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Pressure test after puncturing a fuel hose blister

Aviation Mechanic Powerplant (AMP) practice question 17 of 20 on Engine Fuel and Fuel Metering Systems. ACS element AM.III.I.K12 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONA blister on the outer cover of a fuel hose is punctured with a pin and only air escapes. If the hose has a working pressure of 300 psi, at what pressure should the hose be tested?

  1. A450 psi
  2. B300 psi, the working pressure
  3. C600 psi
Show the answer and explanation

Correct answer: A. 450 psi

  • A — correct When only air emerges from a punctured blister, the hose is tested at one and one-half times its working pressure, and 300 multiplied by 1.5 equals 450.
  • B — incorrect Testing at the working pressure would prove nothing beyond normal service; the prescribed test applies a margin above the working pressure.
  • C — incorrect Six hundred psi is twice the working pressure, not the one and one-half times called for by the inspection procedure.

BACKGROUND

Blisters may form on the outer synthetic rubber cover of a fuel hose, and they do not necessarily affect the serviceability of the hose. When a blister is found, the hose is removed from the aircraft and the blister is punctured with a pin so that it collapses. If fluid such as oil, fuel, or hydraulic fluid emerges from the pinhole, the hose is rejected. If only air emerges, the hose is pressure tested at one and one-half times the working pressure, and if no fluid leakage occurs it may be regarded as serviceable. Puncturing the outer cover of hoses exposed to the elements should otherwise be avoided, since corrosive elements such as water can then attack the wire braiding.

STUDY TIP

Work the arithmetic before looking at the answers, then confirm the decision rule: fluid means reject outright, air means test. Do not confuse the one-and-a-half-times test factor with a doubling.

KEY POINTS

  • A punctured blister that releases fluid means the hose is rejected.
  • A punctured blister that releases only air calls for a test at 1.5 times working pressure.
  • A hose passing that test with no fluid leakage may be regarded as serviceable.

SOURCES

  • amp-powerplant/ch02.txt "Lines & Fittings"
Practice the Aviation Mechanic Powerplant (AMP) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON ENGINE FUEL AND FUEL METERING SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.