ASA AMT A&R QUESTIONS WITH COMPLETE SOLUTIONS

What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft? Correct Answer: 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? Correct Answer: six What kind of connecting rod arrangement is used in a radial engine? Correct Answer: 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? Correct Answer: Gray cast iron. What is the reason for using hydraulic valve lifters in an aircraft engine? Correct Answer: 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 crank shaft speed in a horizontally opposed engine? Correct Answer: The camshaft turns at 1/2 of the crank shaft speed What kind of main bearings are using a horizontally opposed engine Correct Answer: Steele backed, lead alloy bearing inserts On what stroke is the piston of a reciprocating engine when the intake valve begins to open? Correct Answer: exhaust stroke On which stroke is the piston of a reciprocating engine when the exhaust valve begins to open Correct Answer: On the power stroke Why are both the hot and cold valve clearances given for most radial engines? Correct Answer: 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 the cam-ground piston Correct Answer: 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? Correct Answer: About 30 degrees of crankshaft rotation before the piston reaches top center on the compression stroke.