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Propeller, Rotor, and Powertrain Maintenance Practices - Vol. 5

1-1 Purpose. This volume provides general informa- 
tion pertaining to aircraft propeller, rotor, and powertrain 
maintenance practices and procedures. The application 
of materials and techniques used on specific aircraft is 
not covered in this volume. Specific aircraft application, 
usage, and substitution are found in the individual aircraft 
maintenance manuals. This volume is of maximum 
benefit to the mechanic who desires information about 
propellers, rotors, and powertrains. This volume fur- 
nishes the mechanic a source of information about how 
to perform various mechanical functions which are used 
on all aircraft. This volume is not a requisitioning author- 
ity, and applicable repair parts and special tools list 
should be consulted to obtain the unit of issue and Na- 
tional Stock Number of the items required for mainte- 
nance. 
1-2 Scope. General information to guide aircraft main- 
tenance personnel is covered within this volume; howev- 
er, no attempt has been made to include special parts or 
equipment which are applicable only to individual or spe- 
cific aircraft. Propeller maintenance practices and proce- 
dures are covered in Chapter NO TAG. Rotor mainte- 
nance practices and procedures are discussed in 
Chapter NO TAG. Powertrain maintenance practices 
and procedures are presented in Chapter NO TAG.

1-3 Consumable Materials. 
1-4 Principles of Helicopter Flight. Basic flight 
theory and aerodynamics are considered in full detail 
when an aircraft is designed. The rotor repairer must 
understand these principles in order to maintain aircraft 
safely and to make repairs that are structurally sound and 
aerodynamically smooth. 
a. Aerodynamics. Aerodynamics deals with the 
motion of air and with the forces acting on objects moving 
through air or remaining stationary in a current of air. The 
same principles of aerodynamics apply to both rotary- 
wing and fixed-wing aircraft. Four forces that affect an 
aircraft at all times are weight, lift, thrust, and drag: 
D Weight is the force exerted on an aircraft by 
gravity. The pull of gravity acts through the air- 
craft's center of gravity, which is the point at 
which an aircraft would balance if suspended. 
The magnitude of this force changes only with a 
change in aircraft weight. 
D Lift is produced by air passing over the wing an 
airplane or over the rotor blades of a helicopter.