General knowledge Flashcards
to familarize with general information of aviation
What errors are vertical speed indicators subject to?
1) lag error
2) reversal-in about changes in attitude the VSI may momentarily show a change in the wrong direction
Define: Yaw
movement of aircraft around the vertical axis
Define: Roll
movement of an aircraft around the longitudinal axis
What is relative humidity?
amount of moisture present in the air compared to amount it is capable of holding
In extremely cold temperature the altimeter will___________?
over-read
Define: Ground Resonance
is a sympathetic vibration between the main rotror system and landing gear when the helicopter is touching the ground
Note: generally only fully articulated rotor systems are susceptable
On turns to or from North the magnetic compass will _____________ the actual reading
lag behind
What are Newtons laws of motion?
1) A body in motion tends to stay in motion
2) An object at rest tends to stay at rest until acted on by another force
3) for every action there is an equal and opposite reaction
What are five principle agents that initiate rising currents of air?
1) convection- air heated by contact with ground
2) Orographic lift-air moving up hill continues upwards especially if unstable
3) Frontal Lift-air masses meet the warmer air is pushed up
4) Mechanical Turbulence-friction between air and ground disrupts lower level air into eddies
5) Convergence- low pressure area, winds are blowing into centre of low and accumulating, the excess air is forced upwards
What is atsmopheric pressure?
is the weight of overlying air measured with a mercury barometer
list three causes of ground resonance
1) Faulty rotor system-weak drag hinge dampers, badly tracked or balanced rotor blades
list and describe the different types of drag
Parasite-created by moving objects
Rotor-Caused by rotor blades in flat or zero pitch
Induced drag- occurs when blades are at a positve angle of attack(producing lift)Induced drag is high in the hover but reduces with translational lift and increased forward speed
Define: Dissymetry of lift
The relative airspeed travelling over the retreating blade is less than the advancing blade resultaning in unequal lift on the blades
Define: Ground effect
s
Define: Translating tendency
s
Define: horizontal from the hub
Refrence datum on the hub of the main rotor
What factor affect the rate of descent in autorotation
weight-heavier=higher rate of descent
Forward speed-above or below the minimum rate of descent speed will result in a higher rate of descent
Density altitude-rate increases with an increase of density altitude
Define Torgue effect
Blades spin counter-clockwise causing an opposite reaction on fuselage turning it clockwise
define: Recirculation
Aceleration of induced air through the disc
Define: Vortex ring state
Intense vortices from induced flow, reenter the rotor blades reducing the lift produced. usually encountered at configurations with an airspeed below 30knots, and a rate of descent higher than 300FPM
Define: Chord line
A straight line running from leading edge to trailing edge of an aerofoil
describe feathering movement of a rotor blade
angular movement of a rotor blade about its longitudinal axis
*any change of pitch is a feathering movement
Define: Induced flow
The rotor blades displace air downwards through the rotor disc
Define Pitch angle
The angle between the chord of a rotor blade and a refrence datum on the hub of the rotor.
Define: Convection
Warm air rises owing to the heating of the ground by the sun, risng currents of air occur
Describe the flapping movement of a rotor blade
the automatic angular movement of a rotor blade about a horzontal axis
What are the main types of rotor systems and describe each
Fully articulated- blades allowed by hinges to flap, drag and feather
Semi-rigid-the blades are allowed by hinges to flap and feather, underslung rotor
Rigid- only feathering hinge
Name 2 types of control orbits
Swash plate
Spider
Define: dragging of a rotor blade
The angular movement of an individual rotor blade about an axis vertical to the blade
What is an transition? translation?
Transition-all accelerations or decelerations of the helicopter as a result of cyclic change
Translation- horizontal movement of the helicopter through the air
Define: Indicated altitude
The reading on the altimeter when it is set to current barometric pressure
Define: Coning
Movement of rotor blades aligning them along the resultant angle of centrifugal force and lift, an increase in lift results an increase in coning angle. An increase of RPM results in a decrease of coning angle
Define: Camber line
A line drawn halfway between upper and lower surface of an aerofoil
Define angle of attack
The angle between the chord and relative airflow
What are 5 factors that affect lift
1) angle of attack of aerofoil
2) airflow velocity
3) air density
4) shape of airfoil
5) surface area of airfoil
Define: Overpitching
Blades pitch-up increasing drag, not enough power to overcome drag
Define: Pitch (as in pitch, roll, yaw)
movement of aircraft around the lateral axis
*lateral axis-wing tip to wing tip
Name the instruments connected to the pitot/static system and from which they get there data from.
Altimeter-static
Vertical speed indicator-static
Airspeed indicator-staic and pitot
Define: Delta hinge
hinge located on the tail rotor, is ofsetto be non-perpindicular to the axis of the tail rotor
Define: Low G
unloading of the disc usually caused by a push over
Define: High G
aircraft experiances load factor greater than 1G due to a turn, climb, or deceleration
Define: True altitude
Exact height above sea level
What are low frequency vibrations usually associated with?
High?
Low?
low-main rotor
medium-tail rotor
High- engine
