How drones fly: systems, batteries, GNSS and theory of flight
RPAS components, C2 links, LiPo batteries, GNSS, lift and stalls, multirotor control, density altitude and load factor for the Canadian drone exams.
Checked against the rules in force on 2026-10-01You do not need to be an engineer to pass the drone exams, but you do need to understand how the aircraft stays in the air and what makes it fail.
The system
An RPAS is the aircraft, the control station and the command and control (C2) link between them. Most small drones use the 2.4 GHz band, which needs no licence and is crowded with Wi-Fi and other devices. Buildings and trees block the signal, so a controller strong enough to reach several kilometres can still lose a drone a few metres away behind an obstacle. Keep clear radio line of sight.
Batteries
Lithium polymer batteries pack a lot of energy and can catch fire if damaged, overcharged or short-circuited. Never fly a swollen battery. Cold reduces capacity, and low energy can make a drone behave unpredictably. Manufacturer flight times are estimates; wind, temperature and payload all shorten them.
GNSS
Position needs signals from at least four satellites. GNSS altitude can be off by tens of feet. Without a fix, many drones switch to an attitude mode and drift with the wind, so practise manual flying in a safe open area.
Lift, drag and stalls
The four forces are lift, weight, thrust and drag. Lift acts perpendicular to the relative wind. Exceed the critical angle of attack and the wing or rotor blade stalls, whatever the speed. Induced drag is greatest at low speed; parasite drag grows with speed.
Multirotors
Half the rotors turn clockwise and half counter-clockwise so their torque cancels. To yaw, the drone speeds up one pair and slows the other. To move forward it tilts, pointing part of the thrust in that direction. Close to the ground it gains ground effect; descending fast straight down into its own downwash can cause vortex ring state.
Performance
High density altitude (high elevation, heat, humidity, low pressure) means thin air, less thrust and shorter flights. In a level turn the load factor rises with bank: about 2 G at 60°, and stall speed rises with the square root of the load factor.
Sources: TC AIM RPA 3.2.1.2 · TC AIM RPA 3.2.13 · TP 15263 sec. 2, 7
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Free sample questions with a debrief for each answer.
Which component is often called the 'brain' of a drone, combining sensor data and pilot inputs into commands for the motors?
What are the four forces acting on an aircraft in flight?
Why does a multirotor need less power to hover just above the ground than high above it?
How does a hot, humid day at a high-elevation site affect the performance of a small multirotor UA?
In a coordinated, level turn at a 60° bank, what is the load factor?
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