Definition
An FAA Advisory Circular that provides guidance and acceptable means, but not the only means, for showing compliance with the airworthiness standards in 14 CFR Part 27 for normal category rotorcraft (helicopters with a maximum certificated takeoff weight of 7,000 pounds or less and nine or fewer passenger seats). It explains how manufacturers should demonstrate that a small helicopter design meets safety requirements during certification.
Plain English
An FAA guidance document that tells helicopter manufacturers how to prove their small helicopter is safe enough to be approved for sale and use.
Context Anchor
You may see AC 27-1 referenced when reading about helicopter flight manual limitations, certification rules, or the reasons certain helicopter operating limits are required.
Derivation
‘Advisory Circular’ comes from ‘advise’ (Latin advisare, to consider or recommend) and ‘circular’ (a document circulated for information). The number 27 matches 14 CFR Part 27, the regulation it supports. The ‘-1’ marks it as the primary AC for that part.
Why Pilots Care
The limitations a pilot must follow in the Rotorcraft Flight Manual trace back to how the helicopter was certified under this document. Knowing it exists helps a pilot understand why certain limits are firm rules, not suggestions.
Intuition Check
Do not read “AC” here as air conditioning or electrical current. In this FAA reference, AC means Advisory Circular, a guidance document from the FAA.
Example Sentence 1
The flight manual limitations for this small helicopter were established during certification under AC 27-1.
Example Sentence 2
Chapter 7 of the Instrument Procedures Handbook directs the reader to AC 27-1 for detailed guidance on establishing helicopter operating limitations.