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Routine hydraulic fluid sampling interval

Aviation Mechanic Airframe (AMA) practice question 9 of 15 on Hydraulic and Pneumatic Systems. ACS element AM.II.F.K4 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA hydraulic system was last sampled 14 months ago and has accumulated 2,800 flight hours since that sample. Under the routine sampling schedule, the system

  1. Ais due for a fluid sample now
  2. Bis not due until 3,000 hours are reached
  3. Cis not due for another 10 months
Show the answer and explanation

Correct answer: A. is due for a fluid sample now

  • A — correct Routine sampling calls for each system to be sampled at least once a year, so a system last sampled 14 months ago is overdue regardless of the hours flown.
  • B — incorrect The hour figure is only one of the triggers; the calendar requirement of at least once a year has already been exceeded.
  • C — incorrect There is no two-year sampling interval; the calendar trigger is one year, which has already passed.

BACKGROUND

Whenever it is suspected that a hydraulic system has become contaminated, or the system has been operated above the specified maximum temperature, a check of the system should be made. Hydraulic liquid that appears clean to the naked eye may still be contaminated to the point that it is unfit for use, so visual inspection does not determine the total amount of contamination. The sampling schedule has three parts: routine sampling at least once a year, or every 3,000 flight hours, or whenever the airframe manufacturer suggests; unscheduled sampling when a malfunction may have a fluid-related cause; and sampling before and after maintenance when contamination is suspected. Because the routine triggers are alternatives, whichever comes first governs.

STUDY TIP

Treat calendar time and flight hours as separate triggers and act on whichever arrives first; questions often supply one figure that is met and one that is not.

KEY POINTS

  • Routine sampling is at least yearly, or every 3,000 flight hours, or as the airframe manufacturer suggests.
  • Whichever routine trigger comes first governs.
  • Samples are also taken for suspected fluid-related malfunctions and before and after contamination-related maintenance.

SOURCES

  • sources/ama-airframe/ch12.txt "Hydraulic Sampling Schedule"
  • sources/ama-airframe/ch12.txt "Contamination Check"
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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.