ACS codes · Powerplant · Engine Exhaust and Reverser Systems
AM.III.L.K4 · Knowledge
Thrust reverser theory, components, and operation
Updated October 25, 2026 · element text from the FAA Aviation Mechanic ACS (FAA-S-ACS-1)
Practice AM.III.L.K4 out loud, free
What the ACS says
Thrust reverser theory, components, and operation.
A sample oral question on this element
“How does a mechanical-blockage reverser differ from an aerodynamic-blockage reverser?”
Study source: FAA-H-8083-32B (Aviation Maintenance Technician Handbook, Powerplant), chapter 3, page 3-27
If this code is on your test report
Your Airman Knowledge Test Report (AKTR) lists an ACS code for every knowledge area you missed on the written test. On the A&P oral, each of those codes adds one question to that section, on top of a minimum of four random questions (FAA Mechanic Test Generator FAQ). So if AM.III.L.K4 is on your AKTR, expect the examiner to ask about it. More on how codes turn into oral questions: A&P ACS codes: know your codes before the oral.
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