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Upright standing time for a laid-down acetylene cylinder

Aviation Mechanic Airframe (AMA) practice question 20 of 20 on Metallic Structures. ACS element AM.II.A.K10 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONAn acetylene cylinder has been lying on its side for 4 hours. How long must it stand upright before it is used?

  1. AAt least 24 hours in any case
  2. BThe same 4 hours it was on its side
  3. CAt least 8 hours
Show the answer and explanation

Correct answer: C. At least 8 hours

  • A — incorrect The required time is tied to how long the cylinder lay down, not set as a fixed period regardless of that.
  • B — incorrect An equal period is only half of what the rule requires, which is at least twice the time spent on its side.
  • C — correct A cylinder placed on its side must be stored upright for at least twice as long before use, and twice 4 hours is 8 hours.

BACKGROUND

All gas cylinders should be stored and transported upright, and this matters most for acetylene cylinders because they contain an absorbent material saturated with liquid acetone. If a cylinder is laid on its side, acetone can enter and contaminate the regulator, hose, and torch, leading to fuel starvation and a resulting flashback in the system. When an acetylene cylinder must be placed on its side for a period of time, it has to stand upright for at least twice that long before it is used. Cylinders should also be secured, usually with a chain, in a permanent location or in a suitable mobile cart, and the protective steel cap should stay on until the cylinder is put into service. These handling rules are part of the systematic setup order the handbook prescribes to avoid equipment damage and personal injury.

STUDY TIP

Read these timing questions carefully: the rule is twice the time on its side, not an equal time and not a fixed number of hours.

KEY POINTS

  • Acetylene cylinders are stored and transported upright because of the liquid acetone inside.
  • A cylinder laid on its side must stand upright at least twice that long before use.
  • Acetone carried into the regulator, hose, or torch can cause fuel starvation and flashback.

SOURCES

  • sources/ama-airframe/ch05.txt "Equipment Setup — Gas Cylinders"
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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.