Ch. 7 Balance & Weight Flashcards
The Center of Gravity (CG) position must be described in 3 different axes- what are they?
Longitudinal, lateral, & vertical
The CG must be measured for relative position in each of these planes.
Weight consists of 3 basic elements- what are they?
- Empty or basic weight
- Payload (useful, disposable weights; pilots, baggage, fuel)
- Gross (sum of 1 & 2)
Define datum
The point to measure the distance of disposable weights & their moment arms.
Aka “station 0”
2 datums that are commonly used are the one placed ahead of the _____ and one placed at the _____.
Nose; rotor mast
CG Location formula
Total Moment / Total Weight
Moment formula
Objects arm x it’s weight
Ex. Empty CG
99.3” x 1,200lbs = 119,160
99.3” = inches from datum
The _____ CG is the most commonly changed CG & also the one with the most immediately noticeable effect.
Longitudinal
Ex. In a zero-airspeed hover, the pilot will see a longitudinal cyclic is more aft than with a neutral CG. This is due from the fuselage hanging nose-down below the rotor disk moving the CG forward.
The _____ (longitudinal/lateral/vertical) CG envelop is the reason why some helicopters can’t handle someone hanging from the skids, when others can.
Lateral
The tendency of the tail rotor to push the helicopter sideways is called _____.
Translating tendency or tail rotor drift
The principal method for correcting for translating tendency is to tilt the _____ vector of the main rotor.
Thrust
The principal method for correcting for translating tendency is to tilt the _____ vector of the main rotor.
Thrust
Correcting for translating tendency is accomplished by what 3 ways?
- The pilot: adjusting controls
- Rigged flight controls: puts bias in tilt to the left
- Mounting the main rotor transmission so the drift shaft is tilted to the left permanently
The first 2 will result in a “left skid low” attitude of the helicopter.
What is helicopter trim?
The balance of moments of the aircraft center of gravity determines the attitude adopted by the airframe & when this balance is achieved, the helicopter is said to be trimmed.
Aka keeping all of the forces/systems in balance
What is helicopter trim?
The balance of moments of the aircraft center of gravity determines the attitude adopted by the airframe & when this balance is achieved, the helicopter is said to be trimmed.
Aka keeping all of the forces/systems in balance
Reducing/lifting the collective simultaneously reduces/increases the size of the _____ & _____ vectors.
Thrust & lift
Reducing/lifting the cyclic changes the tilt of these 2 vectors.
