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Static system leak check tolerance

Aviation Mechanic Airframe (AMA) practice question 10 of 20 on Aircraft Instrument Systems. ACS element AM.II.H.K18 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONDuring a static system leak check the system is evacuated until the altimeter indicates 1,000 feet, then sealed. After 1 minute the altimeter reads 880 feet. How should the technician regard this result?

  1. AAcceptable; the loss is under 200 feet.
  2. BAcceptable; only pitot leaks are limited.
  3. CA failure; the loss exceeds 100 feet.
Show the answer and explanation

Correct answer: C. A failure; the loss exceeds 100 feet.

  • A — incorrect No 200-foot allowance exists; the stated limit for the 1-minute observation is 100 feet.
  • B — incorrect The static portion carries its own leak limit, and the pitot portion is checked in a similar fashion.
  • C — correct The loss is 120 feet in 1 minute, and a loss of altitude of more than 100 feet is not permissible.

BACKGROUND

Aircraft pitot-static systems must be tested for leaks after installation of any component parts or when a system malfunction is suspected, and every 24 months on an aircraft certified for and flown under instrument flight rules as called out in 14 CFR part 91, section 91.411. Certified airframe and powerplant technicians may perform this leak test. A testing device is connected into the static system at the static vent end, pressure is reduced until the altimeter indicates 1,000 feet, then the system is sealed and observed for 1 minute; a loss of altitude of more than 100 feet is not permissible. Most leaks occur at fittings, and pressure and suction must always be applied and released slowly to avoid damaging the instruments. The altimeter test itself is different: 14 CFR part 91, section 91.411 requires it within the previous 24 months, and it must be conducted by the manufacturer or a certified repair station rather than by an airframe and powerplant mechanic.

STUDY TIP

Keep the two 24-month checks separate in your mind: the technician may do the static leak check, but only a manufacturer or certified repair station may do the altimeter test.

KEY POINTS

  • Reduce static system pressure to indicate 1,000 feet, seal, and observe for 1 minute.
  • A loss of more than 100 feet in that minute fails the check.
  • Airframe and powerplant technicians may run the leak check but not the altimeter test.

SOURCES

  • 14 CFR 91.411
  • sources/ama-airframe/ch10.txt "Pitot-Static System Maintenance & Tests"
  • sources/ama-airframe/ch10.txt "Altimeter Tests"
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MORE ON AIRCRAFT INSTRUMENT SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.