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A&P Powerplant oral: free sample

10 oral questions from across the Powerplant subjects. Say each answer out loud, reveal the model answer, and tick the key points you hit. The real oral is closed book and needs 70% of the whole section.

questions
10
questions
book, like the real oral
Closed
book, like the real oral
to pass the real oral
70%
to pass the real oral

Free practical project guide

Identify the parts of a cylinder.

Reciprocating Engines · AM.III.A.S4 · paper task

What you are likely to be given

A cylinder assembly or cutaway from an air-cooled engine, or a drawing of one, and the engine manufacturer's manual and parts catalog.

The standard to meet

Each part pointed to is named correctly and its purpose explained in a sentence: head, barrel, fins, valve parts, guides, seats, springs, retainers and keys, rocker arms, push rods and spark plug bushings. The candidate can find the cylinder number from the manufacturer's numbering system.

Steps

  1. 1Name the two major parts: the aluminum alloy cylinder head and the steel cylinder barrel. The head is heated and screwed onto the chilled barrel; when the head cools and the barrel warms, a gastight joint results.
  2. 2On the head, point out the intake and exhaust valve ports, the spark plug openings (bronze or steel bushings, or Heli-Coil inserts), the valve guides, the valve seats, the rocker arm bushings and the cooling fins.
  3. 3Explain the combustion chamber: the inner shape of the head is generally semispherical, which is stronger and helps scavenge exhaust gases.
  4. 4On the barrel, point out the nitrided steel bore, the integral cooling fins and the mounting flange. Note any color band between the flange and the lowest fin that shows oversize or chrome plating.
  5. 5Name the parts of a valve: head, face, neck, stem and tip, and the groove near the tip for the split stem keys. Valve faces are usually ground to 30 or 45 degrees.
  6. 6Name the valve operating parts at the cylinder: push rod and push rod housing, rocker arm with its adjusting screw, two or three valve springs per valve, and the spring retainer held by the split locks.
  7. 7Find the cylinder number from the manufacturer's manual, since the numbering of opposed engine cylinders is not standard.

Where to look

  • AMT Powerplant (FAA-H-8083-32B), ch. 1, pp. 1-14 and 1-15 (cylinders, heads, barrels, cylinder numbering)
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, pp. 1-17 and 1-18 (valve construction, valve operating mechanism)
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-21 (push rods, rocker arms, valve springs)
  • The engine manufacturer's manual and parts catalog: part names, cylinder numbering

Safety

  • Never cut open a sodium-filled valve or treat it in a way that could rupture it. Exposed sodium can cause a fire or explosion.
  • Handle the cylinder carefully: fins damaged by tools or careless handling are where exterior cracks show up.

Common mistakes that fail the project

  • Treating intake and exhaust valves as interchangeable. Even when they look alike, the face materials differ; the intake valve usually has a flat milled on its tip.
  • Mixing up the valve guide (which guides the stem) and the valve seat (the hardened ring the valve face seals against).
  • Assuming a cylinder number without checking the manufacturer's numbering system.

Practice questions

Like the two questions the examiner asks during each project. The practical is open book, so knowing where to look counts.

Q1. Why is there more cooling fin area on one part of the cylinder head?Reveal

The exhaust valve region is the hottest part of the internal surface, so more fin area is provided around the outside of the cylinder in that section.

AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-15

Q2. How would you recognize a chrome-plated cylinder, and what does that mean for the piston rings?Reveal

It is usually identified by a paint band, usually international orange, around the barrel between the mounting flange and the lowest barrel fin. Chrome-plated piston rings must not be used in it; chromium-plated cylinders use cast iron rings.

AMT Powerplant (FAA-H-8083-32B), ch. 10, p. 10-41; ch. 1, p. 1-15

Q3. What holds the valve spring retainer on the valve stem?Reveal

Split stem keys (locks). They fit a machined groove near the stem tip and the recess in the spring retainer, forming a lock ring.

AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-17; ch. 1, p. 1-21

FAA sources

  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-14
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-15
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-17
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-18
  • AMT Powerplant (FAA-H-8083-32B), ch. 1, p. 1-21
  • AMT Powerplant (FAA-H-8083-32B), ch. 10, p. 10-4
  • AMT Powerplant (FAA-H-8083-32B), ch. 10, p. 10-41