Flight Test Calibration Report

FAR 21.39 — Flight Test Calibration Report

FAR 21.39 requires type certificate applicants to submit instrument calibration and test correction reports to the FAA, and allow verification flight tests.

In Plain English

FAR 21.39 is a type certification requirement that applies to manufacturers (applicants), not individual pilots. It governs how flight test data must be documented and verified before the FAA issues a type certificate for an aircraft.

The rule applies to applicants seeking a type certificate in any of these categories:

Normal
Utility
Acrobatic
Commuter
Transport

Under this section, the applicant must:

Submit a report to the FAA showing the computations and tests used to calibrate the instruments used during flight testing.
Show how raw test results were corrected to standard atmospheric conditions (so performance numbers are comparable and accurate).
Allow the FAA to conduct any flight tests it deems necessary to verify the accuracy of that report.

Why it matters operationally: the performance data pilots rely on in the AFM/POH — takeoff distances, climb rates, stall speeds — traces back to flight tests verified under rules like FAR 21.39. Accurate calibration ensures the published numbers are trustworthy.

Regulation Text

14 CFR § 21.39

§ 21.39 Flight test instrument calibration and correction report. (a) Each applicant for a normal, utility, acrobatic, commuter, or transport category aircraft type certificate must submit a report to the FAA showing the computations and tests required in connection with the calibration of instruments used for test purposes and in the correction of test results to standard atmospheric conditions. (b) Each applicant must allow the FAA to conduct any flight tests that he finds necessary to check the accuracy of the report submitted under paragraph (a) of this section. [Doc. No. 5085, 29 FR 14564, Oct. 24, 1964, as amended by Amdt. 21-59, 52 FR 1835, Jan. 15, 1987]

Oral Exam Questions a DPE Might Ask

Q1Who does FAR 21.39 apply to, and what does it require?

Per FAR 21.39, it applies to applicants for a normal, utility, acrobatic, commuter, or transport category type certificate, who must submit a report showing instrument calibration computations and the correction of test results to standard atmospheric conditions.

Q2Why does FAR 21.39 require test results to be corrected to standard atmospheric conditions?

FAR 21.39 requires the correction so the FAA can evaluate aircraft performance on a consistent baseline, since raw flight test data is influenced by the actual temperature, pressure, and density on test day.

Q3Can the FAA perform its own flight tests to verify a manufacturer's calibration report?

Yes. Under FAR 21.39(b), the applicant must allow the FAA to conduct any flight tests it finds necessary to check the accuracy of the calibration and correction report submitted under paragraph (a).

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Related Sections in Part 21

§ 21.1

Certification Procedures

§ 21.101

Type Certificate Changes