A&P Reciprocating Engine Overhaul Questions and Answers — Questions and Answers
Question 1: During a reciprocating engine overhaul, a Magnaflux inspection is performed on the steel crankshaft. What is the primary purpose of this inspection?
- To measure the crankshaft for journal out-of-round conditions.
- To detect surface and near-surface cracks or discontinuities. (Correct answer)
- To verify the chemical composition and hardness of the steel.
- To remove residual magnetism from the part after engine operation.
Correct answer: To detect surface and near-surface cracks or discontinuities.
Magnaflux, or Magnetic Particle Inspection (MPI), is a nondestructive testing method used to find surface and slightly subsurface discontinuities in ferromagnetic materials like steel. The process involves magnetizing the part and applying iron particles, which will gather at any magnetic flux leakage fields caused by cracks, clearly indicating the flaw.
Question 2: A technician is assembling a cylinder onto a reciprocating engine and is preparing to torque the cylinder base nuts. According to most manufacturer's instructions, what is the proper general procedure for torquing these nuts?
- Torque the nuts to the final value in a single step, starting with the largest stud.
- Hand-tighten all nuts, then fully torque each one in a clockwise pattern.
- Torque all nuts to half the specified value in sequence, then to the final value in the same sequence. (Correct answer)
- Fully torque the two nuts on the crankcase parting line first, then the remaining nuts.
Correct answer: Torque all nuts to half the specified value in sequence, then to the final value in the same sequence.
Proper procedure for torquing cylinder base nuts typically involves a multi-step process to ensure even pressure and prevent warping. The nuts are first torqued to an intermediate value (often half of the final spec) in a specified sequence, and then the process is repeated to bring them to the final torque value. This ensures the cylinder is seated correctly and stress is evenly distributed.
Question 3: After grinding the valves and valve seats in a cylinder head, what is the purpose of the lapping procedure that follows?
- To measure the clearance between the valve stem and guide.
- To harden the surface of the valve face and seat.
- To ensure a perfect, gas-tight seal between the valve face and the seat. (Correct answer)
- To remove any carbon deposits from the combustion chamber.
Correct answer: To ensure a perfect, gas-tight seal between the valve face and the seat.
Valve lapping uses a special abrasive paste applied between the valve face and its seat. The valve is then rotated against the seat, which creates a fine, smooth, and perfectly matched sealing surface. This ensures maximum compression and prevents the leakage of combustion gases.
Question 4: When installing new piston rings, a technician notes that one of the compression rings has a small dot or the word "TOP" marked on one side. How should this ring be oriented in the piston groove?
- The mark should be positioned facing the bottom of the piston (the skirt).
- The orientation does not matter as the ring is symmetrical.
- The mark should be positioned facing the top of the piston (the crown). (Correct answer)
- The mark should be aligned with the piston pin.
Correct answer: The mark should be positioned facing the top of the piston (the crown).
Many piston rings are directional and have a specific profile or taper to function correctly for sealing and oil control. A mark, such as a dot or the word "TOP," indicates the side of the ring that must face upwards, toward the crown of the piston. Installing a directional ring upside down can lead to excessive oil consumption and poor compression.
Question 5: A technician is inspecting a connecting rod from a recently disassembled engine. Which of the following conditions would be cause for mandatory rejection of the part?
- Minor discoloration on the beam of the rod.
- Piston pin bushing shows signs of normal operational wear.
- The connecting rod exhibits a slight twist or bend beyond serviceable limits. (Correct answer)
- Surface rust is present on the non-machined surfaces.
Correct answer: The connecting rod exhibits a slight twist or bend beyond serviceable limits.
The straightness of a connecting rod is critical. Any bend or twist beyond the manufacturer's specified limits will cause misalignment of the piston and bearings, leading to uneven wear, excessive friction, and ultimately catastrophic engine failure. Such a part cannot be repaired and must be rejected.
Question 6: An engine has been overhauled according to the manufacturer's manual using a combination of new parts and used parts that conform to "serviceable limits." How is the total time in service (TIS) on the engine logbook affected?
- The total time is reset to zero, as it is considered a "zero-time" engine.
- The total time is cut in half, reflecting the new condition of many parts.
- The total time continues from where it was before the overhaul.
- A new logbook is started, and the old time is archived. (Correct answer)
Correct answer: A new logbook is started, and the old time is archived.
According to FAA guidance, when an engine is overhauled to serviceable limits (as opposed to being rebuilt by the manufacturer to new limits), the total time on the engine and its records continues. Only a "rebuilt" engine, which is brought to the same tolerances and limits as a new engine by the manufacturer, can be granted zero time.
A&P Reciprocating Engine Overhaul Questions and Answers
During a reciprocating engine overhaul, a Magnaflux inspection is performed on the steel crankshaft.
What is the primary purpose of this inspection?