CASA B1-15c Gas Turbine Engine Maintenance PDF

MODULE 15 Category B1.1 and B1.3 Licences CASA B1-15c Gas Turbine Engine Maintenance Copyright © 2020 Aviation Australia All rights reserved. No part of this document may be reproduced, transferred, sold or otherwise disposed of, without the written permission of Aviation Australia. CONTROLLED DOCUM...

MODULE 15 Category B1.1 and B1.3 Licences CASA B1-15c Gas Turbine Engine Maintenance Copyright © 2020 Aviation Australia All rights reserved. No part of this document may be reproduced, transferred, sold or otherwise disposed of, without the written permission of Aviation Australia. CONTROLLED DOCUMENT 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 2 of 104 Knowledge Levels Category A, B1, B2 and C Aircraft Maintenance Licence Basic knowledge for categories A, B1 and B2 are indicated by the allocation of knowledge levels indicators (1, 2 or 3) against each applicable subject. Category C applicants must meet either the category B1 or the category B2 basic knowledge levels. The knowledge level indicators are defined as follows: LEVEL 1 Objectives: The applicant should be familiar with the basic elements of the subject. The applicant should be able to give a simple description of the whole subject, using common words and examples. The applicant should be able to use typical terms. LEVEL 2 A general knowledge of the theoretical and practical aspects of the subject. An ability to apply that knowledge. Objectives: The applicant should be able to understand the theoretical fundamentals of the subject. The applicant should be able to give a general description of the subject using, as appropriate, typical examples. The applicant should be able to use mathematical formulae in conjunction with physical laws describing the subject. The applicant should be able to read and understand sketches, drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using detailed procedures. LEVEL 3 A detailed knowledge of the theoretical and practical aspects of the subject. A capacity to combine and apply the separate elements of knowledge in a logical and comprehensive manner. Objectives: The applicant should know the theory of the subject and interrelationships with other subjects. The applicant should be able to give a detailed description of the subject using theoretical fundamentals and specific examples. The applicant should understand and be able to use mathematical formulae related to the subject. The applicant should be able to read, understand and prepare sketches, simple drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using manufacturer's instructions. The applicant should be able to interpret results from various sources and measurements and apply corrective action where appropriate. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 3 of 104 Table of Contents Auxiliary Power Units (15.18) Learning Objectives 7 7 Auxiliary Power Units (APUs) 8 Introduction to Auxiliary Power Units 8 APU Control Functions 12 APU Control Units 14 Electronic Speed-Sensing Unit 15 Electronic Control Box 16 Producing Bleed Air 19 APU Cooling 25 APU Fuel System 25 Fuel Line Shrouds 26 Starting the APU 27 Stopping the APU 28 Automatic Shutdown 30 Ground-Running Precautions 31 APU Ground-Run Test Power Plant Installation (15.19) Learning Objectives 32 Power Plant Installations 35 34 34 Firewalls and Fireproof Bulkheads 35 Cowlings 36 Acoustic Panels 43 Engine Mounts 45 Hoses and Pipes 49 Electrical Harnesses 49 Engine-Lifting and Transport Points 52 Engine Control Cables and Rods 55 Drains Engine Monitoring and Ground Operations (15.21) 59 62 Learning Objectives 62 Maintenance Engine Runs 63 2022-08-24 Purpose of Maintenance Engine Runs 63 Preparation for Engine Running 63 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 4 of 104 Engine Running 71 Factors Affecting Engine Performance 77 Introduction to Factors Affecting Engine Performance 77 Design Factors 77 Engine RPM 77 Power Limiting 78 Adjustments 78 Performance Checks 78 Trend Monitoring 80 Purpose of Trend Monitoring 80 Performance Parameters 80 Graphical Presentation 81 Spectrometric Oil Analysis Program 82 Vibration Monitoring 84 Borescope Inspection 84 Damage Inspections 88 Damage Inspection Precautions 88 Fan Blades 88 Blade Shingling 88 Inlet Guide Vanes 89 Compressor Blades 90 Turbine Nozzle Guide Vanes and Blades 91 Exhaust Section 92 Compressor Washing 93 Compressor Washing and Cleaning 93 Foreign Object Damage Engine Storage and Preservation (15.22) 94 95 Learning Objectives 95 Engine Storage and Preservation 96 2022-08-24 Purpose of Engine Storage and Preservation 96 Preservation 97 Fuel System Preservation 98 Oil System Preservation 98 Storage Containers 99 Inspection of Stored Engines 101 Engine Transport 101 De-Preservation 102 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 5 of 104 Accessory De-Preservation 103 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 6 of 104 Auxiliary Power Units (15.18) Learning Objectives 15.18.1 Summarise the purpose and the operational benefits of an aircraft having an APU (Level 2). 15.18.2 Describe key APU installation features, sub-systems and components and identify how each component contributes to the operation of the APU (Level 2). 15.18.3 Describe the purpose, configuration and operation of APU protective systems (Level 2). 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 7 of 104 Auxiliary Power Units (APUs) Introduction to Auxiliary Power Units Turbine-powered transport aircraft require large amounts of power for starting and operation. For example, substantial electrical power is sometimes needed for passenger amenities such as lighting, entertainment and food preparation. In addition, engine starting and ground air-conditioning require a high-volume pneumatic air source that frequently is not available at remote airports. To meet these demands for ground power when the aircraft engines are not running, most large turbine aircraft are equipped with auxiliary power units, or APUs. Common APU location A typical APU consists of a small turbine power plant driving an electric generator identical to those mounted on the aircraft’s engines. In addition, an APU’s compressor or a separate load compressor supplies bleed air to the aircraft’s pneumatic system for heating, cooling, anti-ice and engine starting. As with any other gas turbine engine, bleed air loads generally place the greatest demand on an APU. A typical small APU uses a single centrifugal compressor to supply air for combustion and bleed air. However, axial flow and centri-axial flow configurations are also used in larger units. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 8 of 104 APU drives an AC generator to provide electrical power An APU is typically started using its own electric starter motor and aircraft battery power. With fuel supplied from one of the aircraft’s main fuel tanks, an APU can start, provide electric power, heat or cool the cabin, and start the main engines without the aid of any ground or portable power source. APUs are designed as constant-speed engines with no manual control. Once started, APUs run at a rated speed regardless of the electrical or pneumatic load demands. They have their own automatic control and safety devices and their own fire protection system. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 9 of 104 Typical APU tail installation Auxiliary Power Unit (APU) 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 10 of 104 Single compressor and single turbine Fuel flow is adjusted depending on demand to keep the APU running at constant speed. A typical system utilising mechanical and pneumatic control is shown. However, modern APU control systems are electronic. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 11 of 104 APU control systems Fuel for APU operation is drawn from aircraft fuel tanks. Typically, a fuel pump is dedicated to supplying the APU. Fuel pump capacity exceeds the flow required for APU operation, so it is necessary to bypass some of the fuel. Once APU start is initiated, a fuel solenoid opens when oil pressure is sensed and at an engine rpm determined by an electronic control unit. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 12 of 104 APU Control Functions Automatic control of the APU governs two functions: Engine rpm Exhaust Gas Temperature (EGT). The fuel control unit (FCU) governor is a series of flyweights held in place by a spring. The position of the flyweights determines the position of the fuel metering valve, shown at the bottom of the governor unit. The governor controls the scheduling of fuel from 95-100% RPM. The position of the valve determines how much fuel bypasses out of the governor back to the pump inlet and how much fuel flows through the solenoid to the APU combustor. As rpm increases, the flyweights fly outwards under centrifugal force. As they do this, the linkages are forced against the spring and the valve opens. In this way, the flyweight governor controls and limits the rpm and progressively schedules fuel when the APU is starting. When the APU is running on-speed, the valve position ensures equilibrium between fuel flowing into the FCU and fuel diverted back to the fuel pump inlet, maintaining rpm. The acceleration limiter functions as a pressure-regulating valve whose setting is varied by the Compressor Discharge Pressure (CDP). CDP and spring pressure hold the governor fuel bypass valve closed. The acceleration limiter controls the fuel flow to ensure the correct quantity to accelerate the engine. As the engine accelerates, the fuel flow is constantly increasing. After the engine lights off during the start sequence, CDP then varies with the airflow, rpm and ambient conditions and gives a reasonable indication of the amount of fuel necessary to manage the acceleration.The acceleration limiter controls the scheduling of fuel from 0-95% RPM. APU fuel control unit 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 13 of 104 APU Over-Temperature Protection System EGT is limited by a ground-adjustable pneumatic thermostat valve positioned in the exhaust duct. If the exhaust temperature exceeds a certain value, the thermostat valve opens, bleeding off some pressurised air from the acceleration limiter. This opens the acceleration limiter, with the result that the fuel flow to the APU decreases and lowers the EGT. The thermostat is a temperature-actuated air valve normally closed and connected pneumatically to the acceleration limiter. Pneumatic thermostat valve 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 14 of 104 APU Control Units There are two broad types of APU Control Units: Electronic speed-sensing unit Electronic Control Box or Unit (ECB). Electronic speed-sensing units provide start sequencing, fault monitoring and protection while a conventional hydro-pneumatic fuel control governs the loaded and unloaded engine EGT and rpm. Full Authority Digital Engine Control (FADEC) uses an ECB which automatically controls all functions, including speed governing. Engine Control Box (ECB) 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 15 of 104 Electronic Speed-Sensing Unit The electronic speed-sensing unit controls and monitors the following sequence: Regulates starter motor operation and cut-off Opens the APU fuel fire shut-off valve Opens the fuel solenoid valve to start Energises and de-energises the ignition cycle Opens the surge bleed valve Records start cycles or runtime Arms the bleed air system. APU on-speed governing is controlled by the hydro-pneumatic fuel control unit. APU EGT is controlled by the pneumatic thermostat valve. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 16 of 104 Electronic Control Box Modern APU controllers are commonly referred to as the auxiliary power unit’s Electronic Control Box, or ECB. The ECB is a full-authority, microprocessor-based digital controller. Once a start is initiated, all further control of the APU is fully automatic and is provided by the ECB. Specifically, the ECB controls the engine starting sequence, acceleration, governed speed operation, operation within temperature limits, inlet guide vane position, surge valve position, and both normal and protective shutdown sequences. In addition to controlling the APU, the ECB has an integral BITE (Built-In Test Equipment) capability specifically incorporated to shorten diagnostic operations involved in troubleshooting and corrective maintenance. The ECB continuously monitors and stores shutdown fault information along with failures of certain Line Replaceable Units (LRUs). Fault information is stored in the box for later interrogation, and the box also provides cockpit fault display and diagnostic information from a central maintenance computer interface. ECAM APU screen 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 17 of 104 Typical Operation When the APU master switch is selected to ON, power is supplied to the electronic speed-sensing unit (APU control box), an indicator ‘APU’ light illuminates and the APU air intake door opens. When the intake door is fully open, power is supplied to the start circuit. After the START button is momentarily pressed or the start switch is moved, the start control relay is energised and remains energised. The electronic speed-sensing unit controls and monitors the following sequence: A light in the START button comes on and the APU starter motor cranks the APU. The APU fuel fire shut-off valve opens. The fuel solenoid valve opens at 10% rpm. Ignition is energised. The anti-surge bleed valve opens. At 45%, the starter is de-energised. At 95%, ignition is de-energised. The hour meter starts recording APU runtime. The bleed air system is armed. Automatic protection circuits are installed to shut down the APU in case of fire, low oil pressure or overspeed. In case of fire, the fire shut-off relay changes over, interrupting the power to the main relay. The result is the control circuit de-energises, the fuel valves close and the APU stops. The air intake door also closes, and automatic fire extinguishing takes place. In case of low oil pressure above 45% speed, the oil pressure switch signals the electronic speedsensing unit to change over and de-energises the turbine hold relay. The result is both fuel valves close and the APU stops. In case of an overspeed, the overspeed circuit closes the fuel valves and stops the APU. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 18 of 104 Typical APU control Producing Bleed Air There are two basic methods of producing compressed (bleed) air from an APU: Bleed air is taken from the APU compressor (left image below). Bleed air is taken from a separate load compressor (right image below). The load compressor is a separate compressor used only for generating bleed air for the aircraft systems. It is typically directly coupled on a common shaft to the gas generator compressor. Bleed air 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 19 of 104 There are two bleed air valves: Load control valve Surge bleed valve. The load control valve is a Pressure-Regulating and Shut-Off Valve. It controls the passage and pressure of compressed air to the aircraft pneumatic system. The surge bleed valve (sometimes also called a surge control valve) protects the APU compressor from stalls and surges that may occur as a result of bleed air being taken off the compressor. With the APU running, these two bleed valve positions oppose one another. That is, when one valve is open, the other valve is closed. Load control valve - open (LHS) - closed (RHS) When the flight deck APU bleed air switch is in the OFF position, the load control valve is closed and the surge bleed valve is open. Switching within the load control valve signals the surge bleed valve. If the load control valve fails to open when bleed air is selected, the surge valve remains open. The surge bleed valve is open when bleed air is not selected ON to ‘relieve’ the compressor, reducing the chance of compressor surge and reducing EGT. The surge bleed valve also offloads the APU compressor during APU start. As soon as APU bleed air is selected ON, the surge bleed valve closes. Typically, the load control valve is designed to fail in the CLOSED position. This is termed ‘fail-safe closed’. Load Control Valve With the APU running at or near 100% (on-speed condition), the bleed air system is now armed and available. Most cockpits have a bleed air switch for all sources of pneumatic power, i.e. engines, APU and external ground pneumatic power. Placing the APU bleed air switch in the cockpit to ON opens the APU load control valve and closes the surge bleed valve, if fitted. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 20 of 104 When the APU bleed is selected ON, the solenoid valve energises and retracts the ball assembly and allows compressor discharge pressure (CDP; red) to act on the butterfly actuator. This moves the butterfly valve towards OPEN. Whenever the APU is running, air pressure is acting on the rate control diaphragm (purple), and when the valve starts to open, this pressure decreases as air flows through the aircraft ducting. This has the effect of allowing the poppet valve to raise and allow some CDP to escape. Now there is less pressure acting on top of the butterfly actuator, slowing its opening speed. The speed with which the bleed air pressure dissipates from the rate control diaphragm is governed by the rate adjustment screw, and this controls the speed at which the butterfly opens. When bleed air is selected ON, the pneumatic thermostat control valve closes, which switches the pneumatic thermostat connection to the butterfly actuator valve (previously it was connected to the acceleration limiter for start). The pneumatic thermostat valve ensures that EGT is held within limits when air is bled off the compressor. If a high EGT is sensed, the pneumatic thermostat opens and relieves control pressure from the butterfly actuator. This moves the valve towards CLOSED, reducing the output of bleed air, thus lowering EGT. Some systems have separate thermostats for fuel acceleration limiting and bleed air. The bleed air function perform by an APU is to supply compressed air for air conditioning and engine starting. But it also provides bleed air for other cabin services, hydraulic system reservoir pressurising and anti-icing. Load control valve operation 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 21 of 104 An APU operating in harsh conditions, with degraded performance or under high load demand, may experience difficulty supplying both electrical power and bleed air loads within a normal EGT range. An example of this may be supplying electrical power for the whole aircraft and also pneumatic power for engine start while on the ground with hot outside air temperatures. In these cases, APU electrical loads usually have priority. They are controlled electronically and sometimes load shedding is built into the system. For example, galley power (power to ovens and coffee/tea makers) are tripped off when ENGINE START is selected. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 22 of 104 Load Compressor In more complex APUs, the power section drives a separate single-stage compressor and the accessory gearbox. This additional compressor is dedicated to supplying bleed air and is called the load compressor. The load compressor is supplied with air from the same air inlet as the power section compressor (gas generator). The supply of compressed air to the aircraft pneumatic system is controlled by a bleed air load control valve. In contrast to the previous description of the load control valve as a pressureregulating valve, this valve is simply an open/closed shut-off valve. The energy required to drive the load compressor is obtained from the turbine. The fuel flow and EGT increase as the bleed air load on the load compressor increases. When bleed air is not required, simply closing the bleed air load control valve does not unload the load compressor efficiently, and the load compressor continues to extract power from the turbine. To alleviate the demand on the turbine, the load compressor is often equipped with variable inlet guide vanes (VIGVs). When aircraft bleed demand is low or when the bleed air load control valve is closed, the ECB signals the VIGV actuator to close the VIGVs. This offloads the load compressor. To prevent the load compressor from stalling at minimum airflows, the ECB controls the surge control valve to dump the unwanted bleed air overboard. Current versions of ECB-controlled APUs incorporate the load control valve and surge valve into one valve known as a Bleed Control Valve, which is fully controlled by the ECB. The ability to match bleed air output to aircraft demand reduces fuel flow, EGT, wear and tear on the APU hardware, and operating costs. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 23 of 104 APU ECB engine bleed control valve APU control valves 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 24 of 104 The VIGVs are controlled by the ECB, which matches the load compressor output to the demand. The ECB modulates the VIGVs between open and closed, and also adjusts the fuel flow to maintain optimum EGT. The ECB also governs the APU protection modes, holds faults in memory, allows Built-In Test (BITE) testing and stores operating data. APU Cooling To cool the APU, ambient or ram air enters the APU intake plenum area, where a portion is tapped as cooling air for the APU compartment, oil cooler and generator. Most large APUs use a cooling fan to induce cooling airflow and increase the cooling air pressure. Typically, the cooling fan is driven by the APU gear train. The inlet to the cooling fan is ducted from the APU inlet plenum or a dedicated outside air intake via a motor-driven inlet door. APU cooling 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 25 of 104 APU Fuel System The APU fuel system provides the APU with the proper fuel scheduling for all phases of operation. A typical system consists of the aircraft fuel supply that includes the: APU boost pump APU fuel shut-off valve Fuel supply line. The APU fuel system supplies fuel from the aircraft to the APU fuel pump and filter. The FCU receives pressurised fuel and meters it to fuel nozzles through a flow divider and fuel manifolds. On FADEC APUs, the fuel is also used in the APU air control system as hydraulic servo power for the Inlet Guide Vane (IGV) actuator. Fuel is also used to cool the APU oil. This fuel, in turn, is heated and returned to the fuel pump and filter assembly to prevent ice from restricting flow through the filter. APU fuel system 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 26 of 104 Fuel Line Shrouds In the most common APU configuration, the APU fuel system receives fuel from the aircraft wing tanks through a shrouded line. Where the fuel supply lines to the engines and APU pass the pressurised aft cargo compartment and pressurised cabin, a shroud is installed to prevent fuel vapour from entering the cabin. In case of a leaking fuel supply line, the shrouds ensure the fuel is drained overboard via the overboard drain line and a drain port at the lower end of the wing fairing. This port is also used for the drain valve in the engine fuel supply line. APU fuel shroud 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 27 of 104 Starting the APU Before starting any APU, check the integrity of the fire-detection system by performing an APU fire test. Once the APU start sequence has been initiated, acceleration and on-speed control are fully automatic in APUs with FADEC/ECB. However, it is still good practice to monitor APU EGT during the start. Depending on the aircraft, sometimes this is not possible if the aircraft is on battery power. A typical start procedure follows: Turn battery switch to ON. Turn APU master switch to ON. Wait for the APU inlet door to open. Turn APU start switch to START or press button. The starter motor is engaged and the APU cranks. The ignition circuit is energised at about 10% rpm and fuel is introduced. Check for light off and acceleration. The starter cuts out at 45%–50%. Check for acceleration and watch EGT rise. The ignition circuit disengages at approximately 95%. Continue to monitor acceleration and EGT. EGT should stabilise. Depending on the model, APU is on-speed at 100% ±1%. When it is on-speed, the bleed air system is armed. Some models quote on-speed rpm according to the load, e.g. 100% for generator only, 102% for generator and bleed air on. Typical overspeed protection might occur at 105%. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 28 of 104 Stopping the APU Manual Shutdown Stopping the APU involves shutting the fuel shut-off valve. Depending on aircraft type, the normal shutdown procedure is pressing the STOP button or selecting the APU push-button or toggle switch to OFF. In many aircraft, the normal shutdown uses the overspeed protection function to stop the APU. The electronic speed-sensing unit or ECB signals the fuel solenoid to close. This proves the integrity of the overspeed protection system. If the normal shutdown does not stop the APU, the cause must be investigated. Stopping the APU 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 29 of 104 Depending on the aircraft, an APU can also be shut down by any of the following switching procedures: Battery switch – OFF APU master switch – OFF APU control circuit breaker – trip APU fire handle – CLOSED External APU stop switch – STOP. B737 APU ground shutdown and warning 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 30 of 104 Automatic Shutdown To protect the aircraft and APU from damage, the APU automatically shuts down if any of the following occur: Overspeed – actual or test Fire warning – actual or test Low oil pressure High oil temperature Excessive EGT (ECB controlled) Vibrations (ECB controlled). Different aircraft and APU types and models behave differently for an automatic shutdown during an actual fire warning and an APU fire test process. For example, in later model Boeing and Airbus aircraft, the APU automatically shuts down during an actual fire warning only when the aircraft is on the ground. When the aircraft is in the air, the pilot is required to shut the APU down manually during an actual fire warning. Automatic shutdown 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 31 of 104 Ground-Running Precautions The APU is fitted in its own fireproof compartment with fire-detection circuitry and a dedicated fire extinguisher. The operator must be aware that running the APU with the cowlings open compromises the firesensing and extinguishing capabilities. The compartment is constructed to minimise the possibility of fire. If during ground tests it is necessary to run the APU with the cowlings open, it must be monitored by trained personnel with appropriate firefighting equipment. Prior to starting any APU, the operator should always conduct an APU fire test to check the integrity of the APU fire-detecting circuitry and extinguisher. Boeing 737 APU compartment 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 32 of 104 APU Ground-Run Test An APU ground run is used to verify the normal operation and condition of the APU. It usually involves starting and stabilising the APU, then progressively applying pneumatic and electrical loads. This checks the automatic load control and EGT-limiting functions. In some aircraft, a record of EGT is made with every progressive load applied. These records form part of ongoing trend analysis for the APU to gauge the internal condition of the engine. Some aircraft have no cockpit indication other than an indicator light showing that the APU is onspeed and supplying AC electrical power. Start parameters are automatically monitored by the APU protective circuitry. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 33 of 104 Power Plant Installation (15.19) Learning Objectives 15.19.1 Describe the configuration of power plant installations (Level 2). 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 34 of 104 Power Plant Installations Firewalls and Fireproof Bulkheads Firewalls and fireproof bulkheads are made of stainless steel, Inconel or titanium and provide protection against fire, heat and corrosion. Flexible fireproof silicone rubber seals surround them and form a snug fit with the engine cowling. The firewall creates a barrier to hazardous gas, fluids, excess heat or flame. Firewalls and fire seals They must be constructed so that no hazardous quantity of air, fluids or flame can pass from one compartment to another. All openings must be sealed with close-fitting fireproof grommets, bushings or firewall fittings. They are not made from aluminium, which would melt in a fire. If a firewall is damaged, the engine compartment fire containment capability may be compromised. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 35 of 104 Firewalls There is also a stainless-steel firewall between the engine and the pylon to prevent the spread of fire to the pylon. Passing through the firewall, flexible lines for fuel and oil are made of fireproof material. Rigid lines, cables and pulleys are also made from stainless steel. Firewalls 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 36 of 104 Cowlings To provide the power plant with a good aerodynamic profile 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 flow to, and around, the engines. These compartments must form a zone to contain fire 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 CASA Part 66 - Training Materials Only Page 37 of 104 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 airflow 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 flight environment, direct airflow as necessary for proper power plant operation and provide support functions (fire protection, over-pressure protection, drainage). 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 38 of 104 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 fitted 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 CASA Part 66 - Training Materials Only Page 39 of 104 Turbofan engines have more robust cowling, usually divided into two or more sections. Turbofan cowls A common configuration 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 firewalls 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 fibre, aramid and glass fibre 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 CASA Part 66 - Training Materials Only Page 40 of 104 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 CASA Part 66 - Training Materials Only Page 41 of 104 Reverser cowls Cowl stays must be fitted when working under open cowls. Stays are normally permanent fittings 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 CASA Part 66 - Training Materials Only Page 42 of 104 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 CASA Part 66 - Training Materials Only Page 43 of 104 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 specific 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 reflecting and acoustic absorbing materials are used on the inside of cowlings. Radiant heat is reflected 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 CASA Part 66 - Training Materials Only Page 44 of 104 Thermal and acoustic linings 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 45 of 104 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 CASA Part 66 - Training Materials Only Page 46 of 104 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 fittings. Cone bolts 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 47 of 104 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 CASA Part 66 - Training Materials Only Page 48 of 104 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 specific 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 fits. 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 fitting a hose, ensure it is not twisted or stretched tight between the two fittings and never exceed the minimum bend radius. Attach support clamps as specified in the maintenance manual to prevent rubbing with other engine components. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 49 of 104 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 fluid- 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 CASA Part 66 - Training Materials Only Page 50 of 104 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 firewall, 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 CASA Part 66 - Training Materials Only Page 51 of 104 Connectors and feeders 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 52 of 104 Engine-Lifting and Transport Points Engine removal and installation may be carried out with the aid of a mobile crane or by handoperated lever hoists attached to lifting beams temporarily fitted 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 flight. Lifting and transport points 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 53 of 104 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 CASA Part 66 - Training Materials Only Page 54 of 104 Engine lifting setup Relevant Youtube link: Boeing 777 Engine Change (Video) 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 55 of 104 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 configuration 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 CASA Part 66 - Training Materials Only Page 56 of 104 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 CASA Part 66 - Training Materials Only Page 57 of 104 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 CASA Part 66 - Training Materials Only Page 58 of 104 Thrust levers in a Boeing 737 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 59 of 104 Drains The drain and vent system is divided into two parts: one which retains drained fluids until expelled during flight (reservoir), and one which discharges fluid 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 fluid 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 fluid-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 CASA Part 66 - Training Materials Only Page 60 of 104 Drains 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 61 of 104 Engine Monitoring and Ground Operations (15.21) Learning Objectives 15.21.1 Provide a detailed description of procedures for starting and ground run-up (Level 3). 15.21.2 Interpret engine and ambient parameters to calculate engine power output (Level 3). 15.21.3 Provide a detailed explanation of trend monitoring (including oil analysis, vibration and borescope) (Level 3). 15.21.4 Provide a detailed description of the inspection of a gas turbine engine and components to criteria, tolerances and data specified by the engine manufacturer (Level 3). 15.21.5 Describe compressor washing and cleaning (Level 3). 15.21.6 Describe foreign object damage (Level 3). 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 62 of 104 Maintenance Engine Runs Purpose of Maintenance Engine Runs Maintenance engine runs are carried out for a variety of reasons, including: Testing following repair or overhaul – carried out in a test cell Fault detection and correction – confirms a reported fault, diagnose the fault, confirm the rectification and remedy the fault Performance monitoring – carried out at various intervals to confirm the power output or serviceability of an engine, with results closely monitored and graphed Engine removal and installation – confirms serviceability pre-removal or post installation and checks for the presence of any leaks Aircraft system power supply – carried out to enable other systems on the aircraft to be tested or operated. B737 - RR Trent 1000 full power run 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 63 of 104 Preparation for Engine Running Before starting an engine, a good practice is to carry out a walk-around check of the entire aircraft. This establishes whether anything is out of place that might cause problems or damage. Check all the main engines – you may need to run more than one engine during the run-up. Engine-related items that should be checked include opening access panels to check fluid levels and visually examining the engine inlet, fan, tailpipe and LP turbine. Maintenance ground runs Aircraft come in various sizes and power ratings. While two aircraft may be roughly the same size, there may be a large difference in their weights and the thrust available from their engines. When preparing an aircraft for an engine run, the many considerations come under the following two main headings: Position Conditions. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 64 of 104 Position The position or location of the aircraft has a large effect on what power settings can be used when starting the engines. Considerations that may apply to running aircraft engines are: Aircraft size and weight – dimensions and limits must be considered if an aircraft must be moved to allow for engine running Engine power – safety distances to be observed, tarmac capable of handling jet blast, enough weight on aircraft to maintain brakes at high power Tarmac and surrounding area material – suitable for engine run, weight rated Boeing 737 with damage due to an engine run-up on loose bricks Distance to buildings/roads or airfield facilities – possibility of damage to buildings, structures or vehicles from jet blast Blast deflectors – devices used to change the direction of the jet thrust, which is normally directed upwards. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 65 of 104 Blast deflectors 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 66 of 104 Danger Areas Danger areas around aircraft dramatically increase as soon as the engines are started. The suction from an engine intake is capable of drawing personnel into the engine even at low power settings. Small material such as gravel or sand is easily picked up and erodes compressor and turbine components. At the same time, the jet exhaust may pick up and blow loose dirt, rocks, sand, bits of paving and other debris a large distance from the aircraft. For this reason, the aircraft must be parked in a location where no damage can result from flying particles which are driven from the rear. As can be seen in the diagram below, the areas in front of and behind an aircraft engine are extremely dangerous. The areas shown, for a Boeing 737-600 to 900 aircraft with a CFM56 engine, are only one example. Specific aircraft restrictions as listed in the applicable Aircraft Maintenance Manual (AMM) must be observed when any engine run is attempted. Engine danger areas at idle thrust 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 67 of 104 Engine danger areas at full power Engine inlet danger areas at full power Other danger areas around the engine may include the engine and starter turbine discs. Danger also exists from the propeller of turbo propeller aircraft. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 68 of 104 Warning - propeller danger 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 69 of 104 Conditions The conditions for an engine run require serious consideration of the following points: Fuel requirements – Sufficient fuel must be present to complete the engine run, plus a safety factor. Also, some aircraft have a minimum fuel state that must be in specific fuel tanks prior to start. Noise – Gas turbine engines produce noise levels considered dangerous to humans if no protective devices are worn. Also, running an engine at full power just outside a maintenance facility may curtail work inside. Weather – Wind direction and velocity can change the stability of the engine. Where possible, the engine must be pointed into the wind. Excessive wind in any direction affects the performance figures of the engine. A typical wind direction and velocity restriction graph is shown below. Allowed windspeeds Trim running of engines at high ambient temperatures is often aborted because engine operating limits are exceeded before the trim graph minimum limits are reached. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 70 of 104 Support equipment – Equipment requirements vary with aircraft type and the reason for which the engine is being run. They may include tow motors, tool kits, a fire extinguisher, personnel communication equipment, aircraft steps, wheel chocks and AMMs. Personnel – The number of personnel required for the run should be kept to a minimum, but includes flight deck runners, an outside ground observer and a fire attendant. Communication – Aircraft engines are extremely noisy (up to 160 dB) when operating, so normal means of communication (speaking) are not always effective. Specialised headset communication equipment may be available to make communication easier; these systems use long leads that can present a potential danger around engines which are operating. Maintenance crew during an engine ground run Protective equipment – The correct protective equipment must be worn at all times when engines are running. The equipment required depends on the aircraft and the type of engine run contemplated, but normally includes kidney belts, earmuffs and earplugs, and appropriate clothing. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 71 of 104 Engine Running Local instructions offer guidance regarding the restrictions and authorisations required to carry out engine run procedures. Pre-Start Pre-start is the step of an engine run which involves everything from the notification of a requirement for the engine run to climbing into the aircraft to carry out the engine run. Once you have been tasked to carry out an engine run, the aircraft maintenance documentation should be inspected to determine the requirement for the run and to ensure nothing in the documentation would restrict or prohibit the operation of the engines or aircraft, such as: Fuel status A disconnected VHF radio antenna, preventing communication with the tower Fire bottle squibs that have been removed, stopping use of the fire extinguishers, etc. After confirming the engine run requirements and aircraft serviceability, organise the location for the run, considering: Power settings required Wind Local flying program Positions that are available Other local restrictions. Determine the personnel and equipment required to complete the engine run, taking into account what specialised checks may be required during the run. On arrival at the engine run location, position the aircraft into the wind with appropriate wheel chocks or tie-downs installed. Position the power cart and any unneeded equipment off to the side of the aircraft in the event the aircraft jumps the chocks or holdbacks. The aircraft pre-run walk-around determines that the aircraft, support equipment and surrounding area are in a safe condition (no foreign object damage, or FOD) for the engine run to commence. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 72 of 104 Aircraft walk around Engine Starting and Run As run procedures vary with engine and aircraft types, the exact procedure for running is laid down per type; however, this is a guide to how an engine run would be carried out. Brief all personnel on the required procedures, including responsibilities, safety and emergency procedures. Perform the relevant flight deck entry checks. Perform the relevant pre-start checks and actions. Contact the control tower for start and/or run clearance. The control tower normally requires the aircraft type, tail number and location, number of personnel on board (POB) the aircraft, and duration of the run to be carried out. Obtain clearance from the external safety observer. Carry out the start procedure, taking care to remain within the limits of all parameters, including Exhaust Gas Temperature (EGT), rpm, oil pressure and starter limitations. Carry out the requirements of the engine run. Perform relevant shutdown checks and actions. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 73 of 104 Engine Limitations All engines have a variety of starting and operating limits that must not be exceeded. These may include: Maximum turbine starting temperature Minimum oil pressure for start and operation EGT limits during starting and continuous operation as depicted in the example below. EGT limits Area of Operation Maintenance Required A Starts in Area A must be recorded and immediate corrective action must be taken prior to further start attempts. A borescope inspection must be performed prior to further start attempts. B Starts in Area B must be recorded. Persistent starts in this area are cause for corrective action. C Any operation in Area C requires removal of the engine for overhaul. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 74 of 104 Emergency Procedures Emergency procedures are normally carried out upon the detection of a dangerous situation which, if not acted upon immediately, could damage the engine or aircraft and injure personnel, either inside or outside the aircraft. Emergency situations require that relevant checklist items are performed immediately. Emergency situations could be: Engine fire Engine runaway Engine seizure Engine overheat Aircraft fire Aircraft system failure. Although some of the above may not initially appear to be emergency situations during engine running, they may rapidly accelerate, within seconds, to life-threatening events. In all emergency situations, quick reaction times and crew co‑operation are essential to prevent/minimise damage to the aircraft and prevent crew injury. Note: If at any time during an engine run an emergency situation appears imminent, the best action to take is to follow emergency shutdown procedures to abort the engine run. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 75 of 104 Post-Engine-Run Checks After completion of the engine run, the aircraft should be returned to its standard configuration: If fitted, remove any specialist engine recording equipment and perform engine run leak checks as required. Remove any specialist tie-down equipment. Refit all blanks. Ensure engine and gearbox oil levels are within prescribed limits. Carry out a post-engine-run aircraft walk-around inspection: Look for evidence of air, fuel or oil leaks. Look for FOD damage to the engine intakes and exhausts, propellers and airframe. Refit any panels or doors removed for access or engine running. Refuel the aircraft as necessary. Return all equipment used for the engine run. Complete all necessary documentation. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 76 of 104 Factors Affecting Engine Performance Introduction to Factors Affecting Engine Performance Power output of a gas turbine engine is affected by: Design factors, such as compressor and turbine efficiency and engine pressure ratio (EPR) Operational factors, such as rpm and EGT External factors, such as airspeed, altitude and Outside Ambient Temperature. Design Factors Although design factors cannot be altered, the greater the engine efficiencies and EPR, the greater the resultant engine power output. Engine RPM Gas turbine engines are generally most efficient when operating at maximum allowable rpm. Normal operating range is usually 90%–100% of max allowable. At high engine speeds, thrust increases rapidly with small increases in rpm. Maximum compressor and turbine efficiency are only possible at one specific rpm, therefore engines are designed for best performance at max power. Operation at other power settings degrades specific fuel consumption. RPM vs thrust 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 77 of 104 Turbine Temperature Maximum engine thermal efficiency, fuel efficiency and power output occur at maximum allowable turbine inlet temperature, although severe restrictions are laid down with regard to exceeding maximum EGT to protect the turbine from heat stresses. Power Limiting Low altitude and low ambient temperature both produce high air density, which gives high mass flow for a given engine rpm. High mass flow allows the engine to produce maximum power before the maximum allowable turbine temperature is reached. When this condition occurs, the engine is restricted from increasing burner pressure any further and is said to be power (EPR) limited, thrust limited, N₁ limited or torque limited. High density altitude and temperature conditions reduce air density and mass airflow. Maximum allowable turbine temperature is therefore reached before the engine produces maximum power output. Under these conditions, the engine is said to be temperature limited. If not monitored, these conditions may lead to engine overheat, leading to turbine fatigue through heat stress. Some engines are de-rated so that operational limits are less than design limits. This reduces engine wear and extends engine life. These engines are different from flat rated. Adjustments In service adjustments to non-FADEC gas turbine engines, fuel control units (FCUs) are usually limited to: Throttle rigging Specific gravity Idle rpm Maximum power. An FCU suspected of being faulty should be removed and replaced with a serviceable item. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 78 of 104 Performance Checks Trimming Adjustment of idle rpm and maximum thrust settings must be set to match the manufacturer’s specifications. Idle adjustment sets engine idling rpm to that specified by the manufacturer, allowing for variations in ambient conditions. Depending on the particular engine, maximum power (or thrust) adjustment ensures that the engine is producing rated thrust or shaft horsepower as specified by the manufacturer, and again allowing for variations in ambient conditions. Trimming is carried out whenever engine power output is suspect and after certain maintenance tasks as prescribed by the manufacturer (e.g. engine, FCU or module change). In a turbojet engine, EPR is used as a measure of engine power output. In a turbofan engine, EPR or fan rpm may be used; if the engine is not producing full power, mass flow through the turbine assembly is reduced, and fan rpm is reduced. Turboprop or turboshaft engines use output shaft torque as a measure of engine power output. Part Power Trimming Some engines may be trimmed at less than take-off power. A stop (called a part power trim stop) is placed so that the power lever is blocked before reaching the full power position. Engine trimming is carried out with the power lever against the stop. Acceleration Check When technicians perform an acceleration check, the power level is moved from the idle to full power setting, and engine acceleration time to full power is compared to the manufacturer’s acceleration time. Data Plate Speed Check After manufacture, the engine is test-run and a data plate attached. The data plate records conditions under which required thrust was obtained during part power trimming (e.g. 87.25% N2 at 1.61 EPR and 59 °F). The data plate speed check is carried out by running the engine at 1.61 EPR, noting N2 tachometer indication, correcting the observed figure for any temperature variation from 59 °F, and comparing it with the original rpm figure. Any variation outside manufacturer specified tolerances is an indication that either the FCU needs adjustment or the engine is worn, and maintenance or repair may be necessary. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 79 of 104 Trend Monitoring Purpose of Trend Monitoring Accurate forecasting of impending component failure allows forward planning of a unit’s maintenance commitment by taking advantage of manpower and spares availability and reducing aircraft downtime. Conventional trend monitoring has taken two paths: Mechanical parameters – oil consumption, oil analysis, chip detection and vibration measurements Performance parameters – fuel flow, thrust, rpm, EGT and pressure readings. The more recent advances in microprocessor-aided monitoring, displaying and recording of engine parameters have expanded the information available to both the aircrew and maintenance crew to determine engine condition. Engine trend monitoring is based on the consistency with which a gas turbine engine follows its corrected performance figures at steady-state operating conditions. An engine does not vary from its new or post-overhaul performance figures unless some internal or external effect forces it to do so. If the cause of the deviation can be determined, maintenance action can be taken to correct the fault. Most modern engine manufacturers are making engines which no longer have scheduled overhaul intervals. The engines are manufactured to be modular. This means each major engine sub-assembly, such as a compressor assembly or turbine assembly, is a self-contained module. The engine as a whole is not overhauled, only the engine modules, and then only when a fault occurs. This type of engine maintenance is known as ‘on-condition’ maintenance. With engines now being maintained on an on-condition basis, monitoring their performance trends is crucial. It allows aircraft operators to accurately determine when maintenance on an engine is required and takes maximum advantage of available spares and manpower. Accurate trend monitoring also saves aircraft operators money and aircraft downtime. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 80 of 104 Performance Parameters The following engine and flight indications are required to operate an effective trend monitoring program: Altitude EPR or N₁ rpm N₂ rpm EGT Fuel flow. The instrument indications obtained during flight or during an engine ground run are corrected to a set of standard conditions. The corrected readings are then compared to the average readings previously obtained or the figures from the post-overhaul engine test. Graphical Presentation The data obtained from corrected engine performance figures are plotted on a graph as shown below. This method displays an easily readable record of the engine’s performance trend over a significant time. Any malfunction or deterioration in performance is quickly recognised and maintenance may be scheduled at the most convenient time. Engine performance figures - normal 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 81 of 104 Effective trend monitoring is wholly dependent on accurate observations of engine instruments and the operator’s ability to detect small deviations in the instrument indications. The deviation of two or more parameters generally results from a change in engine performance. If there are minor fluctuations (within the tolerances), the engine should continue to operate normally until its next overhaul. Engine performance figures - abnormal The chart above shows the same parameter data for the same model of engine as the previous chart. This engine was removed for excessive oil consumption. On disassembly, the No. 4 and No. 5 main bearings and carbon oil seals were found to be leaking bleed air into the bearing compartments, causing the problem. Because of the bleed air leak, the engine required more fuel to produce the required thrust. With the addition of more fuel, the compressor rpm of both the low- and high-pressure compressors also increased. If you study the chart, you will see that not only are the oil consumption data high, but so are the fuel flow, N₁ rpm and N₂ rpm data. If these figures were plotted for an engine whose oil consumption was normal, you would suspect that the engine compressor bleed valves were leaking. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 82 of 104 Spectrometric Oil Analysis Program A spectrometric oil analysis program, or SOAP, is another tool available to aircraft operators to help detect developing problems in an engine. Spectrometric analysis of metal particles suspended in oil is possible because metallic ions emit characteristic light spectra when vaporised by an electric arc. Each metal produces a unique spectrum, allowing easy identification of the metals present in the oil samples. The wavelength of spectral lines identifies each metal, and the intensity of a line is used to measure the quantity of that metal in a sample. Engine trend monitoring (SOAP) Alloyed metals in turbine engines may contain amounts of aluminium, iron, chromium, silver, copper, tin, magnesium, lead, nickel or titanium. Silver is accurately measured in concentrations down to one part silver in 2,000,000 parts oil. The wavelength of the spectral line identifies the metal. The intensity of the line measures the quantity of the metal. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 83 of 104 SOAP analysis Vibration Monitoring Engine vibration during flight is also subject to trend monitoring and analysis. Increasing vibration can indicate a deteriorating engine condition. An increasing vibration trend could be caused by pending bearing failure or rotating assembly deterioration or damage. Usually two vibration sensors are fitted: one to the fan case and the other on the turbine case. Vibration intensity at these points can point to the source. A warning lamp on the flight deck warns the pilot when an unacceptable level of vibration is reached so the engine can be shut down before more damage occurs. Vibration monitoring 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 84 of 104 Borescope Inspection A borescope is a viewing device which allows you to visually inspect areas inside a turbine engine without disassembling the engine. A borescope may be compared to a small periscope with an eyepiece at one end and a strong light, mirror and lens at the other end. A conducting cord connects the probe to a control panel for adjusting light intensity and magnification. To aid the inspection process, many gas turbine engines are equipped with openings, or ports, that allow inspection tools to enter. Some of the common tools used for such inspection are the borescope, fibrescope and electronic imaging. Borescope Borescope inspections are carried out following suspected engine damage or as part of a trend monitoring process. Borescope ports are located in the engine gas path, in both the cold and hot sections. To provide a view of each N₂ compressor or turbine blade, the engine can be manually rotated through a manual cranking pad on the accessory gearbox or via a special motor attached to the starter pad. The N₁ can be rotated by hand-turning the fan. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 85 of 104 Engine borescope inspection ports Borescope inspection is often carried out following trend analysis that identifies the following: Deteriorating performance Increasing vibrating Over-temperature Overspeed. Borescope inspection 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 86 of 104 Borescope inspections are also part of routine and special maintenance inspections, such as: FOD Bird strike Lightning strike. Mechanic using a borescope 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 87 of 104 Damage Inspections Damage Inspection Precautions Fan compressor and turbine components are often damaged by loose items left in engine intakes or exhausts. Before performing any work inside intake or exhaust ducts, ensure all loose items are removed from your pockets. Before closing up, thoroughly inspect your work area for loose items, including nuts, bolts, screws, rags, lockwire, tools and personal items. Fan Blades CAUTION: Before entering the inlet, place a soft rubber mat in the inlet duct to protect the inlet lining. Like propellers, fan blades often suffer minor erosion and stone damage. Blade damage is normally dressed by blending out the erosion or nick using a fine file and abrasive cloth. Damage and repair limits are specified in the manufacturer’s maintenance and repair manuals. Any damage to fan blade roots is critical due to the high centrifugal stress loads. Debris, used abrasives, tooling and the protective mat must be removed before the job is finished. Following blade dressing, an engine ground run and vibration survey may be necessary to check for fan imbalance. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 88 of 104 Blade Shingling A specific type of damage that may be caused by FOD is fan blade shingling. Shingling is the overlapping of midspan shrouds on fan blades. Anytime rotating fan blades encounter a force that pushes a blade sideways, shingling can occur. Common causes of shingling include FOD, compressor overspeed and compressor stall. Whenever shingling occurs, you must inspect the top and bottom surfaces of the shrouds involved for scoring or galling. In addition, any blade that encounters shingling typically must be removed and inspected in accordance with the manufacturer’s maintenance manual. If any cracks are found during the inspection, the fan blade must be replaced. Blade shingling 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 89 of 104 Inlet Guide Vanes Inspect inlet guide vanes for FOD damage, and blend out damage in accordance with the AMM; blending should be finished with emery cloth to polish the area and restore the original scratch-free surface. Blade blending 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 90 of 104 Compressor Blades Inspect the compressor for FOD damage, cracking and evidence of blade rub. If damage falls within predetermined limits, record the extent and location of the damage for further reference and to aid trend monitoring. Depending on engine type, it may be possible to carry out in-field repairs and blend out damage in accordance with the AMM; blending should be finished with emery cloth to polish the area and restore the original scratch-free surface. The purpose of blending is to minimise stresses that concentrate at dents, scratches or cracks. The illustration shows some examples of blade damage to an axial flow engine. Blade damage 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 91 of 104 Turbine Nozzle Guide Vanes and Blades Inspect nozzle guide vanes for burnt spots, erosion and cracks. Depending on engine type, it may be possible to carry out in-field replacement. NGV damage Exhaust Section The exhaust section of the engine is susceptible to heat cracking. Inspect the exhaust section and rear of the LP turbine for cracks, warping, buckling, hot spots or carbon deposits. Hot spots or carbon deposits on the exhaust cone are a good indication of faulty fuel nozzle operation. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 92 of 104 Compressor Washing Compressor Washing and Cleaning During normal operation, dirt particles, industrial fallout, salt and volcanic ash accumulate on the compressor stators and blades. These build up over time and reduce compressor efficiency. Reduced EPR, unsatisfactory acceleration and high fuel flow and EGT might indicate a dirty compressor. This contamination can be removed by one of the following recommended processes: Water rinsing Water washing. Compressor washing Before washing and/or rinsing, take precautions to ensure water does not enter the engine’s sensors and fuel control. The AMM describes which sensors and sensing lines need to be removed or blanked off. For a rinse, de-mineralised water is used. For a water wash (performance recovery wash), a detergent and de-mineralised water mixture is used, followed by a de-mineralised water rinse. Most turbofan, turboprop and turboshaft engines are dry motored for the rinse or wash process. After the process is completed, the sensors are reconnected and an idle ground run is carried out to thoroughly dry out the engine. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 93 of 104 A compressor grit wash (comprising of ground walnut shells or apricot pits) was used on older turbojet engines, but with the advancement of cooling technology for turbines where the burnt grit could clog the cooling holes, this process is not used today. Video – Compressor Wash – Relevant Youtube link: Compressor Wash (Video) Relevant Youtube link: Compressor Wash Fuel-Saving Figures (Video) Foreign Object Damage Foreign object damage (FOD) is an ongoing problem for the safe operation of aircraft engines, especially gas turbine turbofan engines. The engine inlet acts as a huge vacuum cleaner and ingests small debris, such as concrete chips or rocks from the ramp and tools that have been carelessly left where they can be sucked up. In flight, birds and ice are the main causes of FOD. Any FOD damage, regardless of how small it is, results in a loss of performance by the engine and may be indicated by an increase in EGT and a decrease in EPR or N₁ fan speed. All technicians must remain extremely vigilant for any FOD lying around the aircraft and remove it before the engines are started. FOD damage Relevant Youtube link: Compressor Damage (Video) 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 94 of 104 Engine Storage and Preservation (15.22) Learning Objectives 15.22.1 Describe preservation and de-preservation for a gas turbine engine and its accessories and systems (Level 2). 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 95 of 104 Engine Storage and Preservation Purpose of Engine Storage and Preservation The primary purpose of engine and accessory preservation is to prevent corrosion and handling damage. Corrosion occurs whenever a base metal such as steel, iron or aluminium combines with oxygen to form an oxide. Therefore, if the base metal is properly sealed, corrosion does not occur. Preservation is performed on engines when they are: Idle for any significant period Going into short- or long-term storage Transported over long distances. The procedures for preserving and de-preserving engines vary depending on the length of inactivity, the type of preservative used and whether the engine may be rotated during the inactive period. Observing engine manufacturers’ instructions for preservation increases the life of the engine when it is not in operation. Basic preservation requirements During short-term storage, the engine is started periodically (e.g. every 10–14 days) to ensure seals and hoses remain flexible and intact and bearings stay coated with oil. If an engine is to be placed in long-term storage, either on-wing or off-wing, the fuel and/or oil system may need to be drained or inhibited. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 96 of 104 Methods vary in detail from one engine type to another, but the engine preservation process is carried out to prevent internal and external deterioration of the engine and its components during storage. A definition of short-term storage is up to 6 months after the last flight. Long-term storage is longer than 6 months after the last flight. Preservation A number of substances can absorb moisture, and one of these is silica gel. This gel does not dissolve when saturated. As a corrosion preventive, bags of silica gel are placed around and inside various accessible parts of a stored engine. It is also used in clear plastic plugs, called dehydrator plugs, which can be screwed into engine openings. Cobalt chloride is added to the silica gel in dehydrator plugs. This additive makes it possible for the plugs to indicate the moisture content or relative humidity of the air surrounding the engine. The cobalt chloride-treated silica gel remains a bright blue colour with low relative humidity, but as the relative humidity increases, the shade of the blue becomes progressively lighter. It becomes lavender at 30% relative humidity and fades through various shades of pink until, at 60%, it is a natural or white colour. With relative humidity below 30%, corrosion does not occur. Therefore, if the plug remains bright blue, the air has so little moisture that internal corrosion is held to a minimum. Dehydrator plug and humidity indicators 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 97 of 104 This same process is used in humidity indicator envelopes that can be fastened to the stored engine and inspected for colour change through a small window in the shipping case. A scheduled inspection system is implemented for engines in storage. In a pressurised container, the pressure must be maintained, and if the indicator turns pink, then the engine must be re-preserved. Details of the procedure used and any special requirements during storage should be recorded (in the engine logbook) and a copy included with the engine documentation. Some manufacturers recommend spraying oil in the compressor while the engine is motoring, while others caution against this practice. Always follow the manufacturer’s instructions. The following is a generic process. Preservation can be on-wing or off, and the materials discussed can be used on either. Fuel System Preservation Disconnect the fuel inlet line to the pump (or fuel heater if fitted) and connect a supply of inhibiting oil. Disconnect the fuel line at the dump valve inlet to prevent inhibiting oil entering the fuel manifold. Place the line in a container to allow drainage. With the ignition and fuel supply valve turned off, and the fuel cut-off lever in the FULL OPEN position, complete a wet motoring cycle. During the cycle, move the power lever from take-off to idle and back to take-off. Repeat the motoring cycle, if necessary, until inhibiting oil flows from the opened fuel line. Do not exceed duty cycle limits for the starter motor. Connect fuel lines and install all engine plugs, caps and covers. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 98 of 104 Oil System Preservation Close the normal fuel supply shut-off valve and rotate the engine with the starter until oil pressure and compressor rpm are indicated. Disengage the starter. Drain all engine oil from the tank and gearboxes. Remove and drain the main oil filter. Add inhibiting oil and rotate the engine as per the AMM. Tag the oil filler cap with the date of preservation. If the engine is to remain in the aircraft, place desiccant (moisture-absorbing material) in the engine compartment, exhaust ducts and inlet ducts. Seal all engine openings to prevent the entry of foreign matter and accumulation of moisture. Preserved engine in storage 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 99 of 104 Storage Containers When engines are removed from the aircraft and stored for any length of time, all openings and pipelines should be blanked and the engine placed in an airtight storage container. The storage container may just be a plastic envelope, a heavy cardboard or wooden box, or a metal container pressurised with an inert gas such as dry nitrogen. Calico bags full of desiccant, such as silica gel, are placed in the storage container. Cover with an airtight moisture seal incorporating inspection windows for observation of the humidity indicators. Storage containers 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 100 of 104 Storage container example Inspection of Stored Engines Engines which have been placed in storage will have a scheduled inspection period. Normally the humidity indicators on the stored engines in the shipping containers are inspected every 30 days. If the humidity indicator shows a colour indicating more that 30% humidity internally, all the desiccant bags should be replaced. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 101 of 104 Engine Transport If an engine is to be transported over long distances, a special transport stand must be used. The engine supports must have adequate suspension or shock absorption. If the engine is to be transported by road, the transport vehicle should be equipped with air-ride suspension. These precautions prevent brinelling of the main engine bearings. Engine transport 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 102 of 104 De-Preservation The de-preservation process is carried out to restore the engine to operational condition, ready for operation on an aircraft. After de-preservation of the fuel, oil systems and accessories, the engine should be run. The procedures set out below should be treated as a basic guide only. The maintenance manual must be closely followed. Typically, de-preservation involves the following steps: Remove the container cover or storage bags and any desiccant material. Remove other covers and blanks, such as those over the intake, exhaust and accessory mounting pads. Inspect exposed and uncovered areas for corrosion and foreign objects. If installing the engine, drain inhibiting fluid from the fuel and/or oil system, recharge tanks and prime the systems (‘wet motor’ prior to start). Ensure that any engine accessories fitted have not exceeded their life limit. Start the engine, run it at idle for a minimum of 5 min to burn off any residual preserving fluid and shut it down. Check the engine oil level and replenish as necessary. Install a new engine oil filter. 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 103 of 104 Accessory De-Preservation Good engine performance depends, in part, on the condition of the engine accessories. Although an engine is in a condition to give top performance after being completely overhauled, any oversight or error in reinstalling the accessories can result in an engine malfunction or irreparable damage. Therefore, follow recommended procedures in the overhaul manual or the instructions that come with overhauled or new accessories regarding de-preservation and preparation for operation. Before de-preservation of any of the accessories enclosed with the engine, refer to the accessory records to determine how long the engine and accessories have been in storage. Some accessories are life-limited and are considered unsafe for use if their storage time exceeds the manufacturer’s time limits. Before installing any replacement accessory, check it visually for signs of corrosion and for freedom of operation. Remove any plastic plugs and movement restraints placed on the accessory for shipment. In addition, lubricate the accessory drive shaft and clean the mounting pad and flange prior to installation. Always install an accessory with new O-rings or gaskets between the mounting pad and the accessory. Installation of accessory de-preservation 2022-08-24 B1-15c Gas Turbine Engine CASA Part 66 - Training Materials Only Page 104 of 104