Powerplant 08 Ignition and Starting Systems

In a turbine engine dc capacitor discharge ignition system, where are the high-voltage pulses formed?. At the breaker. At the triggering transformer. At the rectifier.

In reference to a 'Shower of Sparks' ignition system, (1) the retard breaker points are designed to keep the affected ignition system operating if the advance breaker points should fail during normal engine operation (after start). (2) the timed opening of the retard breaker points is designed to prevent engine 'kickback' during start. Regarding the above statements,. only No. 1 is true. only No. 2 is true. both No. 1 and No. 2 are true.

When a magneto is operating, what is the probable cause for a shift in internal timing?. The rotating magnet loses its magnetism. The distributor gear teeth are wearing on the rotor gear teeth. The cam follower wear and/or the breaker points wear.

Air turbine starters are generally designed so that reduction gear distress or damage may be detected by. characteristic sounds from the starter assembly during engine start. breakage of a shear section on the starter drive shaft. inspection of a magnetic chip detector.

What is the relationship between distributor and crankshaft speed of aircraft reciprocating engines?. The distributor turns at one-half crankshaft speed. The distributor turns at one and one-half crankshaft speed. The crankshaft turns at one-half distributor speed.

What is the purpose of using an impulse coupling with a magneto?. To absorb impulse vibrations between the magneto and the engine. To compensate for backlash in the magneto and the engine gears. To produce a momentary high rotational speed of the magneto.

(Refer to Figure 5.) The type of system depicted is capable of operating with. external power only. either battery or external power. battery power and external power simultaneously.

How are most radial engine spark plug wires connected to the distributor block?. By use of cable-piercing screws. By use of self-locking cable ferrules. By use of terminal sleeves and retaining nuts.

Which of the following statements most accurately describes spark plug heat range?. The length of the threaded portion of the shell usually denotes the spark plug heat range. A hot plug is designed so that the insulator tip is reasonably short to hasten the rate of heat transfer from the tip through the spark plug shell to the cylinder head. A cold plug is designed so that the insulator tip is reasonably short to hasten the rate of heat transfer from the tip through the spark plug shell to the cylinder head.

What would be the result if a magneto breaker point mainspring did not have sufficient tension?. The points will stick. The points will not open to the specified gap. The points will float or bounce.

What component of a dual magneto is shared by both ignition systems?. High-tension coil. Rotating magnet. Capacitor.

The E-gap angle is usually defined as the number of degrees between the neutral position of the rotating magnet and the position. where the contact points close. where the contact points open. of greatest magnetic flux density.

Magneto breaker point opening relative to the position of the rotating magnet and distributor rotor (internal timing) can be set most accurately. during the magneto-to-engine timing operation. during assembly of the magneto before installation on the engine. by setting the points roughly at the required clearance before installing the magneto and then making the fine breaker point adjustment after installation to compensate for wear in the magneto drive train.

How does the ignition system of a gas turbine engine differ from that of a reciprocating engine?. One igniter plug is used in each combustion chamber. Magneto-to-engine timing is not critical. A high-energy spark is required for ignition.

A safety feature usually employed in direct-cranking starters that is used to prevent the starter from reaching burst speed is the. drive shaft shear point. stator nozzle design that chokes airflow and stabilizes turbine wheel speed. spring coupling release.

Which of the following statements regarding magneto switch circuits is NOT true?. In the BOTH position, the right and left magneto circuits are grounded. In the OFF position, neither the right nor left magneto circuits are open. In the RIGHT position, the right magneto circuit is open and the left magneto circuit is grounded.

(Refer to Figure 5.) Which malfunctions will allow the igniters to operate when tested but be inoperative during a start attempt? 1. Conductor No. 10 broken. 2. Conductor No. 11 broken. 3. Ignition relay inoperative. 4. Conductor No. 12 broken. 1 or 4. 2 or 3. 1 or 3.

Defective spark plugs will cause the engine to run rough. during run up. during cruise. at all speeds.

When installing a magneto on an engine, the. piston in the No. 1 cylinder must be a prescribed number of degrees before top center on the compression stroke. magneto breaker points must be just closing. piston in the No. 1 cylinder must be a prescribed number of degrees after top center on the intake stroke.

What is the electrical location of the primary capacitor in a high-tension magneto?. In parallel with the breaker points. In series with the breaker points. In series with the primary and secondary winding.

The secondary coil of a magneto is grounded through the. ignition switch. primary coil. ground side of the breaker points.

Magneto timing drift is caused by erosion of the breaker points and. excessive spark plug gap. wear of the cam followers. loss of magnetism in the rotor.

Which statement is correct regarding the ignition system of a turbine engine?. The system is normally de-energized as soon as the engine starts. It is energized during the starting and warmup periods only. The system generally includes a polar inductor-type magneto.

(1) The platinum and iridium ground electrodes used on fine wire spark plugs are extremely brittle and can be broken if they are improperly handled or adjusted. (2) When gapping massive-electrode spark plugs, a wire gauge should be inserted between the center and ground electrodes while moving the ground electrode in order to avoid setting the gap too close. Regarding the above statements,. only No. 1 is true. only No. 2 is true. both No. 1 and No. 2 are true.

When using an electric starter motor, current usage. is highest at the start of motor rotation. remains relatively constant throughout the starting cycle. is highest just before starter cutoff (at highest RPM).

Failure of an engine to cease firing after turning the magneto switch off is an indication of. an open high tension lead. an open P-lead to ground. a grounded magneto switch.

How is the strength of a magneto magnet checked?. Hold the points open and check the output of the primary coil with an ac ammeter while operating the magneto at a specified speed. Check the ac voltage reading at the breaker points. Check the output of the secondary coil with an ac ammeter while operating the magneto at a specified speed.

If a spark plug lead becomes grounded, the. magneto will not be affected. distributor rotor finger will discharge to the next closest electrode within the distributor. capacitor will break down.

What will be the results of increasing the gap of the breaker points in a magneto?. Retard the spark and increase its intensity. Advance the spark and decrease its intensity. Retard the spark and decrease its intensity.

What will be the result of using too hot a spark plug?. Fouling of plug. Preignition. Burned capacitor.

A defective primary capacitor in a magneto is indicated by. a fine-grained frosted appearance of the breaker points. burned and pitted breaker points. a weak spark.

Spark plug fouling caused by lead deposits occurs most often. during cruise with rich mixture. when cylinder head temperatures are relatively low. when cylinder head temperatures are high.

Which of the following are distinct circuits of a high tension magneto?. Magnetic, primary, and secondary. Magnetic, E-gap, and P lead. Primary, P lead, and secondary.

In a high-tension ignition system, a primary capacitor of too low a capacity will cause. excessive primary voltage. excessively high secondary voltage. the breaker contacts to burn.

If new breaker points are installed in a magneto on an engine, it will be necessary to time the. magneto internally and the magneto to the engine. breaker points to the No. 1 cylinder. magneto drive to the engine.

What are two parts of a distributor in an aircraft engine ignition system? 1. Coil. 2. Block. 3. Stator. 4. Rotor. 5. Transformer. 2 and 4. 3 and 4. 2 and 5.

What is the purpose of a safety gap in some magnetos?. To discharge the secondary coil's voltage if an open occurs in the secondary circuit. To ground the magneto when the ignition switch is off. To prevent flashover in the distributor.

When removing a shielded spark plug, which of the following is most likely to be damaged?. Center electrode. Shell section. Core insulator.

The primary advantage of pneumatic (air turbine) starters over comparable electric starters for turbine engines is. a significant lack of wear to the commutator. that it does not disengage until the engine reaches idle. high power-to-weight ratio.

(Refer to Figure 5.) With power applied to the bus bar, what switch changes will allow the ignition exciters test switch to function?. Engine master switch, battery switch, and power lever switch. Engine master switch, start switch, and test switch. Engine master switch and ignition switch.

In a high-tension ignition system, the current in the magneto secondary winding is. conducted from the primary winding via the discharge of the capacitor. induced when the primary circuit is interrupted. induced when the primary circuit discharges via the breaker points.

Capacitance afterfiring in most modern spark plugs is reduced by the use of. fine wire electrodes. a built-in resistor in each plug. aluminum oxide insulation.

.The magnetic circuit of a magneto consists of a permanent multi-pole rotating magnet. The core is made of. hard steel. soft iron. electrical steel.

Magneto breaker points must be timed to open when the. rotating magnet is positioned a few degrees before neutral. greatest magnetic field stress exists in the magnetic circuit. rotating magnet is in the full register position.

When testing a magneto distributor block for electrical leakage, which of the following pieces of test equipment should be used?. A high-tension harness tester. A continuity tester. A high-range ammeter.

Ignition check during engine runup indicates a slow drop in RPM. This is usually caused by. defective spark plugs. a defective high-tension lead. incorrect ignition timing or valve adjustment.

The spark is produced in a magneto ignition system when the breaker points are. fully open. beginning to open. fully closed.

When the ignition switch of a single (reciprocating) engine aircraft is turned to the OFF position,. the primary circuits of both magnetos are grounded. the secondary circuits of both magnetos are opened. all circuits are automatically opened.

Advantages of dual ignition in aircraft engines include providing a backup magneto system, increasing the output power of the engine, and. permitting the use of lower grade fuels. increasing the intensity of the spark at the spark plugs. increasing the output power of the engine.

In an aircraft ignition system, one of the functions of the capacitor is to. regulate the flow of current between the primary and secondary coil. facilitate a more rapid collapse of the magnetic field in the primary coil. stop the flow of magnetic lines of force when the points open.

What likely effect would a cracked distributor rotor have on a magneto?. Ground the secondary circuit through the crack. Fire two cylinders simultaneously. Ground the primary circuit through the crack.

The purpose of staggered ignition is to compensate for. short ignition harness. rich fuel/air mixture around exhaust valve. diluted fuel/air mixture around exhaust valve.

What will be the effect if the spark plugs are gapped too wide?. Insulation failure. Hard starting. Lead damage.

The capacitor-type ignition system is used almost universally on turbine engines primarily because of its high voltage and. low amperage. long life. high-heat intensity.

Great caution should be exercised in handling damaged hermetically sealed turbine engine igniter transformer units because. compounds in the unit may become a fire or explosion hazard when exposed to the air. some contain radioactive material. some contain toxic chemicals.

Airflow to the pneumatic starter from a ground unit is normally prevented from causing starter overspeed during engine start by. stator nozzle design that chokes airflow and stabilizes turbine wheel speed. activation of a flyweight cutout switch. a preset timed cutoff of the airflow at the source.

In a four-stroke cycle aircraft engine, when does the ignition event take place?. Before the piston reaches TDC on compression stroke. After the piston reaches TDC on power stroke. After the piston reaches TDC on compression stroke.

Generally, when removing a turbine engine igniter plug, in order to eliminate the possibility of the technician receiving a lethal shock, the ignition switch is turned off and. disconnected from the power supply circuit. the igniter lead is disconnected from the plug and the center electrode grounded to the engine after disconnecting the transformer-exciter input lead and waiting the prescribed time. the transformer-exciter input lead is disconnected and the center electrode grounded to the engine after disconnecting the igniter lead from the plug and waiting the prescribed time.

A spark plug is fouled when. its spark grounds by jumping electrodes. it causes preignition. its spark grounds without jumping electrodes.

.(Refer to Figure 5.) With power applied to the bus bar, what wire supplies standby power to the starter relay contact?. 4. 7. 8.

Sharp bends should be avoided in ignition leads primarily because. weak points may develop in the insulation through which high tension current can leak. ignition lead wire conductor material is brittle and may break. ignition lead shielding effectiveness will be reduced.

How many secondary coils are required in a low-tension ignition system on an 18-cylinder engine?. 36. 18. 9.

When performing a magneto ground check on an engine, correct operation is indicated by. a slight increase in RPM. no drop in RPM. a slight drop in RPM.

(Refer to Figure 5.) When an external power source is connected to the aircraft,. the battery cannot be connected to the bus. both battery power and external power are available to the bus. the starter relay coil has a path to ground.

Aircraft magneto housings are usually ventilated in order to. prevent the entrance of outside air which may contain moisture. allow heated air from the accessory compartment to keep the internal parts of the magneto dry. provide cooling and remove corrosive gases produced by normal arcing.

Spark plugs are considered worn out when the. electrodes have worn away to about one-half of their original dimensions. center electrode edges have become rounded. electrodes have worn away to about two-thirds of their original dimensions.

The numbers appearing on the ignition distributor block indicate the. sparking order of the distributor. relation between distributor terminal numbers and cylinder numbers. firing order of the engine.

Which of the following, obtained during magneto check at 1,700 RPM, indicates a short (grounded) circuit between the right magneto primary and the ignition switch?. BOTH -- 1,700 RPM, R -- 1,625 RPM, L -- 1,700 RPM, OFF -- 1,625 RPM. BOTH -- 1,700 RPM, R -- 0 RPM, L -- 1,700 RPM, OFF -- 0 RPM. BOTH -- 1,700 RPM, R -- 0 RPM, L -- 1,675 RPM, OFF -- 0 RPM.

Capacitance afterfiring of a spark plug is caused by. the stored energy in the ignition shielded lead unloading after normal timed ignition. excessive center electrode erosion. constant polarity firing.

Which of the following would be cause for rejection of a spark plug?. Carbon fouling of the electrode and insulator. Insulator tip cracked. Lead fouling of the electrode and insulator.

Spark plug heat range is determined by. the reach of the spark plug. its ability to transfer heat to the cylinder head. the number of ground electrodes.

When internally timing a magneto, the breaker points begin to open when. the piston has just passed TDC at the end of the compression stroke. the magnet poles are a few degrees beyond the neutral position. the magnet poles are fully aligned with the pole shoes.

If it is found that a shielded ignition system does not adequately reduce ignition noise, it may be necessary to install. a second layer of shielding. a filter between the magneto and magneto switch. bonding wires from the shielding to ground.

The constrained-gap igniter plug used in some gas turbine engines operates at a cooler temperature because. it projects into the combustion chamber. the applied voltage is less. the construction is such that the spark occurs beyond the face of the combustion chamber liner.

In the aircraft magneto system, if the P-lead is disconnected, the magneto will be. on regardless of ignition switch position. grounded regardless of ignition switch position. open regardless of ignition switch position.

A magneto ignition switch is connected. in series with the breaker points. parallel to the breaker points. in series with the primary capacitor and parallel to the breaker points.

(Refer to Figure 5.) If wire No. 8 is broken or disconnected after starter rotation is initiated, and the power lever is advanced, the. starting sequence will continue normally. starter will shut down, but the igniters will continue to fire. starting sequence will discontinue.

The purpose of a safety gap in a magneto is to. prevent burning out the primary winding. protect the high-voltage winding from damage. prevent burning of contact points.

If an aircraft ignition switch is turned off and the engine continues to run normally, the trouble is probably caused by. an open ground lead in the magneto. arcing magneto breaker points. primary lead grounding.

Ignition check during engine runup indicates excessive RPM drop during operation on the right magneto. The major portion of the RPM loss occurs rapidly after switching to the right magneto position (fast drop). The most likely cause is. faulty or fouled spark plugs. incorrect ignition timing on both magnetos. one or more dead cylinders.

A clicking sound heard at engine coast-down in a pneumatic starter incorporating a sprag clutch ratchet assembly is an indication of. gear tooth and/or pawl damage. one or more broken pawl springs. the pawls re-contacting and riding on the ratchet gear.

When the switch is off in a battery ignition system, the primary circuit is. grounded. opened. shorted.

When using a timing light to time a magneto to an aircraft engine, the magneto switch should be placed in the. BOTH position. OFF position. LEFT or RIGHT position (either one).

What is a result of 'flashover' in a distributor?. Intense voltage at the spark plug. Reversal of current flow. Conductive carbon trail.

In a low-tension ignition system, each spark plug requires an individual. capacitor. breaker assembly. secondary coil.

In a typical starter-generator system, under which of the following starting circumstances may it be necessary to use the start stop button?. Hung start. Hot start. Contacts stick open.

The purpose of an under current relay in a starter-generator system is to. provide a backup for the starter relay. disconnect power from the starter-generator and ignition when sufficient engine speed is reached. keep current flow to the starter-generator under the circuit capacity maximum.

When using an electric starter motor, the current flow through it. is highest just before starter cutoff (at highest RPM). remains relatively constant throughout the starting cycle. is highest at the start of motor rotation.

Magneto pole shoes are generally made of. laminations of high-grade soft iron. laminations of high-grade Alnico. pieces of high-carbon iron.

At what RPM is a reciprocating engine ignition switch check made?. 1,500 RPM. The slowest possible RPM. Full throttle RPM.

Using a cold spark plug in a high-compression aircraft engine would probably result in. normal operation. a fouled plug. detonation.

The spark occurs at the spark plug when the ignition's. secondary circuit is completed. primary circuit is completed. primary circuit is broken.

Upon inspection of the spark plugs in an aircraft engine, the plugs were found caked with a heavy black soot. This indicates. worn oil seal rings. a rich mixture. a lean mixture.

Alignment of the marks provided for internal timing of a magneto indicates that the. breaker points are just beginning to close for No. 1 cylinder. magneto is in E-gap position. No. 1 cylinder is on TDC of compression stroke.

As an aircraft engine's speed is increased, the voltage induced in the primary coil of the magneto. remains constant. increases. varies with the setting of the voltage regulator.

The type of ignition system used on most turbine aircraft engines is. high resistance. low tension. capacitor discharge.

What components make up the magnetic system of a magneto?. Pole shoes, the pole shoe extensions, and the primary coil. Primary and secondary coils. Rotating magnet, the pole shoes, the pole shoe extensions, and the coil core.

The term 'reach,' as applied to spark plug design and/or type, indicates the. linear distance from the shell gasket seat to the end of the threads on the shell skirt. length of center electrode exposed to the flame of combustion. length of the shielded barrel.

How does high-tension ignition shielding tend to reduce radio interference?. Prevents ignition flashover at high altitudes. Reduces voltage drop in the transmission of high-tension current. Receives and grounds high-frequency waves coming from the magneto and high-tension ignition leads.

A safety feature usually employed in pneumatic starters that is used if the clutch does not release from the engine drive at the proper time during start is the. flyweight cutout switch. spring coupling release. drive shaft shear point.

Igniter plugs used in turbine engines have a long service life because they. have a high intensity spark. operate continuously with a lower spark. do not require continuous operation.

If the ground wire of a magneto is disconnected at the ignition switch, the result will be the. affected magneto will be isolated and the engine will run on the opposite magneto. engine will stop running. engine will not stop running when the ignition switch is turned off.

In the event a pneumatic start valve will not operate and the manual override must be used, the starter T-handle must be closed at scheduled starter drop out because. the starter will overheat. the starter will overspeed at a given N^2. the starter oil will be blown overboard.

In order to turn a magneto off, the primary circuit must be. grounded. opened. shorted.

When will the voltage in the secondary winding of a magneto, installed on a normally operating engine, be at its highest value?. Just prior to spark plug firing. Toward the latter part of the spark duration when the flame front reaches its maximum velocity. Immediately after the breaker points close.

Why are turbine engine igniters less susceptible to fouling than reciprocating engine spark plugs?. The high-intensity spark cleans the igniter. The frequency of the spark is less for igniters. Turbine igniters operate at cooler temperatures.

When timing a magneto internally, the alignment of the timing marks indicates that the. breaker points are just closing. magnets are in the neutral position. magnets are in the E-gap position.

The electrical circuit from the spark plug back to the magneto is completed by grounding through the. engine structure. P-lead. cockpit switch.

Which of the following are included in a typical turbine engine ignition system? 1. Two igniter plugs. 2. Two transformers. 3. One exciter unit. 4. Two intermediate ignition leads. 5. Two low-tension igniter leads. 6. Two high-tension igniter leads. 2, 3, 4. 1, 4, 5. 1, 3, 6.

What is the approximate position of the rotating magnet in a high-tension magneto when the points first close?. Full register. Neutral. A few degrees after neutral.

What should be used to clean grease or carbon tracks from capacitors or coils that are used in magnetos?. Solvent. Acetone. Naphtha.

The amount of voltage generated in any magneto secondary coil is determined by the number of windings and by the. rate of buildup of the magnetic field around the primary coil. rate of collapse of the magnetic field around the primary coil. amount of charge released by the capacitor.

A certain nine-cylinder radial engine used a noncompensated single-unit, dual-type magneto with a four-pole rotating magnet and separately mounted distributors. Which of the following will have the lowest RPM at any given engine speed?. Breaker cam. Engine crankshaft. Distributors.

Which of the following breaker point characteristics is associated with a faulty capacitor?. Crowned. Fine grained. Coarse grained.

Why do turbine engine ignition systems require high energy?. To ignite the fuel under conditions of high altitude and high temperatures. Because the applied voltage is much greater. To ignite the fuel under conditions of high altitude and low temperatures.

When internally timing a magneto, the breaker points begin to open when the rotating magnet is. fully aligned with the pole shoes. a few degrees past full alignment with the pole shoes. a few degrees past the neutral position.

The greatest density of flux lines in the magnetic circuit of a rotating magnet-type magneto occurs when the magnet is in what position?. Full alignment with the field shoe faces. A certain angular displacement beyond the neutral position, referred to as E-gap angle or position. The position where the contact points open.

What is the radial location of the two north poles of a four-pole rotating magnet in a high-tension magneto?. 180° apart. 270° apart. 90° apart.

Why are high-tension ignition cables frequently routed from the distributors to the spark plugs in flexible metallic conduits?. To eliminate high altitude flashover. To reduce the formation of corona and nitric oxide on the cable insulation. To reduce the effect of the high-frequency electromagnetic waves emanated during operation.

Which of the following could cause damage to the nose ceramic or to the electrode of an aircraft spark plug?. Plug installed without a copper gasket. Improper gapping procedure. Excessive magneto voltage.

If staggered ignition timing is used, the. spark plug nearest the exhaust valve will fire first. spark will be automatically advanced as engine speed increases. spark plug nearest the intake valve will fire first.

What test instrument could be used to test an ignition harness for suspected leakage?. A high tension lead tester. A high voltage dc voltmeter. A high amperage dc ammeter.

What is the difference between a low-tension and a high-tension engine ignition system?. A low-tension system produces relatively low voltage at the spark plug as compared to a high-tension system. A high-tension system is designed for high-altitude aircraft, while a low-tension system is for low- to medium-altitude aircraft. A low-tension system uses a transformer coil near the spark plugs to boost voltage, while the high-tension system voltage is constant from the magneto to the spark plugs.

Pneumatic starters are usually designed with what types of airflow impingement systems?. Radial inward flow turbine and axial-flow turbine. Centrifugal compressor and axial-flow compressor. Double entry centrifugal outward flow and axial-flow turbines.

(Refer to Figure 5.) Which malfunctions will allow the igniters to operate normally during start but be inoperative when tested? 1. Conductor No. 14 broken. 2. Conductor No. 10 broken. 3. Conductor No. 15 broken. 4. Conductor No. 12 broken. 2 or 4. 1 or 3. 3 or 4.

Thermocouples are usually inserted or installed on the. front cylinder of the engine. rear cylinder of the engine. hottest cylinder of the engine.

Hot spark plugs are generally used in aircraft powerplants. with comparatively high compression or high operating temperatures. with comparatively low operating temperatures. which produce high power per cubic inch displacement.

When a 'Shower of Sparks' ignition system is activated at an engine start, a spark plug fires. as soon as the advance breaker points open. only while both the retard and advance breaker points are closed. only while both the retard and advance breaker points are open.

Inspection of pneumatic starters by maintenance technicians usually includes checking the. oil level and magnetic drain plug condition. stator and rotor blades for FOD. rotor alignment.

A spark plug's heat range is the result of. the area of the plug exposed to the cooling airstream. its ability to transfer heat from the firing end of the spark plug to the cylinder head. the heat intensity of the spark.

When does battery current flow through the primary circuit of a battery ignition coil?. Only when the breaker points are open. At all times when the ignition switch is on. When the breaker points are closed and the ignition switch is on.

Shielding is used on spark plug and ignition wires to. protect the wires from short circuits as a result of chafing or rubbing. prevent outside electromagnetic emissions from disrupting the operation of the ignition system. prevent interference with radio reception.