Columbia subject headings:
Airworthiness certificates--United States--Handbooks, manuals, etc.
Helicopters--United States--Airworthiness--Handbooks, manuals, etc.
Rotors (Helicopters)--Certification--United States--Handbooks, manuals, etc.
Harvard subject headings:
Princeton subject headings:
Airworthiness certificates--United States--Handbooks, manuals, etc.
Helicopters--United States--Airworthiness--Handbooks, manuals, etc.
Rotors (Helicopters)--Certification--United States--Handbooks, manuals, etc.