11.2 Weight & Balance, Contamination & Winter Ops

11.2 Weight & Balance, Contamination & Winter Ops

Quick Answer: Keep CG inside the approved envelope using correct empty/gross weight and careful external load planning. Remove critical surface contamination (frost, ice, snow, water, improvised tape) before flight. In winter, manage battery cold soak, icing, and shortened endurance. Avoid thunderstorms, respect wildlife/conservation, stay aware of runway numbering near aerodromes, control PED interference, and understand how bank and speed set turn radius for mapping orbits.

Weight-and-balance and environmental contamination are “quiet” exam topics that become loud accident causes. A perfectly authorized Advanced flight still fails if the aircraft is overweight, nose-heavy, ice-contaminated, or flying a mapping grid that demands a turn radius the airframe cannot fly at that speed.

Centre of gravity (CG) location

The centre of gravity is the point where the aircraft’s weight is considered to act. For multirotors and fixed-wing RPAS, CG must stay within the manufacturer envelope:

CG shifts when you add gimbals, dual batteries, speakers, sample boxes, antennas, or side-mounted sensors. After every configuration change, reassess mass and CG—do not assume “it was fine last month with a lighter camera.”

Empty weight, gross weight, and external loads

• Empty / basic empty weight — airframe and standard equipment without disposable load (definitions vary by manufacturer; use their weighing procedure).
• Gross / maximum take-off weight (MTOW) — maximum allowable weight for flight; never exceed it for “just one more battery.”
• Useful load — difference available for batteries, payload, and fuel if applicable.

External loads (underslung packages, non-streamlined sensors, tethered elements where authorized) increase:

1. Mass → higher power, lower endurance, lower hover ceiling
2. Drag → reduced forward speed, higher energy for the same groundspeed
3. Snag risk → lines and brackets catch on trees, fences, and structures
4. Dynamic CG — swinging underslung loads move the effective CG in flight

CAR 901.43 themes still ban hazardous/unauthorized payloads; weight-and-balance success does not legalize a prohibited load. 901.50 (dropping objects—covered in Section 11.4) interacts with external-load missions: if the job is to release something, that is a separate regulatory question, not only a CG question.

Critical surface contamination

Critical surfaces are those that must be clean for safe flight—typically wings, propellers/rotors, stabilizers, and other lifting or control surfaces. Contamination includes frost, ice, snow, slush, standing water, mud, and tape or covers left on pitot/ports or airfoils.

Why contamination is so dangerous

Even thin frost can destroy smooth airflow, reduce lift, increase drag, and trigger early stall or loss of rotor efficiency. Ice adds mass and can shed asymmetrically. Snow/water on props throws imbalance and vibration. Tape left on a wing or sensor can act as a spoiler.

Rule: If critical surfaces are contaminated, do not fly until they are clean and dry per manufacturer guidance. “It will blow off after takeoff” is a classic fatal assumption in all aviation, including RPAS.

Winter operations and battery cold soak

Winter Advanced ops combine performance, battery chemistry, and human factors:

Battery cold soak

Lithium batteries stored or staged in cold soak deliver lower effective capacity, higher internal resistance, and sudden voltage sag under load. Operational mitigations:

1. Keep packs in insulated cases; warm them to manufacturer-recommended temperature before high-load flight.
2. Do not install a frozen pack and expect summer endurance numbers.
3. Hover-check power draw early; abort if voltage sag is abnormal.
4. Plan larger energy reserves; cold + wind + payload stacks risk.
5. Charge and store per manufacturer temperature limits—charging a pack that is too cold can damage it.

Other winter hazards

• Structural icing in visible moisture and freezing temperatures—RPAS without certified icing protection should avoid known icing conditions
• Snow glare and whiteout reduce visual contact (VLOS/EVLOS)
• Frost on props overnight even when air temperature is near freezing in the morning sun cycle
• Reduced friction on landing pads (ice) → tip-over on touchdown
• Crew cold stress and thicker gloves reducing fine motor GCS control

Thunderstorm avoidance

Thunderstorms produce severe turbulence, wind shear, downbursts, hail, lightning, and rapid wind shifts. For RPAS:

• Do not launch toward, under, or near active thunderstorm cells
• Outflow boundaries can hit the site with violent wind before rain arrives
• Lightning risk exists to crew holding controllers and to the aircraft
• If a cell develops after launch, land immediately in the safest ELZ—do not try to “finish the last orbit”

Exam posture: avoidance is the strategy; small drones are not storm-penetrating research aircraft.

Wildlife hazards and conservation

Birds can strike props or cause abrupt avoidance manoeuvres; nesting seasons increase aggression. Conservation and wildlife rules (federal, provincial, park bylaws) may prohibit disturbing wildlife even when CARs would otherwise allow the flight profile. Site survey should note:

• Known nesting or migratory concentrations
• Park or sanctuary restrictions
• Livestock that may panic under multirotor noise

Give wildlife right of practical respect: climb, offset, or land rather than chase animals for footage.

Runway numbering awareness near aerodromes

Runways are numbered by magnetic orientation divided by ten (e.g., roughly magnetic heading 270 → runway 27; reciprocal 09). Near aerodromes this helps you:

• Predict departure and arrival directions from ATIS/winds
• Understand which way traffic will fly the circuit
• Brief lost-link paths that do not drift onto final for the active runway

You are not joining the circuit with a multirotor, but situational awareness of the active runway is part of professional vicinity operations (CAR 901.47 themes).

PED interference

Portable electronic devices (PEDs)—phones, tablets, high-power radios, poorly shielded cameras, portable Wi-Fi hotspots—can interfere with:

• Command-and-control links
• GNSS receivers
• Magnetometers (compass) when placed against the airframe or GCS antenna

Mitigations: follow manufacturer EMI guidance; separate high-power transmitters from the control link antennas; disable unnecessary radios during critical launch/recovery; never mount an untested RF transmitter on a declared aircraft without assessing EMI and configuration control.

Bank, speed, and turn radius (mapping orbits)

For mapping, inspection orbits, and grid turns, turn radius is governed by physics approximately:

Radius ∝ V² / tan(φ) (for a coordinated level turn), where V is true airspeed and φ is bank angle.

Implications:

Exceeding bank or speed limits for a “tighter shot” risks tip-over, GNSS-denied oscillation, or structural/prop overload. Plan orbit geometry on the ground so the aircraft’s performance envelope can actually fly the path inside the safety perimeter.

Putting the section together for exam day

Scenario stems often combine two ideas: “cold morning, frost on wings, heavy dual battery, mapping orbit around a tower near an airport.” Correct answers usually require: decontaminate, recheck weight/CG, warm batteries, respect wind and AFM, avoid storms, and size the orbit to speed/bank reality—not “Advanced certificate means push on.”

Bottom line: Weight and CG are configuration control. Contamination is a no-go until clean. Winter multiplies battery and icing risk. Thunderstorms and wildlife are avoidance problems. Runway numbers inform traffic awareness. PEDs can break your link. Turn radius is physics—design the orbit the aircraft can fly.