Power Plant Installation (15.19) PDF

Power Plant Installation (15.19) Learning Objectives 15.19.1 Describe the con guration of power plant installations (Level 2). 2022-08-24 B1-15c Gas Turbine Engine Page 34 of 104 CASA Part 66 - Training Materials On...

Power Plant Installation (15.19) Learning Objectives 15.19.1 Describe the con guration of power plant installations (Level 2). 2022-08-24 B1-15c Gas Turbine Engine Page 34 of 104 CASA Part 66 - Training Materials Only  Power Plant Installations Firewalls and Fireproof Bulkheads Firewalls and reproof bulkheads are made of stainless steel, Inconel or titanium and provide protection against re, heat and corrosion. Flexible reproof silicone rubber seals surround them and form a snug t with the engine cowling. The rewall creates a barrier to hazardous gas, uids, excess heat or ame. Firewalls and re seals They must be constructed so that no hazardous quantity of air, uids or ame can pass from one compartment to another. All openings must be sealed with close- tting reproof grommets, bushings or rewall ttings. They are not made from aluminium, which would melt in a re. If a rewall is damaged, the engine compartment re containment capability may be compromised. 2022-08-24 B1-15c Gas Turbine Engine Page 35 of 104 CASA Part 66 - Training Materials Only  Firewalls There is also a stainless-steel rewall between the engine and the pylon to prevent the spread of re to the pylon. Passing through the rewall, exible lines for fuel and oil are made of reproof material. Rigid lines, cables and pulleys are also made from stainless steel. Firewalls 2022-08-24 B1-15c Gas Turbine Engine Page 36 of 104 CASA Part 66 - Training Materials Only  Cowlings To provide the power plant with a good aerodynamic pro le which blends smoothly into the aircraft structure, there is a requirement to enclose the engine with cowling. These compartments must be aerodynamically smooth and allow air to ow to, and around, the engines. These compartments must form a zone to contain re and noxious fumes and they also minimise engine noise. The area where the engine is housed, in multi-engine aircraft, is termed the nacelle. Nacelles may be attached to the wing or fuselage. The pylon is the interface between the engine and the airframe and is part of the nacelle. The engine is attached to the pylon, and the pylon is attached to the airframe. Panels which surround the engine are termed cowls. They form part of, and are attached to, the nacelle. Nacelles and cowlings 2022-08-24 B1-15c Gas Turbine Engine Page 37 of 104 CASA Part 66 - Training Materials Only  Nacelles and cowlings Engine nacelles may incorporate: Thrust reversers or reverser support structures for turbine engines Ram air ducting for external component cooling Vent inlets/outlets for air ow through the nacelle Fire detection and protection systems Electrical and instrumentation wiring Fluid lines such as fuel, oil, pneumatic and hydraulic. Engine cowlings minimise aerodynamic drag of the engine installation. They protect components within the cowl from the hostile ight environment, direct air ow as necessary for proper power plant operation and provide support functions ( re protection, over-pressure protection, drainage). 2022-08-24 B1-15c Gas Turbine Engine Page 38 of 104 CASA Part 66 - Training Materials Only  Cowls Turbojet cowlings are fairly simple structures with the cowls divided into inboard and outboard halves which are hinged at the top and latched at the bottom. Cowlings are tted with quick-release fasteners to enable easy access for servicing. Pratt and Whitney JT8D on a DC-9 aircraft 2022-08-24 B1-15c Gas Turbine Engine Page 39 of 104 CASA Part 66 - Training Materials Only  Turbofan engines have more robust cowling, usually divided into two or more sections. Turbofan cowls A common con guration of large, turbofan engine cowling with separate core cowls is: Fixed inlet cowl Opening fan cowls Opening reverser cowls Opening core cowls Fixed exhaust nozzle and cone (plug). Modern high-bypass fan engine reverser cowls often incorporate the core cowls and rewalls into one structure. To gain access to the engine core, the fan cowls and reverser cowls need to be open. The cowls are raised hydraulically by an external or onboard hand pump or by an electric pump. The exhaust nozzle and plug are power plant section components. These cowls are heavy, complex composite structures manufactured from carbon bre, aramid and glass bre with honeycomb cores. They are easily removed, but require slinging due to their heavy weight. Turbofan cowlings, like most, are hinged at the top and latched at the bottom. 2022-08-24 B1-15c Gas Turbine Engine Page 40 of 104 CASA Part 66 - Training Materials Only  Reverser cowls Reverser cowls may incorporate the following: Fan reverser blocker doors and mechanism Reverser lockout provisions Hydraulic plumbing Electrical harnesses Fire-detection loops Cowl latches. Thrust reverser cowl halves are very heavy composite structures. In some designs, they incorporate the fan duct, the core cowl and the following: Thrust reverser blocker doors, their actuating mechanisms, and plumbing Pneumatic ducting Fire-detection loops Cowl latches. Due to their heavy weight, reverser cowls require jacking to open and close them. They often include their own hydraulic actuators for raising and lowering. The hydraulic cowl jacks are part of the structure and often include an onboard jacking system using either a hand-operated or electric motor-driven hydraulic pump, or both. Some aircraft types require a separate workshop hand pump. 2022-08-24 B1-15c Gas Turbine Engine Page 41 of 104 CASA Part 66 - Training Materials Only  Reverser cowls Cowl stays must be tted when working under open cowls. Stays are normally permanent ttings stowed on the engine structure. Some jacks incorporate locking devices which prevent the jacks from accidentally collapsing. Never rely on the cowl jacking system to safely hold the cowls open. 2022-08-24 B1-15c Gas Turbine Engine Page 42 of 104 CASA Part 66 - Training Materials Only  Turboprop Engine Cowlings Turboprop engine cowlings range from simple to complex. They are hinged and latched assemblies. Like turbojet or turbofan engines, they can include air inlets and outlets for power plant components and for compartment or accessory cooling. Turboprop cowl 2022-08-24 B1-15c Gas Turbine Engine Page 43 of 104 CASA Part 66 - Training Materials Only  Acoustic Panels With regulators continually reducing the allowed noise levels coming from aircraft engines, one method engine manufacturers have introduced is installing noise absorbent liners around the inside walls of both the inlet and exhaust of most gas turbine-powered aircraft. The lining is constructed of a porous face sheeting that inhibits the motion of the sound waves. The depth of the cavity between the absorber and the solid backing is tuned to suppress the required part of the noise spectrum. In inlets, a common material is lightweight honeycomb composite. For added strength, the inner lining is made from perforated metal or stainless steel mesh. The disadvantages of using liners to reduce noise are the addition of weight and the increase in speci c fuel consumption caused by the increasing friction of the duct walls. The inner lining should be protected by a rubber mat when working inside the inlet. Ensure the mat is removed before rotating or running the engine. Acoustic linings Thermal re ecting and acoustic absorbing materials are used on the inside of cowlings. Radiant heat is re ected away from the underside of the structure. Noise is converted into heat by the acoustic component of the lining. 2022-08-24 B1-15c Gas Turbine Engine Page 44 of 104 CASA Part 66 - Training Materials Only  Thermal and acoustic linings 2022-08-24 B1-15c Gas Turbine Engine Page 45 of 104 CASA Part 66 - Training Materials Only  Engine Mounts Engine mounts vary widely in appearance and construction due to the differing engine positions on different aircraft. Many aircraft have engine attachments designed to allow for quick removal and installation of the complete engine and mount assembly. Structurally, the rear fuselage engine mounts to the reinforced fuselage frame. Engine mounts support the weight of the engine and transfer thrust to the aircraft. The turbojet and turbofan engines have forward and aft mounting points. Thrust-producing gas turbine engines develop little torque; however, sometimes special thrust links are used. The engine mounts are designed to accommodate expansion and contraction of the engine casings, both radially and axially. Front engine mount (737) Rear engine mount (737) 2022-08-24 B1-15c Gas Turbine Engine Page 46 of 104 CASA Part 66 - Training Materials Only  Engine mounts Cone Bolts Many engine mounts utilise cone bolt attachments. As the name implies, these bolts are conical in shape, which increases the contact area between the bolt and bolt hole and precisely centres the engine in the mounts. Other designs achieve these features using wedge- or tenon-shaped mount ttings. Cone bolts 2022-08-24 B1-15c Gas Turbine Engine Page 47 of 104 CASA Part 66 - Training Materials Only  Vibration Isolators Some turbojet, turbofan and APU mounts incorporate vibration isolators to isolate the aircraft structure from adverse engine vibrations. These engines have low vibration compared to turboprops. All turboprop and turboshaft engine mounts incorporate vibration isolators, which reduce the amount of engine and propeller vibration transferred into the airframe. Vibration isolators commonly use a rubber sandwich between the isolator body and its inner sleeve. Engine mount vibration isolators Small turboprop engine mounts are often tube structures made from chrome molybdenum steel alloy designed to support torque loadings produced at the propeller. 2022-08-24 B1-15c Gas Turbine Engine Page 48 of 104 CASA Part 66 - Training Materials Only  Turboprop engine mounts Hoses and Pipes Extensive hoses, pipes, tubing and ducting are part of an engine installation. They are all connected and supported in a very speci c way according to the manufacturer’s instructions. Failure to follow the correct procedure could lead to failure of the line. Rigid pipes are usually made from stainless steel, which is strong and corrosion-resistant. Make sure the pipes do not chafe against the engine structure, electrical wiring or control cables. If replacing a pipe, ensure that it is replaced with the same part number; a straight pipe cannot replace a pipe that has bends, even if it ts. The bends allow for strain on the pipe caused by temperature change and vibration. Flexible hoses are used in areas of high vibration or where stationary components need to be connected to a moving or vibrating component. When tting a hose, ensure it is not twisted or stretched tight between the two ttings and never exceed the minimum bend radius. Attach support clamps as speci ed in the maintenance manual to prevent rubbing with other engine components. 2022-08-24 B1-15c Gas Turbine Engine Page 49 of 104 CASA Part 66 - Training Materials Only  Electrical Harnesses The engine electrical system is fed through wiring bundled into a harness. The engine harness typically connects to the airframe electrical system at the pylon or nacelle with quick disconnect connectors. The harness is designed to be replaceable, either as a complete assembly or in sections as required. To prevent movement and damage during service, the electrical harnesses are supported by insulated clamps or clips and protected by uid- and heatproof conduits; the condition of clips and conduits is routinely checked to ensure serviceability. All harnesses are of sealed construction and have double shielding (over-braid and shielded wire) for EMI/lightning protection. Fire-detector harnesses in the core area are not fully sealed. On braid-shielded harnesses, a dedicated mechanical protection between the braid and the topcoat of wires is provided such that penetration of the shielding in wire topcoat is not possible. Electrical harness 2022-08-24 B1-15c Gas Turbine Engine Page 50 of 104 CASA Part 66 - Training Materials Only  Electrical Feeders Feeder cables provide electrical power from the engine-driven generators to the aircraft’s system. Feeders are normally large-section copper and/or aluminium cables. In some aircraft, the cables are one-piece installations from generator to aircraft bus. On larger aircraft, high-temperature copper is used from the generator to the pylon or rewall, then spliced into thicker aluminium cables to save weight over long lengths. Electrical feeder The electrical harness, hydraulic plumbing, feeders, fuel and air are connected at a central location. This permits easy disconnection and connection for engine changes and maintenance. 2022-08-24 B1-15c Gas Turbine Engine Page 51 of 104 CASA Part 66 - Training Materials Only  Connectors and feeders 2022-08-24 B1-15c Gas Turbine Engine Page 52 of 104 CASA Part 66 - Training Materials Only  Engine-Lifting and Transport Points Engine removal and installation may be carried out with the aid of a mobile crane or by hand- operated lever hoists attached to lifting beams temporarily tted to the nacelle/pylon. The lifting beams form part of the engine change tool kit. Also included in the tool kit is a dynamometer for each lever hoist. The purpose of the dynamometers is to gauge the weight of the engine and cradle. Knowing this combined weight allows maintenance personnel to determine when the correct preload has been applied to the engine mount–pylon mount mating surfaces before loosening or torquing the engine-mount bolts. The engine-lifting points are separate from the engine-mount points and support the weight of the engine and power plant for ground handling and transport only. They are not designed to support thrust loads. The lifting points are found on the strength locations of the engine, usually the fan case/LP compressor and the LP turbine casing. During engine test cell operation, the engine- or airframe-mount points are used to attach the engine to the test bed. Typically, lifting and cradle lugs or brackets are attached to the engine-lifting points, and are removed before ight. Lifting and transport points 2022-08-24 B1-15c Gas Turbine Engine Page 53 of 104 CASA Part 66 - Training Materials Only  Engine Lifting During engine removal, the engine transport cradle is lifted into position via a beam and hoist assemblies. The cradle is bolted to the engine-lifting points, and then the engine weight is taken up by the lever hoists until the load cells show that the full weight of the engine is supported. The engine weight at each of the lifting points can be found in the power plant section (ATA 71-10) of the Aircraft Maintenance Manual. The engine-mount bolts can be loosened only after the full engine weight is supported. Engine lifting During engine installation, the engine and its transport cradle are lifted into position. The engineers guide the engine into the pylon engine mounts. After contact with the mounts, the lever hoists are further raised until the load cell reading increases. This shows that the engine is in full contact with the pylon mounts. After the engine mount nuts and bolts are torqued, the cradle is lowered to the ground. The lifting tool kit may be then removed from the pylon. 2022-08-24 B1-15c Gas Turbine Engine Page 54 of 104 CASA Part 66 - Training Materials Only  Engine lifting setup Relevant Youtube link: Boeing 777 Engine Change (Video) 2022-08-24 B1-15c Gas Turbine Engine Page 55 of 104 CASA Part 66 - Training Materials Only  Engine Control Cables and Rods The major requirement of engine controls is that each engine must have its own individual means of starting and power change. Thrust or power levers typically move a cable run which is connected directly to the fuel control unit (FCU) at the engine. B737 power levers Each engine control linkages transmit command inputs from the cockpit to the FCU. These command inputs may be: Engine start and shutdown Thrust or power changes Reverse thrust selection. The throttle and High-Pressure Shut-Off Valve often operate micro-switches. Throttle switches may operate the following: Auto-throttle Bleed air supply Take-off con guration warning. High-Pressure Shut-Off Valve switches may be used to initiate ignition when the start lever is moved to START/OPEN. 2022-08-24 B1-15c Gas Turbine Engine Page 56 of 104 CASA Part 66 - Training Materials Only  F-28 engine controls Most engine control levers are mounted in a central pedestal in the cockpit. These levers transfer linear motion into rotary motion. On older aircraft, the lever movement is typically transmitted via chain and sprocket or control rods to the cable quadrant. The example below shows the engine controls movement transmitted in this manner. 2022-08-24 B1-15c Gas Turbine Engine Page 57 of 104 CASA Part 66 - Training Materials Only  Engine start and power levers Modern aircraft engine control systems supply manual and automatic inputs to operate the engine and consist of: Forward Thrust Lever (Throttle) The Thrust Lever Resolver is used to enter input into the Electronic Engine Control (EEC) to control the engine. Start Lever The start lever opens the high-pressure fuel shut-off valve and initiates ignition. Reverse Thrust Lever The Reverse Thrust Interlock solenoid limits the range of motion of the reverse thrust lever. This prevents the thrust going above idle until the thrust reverse translating cowl is near the fully deployed position. 2022-08-24 B1-15c Gas Turbine Engine Page 58 of 104 CASA Part 66 - Training Materials Only  Thrust levers in a Boeing 737 2022-08-24 B1-15c Gas Turbine Engine Page 59 of 104 CASA Part 66 - Training Materials Only  Drains The drain and vent system is divided into two parts: one which retains drained uids until expelled during ight (reservoir), and one which discharges uid directly overboard through the cowl or nacelle mast drain. The drain mast protrudes through the cowl doors into the airstream. Except in the combustor drain, during normal operation, fuel, oil or hydraulic uid should not be present in the drain line outlets. Although leaks are not desirable, some leakage is allowed. Limits, given as drips per minute, can be found in the maintenance manuals. Sometimes placards, adjacent to the drain outlet, are provided to identify the origin of any leaks. On modern aircraft, engine and nacelle drains are also centrally located. Drains are provided for uid-handling components as well as for the nacelle/pylon and the cowls. They include: Hydraulic pump case drains Fuel pump case drain CSD or IDG case drains Fuel line shroud drain VSV and bleed actuator drains Combustor drains Oil tank scupper. Drains 2022-08-24 B1-15c Gas Turbine Engine Page 60 of 104 CASA Part 66 - Training Materials Only  Drains 2022-08-24 B1-15c Gas Turbine Engine Page 61 of 104 CASA Part 66 - Training Materials Only