Practice Test Geeks(ACS) Airman Certification Standard Certified Mechanic Practice Test
← All ACS Flashcard Decks

Fuel Systems & Aircraft Plumbing Flashcards

6 cards from real ACS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 Fuel Systems & Aircraft Plumbing flashcards as text

  1. What is the maximum allowable bend radius violation that can occur when bending aluminum aircraft tubing?

    Answer: No kinking is acceptable — kinked tubing must be replaced

    Any kink in aluminum aircraft tubing significantly weakens it and creates stress concentration points — kinked tubing must always be replaced, never repaired or reused.

  2. When making a flared tube fitting for an aircraft fuel line, the correct flare angle for AN (Army-Navy) fittings is:

    Answer: 37 degrees (double flare equivalent per AN standard)

    AN (Army-Navy) standard fittings use a 37-degree flare angle, which is different from the 45-degree flare used in automotive applications.

  3. What is the purpose of a firewall shutoff valve (fuel selector/firewall valve) in an aircraft fuel system?

    Answer: To allow the crew to stop fuel flow to the engine compartment in the event of an engine fire or fuel leak

    The firewall shutoff valve allows the flight crew to cut fuel flow to the engine compartment to starve a fire or stop a fuel leak from reaching the engine bay.

  4. What document governs the minimum bend radii and tube material specifications for aircraft fluid lines?

    Answer: AC 43.13-1B Chapter 9 and the applicable aircraft maintenance manual

    AC 43.13-1B Chapter 9 provides the FAA-accepted data for aircraft plumbing including bend radii, materials, flare types, and installation standards, supplemented by the AMM.

  5. How should an aircraft mechanic test a repaired fuel system for leaks before returning the aircraft to service?

    Answer: Pressure test or operational test per the AMM with fuel system pressurized and all connections checked for leaks

    After repair, the fuel system must be leak-tested per the AMM procedure, typically by pressurizing the system and inspecting all connections, fittings, and repaired areas for any leakage.

  6. What is the purpose of a fuel heat exchanger on a turbine aircraft?

    Answer: To use fuel to cool engine oil while also preventing fuel system icing by warming the fuel

    The fuel-oil heat exchanger cools hot engine oil using cooler fuel as the heat sink, simultaneously warming the fuel to prevent ice crystal formation in the fuel system.