Army Flight Warrant Officer SIFT Test Study Guide with Complete Solutions
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Course
SIFT
Institution
SIFT
Army Flight Warrant Officer SIFT Test
Study Guide with Complete Solutions
Helicopter Structure - Answer-The typical structure of a helicopter is a fuselage (the body of the
craft) with a mast protruding upward out of it. The engine of the craft drives power upward through the
mast to the rotor ...
all of the power from the engine can be used for lift. Consequently, tandem rotor helicopters are some of
the fastest and most powerful in existence.
Thrust - Answer✔✔-Thrust is created by the engine, or engines, of the helicopter. It is transferred into
motion via the mast and rotors. Sufficient thrust is needed to overcome the drag and the weight of the
helicopter and keep it moving forward.
Drag - Answer✔✔-Drag is a force which acts against thrust. In the case of helicopters, drag is caused by
the shape and size of the aircraft disrupting the flow of air as it travels. There are several types of drag
which impact helicopters.
Profile Drag - Answer✔✔-Profile drag is caused by the frictional resistance of helicopter blades passing
through the air. It has two components: form drag and skin friction.
Form Drag - Answer✔✔-Form drag increases as the speed of the helicopter increases.
Skin Friction - Answer✔✔-Skin friction is caused by microscopic roughness of the helicopter blades. Any
roughness on the surface causes air to become trapped and drag to increase.
Induced Drag - Answer✔✔-Induced drag is caused by airflow circulation around the blades creating
vortices. This type of drag increases when the helicopter is flying at lower speeds, and decreases when it
is flying at higher speeds. During low speed flight, induced drag is the main cause of drag for helicopters.
Parasite Drag - Answer✔✔-Parasite drag is the drag created by the helicopter components that are
external to the fuselage. For example, the landing gear, cowlings and doors can all create parasite drag.
Parasite drag slows down the speed of a helicopter by opposing thrust.
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