Langley Flying School Private Pilot Groundschool Manual Sample ...

More documents

Recommendations

Info

Private and Recreational Pilot Groundschool Manual Page 42Langley Flying School, Inc.The effects of carburettor icing are usually subtle power loss and progressive engine failure.Their causes are vaporisation and expansion.Vaporisation of fuel requires heat and as fuel is vaporised, heat is taken from the surrounding air; the temperaturedrop in the mixing chamber air can be as much as 30C., thereby freezing any water in the air (fuel vaporizationice).Carburettors have a venturi that is designed to create a low pressure (vacuum) that draws in the fuel; expansion of agas causes cooling (approximately 3C.), and moisture can freeze and collect on the throttle valve at base of venturi(throttle ice).When faced with carburettor icing, the first response is to apply carburettor heat—this action should be the firstaction in engine failure just in case the cause of trouble is ice (if carburettor heat is not applied immediately, usableheat from the exhaust manifold may be lost as the engine cools following the failure); if there is no ice, there will bea crisp drop in RPM. If there is ice there will usually be no immediate change, but this will be quickly followed byengine roughness as water from the melted ice is ingested into the induction system.The two-minute rule is used when in doubt about icing: turn the carburettor heat on for at least two minutes andadjust the mixture to maximize engine performance; remember that carburettor heat degrades engine performance asit effectively decreases the density of the air entering the carburettor.Fuel injected engines are not affected by carburettor icing, but in addition to throttle ice and fuel vaporization ice, athird form of icing, referred to as impact ice, can adversely affect both carburettor engines and fuel injected engines.Impact icing occurs when ice builds on the external airframe during flight, including the air-intake and filteringsystems for the engine.Excessive ice on the air-intake system will effectively choke and eventually starve the engine of airflow; for thisreason the selection of carburettor heat also provides an alternate heated source of air (the air is drawn from a hotbox mounted on the exhaust manifold, but the air entering the hot box is non-filtered air drawn from the enginecompartment); in contrast, fuel-injected engines have an “alternate air” source which can be selected in the cockpitwhich draws air into the engine from an engine compartment source.Superchargers and TurbochargersSupercharger and Turbocharger engine design providegreater altitude performance by creating a forcedinduction (boost) through the use of a compressor.Superchargers are compressors driven by the engine andmounted between the carburettor and intake manifold.Turbochargers are compressors driven by an exhaustturbine and mounted between air intake and thecarburettor.IgnitionTwo independent magnetos (engine-driven generator)that generates low tension current, transforms it into hightension current, and distributes it to individual sparkplugs.Dual ignition provides safety and improved performance;failure of one will result in a 75 RPM reduction inperformance (typically a 3% power reduction). Bothmagnetos are selected for normal flight, and this ischecked by the pilot prior to takeoff using the magnetoswitch in cockpit (the circuits can be grounded). In theevent that one magneto fails during flight, the pilot isable to disconnect the failed magneto by selectivelygrounding it, allowing the engine to run on the normalLeftMagnetoCrankcaseBottom PlugTop PlugRightMagneto© 2012 David L. Parry
Private and Recreational Pilot Groundschool Manual Page 43Langley Flying School, Inc.functioning magneto (failure to ground a misfiring magneto could cause serious damage to the engine).Here are two rules to follow:1. Always ensure magnetos are dead during shut down.2. Never rotate the prop of an aeroplane 26It is important to know that unless the primary circuit is grounded by selecting the “off” position with the cockpitmagneto switch, the engine can still fire. The off position effectively grounds the primary circuit, therebyinterrupting the flow of electrical energy. If the grounding connection associated with the magneto switch ismalfunctioning and the circuit is not interrupted, this so-called “live mag” can be extremely hazardous to anyonetouching the propeller as the engine could unexpectedly start merely from physical pressure.Electrical PowerAircraft electrical power is derived from an alternator or generator, which provides electrical power to the aircraftsystems during flight and recharges the battery. The battery, in turn, is used to start the engine and serves as abackup for electrical power should the alternator or generator fail.Most aircraft have alternators, but some have generators; generators cannot produce sufficient electrical charge topower the aircraft systems at low RPM, while alternators provide constant power at any RPM setting.While a generator can bring a dead battery back to life, an alternator cannot.Electrical systems have voltage regulators which safeguard the systems from alternator or generator overload andensures the battery is not overcharged.The bus bar provides the arteries through which the electricalenergy is distributed to the electrical circuits, which in turnare connected to the various electrical components of theaircraft.Each circuit is protected by a circuit breaker or other type offuse that protects the connected components from excessvoltage or short-circuits.The network of circuit breakers is usually the “push to reset”type which can be readily done during flight.Electrical components such as radio equipment can bedamaged from the voltage drop associated with engine start,and for this reason, all electrical components should be turnedoff prior to engine start.Two types of electrical monitoring instruments are theammeter, which measures the rate of flow associated with thecurrent being produced, and the voltmeter, which indicates thevoltage in the system.An ammeter should always indicate a reading that is positive(+) of zero.01020ALTAMPERES3040Alternator LoadAmmeterAMMETERS-40-20 0AMPS+20+40Charge/DischargeAmmeterThe Alternator Load Ammeter (ALA) and the Charge/DischargeAmmeter (CDA) are the two primary types of ammeters. TheALA displays the amount of electrical load exerted on analternator or generator, while the CDA indicates either the rate ofcharge or discharge to the battery. When the CDA needle is tothe left of centre (negative value), more electrical energy is beingused by the aircraft than is being replaced by the generatingsystem. By comparison, an ALA reading of “zero” (0) indicates noelectrical energy is being produced by the generating system.Generator-power aircraft at idle (during pre-takeoff, for example)normally indicate a negative value as the generator is turning tooslow; in contrast, the ammeter values will remain constantregardless of idle speed.26 The magnetos are equipped with impulse coupling, a mechanism that rapidly spins the magneto during starting. Accordingly, all that isrequired to start an aircraft engine is the trigger of the impulse couple (just touching the propeller could do this if the propeller is in the rightposition)—if the magnetos have been left on, the engine will likely start if an impulse couple is triggered. For the same reason, if you ever haveto move a propeller by hand (commonly required when moving aircraft around the ramp), be sure you rotate the propeller opposite to its normalrotation direction—this will not trigger the impulse coupling.© 2012 David L. Parry
Page 1: Celebrating 18 Years of Flight Trai
Page 4 and 5: Private and Recreational Pilot Grou
Page 58: Private and Recreational Pilot Grou

Langley Flying School Private Pilot Groundschool Manual Sample ...

Create successful ePaper yourself

Delete template?

Save as template?