Piston Engine Maintenance Intro

Definitions

• Define means describing the nature or basic qualities
• State means specifying something in words or writing
• Identify means establishing the identity
• List involves itemizing
• Describe means representing an idea to allow someone to form an idea of it
• Explain means making known in detail by offering reason for cause and effect

Study Resources

• For engine maintenance, recommended study materials contain the A&P Technician Powerplant Textbook from Jeppesen Sanderson.
• "Aircraft Powerplants" Fifth Edition by R.Bent and J.McKinley (1985) is recommended.
• "Essential Physics, Book One", Second Edition by D.Christian, and W.Crossley (1987).
• The B1-16c Student Handout is also a resource.

Introduction to Piston Engine Maintenance

• This subject familiarizes individuals with Piston Engine Maintenance.
• After completing the following topics, students are able to describe powerplant configurations, explain engine operation, and perform storage/preservation tasks.

Powerplant Installation

• Firewalls are key components.
• Cowlings are also key.
• Acoustic panels, engine mounts, and anti-vibration mounts are included.
• Hoses, pipes, feeders and connectors are installed.
• Wiring looms, control cables/rods, lifting points and drains are all part of the installation.

Engine Monitoring and Ground Operation

• Procedures for starting and ground run-up are important.
• Interpreting engine power output indications and parameters is very important.
• Inspection of engines and components to manufacturer specs is a big part of the learning.

Engine Storage and Preservation

• Preservation and depreservation of engines, accessories, and system components happens here.

Powerplant Installation (Topic 16.11)

• Reciprocating engines provide torque to drive a prop or rotor, and forces must transmit to the airframe.
• Engines need additional components to be installed in the airframe.
• The interface between engine and airframe is called 'Power Plant Section'.
• The Power Plant Section includes cowlings, firewalls, engine mounts, fluid line plumbing, feeders, electrical harnesses, control cables/rods, and drains.

Nacelles and Cowlings

• The 'Nacelle' is the area housing the engine in multi-engine aircraft, attached to the wing or fuselage.
• The pylon is the interface between the engine and airframe, engine attaches to the pylon.
• 'Cowls' are panels surrounding the engine, part of the nacelle.
• Engine cowling minimizes aerodynamic drag and protects components, directs airflow and supports fire protection/drainage.
• Cowling parts include inlet/nose, upper, lower, and side cowls.
• Cowlings are closed in the opposite sequence used for opening.

Radial Engine Cowling

• Air cooling causes drag, unacceptable in early aircraft exceeding 120 mph.
• The Townend Ring is an aerofoil ring installed around a radial engine.
• Aerofoil shape smooths airflow, improving uniformity around the engine, possibly reducing drag by 11%.
• The NACA Cowling, developed in the 1930s, is a streamlined cowling covering a radial engine and extends back to the fuselage.
• NACA Cowlings use aerofoil shape to produce thrust by converting incoming air into a solid jet blast.

Opposed Engine Cowling

• Early opposed engines had cylinders stuck out in the airstream for cooling.
• Thin metal hoods directed air between cylinder fins because cylinders were directly behind each other.
• Modern reciprocating engine cowlings enclose the entire engine.
• Cooling air enters two forward openings and exits one or more openings at cowl's bottom rear.
• Rubberized strips seal the cowling to prevent air leakage producing pressure cooling.
• Ram effect makes cooling air enter the cowling with above ambient pressure,
• Outlet flaring on lower cowls creates low pressure as outside air flows by.
• Cylinder air gets drawn through the cylinders and out the lower cowl.

Cowl Flaps

• Cowl flaps can control the amount of cooling air flowing through the cowling.
• Hinged doors are at the bottom rear of the cowling where cooling air exits.
• Stronger low pressure area in lower cowl and increased airflow happens when cowl flaps are open.
• When cowl flaps are closed, the low pressure area weakens, decreasing airflow between cylinders.
• Cowl flaps are fully open for ground operations where airflow is reduced.
• In level flight, more air into the cowling allows cowl flaps to close and get rid of drag.

Firewalls

• A firewall is a fireproof bulkhead between the engine and the airframe to stop fire spread.
• Most firewalls are made from galvanized or stainless steel.
• All electrical wiring, plumbing, and engine controls are sealed where crossing the firewall.
• The firewall edges must be properly sealed where joining the structure, and must stay free of cracks and holes.

Engine Noise

• Engine noise is limited by federal regulations and can cause physical injury
• One method to reduce noise involves use of a noise suppression blanket.
• A sound can consist of a combination of many waves in a wide range of frequencies, or it can consist of a pure tone which is a single-frequency wave that follows the sine wave pattern.
• Sound is pressure waves in the air able to be heard.
• Noise produces a turbine engine consists of frequencies audible to the human ear with intensities reaching levels which can be destructive.
• Sound intensity is measured in decibels (dB).
• One decibel is one-tenth of a bel (B), the basic unit.
• A barely audible sound has an intensity of 1 B.
• A turbine engine nears 155 dB (15.5 B) on takeoff.
• On the decibel scale, sound intensity increases logarithmically.
• Doubling the decibel level squares the intensity; tripling it cubes the intensity.
• Sounds over 100 dB are intense.
• The human ear can evaluate a max of 120 dB, above which ear damage can occur .
• A noise suppression blanket contains fibrous insulating material covered in dimpled stainless steel.
• Acoustically materials are applied to the exhaust system for noise reduction.
• Fuselage linings use sound absorbing material encased in fireproof material for passenger comfort.

Engine Mounts

• Engine mounts require inspecting for bends, dents, flat spots, or elongated bolt holes.
• Dye penetrants help reveal cracks, porous areas, or defects.
• Magnetic particle inspection checks ferrous parts like mounting bolts.
• Engine mount structures are often constructed from formed/riveted sheet metal rails, forged alloy fittings, or welded alloy steel tubing.
• Riveted aluminum mount structures are generally use for large horizontally opposed engines on multi-engine aircraft.
• Steel tube mounts are for small/large horizontally opposed and radial engines.
• Steel tube engine mounting structures bolt to the engine firewall, separating engine and firewall.
• Dynafocal engine mounts are used in modern reciprocating aircraft where engine mounting points point inward to the engine centre of gravity.
• This design prevents transmission of engine vibration to the airframe.
• Vibration-isolating shock mounts dampen engine vibrations, permitting limited engine movement.
• Shock mounts include rubber components for engine weight to rest on.
• The rubber absorbs much engine vibration, reducing that to the airframe.

Anti-Vibration Mounts

• A typical engine mounting structure incorporates vibration isolating shock mounts to dampen vibrations and keep movement restricted.
• Shock mounts have rubber so the engine weight rests on the rubber
• This rubber absorbs engine vibration thus reducing it to the airframe.
• Mounts must be replaced in full sets
• Each set includes a front and rear mount
• Isolators set has two different types of mount
• One mount when fitted takes the load while the other takes the tension
• Regular maintenance ensures correct fitment.

Flexible Hoses

• Information to identify the hose is made up of:
  • The year and quarter of manufacture
  • The manufacturers part number and name/symbol
• Flexible hose size equals inside diameter in 1/16" increments.
• The dash number is the size of the hose
• MIL-SPEC number
• A lay line indicates twisting after installation (should be straight).
• Line color indicates the fluid line carries.
• Aircraft hoses are classified by pressure they can withstand.

Low Pressure Hose

• Low pressure hoses have a seamless inner tube and reinforcement made of single layer of cotton braid and an outer cover of ribbed or smooth rubber.
• Most air or vacuum hoses and some instrument lines are low pressure lines.
• Max pressure is 300 psi.

Medium Pressure Hose

• Seamless inner liner with one layer of cotton braid and one layer of stainless steel reinforcement.
• A rough oil resistant rubber impregnated cotton outer cover, plus a stainless steel outer braid for medium pressure hose
• Used for oil and coolant lines at pressures up to 1500psi.

High Pressure Hose

• High pressure hoses have synthetic rubber inner liner wrapped with two or more steel braids as reinforcement and a smooth synthetic rubber outer cover.
• They are for hydraulic system lines.
• Max pressure is >3000 psi
• Softer aluminum tubing (pure 1100) is used for low pressure systems under 1000psi - instrument/ventilating air.
• Low pressure fuel, oil, and medium pressure hydraulic/pneumatic systems (1000 to 15000psi) use stronger alloys such as 5052 – O.
• Corrosion resistant steel is used in high pressure systems (3000psi), including hydraulic, pneumatic, & oxygen systems.
• It's also used in areas with dirt, debris , corrosion from moisture, exhaust fumes, and salt air such as flap wells & external brake lines.

Fire Resistant Hoses

• Engine compartment hoses need to be fire resistant.
• FAA 'fire resistant' hoses withstand a 5-minute flame exposure without failure, under normal fluid pressure and flow conditions (FAA AC 33.17-1A).
• Fire resistance comes from using slip-on fire sleeving, encasing the hose in fire resistant silicone during manufacture (e.g. Teflon/PTFE hoses), or increasing wall thickness.

Special Maintenance of Slip-On Fire Sleeving

• Fire sleeving must cover the end fitting,.
• Maintainers need to identify nicks, cuts, manufacturing defects beneath slip-on fire sleeves.
• Unsealed hose sleeve ends can allow fuel, oil, or moisture to stay against the outer braid.
• Trapped water may cause corrosion of the hose outer braid and cause rupture during engine operation.
• Oil or fuel contamination inside the fire sleeve greatly reduces the fire resistance.

Universal Bulkhead Fitting

• Bulkhead fittings support a line passing through a bulkhead (straight machine threads, like nuts/bolts).
• Flared tube connections, crush washers, or synthetic seals are needed to tighten connections for fluids.
• Aluminium alloy and corrosion-resistant steel replaced copper in most uses,
• An AN Universal fitting supports a line through a bulkhead, and are available in all fitting standards
• Seals or O-rings seal fluid-tight where fittings passes through the bulkhead.

Feeders

• Feeder cables send electrical power from engine-driven generators to aircraft systems
• They also carry connectors through bulkheads/firewalls.
• Feeders are large section copper/aluminum cables.
• Some aircraft use one piece cables from the generator to the aircraft bus.
• Larger aircraft use high temp copper from the generator to the pylon or firewall, then splice into thicker aluminum cables for weight savings.

Connectors

• Connectors get often installed on wiring that's frequently disconnected.
• Wiring supplying avionic components uses multi-pin connectors for easy removal for maintenance.
• AN and MS connectors are frequent in aircraft electrical circuits in a lot of sizes/types.
• Mating connectors includes one has female contacts (sockets, another with male contacts (pins).
• Ground side of conductor connects to a male connector, power to the female connector to prevent accidental shorts when mating connectors are separated.
• Wires connect via tapered pins crimped onto the wire end that are then slipped into a tapered hole.
• A special tool removes/replaces the pin if needed.
• Some connector plugs needs soldering the wires into each end of a connector.
• To install a soldered connector, strip insulation leaving a 1/32 inch of bare wire beyond insulation.
• Next, slip on a specified length of insulated tubing over the end of each wire.
• Tin the stripped wire, then fill end of each pin (or solder pot) with solder.
• While keeping the melted solder in a solder pot, insert the wire.
• Keep wire completely still until the solder solidifies.
• Movement before solidification results in a granular solder appearance and excessive resistance.
• Clean any flux residues with an approved cleaner after soldering all wires.
• Inspect the soldering on the connector before final assembly
• The solder should completely fill each pot, with a rounded top
• Do not let the solder wick into strands or it becomes brittle and breaks when bent.
• Once all solder joints look good, slip tubing over each solder pot.
• Spot tie the bundle just above the tubing.
• Electrical leads are connected at the accessory or firewall.
• AN/MS connectors are for simple disconnections.
• A typical AN/MS connector includes a plug/receptacle assembly for one/more wires.
• The plug assembly screws to the receptacle, and secured with safety wire to prevent accidental disconnections during aircraft operation.
• Other wiring setups use a junction box that serves as a disconnect point.
• Leads are ring connectors secured by nut/washer.
• Disconnection comes down to removing the nut, and lifting off the ring terminal.
• Small aircraft electrical systems use knife/wrist-lock connectors in a protective sheathing.
• To disconnect it, remove the sheathing, and just separate the connector.
• To keep dirt and moisture out, wrap disconnected connectors with moisture proof tape.
• Coil loose cables/secure conduits to prevent entanglement/damage hen engine gets removed.
• Wires lacking clear identification need labeling to reduce confusion on reinstall.

Methods for Determining Current Carrying Capacity of Wires

• Electrical wire data is in single wire (free air) and bundled-in-harness forms.
• The data contains derating factors for altitude plus graphical/tabular use info.
• Wire may have more current capacity than connector contacts allow. Thus, contact rating dictates allowable current.
• Larger gauge wires may fit within crimp range of connector contacts that are rated for required current.
• Derating comes from bundle curves.

Heat Aging on Wire Insulation

• Because electrical wire inspection comes infrequently, special consideration to heat aging is done for wire type selection.
• Primary consideration is the wire's resistance to heat.
• The selection of wire should be under the most severe operating conditions if wire operates at high temperatures due to ambient heat, current loading, or the 2.

Maximum Operating Temperature

• The current that causes a temperature steady state should not be more than the wire's rated temperature.
• The wire’s max rated temperature needs basing on ability to withstand continuous operation without degrading.

Single Wire, Free Air

• The determination of wire current is initially to find the max allowable temperature difference.

Wires in a Harness

• Current is lower than that of single wire as wires get bundled.
• The amount depends of the number of wires in bundle plus function of the total bundle use rate.

Rods and Control Cables

• The bellcrank in engine installations with actuator, may need removal to remove a control rod.
• Turnbuckle joining the bellcrank actuator cable must then be removed.
• Mark the control cable end threads at the turnbuckle before removal.
• The marks makes reinstalling in the original position a simple matter before controls get a final trim.

Engine Control Disconnection

• Engine control rods and cables allow cockpit control of the throttle and mixture.
• Control rods have threads at both ends: clevis at one end, rod end bearing on the other.
• On most aircraft, connection of the rod end bearing to has a bolt with castle nut and cotter pin.
• Remove cotter pin and castle nut (if installed), then the bolt, to remove a control rod.
• Following engine control linkage disconnection, inspect all nuts and bolts for wear.
• Replace cotter pins, but if nuts and bolts need reuse, put them back on the rod ends to prevent loss.
• All control rods gets completely taken off or simply tied back to not get bent or broken.

Lifting Points

• When all engine connections are disconnected, the engine is ready for hoisting.
• Preparation means that the removal procedure is a simple task.
• A decision to remove the engine alone or together with the mount, needs happens.
• Standard overall only includes the engine not mount.
• If replacing with quick engine change assembly (QECA) the point comes at the firewall needing the mount.
• A QECA = power plant with accessories on the engine.
• Radial engine QECA's may include nacelles, thus would be part of the removal.
• After it’s freed from attach points, a sling needs installing allowing weight to be supported.
• Locations and sling/hoist layout vary.
• Engine manufacturers usually provide hoist apparatus info.
• Inspect slings/hoists plus determine their safe-to-use.
• Make sure the hoist lifts the engine safely by being conscious of the lift arm's length.
• The lift capacity greatly gets lessened when the arm gets max extended.

Engine Drains

• Drains allow excess fluids to automatically exit to prevent flammable buildup in the nacelle/engine compartment.
• Drains connect to fuel pump, induction manifold (closed in run, open when stops), and fuel line shrouds.
• Valves are fitted to drain fluids from engine lubrication, fuel for maintenance/inspection:
  • Fuel filer (for maintenance/fuel sampling)
  • Engine Sump (open to drain during maintenance)

Engine Monitoring and Ground Operation (Topic 16.12)

• In Australia, CASA controls all civil aviation so personnel must follow. awareness of:
  • CASR 1988 (Car 30 Licensing Requirements).
  • CASR 1998 (Part 66 Licensing Requirements).
  • Advisory Circulars (AC).
  • Airworthiness Directives (AD).
  • Service Bulletins (SB).
  • Operator's Maintenance Control Manual (MCM).
  • The Aircraft Flight Manuals (AFM).
  • Pilot Operating Handbooks (POH).
  • Aircraft Technical Logs.
  • Aircraft Log Book.
  • Engine Log Book.
  • Propeller Log Book.

Starting Piston Engines

• Only qualified and approved personnel (LAMEs on Type) may start up aero engines.
• A training program in accordance to Advisory Circular AC 66-3(1) is designed plus approved by Chief Engineer.
• Once trained the Chief Engineer and Chief Pilot then assess competency.
• The first three (3) start ups occur under the delegate supervision of Chief Pilot.
• The qualification remains of file with CASA for audit.
• Possessing a Radio telephone Operator's Cert is also needed.
• Always conduct a full pre-flight inspection/safety check prior to starting any engine/after.
• Meteorological info making sure safe conditions needs consulting.
• Engine run check sheets allowing recording engine parameters during run-up must stay.
• Suitable ISA charts should allow comparing engine efficiency versus standard.
• Follow the particular starting procedures for each engine.
• Precise instructions to install and the Pilots' Operating Handbook (POH)/Aircraft Flight Manual (AFM).

Ground Operation

• Engine run-up can present personnel and damage, so precautions are needed.
• Run-ups occur in designated places.
• Position aircraft on clean level points aimed so blast does not move anything in hangar on onto adjacent airplanes.
• Don't rely brakes solely, chock wheels or tie aircraft to keep.
• Service such that ground power, should be well separate to prop strike, wheels safely situated along chocks and brakes.
• Additionally, fire extinguishers require nearby as well as personnel clear of the area.
• Establish communication.

Hydraulic Lock

• Radial engines following shutdown have oil build up where fluid accumulates in lower cylinder and intake.
• Damage occurs due to fluids not being compressible.
• The hydraulic lock needs inspection (engines sitting for 30 mins)
• Ignition switch to OFF and rotate the propeller in to make turn of the prop 360 degree for minimal 2 times
• Effort increases if some liquid enters cylinder
• Removing the spark plug and the front prop is the better way if there is a lock-up present.
• Never pull propeller in the other rotation since that could affect the cylinder with a full or partial start.

Engine Ground Fires

• Engine starting provides possibility fire as primed fuel works into system and backfires.
• The position of the nearest fire safety equipment needs recognition.

Engine Instrumentation

• Engine instrumentation understanding requires importance to operators and troubleshoot.
• This knowledge requires knowing indicator markings to help with performance.
• Markings enable distinguishing various operations.

Instrument Range Markings

• Range markings base found on Type Certificate Data Sheet. Traditionally, indications = green, blue, yellow, plus red indications.
• Green arcs is the most used safe, operating point.
• Upper end, is continuous operation as low = stop.
• Green-arc is non restricted usually.
• Blue-arcs = unique circumstances. Fuel flow flying above a height is example.
• Rarely is blue seen, such as tachometer, pressure cylinder or others.
• Yellow time limits operation.
• Yellow omitted.
• Indication in a change need to changing or some issue.
• The red line = min or max. operation with line danger operating.
• Triangle with markings showing.

Starting Engine with Float Carburetors

• Trainers with up to 300 hp are equipped
• There exist steps to ensure
  • Aircraft are positioned away and prevent for gravel.
  • Chocks in main wheels after setting.
  • Have the nearest extinguishes ready.
• Engine is to be prepared.
  • Turn the batteries.
  • Select a tank.
  • Carburetor is then Cooled.
  • A CONSTANT SPEED propeller is set the pitch set at low.

Operations Handbook

• Manuals approved list from NAA. Operating Conditions include POH.

Starting with Teledyne

• Fuel gets starts more often.

Engine Instrumentation.

• ON the battery then selecting he proper tanks.
• Direct with a Air Direct.
• 148 then RICH on mixture.
• Check no one moves it.
• Then move flow IGN.
• The oil goes back to throttle.
• Inspect then do some actions.

Stopping procedure

• Instructions on engine. The SHUTOFF place is the best on any operation.
• All burns for all possible actions.

Piston-Engine Ground Test

• Condition of the engine and loose pebbles or a spot for rotor is needed.
• Position will protect and ensure to.

Inspections

• The alternator must work. If not, set to stop then move through the stop.
• Magneto, after raising speeds the Ignition switch has to check properly. The drop have to be. If it will not be safe, move the right of it.
• They each should drop smoothly.
• The oil after fuel inspections goes to its.
• Set governors
• Static is the proper test.

Magneto Checks

• Testing can start with dual checks. The two system check is key. For the mixture into 2 is more combustion.
• Flight prep does it for proper burning. If the engine acts that ways, a less engine run or RPM.
• The checks is made after this and if not operating rough, inspect the.
• RPM will set. if humidity, airport is needed.
• No drops with no drops means wrong test.
• If cylinders are poor actions and will start rough.
• The check needs stabilization.

Power Curves

• Charts from develop for each RPM to indicator
• Power curve will show. to the.
• To show operation has it to.
• to the show its.
• Specific shows more of the. action times.

Mixture Vs Power

• The graph shows horsepower.
• Power show be.

Air Fuel

• The temperature is best under the.

Cylinder Checks

• Test can do what actions work.
• Some one or to the will see issue lacking work.
• Can be made from cylinder.
• Troubles might be.
• Rough operation if cylinder does not operate warm.
• Follow proper air.
• Cylinder under operate.
• The testers test.

Compression

• If piston has piston cylinder in the chamber.

Differential Testing

• Power requires valves open.
• Most leak if there some to.
• Test as is then is.
• Run engine is test fresh action.
• Oil and times makes the test more.
• Actions as is.
• Remove testing area.
• Cylinder up top of wheel.
• Do it.
• Test is good open tests

Directs Tests

• As is you cylinder.
• Air check does it.
• Most action checks does this.
• Remove does it.
• Action clean to be more proper with actions.
• Install. then check actions.