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Standard atmosphere as a test reference

Aviation Mechanic General (AMG) practice question 14 of 20 on Physics for Aviation. ACS element AM.I.J.R2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAircraft performance is computed from flight tests or wind tunnel tests. In order to compare results obtained on different days, the data must be referenced to

  1. Athe density altitude on the first test day
  2. Bthe U.S. Standard Atmosphere
  3. Cthe conditions recorded in the flight manual
Show the answer and explanation

Correct answer: B. the U.S. Standard Atmosphere

  • A — incorrect Conditions on any particular day are not a fixed standard. The reference must be a defined set of standard conditions, not one day's measurements.
  • B — correct Atmospheric conditions vary continuously, so a set group of standards is used as a point of reference. In the United States that reference is the U.S. Standard Atmosphere.
  • C — incorrect The flight manual presents charts derived from test data; it is not the reference condition to which test results are corrected.

BACKGROUND

When aircraft performance is computed, whether through flight tests or wind tunnel tests, a standard reference condition must be determined first so that results can be compared with those of similar tests. Atmospheric conditions vary continuously, and it is generally not possible to obtain exactly the same conditions on two different days or even two successive flights. For this reason a set group of standards is used as a point of reference. The set of standard conditions used in the United States is the U.S. Standard Atmosphere, which specifies sea level values of 29.92 in Hg, 15 °C (59 °F), and gravity of 32.174 fps/s and agrees with the ICAO Standard Atmosphere over their common range.

STUDY TIP

Whenever test or performance data are involved, remember that the standard atmosphere exists to make results from different days comparable.

KEY POINTS

  • Atmospheric conditions never repeat exactly between tests
  • A fixed standard is needed as a reference for comparison
  • The U.S. Standard Atmosphere is that reference in the United States

SOURCES

  • FAA-H-8083-30B ch05 "Standard Atmosphere"
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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.