ASA Powerplant Exam Questions And Answers (verified 100% correctly) Latest oral study guide

ASA Powerplant Exam Questions And Answers (verified 100% correctly) Latest oral study guide What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft? - answers The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? - answers Six What kind of connecting rod arrangement is used in a radial engine? - answers A master rod connects the single throw of the crankshaft with a piston. All of the other pistons are connected to the master rod with link rods Of what material are most piston rings made? - answers Gray cast iron What is the reason for using hydraulic valve lifters in an aircraft engine? - answers Hydraulic valve lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the valve train components At what speed does the camshaft turn, relative to the crankshaft speed in a horizontally opposed engine? - answers The camshaft turns at one half of the crankshaft speed What kind of main bearings are used in a horizontally opposed engine? - answers Steel-backed, lead-alloy bearing inserts On what stroke is the piston of a reciprocating engine when the intake valve begins to open? - answers On the exhaust stroke On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? - answers On the power stroke Why are both the hot and cold valve clearances give for most radial engine? - answers The hot clearance is given for valve timing purposes. The timing is adjusted with the valves in cylinder number one, set with the hot clearance. When the timing is set, all of the valves are adjusted to their cold clearance. What is meant by a cam-ground piston? - answers A piston that is not perfectly round. Its dimension parallel with the wrist pin is several thousandths of an inch less than its dimension perpendicular to the wrist pin. When the piston reaches operating temperature, the metal in the piston pin boss expands enough that the piston becomes perfectly round Where is the piston in a reciprocating engine when the ignition spark occurs? - answers About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke What is meant by a full-floating wrist pin? - answers A wrist pin that is not clamped in either the piston or the connecting rod. Full-floating wrist pins are kept from scoring the cylinder walls by soft metal plugs in their ends Why do most aircraft reciprocating engines use more than one spring on each valve? - answers By using more than one spring and having the wire diameter and pitch of the springs different, valve float is minimized. The springs have different resonant frequencies, so at least one spring will always be exerting a force on the valve Would excessive valve clearance cause the valves to open early or late? - answers Excessive clearance will cause the valve to open late and close early What is the purpose of valve overlap in a reciprocating engine? - answers Valve overlap allows the inertia of the exhaust gases leaving the cylinder to help the fresh induction charge start flowing into the cylinder What type of piston rings are installed on the pistons of an aircraft reciprocating engine? - answers Compression rings, oil control rings, and oil wiper rings Why are some exhaust valves partially filled with metallic sodium? - answers The metallic sodium melts at engine operating temperature and sloshes back and forth inside the hollow valve. It picks up heat from the valve head and transfers it into the valve stem, so it can be transferred to the cylinder head through the valve guide What causes detonation in an aircraft engine? - answers Excessive heat and pressure in the engine cylinder causes the fuel-air mixture to reach its critical pressure and temperature. Under these conditions, the mixture explodes rather than burns. This explosion is called detonation Why is a compression check important for determining the condition of an aircraft reciprocating engine? - answers A compression check can determine the condition of the seal between the piston rings and the cylinder walls, and the seal between the intake and exhaust valves and their seats What is meant by the compression ratio of a reciprocating engine? - answers The ratio of the volume of the cylinder with the piston at the bottom of its stroke to the volume with the piston at the top of its stroke What are the two basic sections of a turbine engine? - answers The hot section and the cold section What are the two basic types of compressors that are used in aircraft turbine engines? - answers Axial-flow and centrifugal What is the purpose of the stators in an axial-flow compressor? - answers The stators convert some velocity energy into pressure energy and change the direction of the air so it is proper for the next stage of rotors What are three types of combustors used on aircraft turbine engines? - answers Cantype, annular-type, and can-annular-type How many igniters are there normally in an aircraft turbine engine? - answers Two What is the main purpose of the turbine nozzle in an aircraft turbine engine? - answers The turbine nozzle directs the hot gases as they leave the combustors so they will turn the turbine wheel with maximum efficiency What is meant by a free-turbine turboshaft engine? - answers A turboshaft engine that has a turbine wheel, or stage of turbine wheels, that is not used to drive the compressor of the gas generator section of the engine. This free turbine drives the propeller in a turboprop engine or the transmission and rotor of a helicopter Why do some axial-flow turbine engines have more than one set of turbines and compressors? - answers A two-spool turbine engine has a low-pressure and a highpressure compressor, each driven by its own turbine. The two independent systems operate at the speed at which they are most efficient What kind of bearings are used to support the rotor shaft of an aircraft turbine engine? - answers Anti-friction bearings, such as ball bearings or roller bearings What is meant by a turbofan engine? - answers An axial-flow turbine engine in which the first stage of compressor blades are lengthened, so they can force air around the outside of the gas generator portion of the engine Where can you find the limits of repair allowed for the compressor blades of an aircraft turbine engine? - answers In the FAA-approved service manual issued by the manufacturer of the engine Why is it important that a turbojet engine be allowed to cool before it is shut down after it has been operated at a high power setting? - answers If the engine is shut down while it is hot, there is a possiblity that the shroud will contract around the turbine wheel and seize the rotor What is meant by a hung start in a turbine engine? - answers A start in which ignition occurs, but the engine does not accelerate to a self-sustaining speed