SIFT Study Guide with Accurate
Solutions
what is lift? - ANS-difference in air pressure
how does a helicopter generate lift? - ANS-Reduced pressure above the airfoil pushes it
downward.
pressure below pushes upward.
air pressure is greater below the airfoil
what are the three subcategories of Drag? - ANS-parasitic, profile, induced
what is parasitic drag? - ANS-caused by non-lift portions of helicopter (fuselage, landing
gear, etc.)
increases with speed (dominant at high airspeeds)
what is profile drag? - ANS-created by the friction resistance of spinning airfoils.
increases with velocity, but only slightly
remains moderate throughout, not dominant nor negligible
what is induced drag? - ANS-when blades spin, they leave a small gap of air behind
them, creating a vortex pushed in the opposite direction of lift. Pushes helicopter back
as it moves forward
The greater the AOA the greater the induced drag
decreases with airspeed. Dominant force at low speeds
what is the basic empty weight? - ANS-weight when everything unattached in removed
what is max Gross wieght? - ANS-max weight a helicopter can bear safely
what is max internal gross weight - ANS-max weight within the helicopter
what is max external weight - ANS-max weight supported externally by helicopter.
Solutions
what is lift? - ANS-difference in air pressure
how does a helicopter generate lift? - ANS-Reduced pressure above the airfoil pushes it
downward.
pressure below pushes upward.
air pressure is greater below the airfoil
what are the three subcategories of Drag? - ANS-parasitic, profile, induced
what is parasitic drag? - ANS-caused by non-lift portions of helicopter (fuselage, landing
gear, etc.)
increases with speed (dominant at high airspeeds)
what is profile drag? - ANS-created by the friction resistance of spinning airfoils.
increases with velocity, but only slightly
remains moderate throughout, not dominant nor negligible
what is induced drag? - ANS-when blades spin, they leave a small gap of air behind
them, creating a vortex pushed in the opposite direction of lift. Pushes helicopter back
as it moves forward
The greater the AOA the greater the induced drag
decreases with airspeed. Dominant force at low speeds
what is the basic empty weight? - ANS-weight when everything unattached in removed
what is max Gross wieght? - ANS-max weight a helicopter can bear safely
what is max internal gross weight - ANS-max weight within the helicopter
what is max external weight - ANS-max weight supported externally by helicopter.
