SIFT (Army Aviation) Exam Questions
with Verified Solutions
Profile drag - ANSWER-Caused by the blades frictional resistance
Induced drag - ANSWER-Downwash
Parasite drag - ANSWER-Components attached to a helicopter that dont contribute to
lift
Total drag - ANSWER-Sum of profile, induced, and parasite drag.
Bernoullis principle - ANSWER-As flow increases, pressure decreases
Phases of flight - ANSWER-Takeoff, climb, cruise, descent, landing.
Flat and curved side pressure - ANSWER-Flat side is high pressure, curved side is low
pressure
Angle of attack - ANSWER-Angle between the chord line and the relative wind ( it's an
aerodynamic angle)
angle of incidence - ANSWER-Angle between chord line and the rotor systems place of
rotation ( mechanical angle)
Stall region - ANSWER-The inner one quarter of the blade.
Driving region - ANSWER-In between the stall and driven region.
Driven region - ANSWER-The outer 30% of a blade.
Blade twist - ANSWER-Greater pitch angles near the root and shallower near the blade
tip
Effective translational lift - ANSWER-Experienced between 16 to 24 knots
In ground effect - ANSWER-Additional lift is provided from the ground when the altitude
is one length or less then the main rotor diameter.
Rotational relative wind - ANSWER-Tip path plane, wind velocity is greatest at the tip of
each blade
, Rotor system parts (4) - ANSWER-Hub, tip, root,twist
Total aerodynamic force - ANSWER-Two components comprise this lift and drag
Translating tendency ( drift ) - ANSWER-A helicopter with one main rotor tends to drift in
the direction of the tail rotor thrust
First law of motion - ANSWER-Until acted on by an external force, an objects velocity
will remain constant ( an object at rest will remain at rest and in object in motion will
remain in motion until a force is applied)
Second law of motion - ANSWER-Algebraically is F=m*a ( how the velocity of an object
changes when it is subject to another force)
Third law of motion - ANSWER-for every action there is an equal and opposite reaction
Acceleration of gravity - ANSWER-Is 9.81 m/s squared
Torque equation - ANSWER-T= F*r
Gravitation potential energy - ANSWER-PE= m*g*h (m is mass, g is 9.81, and h is
height)
Work equation - ANSWER-W=F*d
Stiction friction - ANSWER-Force necessary to start sliding an object
Simple machines - ANSWER-Devices that change the direction or magnitude of force
mechanical advantage - ANSWER-Defined as the output force dived by the force
applied
Class 1 lever - ANSWER-Mechanical advantage is the same on each side
class 2 lever - ANSWER-Mechanical advantage greater than one ( out put closer to
fulcrum)
Class 3 lever - ANSWER-Mechanical advantage less than 1 (output further from
fulcrum)
Pascals law - ANSWER-Transmission of pressure
High reconnaissance - ANSWER-This is used to direction and speed of wind, a
touchdown point, suitability of landing area, approach and departure, and obstacles for
both ( good at 300 to 500 feet)
with Verified Solutions
Profile drag - ANSWER-Caused by the blades frictional resistance
Induced drag - ANSWER-Downwash
Parasite drag - ANSWER-Components attached to a helicopter that dont contribute to
lift
Total drag - ANSWER-Sum of profile, induced, and parasite drag.
Bernoullis principle - ANSWER-As flow increases, pressure decreases
Phases of flight - ANSWER-Takeoff, climb, cruise, descent, landing.
Flat and curved side pressure - ANSWER-Flat side is high pressure, curved side is low
pressure
Angle of attack - ANSWER-Angle between the chord line and the relative wind ( it's an
aerodynamic angle)
angle of incidence - ANSWER-Angle between chord line and the rotor systems place of
rotation ( mechanical angle)
Stall region - ANSWER-The inner one quarter of the blade.
Driving region - ANSWER-In between the stall and driven region.
Driven region - ANSWER-The outer 30% of a blade.
Blade twist - ANSWER-Greater pitch angles near the root and shallower near the blade
tip
Effective translational lift - ANSWER-Experienced between 16 to 24 knots
In ground effect - ANSWER-Additional lift is provided from the ground when the altitude
is one length or less then the main rotor diameter.
Rotational relative wind - ANSWER-Tip path plane, wind velocity is greatest at the tip of
each blade
, Rotor system parts (4) - ANSWER-Hub, tip, root,twist
Total aerodynamic force - ANSWER-Two components comprise this lift and drag
Translating tendency ( drift ) - ANSWER-A helicopter with one main rotor tends to drift in
the direction of the tail rotor thrust
First law of motion - ANSWER-Until acted on by an external force, an objects velocity
will remain constant ( an object at rest will remain at rest and in object in motion will
remain in motion until a force is applied)
Second law of motion - ANSWER-Algebraically is F=m*a ( how the velocity of an object
changes when it is subject to another force)
Third law of motion - ANSWER-for every action there is an equal and opposite reaction
Acceleration of gravity - ANSWER-Is 9.81 m/s squared
Torque equation - ANSWER-T= F*r
Gravitation potential energy - ANSWER-PE= m*g*h (m is mass, g is 9.81, and h is
height)
Work equation - ANSWER-W=F*d
Stiction friction - ANSWER-Force necessary to start sliding an object
Simple machines - ANSWER-Devices that change the direction or magnitude of force
mechanical advantage - ANSWER-Defined as the output force dived by the force
applied
Class 1 lever - ANSWER-Mechanical advantage is the same on each side
class 2 lever - ANSWER-Mechanical advantage greater than one ( out put closer to
fulcrum)
Class 3 lever - ANSWER-Mechanical advantage less than 1 (output further from
fulcrum)
Pascals law - ANSWER-Transmission of pressure
High reconnaissance - ANSWER-This is used to direction and speed of wind, a
touchdown point, suitability of landing area, approach and departure, and obstacles for
both ( good at 300 to 500 feet)
