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Absolute pressure of a tire at altitude

Aviation Mechanic Airframe (AMA) practice question 13 of 20 on Aircraft Instrument Systems. ACS element AM.II.H.K3 · 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 tire is inflated to a gauge pressure of 32 psi at a location 10,000 feet above sea level, where atmospheric pressure is approximately 10 psi. What is the approximate absolute pressure in the tire?

  1. A42 psi, the gauge value plus ambient
  2. B22 psi, the gauge value minus ambient
  3. C46.7 psi, the sea level absolute value
Show the answer and explanation

Correct answer: A. 42 psi, the gauge value plus ambient

  • A — correct Absolute pressure is gauge pressure plus the surrounding atmospheric pressure, so 32 psi plus approximately 10 psi gives roughly 42 psi.
  • B — incorrect Subtracting ambient pressure reverses the relationship; atmospheric pressure is added to gauge pressure to obtain absolute pressure.
  • C — incorrect That figure applies to the same tire at sea level, where about 14.7 psi of atmosphere is added instead of about 10 psi.

BACKGROUND

Pressure is always a comparison between two forces. Absolute pressure compares a force to a total vacuum, gauge pressure compares it to the surrounding atmosphere, and differential pressure compares two pressures of interest. Because atmospheric pressure falls with altitude, the same tire inflated to 32 psi gauge has an absolute pressure of about 46.7 psi at sea level but only about 42 psi at 10,000 feet. Gauge pressure is the most common form of measurement and should be assumed unless the instrument is a type known to need absolute pressure, such as the altimeter, the rate-of-climb indicator, or the manifold pressure gauge. Standard pressure, 29.92 inches of mercury or 14.7 psi, is a separate established reference value used with a standard sea level temperature of 15 °C.

STUDY TIP

Work the sea level and 10,000-foot versions of the tire example until adding ambient pressure to gauge pressure is automatic.

KEY POINTS

  • Absolute pressure equals gauge pressure plus surrounding atmospheric pressure.
  • Gauge pressure stays the same while absolute pressure changes with altitude.
  • Altimeters, rate-of-climb indicators, and manifold pressure gauges use absolute pressure.

SOURCES

  • sources/ama-airframe/ch10.txt "Types of Pressure"
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MORE ON AIRCRAFT INSTRUMENT 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.