POWERPLANT ORAL STUDY GUIDE ACTUAL

POWERPLANT ORAL STUDY GUIDE (ACTUAL

-) QUESTIONS AND ANSWERS.

What is meant by creep of the turbine blades? - Answers___A condition of permanent elongation of the turbine blades.Creep is caused by the high temperatures and the high centrifugal loading imposed on the blades

How is the compressor of a turbine engine cleaned? - Answers___An emulsion-type cleaner is sprayed through the engine while it is being motored by the starter or operated at a low speed. The wash is followed by a clean water rinse. More vigorous cleaning is done by injecting a mild abrasive, such as ground-up apricot pits or walnut shells, into the engine while it is operating at low speed

Where is water injected into a turbine engine for cooling purposes? - Answers___Into the compressor inlet and into the engine diffuser case

At what point in a turbine engine is the temperature the highest? - Answers___At the inlet to the high-pressure turbine

What is the basic difference between a low-tension magneto and a high-tension magneto? - Answers___The low-tension ignition system has only one coil in the magneto, and it used a carbon-brush-type distributor. Low voltage is distributed to high-tension transformers that are located on the heads of each cylinder. A high-tension magneto produces high voltage in the magneto coil, and it is sent to the correct spark plug by the built-in high voltage distributor 1 / 4

POWERPLANT ORAL STUDY GUIDE (ACTUAL

-) QUESTIONS AND ANSWERS.

What is meant by an All Weather spark plug? - Answers___A shielded spark plug that has a recess in the shielding in which a resilient grommet on the ignition lead forms a watertight seal

What is meant by the reach of a spark plug? - Answers___The length of the threads on the spark plug that screw into the cylinder head

What is the difference between a hot spark plug and a cold spark plug? - Answers___A hot spark plug has a long path for the heat to travel between the nose core insulator and the spark plug shell. In a cold spark plug, the heat has a shorter distance to travel, and the spark plug operates cooler than a hot spark plug

What is checked when a magneto is internally timed? - Answers___Internally timing a magneto consists of adjusting the breaker points so they will open at the instant the rotating magnet is in its E-gap position, and the distributor rotor is in the position to direct the high voltage to cylinder number one

What is the purpose of a vernier coupling used on some aircraft magneto drives? - Answers___Magnetos that are base mounted must have a vernier coupling between the magneto drive and the engine. This vernier coupling allows the 2 / 4

POWERPLANT ORAL STUDY GUIDE (ACTUAL

-) QUESTIONS AND ANSWERS.

magneto-to engine timing to be varied in increments of less than one degree

What is the advantage of fine-wire spark plugs over massive electrode spark plugs? - Answers___Fine wires spark plugs have a firing end that is more open that that of a massive electrode spark plug. The open firing end allows the gases that contain lead to be purged from the spark plug so they will not form solid lead contaminates

Why is it important that the spark plugs be kept in numbered holes in a tray when they are removed from an engine? - Answers___Spark plugs tell a good deal about the internal condition of the cylinder from which they were taken. By knowing the cylinder from which each spark plugs came, the mechanic can take the proper action when a spark plug indicates such conditions as detonation or overheating

What is the purpose of staggered timing between the two magnetos on an aircraft engine? - Answers___Engines in which the exhaust gas scavenging from the cylinders is uneven use staggered ignition timing. The spark plug nearest the exhaust valve, where the fuel-air moisture is diluted, fires before the spark plug on the intake side. By using staggered timing, the flame front caused by the two spark plugs will meet in the center of the piston

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POWERPLANT ORAL STUDY GUIDE (ACTUAL

-) QUESTIONS AND ANSWERS.

In what position should the ignition switch be placed when using a timing light on the magnetos - Answers___In the both position

Why is it important that a torque wrench always be used when installing spark plugs in an aircraft engine? - Answers___If the spark plugs are not put in tight enough, there is the possibility of a poor seal, and they are put in too tight, there is a danger of cracking the insulation

Why are pressurized magnetos used on most reciprocating- engine-powered aircraft that fly at high altitudes? - Answers___Pressurized air is a better insulator that less dense air. By pressurizing the distributors, the high voltage is kept from arcing across to the wrong electrode and causing vibration and loss of engine power

What type of ignition system is used on most turbine engine?

• Answers___High-intensity, intermittent-duty, capacitor

discharge ignition system

What is meant by the E-gap in magneto timing? - Answers___The E-gap angle is the position of the rotating magnet when the primary current flowing in the magneto coil is the greatest. The breaker points open when the rotating magnet is in its E-gap position

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