AIRFRAME AND POWERPLANT
(A&P) ORAL AND PRACTICAL
STUDY GUIDE 2026 | FAA
MECHANIC O&P EXAM PREP
What is the probable cause of hydraulic lock and how is it remedied? - answer-
Whenever a radial engine remains shut down for more than a few minutes, oil or fuel
may drain into the combustion chambers or intake pipes of the lower, downward
extending cylinders. This is known as hydraulic lock. As the piston moves toward top
center in these cylinders, it will collide with these incompressible liquids. Severe
damage can be caused. The liquid must be removed to remedy the hydraulic lock and
make it safe to start the engine. This is done by removing either the front or rear spark
plugs of the affected cylinders and pulling the engine through by hand in the normal
direction of rotation. Then the spark plugs are reinstalled and the engine is started.
What checks are necessary to verify proper operation of a reciprocating engine? -
answer-A ground check or power check is performed to evaluate the functioning of the
engine by comparing power input as measured by manifold pressure with power output
as measured by RPM (or torque) and comparing these to known acceptable values. It
also includes checking the powerplant and accessory equipment by ear, visual
inspection, and by proper interpretation of instrument readings, control movements,
and switch reactions. Fuel pressure and oil pressure checks must verify that these
pressures are within established tolerances. A cylinder compression test can be
performed if it is suspected that there is a problem with valves, pistons or piston rings. A
magneto safety check exposes problems with the ignition system. Idle speed and idle
mixture checks can also be performed although these relate more to the proper
functioning of the fuel system than the engine itself just as the magneto check focuses
more on ignition system integrity. Reference: FAA-H-8083-30-ATB Page 10-26 to 10-40
Explain the checks necessary to verify proper operation of propeller systems. - answer-
The propeller must be checked to ensure proper operation of the pitch control and pitch
change mechanism. The operation of a controllable pitch propeller is checked by the
indications of the tachometer and manifold pressure gauge when the proper governor
control is moved from one position to another. Each propeller requires a different
procedure. The applicable manufacturer's instructions should be followed.
, What is involved with the correct installation of piston rings and what results if the rings
are incorrectly installed or are worn? - answer-Piston rings prevent leakage of gas
pressure from the combustion chamber while lubricating the cylinder walls and
reducing to a minimum the seepage of oil into the combustion chamber. Worn or broken
piston rings can cause excessive oil consumption and loss of compression. Oil blow-by
into the combustion chamber can lead to sticking valves, spark plug misfiring, as well
as detonation or pre-ignition due to carbonization of the oil. During installation, the
rings are place in the proper grooves facing the correct direction according to the engine
manufacturer's instructions. The ring gaps are staggered around the piston. They are
compressed with a ring compressor to the diameter of the piston as the cylinder is slid
down around the piston making sure that the cylinder and piston plane remain the
same. As the cylinder is lowered around the piston with a straight, even motion, it
displaces the ring compressor as the rings slide into the bore. Rocking or forcing the
cylinder over the piston and rings could cause a ring to escape from the ring compressor
and expand or it could crack or chip a ring or damage the ring land.
What are some procedures for inspecting various engine components during overhaul?
- answer-There are 3 basic categories of inspection during overhaul: visual, structural
non-destructive testing (NDT) and dimensional. The first inspection to be done is the
visual inspection. A preliminary visual inspection should be performed before cleaning
the parts since indications of failure may often be detected from the residual deposits
of metallic particles in some recesses of the engine. Then, parts can be cleaned and
visually inspected. Structural inspections can be performed on parts by methods such
as magnetic particle inspection, dye penetrant, eddy current, ultra sound, and x-ray as
specified by the manufacturer. Finally, using very accurate measuring equipment, each
engine component can be dimensionally evaluated and compared to the service limits
and tolerances set by the manufacturer.
What are the procedures for reciprocating engine maintenance as they pertain to
overhauling an engine? - answer-Aircraft engine maintenance practices, including
overhaul, are performed at specified intervals established by the manufacturer. For an
overhauled engine to be as airworthy as a new engine, worn and damaged parts must
be detected and replaced. This is done by completely disassembling the engine. Visual,
non-destructive, and dimensional inspections are performed. The manufacturer
publishes inspection criterion and a new minimum and serviceable dimension for all
critical component parts. Parts that do not meet these standards must be rejected for
use in the engine. A major overhaul of an engine consists of the complete
reconditioning of the powerplant. This includes disassembly of the crankcase for
access and inspection/rework of the crankshaft and bearings. It is not a major repair
(A&P) ORAL AND PRACTICAL
STUDY GUIDE 2026 | FAA
MECHANIC O&P EXAM PREP
What is the probable cause of hydraulic lock and how is it remedied? - answer-
Whenever a radial engine remains shut down for more than a few minutes, oil or fuel
may drain into the combustion chambers or intake pipes of the lower, downward
extending cylinders. This is known as hydraulic lock. As the piston moves toward top
center in these cylinders, it will collide with these incompressible liquids. Severe
damage can be caused. The liquid must be removed to remedy the hydraulic lock and
make it safe to start the engine. This is done by removing either the front or rear spark
plugs of the affected cylinders and pulling the engine through by hand in the normal
direction of rotation. Then the spark plugs are reinstalled and the engine is started.
What checks are necessary to verify proper operation of a reciprocating engine? -
answer-A ground check or power check is performed to evaluate the functioning of the
engine by comparing power input as measured by manifold pressure with power output
as measured by RPM (or torque) and comparing these to known acceptable values. It
also includes checking the powerplant and accessory equipment by ear, visual
inspection, and by proper interpretation of instrument readings, control movements,
and switch reactions. Fuel pressure and oil pressure checks must verify that these
pressures are within established tolerances. A cylinder compression test can be
performed if it is suspected that there is a problem with valves, pistons or piston rings. A
magneto safety check exposes problems with the ignition system. Idle speed and idle
mixture checks can also be performed although these relate more to the proper
functioning of the fuel system than the engine itself just as the magneto check focuses
more on ignition system integrity. Reference: FAA-H-8083-30-ATB Page 10-26 to 10-40
Explain the checks necessary to verify proper operation of propeller systems. - answer-
The propeller must be checked to ensure proper operation of the pitch control and pitch
change mechanism. The operation of a controllable pitch propeller is checked by the
indications of the tachometer and manifold pressure gauge when the proper governor
control is moved from one position to another. Each propeller requires a different
procedure. The applicable manufacturer's instructions should be followed.
, What is involved with the correct installation of piston rings and what results if the rings
are incorrectly installed or are worn? - answer-Piston rings prevent leakage of gas
pressure from the combustion chamber while lubricating the cylinder walls and
reducing to a minimum the seepage of oil into the combustion chamber. Worn or broken
piston rings can cause excessive oil consumption and loss of compression. Oil blow-by
into the combustion chamber can lead to sticking valves, spark plug misfiring, as well
as detonation or pre-ignition due to carbonization of the oil. During installation, the
rings are place in the proper grooves facing the correct direction according to the engine
manufacturer's instructions. The ring gaps are staggered around the piston. They are
compressed with a ring compressor to the diameter of the piston as the cylinder is slid
down around the piston making sure that the cylinder and piston plane remain the
same. As the cylinder is lowered around the piston with a straight, even motion, it
displaces the ring compressor as the rings slide into the bore. Rocking or forcing the
cylinder over the piston and rings could cause a ring to escape from the ring compressor
and expand or it could crack or chip a ring or damage the ring land.
What are some procedures for inspecting various engine components during overhaul?
- answer-There are 3 basic categories of inspection during overhaul: visual, structural
non-destructive testing (NDT) and dimensional. The first inspection to be done is the
visual inspection. A preliminary visual inspection should be performed before cleaning
the parts since indications of failure may often be detected from the residual deposits
of metallic particles in some recesses of the engine. Then, parts can be cleaned and
visually inspected. Structural inspections can be performed on parts by methods such
as magnetic particle inspection, dye penetrant, eddy current, ultra sound, and x-ray as
specified by the manufacturer. Finally, using very accurate measuring equipment, each
engine component can be dimensionally evaluated and compared to the service limits
and tolerances set by the manufacturer.
What are the procedures for reciprocating engine maintenance as they pertain to
overhauling an engine? - answer-Aircraft engine maintenance practices, including
overhaul, are performed at specified intervals established by the manufacturer. For an
overhauled engine to be as airworthy as a new engine, worn and damaged parts must
be detected and replaced. This is done by completely disassembling the engine. Visual,
non-destructive, and dimensional inspections are performed. The manufacturer
publishes inspection criterion and a new minimum and serviceable dimension for all
critical component parts. Parts that do not meet these standards must be rejected for
use in the engine. A major overhaul of an engine consists of the complete
reconditioning of the powerplant. This includes disassembly of the crankcase for
access and inspection/rework of the crankshaft and bearings. It is not a major repair
