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Dry sump oil level check timing

Aviation Mechanic General (AMG) practice question 7 of 26 on Ground Operations and Servicing. ACS element AM.I.F.K7 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA dry-sump turbine engine has sat overnight and the dipstick reads low. If oil is added to the full mark before the engine is run or motored, the most likely result is

  1. Aa correct level, because dry-sump tanks hold their full quantity when idle.
  2. Boverfilling, because oil seeped into the gearcase returns to the tank.
  3. Cunderfilling, because oil foams and expands when the engine runs.
Show the answer and explanation

Correct answer: B. overfilling, because oil seeped into the gearcase returns to the tank.

  • A — incorrect The opposite is true: while idle, oil seeps from the tank into the gearcase, so the dipstick underreads the true quantity.
  • B — correct Dry-sump systems hide oil that seeps from the tank into the gearcase; that oil does not show on the dipstick until the engine is started or motored, so servicing first overfills the tank.
  • C — incorrect Foaming is why the tank has an expansion space, not a reason the level would be low after servicing; the problem in this scenario is overfilling.

BACKGROUND

Engine oil is checked with a dipstick or sight gauge, and the timing of the check matters. Reciprocating engines are checked after the engine has been inactive, while a turbine engine must be checked just after shutdown. Dry-sump oil systems tend to hide oil that has seeped from the oil tank into the gearcase of the engine; this oil does not show up on the dipstick until the engine has been started or motored. If the tank is serviced before that oil is pumped back, the engine overfills. The tank must never be overfilled because oil foams as it circulates, and the expansion space in the tank allows for this foaming.

STUDY TIP

Remember the check-timing rule: reciprocating after inactivity, turbine just after shutdown, and never top up a dry-sump tank that has been sitting.

KEY POINTS

  • Turbine engine oil is checked just after shutdown.
  • Oil hidden in the gearcase of a dry-sump system does not appear on the dipstick until the engine is run or motored.
  • Servicing before the oil returns overfills the tank.

SOURCES

  • FAA-H-8083-30B ch01 "Servicing Aircraft Air/Nitrogen Oil & Fluids"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.