Aircraft Engine Tests

FAR 21.128 — Aircraft Engine Tests

FAR 21.128 requires manufacturers to test each aircraft engine with break-in runs and operation at rated power. Learn what's tested and why it matters.

In Plain English

FAR 21.128 sets the production test requirements for aircraft engines built under a type certificate. Before a new engine leaves the factory, the manufacturer must run it through a structured test to confirm it actually performs as advertised.

For every engine (except rocket engines, which use a sampling technique instead), the test run must include:

Break-in runs that measure fuel and oil consumption and verify power characteristics at rated maximum continuous power/thrust — and at rated takeoff power/thrust if applicable.
At least five hours of operation at rated maximum continuous power or thrust. If the engine has a rated takeoff power higher than its maximum continuous rating, that five-hour run must include 30 minutes at rated takeoff power or thrust.

The engine can be appropriately mounted on a test stand and measured with current power/thrust instrumentation.

Why it matters: as a pilot, you trust the published performance numbers in your POH. This rule is part of why those numbers are reliable — every engine is proof-tested at full power before delivery, catching defects on the ground rather than in flight.

Regulation Text

14 CFR § 21.128

§ 21.128 Tests: aircraft engines. (a) Each person manufacturing aircraft engines under a type certificate must subject each engine (except rocket engines for which the manufacturer must establish a sampling technique) to an acceptable test run that includes the following: (1) Break-in runs that include a determination of fuel and oil consumption and a determination of power characteristics at rated maximum continuous power or thrust and, if applicable, at rated takeoff power or thrust. (2) At least five hours of operation at rated maximum continuous power or thrust. For engines having a rated takeoff power or thrust higher than rated maximum continuous power or thrust, the five-hour run must include 30 minutes at rated takeoff power or thrust. (b) The test runs required by paragraph (a) of this section may be made with the engine appropriately mounted and using current types of power and thrust measuring equipment. [Doc. No. 5085, 29 FR 14568, Oct. 24, 1964, as amended by Amdt. 21-5, 32 FR 3735, Mar. 4, 1967]

Oral Exam Questions a DPE Might Ask

Q1What testing must a manufacturer perform on each new aircraft engine before delivery?

Per FAR 21.128, each engine built under a type certificate must undergo break-in runs measuring fuel and oil consumption and power characteristics, plus at least five hours at rated maximum continuous power.

Q2If an engine has a takeoff power rating higher than its maximum continuous rating, how is that addressed in the production test?

FAR 21.128 requires that the five-hour maximum continuous power run include 30 minutes at rated takeoff power or thrust to validate performance at that higher rating.

Q3Are there any aircraft engines exempt from individual production testing under this rule?

Yes. FAR 21.128 exempts rocket engines from individual testing; instead, the manufacturer must establish an acceptable sampling technique.

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Related Sections in Part 21

§ 21.1

Certification Procedures