Engine Cooling Methods

Engine Anti-Ice Air Source

• High-pressure (HP) compressor is the source of air for engine anti-ice.

Turbine Case Cooling

• Fan air is used for turbine case cooling.

Secondary Air Engine Cooling

• Secondary air passes through the engine to cool combustion-chamber liners.

Internal Engine Cooling

• Air is drawn from various compressor stages and from the fan air supply for high bypass engines to achieve internal engine cooling.
• Cooling turbine blades allows for increased fuel scheduling, leading to higher RPM and thrust.

Turbine Blade and Nozzle Guide Vane Cooling Methods

• Convection, film, and impingement cooling methods are used for turbine blades and nozzle guide vanes.

Impingement Cooling

• Impingement cooling uses blades to direct cooling air at a 90-degree angle to the internal surface.

External Engine Skin Cooling

• Atmospheric air ducted around the engine is used for cooling the external skin.
• The cooling airflow also removes flammable vapors from the engine compartment to reduce fire risk.

Bleed Air and Icing

• Bleed air, prone to icing, is routed through a shutoff valve controlled from the flight deck, and ducted to areas of the aircraft.

MTCS Zone 1

• Zone 1 includes the fan case, accessory case, and electronic engine control (EEC).

MTCS Zone 1 Venting

• Zone 1 is vented using ram air through an inlet in the nose cowl, exhausted via a louvered vent in the right fan cowling.
• A pressure relief door opens to relieve pressure if it exceeds a limit.

Electrical Motor Starters

• Electrical motor starters are series-wound electric motors, designed to provide high starting torque for large engines.

Pneumatic/Air Turbine Starting System

• Pneumatic or air turbine starting systems are the most widely used starting system in large commercial aircrafts.
• Use of pneumatic or air turbine starting systems requires an external ground source of air supply.
• The starter connects directly to the HP shaft, bypassing the gearbox.

High-Energy Ignition System

• High-energy (H.E.) ignition is used for starting all jet engines.
• A dual system is fitted, including an ignition unit connected to its own igniter plug, where two plugs are situated in different positions in the combustion system

Auto-Ignition Circuit

• Turbine-powered aircraft often have an auto-ignition circuit to ensure instantaneous ignition if an engine loses power from inlet icing avoiding flameout.
• The auto ignition system can sense an EGT drop to initiate auto-ignition.

Cartridge Starter Disadvantage

• A cartridge is needed for each start when using a cartridge starter.

Air Turbine Starter Components

• Oil system lubricates the gears and bearings in the air turbine starter.

Gas Turbine Starter - Gas-Generator Section Components

• Centrifugal compressor, combustion chamber, and turbine are components included in the gas-generator section of the gas turbine starter.

Low Joule AC Continuous Ignition System Advantage

• Installing a low joule AC continuous ignition system to supplement an intermittent duty system removes the time limit.

Air Turbine Starter Failure

• An air turbine starter not operating (no rotation) occurs due to no air supply/electrical open in the cut-out switch or a sheared starter drive coupling.

Thermocouple System Power

• Thermocouple system requires no external power.

Wheatstone Bridge Circuit

• A Wheatstone bridge circuit: three fixed resistors, one resistance thermometer that varies with temperature.

Resistance Thermometers

• The wire sensor in resistance thermometers is made of platinum or nickel, wound on a former of insulating material like mica.

EPR Pressures

• Compressor inlet pressure (P1) and turbine outlet pressure (P6) are the Engine Pressure Ratio (EPR) pressures sensed.

TIT Gauge

• Turbine Inlet Temperature (TIT) indicates the temperature gauge in the flight deck

Vane-Type Flowmeter Placement

• The vane type flowmeter is generally fitted in the low-pressure section of the fuel system.

Tachometer System

• Tachometer: independent electrical system with an engine-driven, three-phase AC generator and a synchronous motor-driven indicator.

Variable Reluctance System

• The "Variable Reluctance" system is the Phonic Wheel and Pulse Probe.

Thermocouple and Seebeck Effect

• Seebeck effect: the heating of one of the junctions allows free electrons from the wire with the greatest electrical potential, to flow into the wire of the lesser electrical potential.

EGT in Gas Turbine Engines

• Gas Turbine engines EGT are usually of the stagnation type because the exhaust velocity is high.

Synchronous Fuel Flowmeter

• In a Synchronous Fuel Flowmeter, fuel enters the transmitter impeller, which is rotated at a constant 60 revolutions per minute by the synchronous impeller motor.

Alumel

• Alumel has an excess of free electrons and is usually colored green, while Chromel has a deficiency and is white.

Gas Turbine Engine EGT

• Gas Turbine engine EGT is usually of the stagnation type.

Dummy Thermocouple

• The dummy thermocouple compensates for ambient air temperature.

Thermocouple Burnout

• The indicator shows no change if a thermocouple burns out.

Synchronous Fuel Flowmeter Fuel Rotation

• The fuel rotates at a constant 60 revolutions per minute in a synchronous fuel flowmeter.

Engine Thrust Indication - Pitot Probe

• Engine Turbine Discharge/Jet Pipe Pressure indications of thrust use a pitot probe to measure dynamic pressure aft of the turbine.
• The output calibrates to a gauge in Lb/in².

Seebeck Effect

• Named for Thomas Johann Seebeck, the heating of one of the junctions, known as the hot junction allows free electrons from the wire with the greatest electrical potential, to flow into the wire of the lesser electrical potential

Ratio Meter Circuit Fault Response

• In a ratio meter circuit, an open circuit in the sensor causes the instrument to go to Full Scale Deflection (FSDA).
• A short circuit in the sensor causes the instrument to go to a minimum (off-scale) position

Bulb-Type Temperature Indicator Fault

• A gauge on a bulb type temperature indicator showing zero indicates two cables shorting together by the sensor.

Turbine Thrust measurement - High Bypass Engine - FAN N1 RPM

• In a high bypass engine, N1 RPM is a thrust analogy because the fan produces 80% of the thrust.

Strain Gauges

• Resistance decreases when shortening force is applied in strain gauges.

Reheat System

• Reheat system increases thrust by increasing the exhaust gas velocity by burning large quantities of fuel in the exhaust.

Methyl/Ethyl Mixture Alcohol Content

• Methyl/ethyl mixtures consist of a blend of 35 to 50 percent alcohol in demineralized or distilled water.

Augmentation Device Reheat System

• Augmentation Device Reheat System uses a Turbojet

Power Augmentation Water

• Demineralized water with not more than 10 parts per million solid is used in a power augmentation system.

Rpn Ground Fine Pitch Stop

• A removable stop for starting and maintaining minimum constant Rpn is named Ground Fine Pitch stop.

Propeller Engine Reduction Gear Purpose

• To reduce the engine speed (RPM) to low speed of propeller so that it doesn't reach the speed of sound.

Flight Fine Pitch Stop Purpose

• A Flight Fine Pitch Stop is a removable stop (+14") which prevents the blade angle from fining off below its preset value with its aim to prevent propeller over-speeding after a CSU failure

Turboprop Engines - Rotational forces

• Turboprops are constant speed engines; the fuel control adjusts the fuel flow in relation to the engine load to hold the RPM constant.

Turboprop Engine Types

• The two basic types of turboprop engines are single-shaft and free-turbine.

Turboprop Engine Reduction Gear

• Epicyclic reduction gears are used on most turboprop modern engines used in masts.

Twin-Engine Helicopter Freewheeling Units

• A helicopter with two engines will have two freewheeling units.

Balancing Helicopter Coupling

• Balancing is required to reduce Helicopter Vibration.

Helicopter Rotor Assembly

• A helicopter has two rotor assemblies.

Helicopter Power Control

• Power control of a helicopter engine uses the Collective Pitch Lever.

Helicopters Commonly Used Freewheeling Unit

• A sprag clutch is the most commonly used freewheeling unit on helicopters.

Freewheeling Unit

• A freewheeling unit is sometimes referred to as the over-running clutch.

Gas Turbine Engine function as a propeller alternative

• Turbo-shaft is a gas turbine engine that delivers power through a shaft to operate something other than a propeller.

Load Compressor Type APU

• Improves life of turbine.

Aircraft APU Pneumatic Bleed

• An electrically operated butterfly valve, also known as the load control valve/bleed valve, controls the amount of compressed air delivered from the APU to the aircraft pneumatic manifold.

Load Compressor APU Pneumatic Load

• All pneumatic load to the aircraft is provided by the load compressor in a load compressor type of APU.

Eductor Function

• An eductor is a convergent duct located around the APU exhaust, creating low pressure, pulling airflow in and around the APU for cooling.

Controlled Drain

• When an engine stops, fuel drains from the fuel manifold and combustion chamber overboard into an ecology drain tank which is a controlled drain.

Nacelles and Pods

• Nacelles and pods are streamlined enclosures used on multi-engine aircraft to house the engines.

Flexible Hose Support in Aircraft

• All flexible hose installations should be supported every 24 inches (2 feet)

Flexible Hose Replacement Statement

• Replacement of a flexible hose should use the same type, size, part number, and length of hose.

Wire Bundle Bend Radius

• The minimum radius for bends in wire groups or bundles is 10 times the outside diameter of the largest wire.

Wire Bundle Deflection

• The maximum deflection allowed for wire groups or bundles between support points is 1/2 inch.

Aircraft Cowlings

• Small access panels for access to particular part of the powerplant that requires frequent inspection or servicing are also common.

Anti-Vibration Mounts

• Anti vibration mounts are vibration isolators consisting of a resilient material permanently enclosed in a complete rubber case, to isolate adverse engine vibrations, however isolators cannot support the engine after resilient material failure

Flexible Hose Hardware

• Flexible hoses that are repaired or overhauled using existing hardware and new hose material should be tested to at least 1.5 times system pressure before installation.

Thermal Switch Fire Detection System

• A thermal switch fire detection system operates using spot detector sensors with a bimetallic thermal switch that closes when heated to a high temperature.

Fire Detection System Components

• A fire detection system includes a detector circuit, alarm circuit, and test circuit.

Continuous Loop Fire Detector Sensor

• Core resistance material prevents current flow at normal temperatures in a continuous loop fire detector system sensor.

Activating Aircraft Turbine Engine Fire Extinguishing Systems

• Most aircraft turbine engine fire extinguishing systems are activated using electrically discharged cartridges.

Kidde Fire Detection System

• Unknown from context.

Thermal Switch Connections

• In series with the indicator lights.

Thermocouple Fire Warning System

• A thermocouple fire warning system includes a relay box, warning lights, and thermocouples.

Widely Used Continuous-Loop Systems

• Kidde and Fenwal systems are two widely used types of continuous-loop systems.

Commercial Aircraft Extinguishing Agent

• Halon 1301 is the most common extinguishing agent used in commercial aircraft.

Engine Shutdown Valve Closure

• During normal engine shutdown, the HP COCK valve is closed.

Criteria for Engine Overhaul

• Operating cycles and operating hours make up the criteria used to determine when an engine overhaul is needed.

Engine Gas Path Washing (procedures)

• post cleaning by water, dry motoring as well as engine ground run is required to remove all the water from the engine.

Spectrometric Oil Analysis Program (SOAP)

• SOAP evaluates the internal condition of a mechanical system.

Engine Inspection

• A boroscope inspection is the inspection method of an internal engine without disassembly.

Blades Shingling

• Overlapping of shroud segment of one blade that is adjacent with another overlaps.

Foreign Object Damage (FOD)

• Foreign object damage (FOD) can be due to concrete chips, rocks from the ramp, or tools left carelessly in the intake, or birds/ice ingested during flight.

Nozzle Vane Damage

• Small nicks on nozzle vanes should be dealt with by blending out the nicks smoothly if they are within limits.

Loose Swirl Vanes

• Loose swirl vanes should be repaired by silver brazing.

Engine Storage Recording

• After placing an engine into storage, details would be recorded in the Engine Log book.

Engine Storage - Desiccant

• Desiccant removes moisture from the air in an engine in storage.

Installed Engines Preservation

• Installed engines must be re-preserved after preservation at least every six months.

MVP Envelope for Engine Preservation

• A moisture vapor proof (MVP) should be unsealed if the humidity indicator turns pink: the desiccant replaced and the envelope resealed.