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Army Flight Warrant Officer SIFT Test Study Guide with Complete Solutions

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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 ...

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  • October 7, 2024
  • 10
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers
  • SIFT
  • SIFT
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EmillyCharlotte
EMILLYCHARLOTTE 2024/2025 ACADEMIC YAER ©2024 EMILLYCHARLOTTE. ALL RIGHTS RESERVED
FIRST PUBLISH SEPTEMBER 2024




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 blades, which are controlled by the pilot. This main rotor is used to generate thrust.

This thrust is balanced by a second rotor, usually a tail rotor, which is intended to account for the effects

of torque. In the USA, UK and Germany, it is conventional for the main rotor to rotate counterclockwise.

The opposite is true in other countries. Throughout this book, reference will be made only to

counterclockwise main rotors.


Single Main Rotor Helicopter - Answer✔✔-This is the most common design for a helicopter -a single

main rotor generating power, with a secondary rotor, such as a tail rotor, used to offset the effects of

torque. One disadvantage of this design is that some power is used for countering torque, rather than

being used solely for lift.


Co-axial Rotor Helicopter - Answer✔✔-This type of helicopter features two sets of blades rotating above

and beneath each other. The two sets of blades are mounted to the same mast, but rotate in opposite

directions to each other. This has the advantage of reducing payload and allowing for greater cargo and

passenger capacity as a result.


Tandem Rotor Helicopter - Answer✔✔-This helicopter design features two main rotating blade sections:

front and rear. Each set of blades rotates counter to the other, meaning that torque is automatically

offset. There is no need for additional measures, such as a tail rotor, to deal with torque. Because of this,

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, EMILLYCHARLOTTE 2024/2025 ACADEMIC YAER ©2024 EMILLYCHARLOTTE. ALL RIGHTS RESERVED
FIRST PUBLISH SEPTEMBER 2024


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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