Aerodynamics, Weight and Balance

This lesson supports study only. It does not replace current CASA, Airservices or approved operator procedures.

Four forces, one aircraft

Lift acts upward, weight acts downward, thrust moves the aircraft forward or upward depending on the design, and drag resists motion through the air.

Angle of attack is the angle between the aerofoil chord line and the relative airflow. Centre of pressure is where the aerodynamic force acts. Centre of gravity is where the aircraft balances.

Aerofoil diagram showing lift, weight, thrust and drag — Put the four forces on the aircraft first, then the words lift, weight, thrust and drag become concrete.

Lift has more than one explanation

The MOS expects remote pilots to understand Bernoulli, Coanda and Newton's third law at a basic level. In practical terms, an aerofoil or rotor creates lift by shaping and accelerating air so that a useful force is produced.

The exam point is useful, but the operational point is better: damaged propellers, wrong payloads, high density altitude or poor loading can reduce the lift and control margin you thought you had.

Diagram explaining Bernoulli and Coanda effects over an aerofoil — The lift explanation is not just formula work. It is a picture of air being shaped, accelerated and deflected.

Loading changes the aircraft

Empty weight, operating weight, maximum gross weight, arm, moment, datum and centre of gravity limits are all ways of describing whether the aircraft is loaded within its approved envelope.

For RPA operations, payloads are the everyday trap. A camera, sprayer tank, LiDAR unit or extra battery can change gross weight, balance, endurance and emergency handling.

Weight and balance diagram showing centre of gravity and loading — A payload is not just extra weight. Where that weight sits changes the balance of the whole aircraft.

Practice Questions

Why can adding a payload change flight safety?

It can change weight, balance, endurance and control margin.
It only changes the colour of the aircraft.
It always improves climb performance.
It removes the need for battery planning.

Answer: It can change weight, balance, endurance and control margin.

Payload affects aircraft loading and can push the RPA outside expected performance or balance limits.

Next step after study

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