IMPORTANCE OF WEIGHT & BALANCE

MEMORY JOGGER #7 

An overloaded aircraft may fail to become airborne, while an out-of-limits centre of gravity seriously affects stability and controllability. Pilots must appreciate the effects of weight and balance on the performance and handling of aircraft, particularly in combination with other performance reducing factors, such as long/wet grass, a 'tired' engine, severe or un-coordinated manoeuvres, turbulence, high ambient temperatures and emergency situations.

Weight
The effects of overloading include:

·       reduced acceleration/greater take-off speed, take-off run, & distance to clear a 50 ft. obstacle
·       decreased angle of climb/reduced obstacle clearance capability after take-off
·       excessive loads on landing gear, especially if the runway is rough
·       reduced ceiling, rate of climb, & range
·       impaired manoeuvrability & controllability
·       increased stall speeds
·       increased landing speeds, requiring a longer runway
·       reduced braking effectiveness & structural strength margins
·       with twin-engine aircraft, failure to climb/maintain height on one engine

Balance
Forward and aft limits on the centre of gravity (cg) are established during type certification; they are the extreme cg positions at which longitudinal stability requirements can be met.

Exceeding the forward cg limit usually results in:

·       difficulty in rotating to take-off attitude
·       increased stall or minimum flying speed against full up elevator
·       extra tail downforce requiring more lift from wing, resulting in greater induced drag. This means higher fuel consumption and reduced range
·       inadequate nose up trim in landing configuration, necessitating a pull force throughout the approach making it more difficult to fly a stable approach
·       difficulty in flaring/holding the nose wheel off after touch down. Inability to hold the nose up during a bounce can result in damaged nose landing gear and propeller
·       increased loads on the nose landing gear

Exceeding the aft cg limit usually results in:

·       pitch-up at low speed & high power, leading to premature rotation on take-off, or inadvertent stall in the climb or during a go-around
·       on a tail wheel type, difficulty in raising the tail/maintaining directional control on the ground
·       difficulty trimming, especially at high power
·       longitudinal instability, particularly in turbulence, with possible reversal of control forces
·       degraded stall qualities to an unknown degree
·       more difficult spin recovery, unexplored spin behaviour, delay in/inability to recover

(Acknowledgements: Goldi Productions Ltd.)


FLY SAFE!
Tony Birth