Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
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 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 lifters keep all the clearance out of the
valve operating mechanism. This decreases the wear of the valve
train components.
,Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
At what speed does the camshaft turn in relation to the crankshaft?
-
correct answer ✅one half the speed of the crankshaft
What kind of main bearings are used in a horizontally opposed
engine? -
correct answer ✅steel backed, lead-alloy inserts
On what stroke is the piston when the intake valve begins to open?
-
correct answer ✅exhaust stroke
On what stroke is the piston when the exhaust valve begins to
close? -
correct answer ✅power stroke
Why are both hot and cold clearances given for radial engines? -
correct answer ✅The hot clearance is given for valve timing
purposes. The timing is adjusted with the valves in the number one
piston adjusted with the hot clearance. When the timing is set, all
of the valves are adjusted to their cold clearance.
,Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
What is meant by "cam-ground" piston? -
correct answer ✅A piston that is not perfectly round. 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 when the ignition spark occurs? -
correct answer ✅30 degrees before TDC
What is a "full-floating" wrist pin? -
correct answer ✅a wrist pin that is not clamped in either the
piston or the connecting rod. soft metal plugs keep the floating pin
from scoring the cylinder wall.
Why do most engines use more than one spring on each valve? -
correct answer ✅Different springs with different diameter and
pitch have different resonant frequencies which minimize valve
float.
Would excessive valve clearance cause the valves to open early or
late? -
correct answer ✅open late and close early
, Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
What is the purpose of valve overlap? (2) -
correct answer ✅Exhaust gas inertia leaving the cylinder helps the
fresh induction charge flow into the cylinder leading to 1) better
volumetric efficiency 2) lower cylinder temperatures.
What types of piston rings are installed on the pistons? -
correct answer ✅compression rings, oil control rings, oil wiper
rings
Why are some exhaust valves partially filled with metallic sodium? -
correct answer ✅It melts at operating temperature. Sloshing back
and forth, it picks up heat, transfers heat to the valve stem which in
turn transfers it to the cylinder head.
What causes detonation? -
correct answer ✅Excessive heat and pressure in the cylinder
causes the fuel-air mixture to reach its critical pressure and
temperature which causes an explosion rather than a controlled
burn.
Oral Questions And Answers
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 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 lifters keep all the clearance out of the
valve operating mechanism. This decreases the wear of the valve
train components.
,Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
At what speed does the camshaft turn in relation to the crankshaft?
-
correct answer ✅one half the speed of the crankshaft
What kind of main bearings are used in a horizontally opposed
engine? -
correct answer ✅steel backed, lead-alloy inserts
On what stroke is the piston when the intake valve begins to open?
-
correct answer ✅exhaust stroke
On what stroke is the piston when the exhaust valve begins to
close? -
correct answer ✅power stroke
Why are both hot and cold clearances given for radial engines? -
correct answer ✅The hot clearance is given for valve timing
purposes. The timing is adjusted with the valves in the number one
piston adjusted with the hot clearance. When the timing is set, all
of the valves are adjusted to their cold clearance.
,Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
What is meant by "cam-ground" piston? -
correct answer ✅A piston that is not perfectly round. 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 when the ignition spark occurs? -
correct answer ✅30 degrees before TDC
What is a "full-floating" wrist pin? -
correct answer ✅a wrist pin that is not clamped in either the
piston or the connecting rod. soft metal plugs keep the floating pin
from scoring the cylinder wall.
Why do most engines use more than one spring on each valve? -
correct answer ✅Different springs with different diameter and
pitch have different resonant frequencies which minimize valve
float.
Would excessive valve clearance cause the valves to open early or
late? -
correct answer ✅open late and close early
, Powerplant ASA/Baker's School List of FAA
Oral Questions And Answers
What is the purpose of valve overlap? (2) -
correct answer ✅Exhaust gas inertia leaving the cylinder helps the
fresh induction charge flow into the cylinder leading to 1) better
volumetric efficiency 2) lower cylinder temperatures.
What types of piston rings are installed on the pistons? -
correct answer ✅compression rings, oil control rings, oil wiper
rings
Why are some exhaust valves partially filled with metallic sodium? -
correct answer ✅It melts at operating temperature. Sloshing back
and forth, it picks up heat, transfers heat to the valve stem which in
turn transfers it to the cylinder head.
What causes detonation? -
correct answer ✅Excessive heat and pressure in the cylinder
causes the fuel-air mixture to reach its critical pressure and
temperature which causes an explosion rather than a controlled
burn.
