Preface The Helicopter Flying Handbook is designed as a technical manual for applicants who are preparing for their private,  commercial, or flight instructor pilot certificates with a helicopter class rating. Certificated flight instructors may find  this handbook a valuable training aid, since detailed coverage of aerodynamics, flight controls, systems, performance,  flight maneuvers, emergencies, and aeronautical decision-making is included. Topics such as weather, navigation, radio  navigation and communications, use of flight information publications, and regulations are available in other Federal  Aviation Administration (FAA) publications. This handbook conforms to pilot training and certification concepts established by the FAA. There are different ways of  teaching, as well as performing, flight procedures and maneuvers, and many variations in the explanations of aerodynamic  theories and principles. This handbook adopts a selective method and concept to flying helicopters. The discussion and  explanations reflect the most commonly used practices and principles. Occasionally the word “must” or similar language  is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve  a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR). Persons working towards a helicopter rating are  advised to review the references from the applicable practical test standards (FAA-S-8081-3 for recreational applicants,  FAA-S-8081-15 for private applicants, and FAA-S-8081-16 for commercial applicants). Resources for study include  FAA-H-8083-25, Pilot’s Handbook of Aeronautical Knowledge, and FAA-H-8083-1, Weight and Balance Handbook, as  these documents contain basic material not duplicated herein. All beginning applicants should refer to FAA-H-8083-25,  Pilot’s Handbook of Aeronautical Knowledge, for study and basic library reference. It is essential for persons using this handbook to become familiar with and apply the pertinent parts of 14 CFR and the  Aeronautical Information Manual (AIM). The AIM is available online at www.faa.gov. The current Flight Standards  Service airman training and testing material and learning statements for all airman certificates and ratings can be obtained  from www.faa.gov. This handbook supersedes FAA-H-8083-21A, Helicopter Flying Handbook, dated 2012. Gyroplane information can be  found in the FAA-H-8083-20, Gyroplane Flying Handbook. This handbook is available for download, in PDF format, from www.faa.gov. This handbook is published by the United States Department of Transportation, Federal Aviation Administration, Airman  Testing Branch, P.O. Box 25082, Oklahoma City, OK 73125. Comments regarding this publication should be emailed to AFS630comments@faa.gov. v