aircraft structural truss assembly.
Fire seals
The fire seals are riveted assemblies constructed out of titanium sheet. Their purpose is to contain the relatively high temperature of the operating engine inside the engine compartment and protect the structure of the helicopter in the event of a fire. They consist of the components that follow:
Forward vertical firewall
The forward vertical firewall is located at the front of the engine compartment and isolates the engine compartment from the transmission compartment. The bottom of the forward vertical firewall shares a boundary with the main driveshaft access panel and the forward end of the horizontal firewall. Portions of the left and right hand transmission cowlings and the forward engine cowling fasten into the top of the forward vertical firewall. The engine oil tank mounts to the forward left hand side of the forward vertical firewall, and it has provisions for the plumbing fluids and electrical harnesses to transfer through it as well.
Main driveshaft access panel
The main driveshaft access panel is located at the bottom center of the forward vertical firewall. It is designed with an elliptical cutout section in the bottom center of the panel to allow clearance for the main rotor gearbox input driveshaft to pass beneath it. It permits access to the main driveshaft and the aft attaching points of the Liquid Inertia Vibration Eliminator (LIVE) mount units to the truss assembly when it is removed. The left and right hand firewall doghouse portions of the panel assembly are designed to be independently removed.
Left firewall
The left firewall is attached along the span of the left-hand side of the horizontal firewall. Portions of the left-hand aft body skin panel, forward engine cowl, inlet barrier filter retainer, and the aft engine cowl assembly all share some combination of attaching boundaries together along the left firewall.
Right firewall
The right firewall is attached along the span of the right-hand side of the horizontal firewall. Portions of the right-hand aft body skin panel, forward engine cowl, inlet barrier filter retainer, and the aft engine cowl assembly all share some combination of attaching boundaries together along the left firewall.
Aft vertical firewall
The aft vertical firewall is located aft of the engine and forward of the oil cooler blower assembly. It attaches along the span of the aft side of the horizontal firewall. This firewall has a section cut out of it to permit the engine exhaust pipe to pass through it. It also has a provision where the fanshaft assembly is designed to to go through it as well. Portions of the aft engine cowl assembly and the aft fairing assembly are fastened along the periphery of the aft vertical firewall.
Horizontal firewall
The horizontal firewall is located below the engine and makes up the floor of the engine compartment between the forward vertical firewall and the aft vertical firewall. It is supported from underneath by the aircraft's mechanical truss assembly, and has a integrated tub area to collect residual fluids that collect on the engine compartment floor. The horizontal firewall has provisions for the plumbing of fluids to transfer through it as well as locations for the engine mount attach points. All of the firewalls in the engine compartment share some boundary with the horizontal firewall.
Aft horizontal firewall
The aft horizontal firewall is attached to the aft side of the aft vertical firewall. It is located below the engine exhaust pipe, and supported from underneath via a support bracket bolted to the upper side of the blower assembly.
Air intake
The air intake channels external ambient air from the aircraft's operating environment, and directs the air into the engine's air inlet necessary for the engine's operation. The air intake is located between the forward and aft engine cowlings. The air intake incorporates an Inlet Barrier Filter (IBF) that is designed to filter air entering the engine air inlet. The IBF protects the engine from foreign objects, dust, sand, and ice entering the engine air inlet during both flight and ground operating conditions. The air intake consists of the components that follow:
Left intake assembly half
The left intake assembly half is a riveted assembly constructed out of titanium sheet. It serves to house the left hand section of the IBF, provides a mounting point for the IBF pressure switch, provides a mounting location on both its forward and aft sides for an engine fire detection sensor assembly, has an integrated flapper valve on its bottom side, and is designed to allow the engine oil breather tube to pass through it.
Right intake assembly half
The right intake assembly half is a riveted assembly constructed out of titanium sheet. It serves to house the right hand section of the IBF, provides a mounting point for an engine fire detection sensor on its aft side, has an integrated flapper valve on its bottom side, and is designed to allow the engine oil breather tube to pass through it.
Operation
The assembly of the left and the right intake assembly halves is enclosed in the IBF and provides a plenum of clean air for the engine air inlet.
Engine drains
The engine drains provide plumbing to evacuate liquids such as oil, fuel, and water from the engine and engine compartment. Evacuating liquids is needed to prevent over pressurization of components, pooling of fluids on the surrounding structure, and safely returning unused fuel to the fuel tank. They consist of the components that follow:
Oil tank drain
The oil tank drain prevents the accumulation of water and oil in the oil tank scupper by letting the water and oil drain away from the helicopter. It consists of a flexible tube secured to the oil tank scupper at the top end. It is secured to the structure for its entire length and the bottom end exits through a hole in the bottom of the aft fuselage.
Forward drain
The forward drain prevents the accumulation of water and oil in the tub of the horizontal firewall by letting the water and oil drain away from the helicopter. It consists of a flexible tube connected to a fitting under the horizontal firewall at the top end. It is secured to the structure for its entire length and the bottom end exits through a hole in the bottom of the aft fuselage.
Aft drains
The aft drains prevent the accumulation of water and oil in the tub of the horizontal firewall by letting the water and oil drain away from the helicopter. They consist of flexible tubes arranged in a Y configuration with the two top ends connected to fittings under the horizontal firewall. A tee fitting joins the two top tubes where the bottom tube is secured to the structure for its entire length and the bottom end exits through a hole in the bottom of the aft fuselage.
Vent lines
The vent lines prevent the pressurization of the oil tank assembly and the engine RGB that could damage oil seals and vents gases overboard through the exhaust tube. They consist of flexible hoses, fittings, and a rigid tube. One line is routed from a vent on the oil tank assembly through a fitting on the forward vertical firewall to a fitting on the engine RGB. The other line is routed from another fitting on top of the engine RGB through the intake assembly to a tube on the exhaust collector/nozzle assembly. Refer to Oil for details on the oil tank assembly and to Exhaust for details on the exhaust collector/nozzle assembly.
Engine drain lines, engine-to-cross fitting
The engine drain lines, engine-to-cross fitting drain unburnt fuel from the engine to a cross fitting. They consist of three flexible hoses connected to three fittings and tubes of the engine.
Engine drain cross fitting
The engine drain cross fitting receives the drained fuel from the three flexible hoses of the engine-to-cross fitting drain lines and lets the fuel flow through a single flexible hose of the cross fitting-to-fuel tank drain line. It consists of a cross fitting connected to an adapter fitting which is installed on the horizontal firewall.
Engine drain line, cross fitting-to-fuel tank
The engine drain line, cross fitting-to-fuel tank transmits the drained fuel from the engine drain cross fitting to the fuel tank. It consists of a flexible hose that is secured to the structure.
Fitting, engine drain line
The engine drain line fitting is the mounting location for the engine drain line. It is located inboard on the expansion plate. Refer to Fuel Storge for details on the expansion plate.
Operation
The expansion space at the top of the oil tank assembly is vented to the top of the engine RGB, which is vented to the atmosphere through the exhaust tube. Gases that can form inside the oil tank assembly and the engine RGB are vented overboard by the vacuum generated by the adapter on the exhaust tube.
