Reciprocating Engine Questions & Answers.
How may it be determined that a reciprocating engine with a dry sump is pre-oiled sufficiently? - CORRECT ANSWER When pre-oiling a dry-sump reciprocating engine, you know there is oil in all the passages when oil flows from the engine return line or fr...
How may it be determined that a reciprocating engine with a dry sump is pre-oiled sufficiently? -
CORRECT ANSWER When pre-oiling a dry-sump reciprocating engine, you know there is oil in all the
passages when oil flows from the engine return line or from the port to which the oil pressure gauge is
connected.
The floating control thermostat, used on some reciprocating engine installations, helps regulate oil
temperature by - CORRECT ANSWER The floating-control thermostat controls the oil cooler air-exit door.
It maintains the oil temperature within the desired limits by controlling the air flow through the oil
cooler.
To reduce the power output of an engine equipped with a constant-speed propeller and operating near
maximum BMEP, the - CORRECT ANSWER When changing the power setting of an engine equipped with
a constant-speed propeller, it is important that the manifold pressure be reduced by retarding the
throttle before the RPM is reduced with the propeller pitch control.
If the wrong sequence is used, the high manifold pressure and the low RPM can produce cylinder
pressures high enough to seriously damage the engine.
After spark plugs from an opposed engine have been serviced, in what position should they be
reinstalled? - CORRECT ANSWER When spark plugs have been cleaned, gapped and tested, they should
be installed in the cylinder next in firing order to the one from which they were removed, and they
should be swapped from bottom to top.
One cause of afterfiring in an aircraft engine is - CORRECT ANSWER After-firing, or torching, is the
burning of the fuel-air mixture in the exhaust manifold after the mixture has passed through the exhaust
valve.
After-firing is usually caused by operation with an excessively rich mixture, such as would be caused by
overpriming, improper use of the mixture control when starting, or by poor ignition.
What is the principal advantage of using propeller reduction gears? - CORRECT ANSWER The horsepower
produced by a reciprocating engine is determined by its RPM. The higher the RPM, the greater the
power. But the efficiency of a propeller decreases as the blade tip speed approaches the speed of sound.
, In order to get the best of both conditions, many of the more powerful aircraft engines drive the
propeller through a set of reduction gears.
Reduction gears allow the engine to turn fast enough to develop the required power. At the same time,
the propeller tip speed is kept low enough that the tips do not approach the speed of sound.
Which of the following would most likely cause a reciprocating engine to backfire through the induction
system at low RPM operation? - CORRECT ANSWER A lean fuel-air mixture burns slower than either a
rich or a chemically-correct mixture. There is a possibility that a lean mixture will still be burning as it is
pushed out through the exhaust valve.
During the time of valve overlap, when both the intake and the exhaust valves are open, the burning
exhaust gases can ignite the fresh fuel-air charge being taken into the cylinder through the intake valve.
This can cause a backfire through the induction system.
What special procedure must be followed when adjusting the valves of an engine equipped with a
floating cam ring? - CORRECT ANSWER Some large radial engines have floating cam rings.
A floating cam ring is held centered over its bearing by the forces exerted by the valve springs.
When checking the valve clearance on an engine equipped with a floating cam, the bearing clearance
must be eliminated by depressing two valves on the opposite side of the engine from the valves being
checked.
Depressing the valves removes the pressure of their valve spring from the cam allowing the cam ring to
move tight against its bearing on the side where the valves are being checked.
Which of the following is a characteristic of a thrust bearing used in most radial engines? - CORRECT
ANSWER Deep-groove ball bearings are used as the thrust bearing in most radial engines. This type of
bearing is the best of those listed for reducing friction while carrying both thrust and radial loads.
During the inspection of an engine control system in which push-pull control rods are used, the threaded
rod ends should - CORRECT ANSWER When installing push-pull control rods in an aircraft, you can
determine that the rod end is properly screwed onto the rod by trying to pass a piece of safety wire
through the inspection hole in the rod. If the rod end is screwed into the rod far enough to cover the
hole, there are enough threads engaged to give the connection the full strength required.
If the oil pressure of a cold engine is higher than at normal operating temperatures, the - CORRECT
ANSWER Many large aircraft reciprocating engines have a compensating oil pressure relief valve that
allows the oil pressure for cold oil to be considerably higher than it allows for warm oil. This higher
pressure allows the thicker, higher viscosity oil to be forced through the engine bearings.
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