SkyDrill

Releasing strut pressure before valve removal

Aviation Mechanic Airframe (AMA) practice question 1 of 17 on Landing Gear Systems. ACS element AM.II.E.R4 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat must be done before the air service valve assembly is unscrewed from a landing gear shock strut?

  1. ARelease all the air pressure in the strut
  2. BDrain all the hydraulic fluid from the strut
  3. CRemove the torque links from the strut
Show the answer and explanation

Correct answer: A. Release all the air pressure in the strut

  • A — correct The servicing procedure releases all air through the service valve, and only after all air has escaped and the strut is compressed is the valve body unscrewed.
  • B — incorrect Fluid is added through the open service valve port after the valve is removed; it is not drained as a prerequisite.
  • C — incorrect Torque links keep the wheels aligned and play no part in servicing the air valve.

BACKGROUND

Deflating a shock strut can be a dangerous operation, and the technician must be thoroughly familiar with the high-pressure service valve at the top of the upper cylinder. Two common valves are used: the AN6287-1, which has a valve core and is rated at 3,000 psi although the core itself is rated only to 2,000 psi, and the MS28889-1, which has no core and is rated at 5,000 psi. Servicing begins by removing the cap, checking the swivel nut for tightness, and depressing any valve core to release trapped pressure while standing to the side of the core's trajectory. The swivel nut is then loosened to let all the air escape, and only when the strut is empty and fully compressed is the core removed and the valve body unscrewed. Re-inflation is done slowly with a threaded fitting from a controlled source of high-pressure air or nitrogen, to avoid excess heating and overinflation.

STUDY TIP

Make releasing the stored gas the first move in every high-pressure strut task, and note the valve ratings while you are there.

KEY POINTS

  • All air must be released before the service valve body is removed.
  • The AN6287-1 valve has a core rated to 2,000 psi; the MS28889-1 has none and is rated 5,000 psi.
  • Inflate slowly from a controlled source of air or nitrogen.

SOURCES

  • FAA-H-8083-31B ch13 "Servicing Shock Struts"
Practice the Aviation Mechanic Airframe (AMA) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON LANDING GEAR 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.