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Titanium tubing prohibited in oxygen systems

Aviation Mechanic General (AMG) practice question 8 of 17 on Fluid Lines and Fittings. ACS element AM.I.D.K1 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhy must titanium tubing and fittings never be used in an oxygen system assembly?

  1. ATitanium's thin walls cannot safely withstand the pressure of a gaseous oxygen system
  2. BA freshly formed titanium surface can spontaneously combust in gaseous oxygen
  3. CTitanium corrodes rapidly when it contacts oxygen at low pressure
Show the answer and explanation

Correct answer: B. A freshly formed titanium surface can spontaneously combust in gaseous oxygen

  • A — incorrect Titanium is 30 percent stronger than steel and is used in hydraulic systems above 1,500 psi; the prohibition is about oxygen reactivity, not pressure strength.
  • B — correct The handbook states that titanium and titanium alloys are oxygen reactive, and that a freshly formed titanium surface exposed to gaseous oxygen can spontaneously combust even at low pressures.
  • C — incorrect The hazard the handbook describes is spontaneous combustion, not corrosion; titanium is widely used for its strength and light weight.

BACKGROUND

Titanium 3AL2.5V tubing and fittings are used extensively in transport category and high-performance aircraft hydraulic systems for pressures above 1,500 psi. Titanium is 30 percent stronger than steel and 50 percent lighter, and it is joined with Cryofit or swaged fittings. However, titanium and titanium alloys are oxygen reactive. If a freshly formed titanium surface is exposed in gaseous oxygen, spontaneous combustion can occur at low pressures, so titanium tubing and fittings must not be used in any oxygen system assembly.

STUDY TIP

Remember the two titanium facts together: excellent for high-pressure hydraulics, forbidden in oxygen systems because of reactivity.

KEY POINTS

  • Titanium 3AL2.5V tubing is used in hydraulic systems above 1,500 psi.
  • Titanium is oxygen reactive; a fresh surface can spontaneously combust in gaseous oxygen at low pressure.
  • Never use titanium tubing or fittings in any oxygen system assembly.

SOURCES

  • FAA-H-8083-30B ch09 "Titanium 3AL2.5V"
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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.