Aerodynamics Flashcards
(37 cards)
Improved rotor efficiency resulting from directional flight is called ____.
Translational lift
____ is a flight condition where a helicopter starts to fly out of its own rotor downwash and moves into clean, undisturbed air that reduces wing tip vortices and causes the rotor to become more efficient (usually between 16 – 24 knots)
Effective Translational Lift (ELT)
____ is a condition of increased drag and decreased lift in the aft portion of the rotor disk compared to the front portion. (Caused by the air having a greater induced velocity and reduced angle of attack in the aft portion of the disk)
Transverse Flow
____ is the tendency of single rotor helicopters to translate in the direction of tail rotor thrust.
Translating Tendency
The difference in lift between the advancing half of the rotor disk and the retreating half is called ____.
Dissymmetry of Lift
____ is the phenomenon resulting from the advancing blade approaching Mach 1 (because of excessive forward speed).
Compressibility
____ is an aerodynamic phenomenon that is characterized by an uncommanded yaw which does not subside of its own accord. (if not corrected can result in the loss of aircraft control)
Loss of Tail Rotor Effectiveness (LTE)
A powered flight condition in which the helicopter settles in its own downwash (resulting in a descent that is aggravated by the increase in power) is known as ____.
Vortex Ring State
____ is when a helicopter exceeds its critical rollover angle with one skid or wheel on the ground. (Requirements: pivot point, roll rate, exceed critical angle – TH-1 is 150)
Dynamic Rollover
____ is when the retreating blade exceeds the critical angle of attack and stalls (causing the aircraft’s nose to pitch up and roll in the direction of the stall).
Retreating Blade Stall
Wind that flows opposite the physical flight path of the airfoil, striking the blade at 90 degrees to the leading edge and parallel to the plane of rotation, and is constantly changing in direction during rotation is known as ____.
Rotational Relative Wind
____ is the downward flow of air through the rotor blades caused by the increased blade pitch angle. (this downward component of air is added to the rotational relative wind.)
Induced Flow
____ is rotational relative wind modified by induced flow.
Resultant Relative Wind
____ is the force that opposes the motion of an aircraft through the air and is the force produced by the resistance of the air on an object passing through it. It’s always parallel to relative wind.
Drag
____ Drag is incurred from frictional resistance of the blades passing through the air.
Profile Drag
____ Drag is incurred as a result of production of lift.
Induced Drag
____ Drag is incurred from the non-lifting portions of the aircraft.
Parasitic/Parasite Drag
The S in the lift equation is ____.
Surface Area
In Ground Effect hover power can be up to ___% less than Out of Ground Effect.
30%
____ and ____ compensate for tail rotor dissymmetry of lift
Flapping and Feathering
Any descent of ____ KIAS and ____ FPM or more with power applied may result in Vortex Ring State
40 KIAS / 800 FPM
In the even of a complete loss of tail rotor thrust, aft cyclic application should be very slow and small to avoid ____.
Mast Bumping
Newton’s 1st Law of motion (inertia) states what?
A body at rest will remain at rest, and a body in motion will remain in motion until acted upon by an external force
What is Newton’s 2nd law of motion? (Acceleration)
The force required to produce change in the motion of a body is directly proportional to it’s mass and the rate of change of it’s velocity.
