6.3 Weather Services & RPAS Weather Minima

6.3 Weather Services & RPAS Weather Minima

Quick Answer: Get weather from aviation-grade sources—METARs/TAFs, NAV CANADA / official aviation weather sites, FIC phone briefings when needed, and ATIS near towered fields. CAR 901.34 ties VLOS flight to manuals + continuous VLOS, adds medium-RPA limits in low ground visibility, and sets BVLOS baselines (≥ 3 miles ground visibility and clear of cloud, with narrow exceptions). CAR 901.35 is a hard icing stop. CAR 901.39 governs night lighting. When CB is nearby, vis kills VLOS, gusts exceed limits, or freezing precip appears—cancel.

Decoding products is useless if you never open a reliable source—or if you launch because a lifestyle weather app showed a sun icon while the METAR reported 1/2SM FG.

Weather services Advanced pilots actually use

Official and aviation-grade sources

FIC telephone: When the picture is complex (mountain weather, rapid frontal passage, conflicting products), a FIC briefing helps you hear the hazard story—not only isolated numbers. Have your route/site, altitudes (even if low AGL), and timing ready before you call.

ATIS: Near controlled airports, ATIS gives the current official aerodrome weather letter and notes (runway, approaches, etc.). RPAS pilots use it as a situational input when operating under authorization near the field—not as permission to enter controlled airspace.

Non-aviation sources: useful cues, weak sole authority

Phone apps, TV weather, and social media radar screenshots can supplement awareness (radar loops, satellite, hyperlocal temp). Caveats:

• Units and update times may be unclear.
• “Feels like” and city-centre sensors miss your lakeshore fog.
• Radar can show rain while surface vis is still legal—or the reverse under virga/dry air.
• Apps rarely speak BKN015 ceiling language or TEMPO risk the way TAFs do.

Rule: Non-aviation tools may start the conversation; aviation products + eyes finish the go/no-go.

CAR 901.34 — Minimum weather conditions

Regulations current through the 2025–2026 Part IX updates structure weather minima by operation type. Know the logic for the exam and the field.

901.34(1) — VLOS operations (core for most Advanced flights)

No pilot shall operate an RPA in a VLOS operation unless weather at the time of flight permits:

(a) the operation to be conducted in accordance with the operating manuals applicable to the RPAS; and

(b) the pilot or any visual observer to conduct the entire flight in visual line-of-sight.

This is not a single numeric “3 SM for every small drone VLOS flight” slogan from foreign Part 107 memory. Canadian 901.34(1) is manual limits + true VLOS. Practical consequences:

• If the manual says max wind 10 m/s or min temp 0 °C, exceeding those values fails (a) even under blue sky.
• If fog, smoke, night contrast failure, or distance makes continuous unaided visual contact impossible, you fail (b) even if an airport 20 NM away reports 15SM.

901.34(2) — Medium RPA VLOS and reduced ground visibility

If ground visibility is four miles or less, no pilot shall operate a medium RPA in VLOS at a distance of more than half the ground visibility, unless operating under an SFOC—RPAS issued under 903.03.

Example teaching math: ground visibility 3 miles → max VLOS distance for that medium RPA operation ≤ 1.5 miles (unless SFOC). This pairs medium-aircraft inertia/visibility with human see-and-avoid limits.

901.34(3)–(4) — BVLOS weather baseline

Subject to subsection (4), BVLOS requires:

• Ground visibility not less than three miles; and
• Aircraft operated clear of cloud.

Subsection (4) allows BVLOS in cloud or with ground visibility less than three miles only if:

• a Standard 922.10 declaration pathway applies and manuals allow those conditions; or
• an SFOC—RPAS authorizes it.

Advanced VLOS pilots still learn this: exam questions and 2025 framework expansions mix VLOS privileges with Level 1 complex / BVLOS weather baselines.

CAR 901.35 — Icing

(1) No pilot shall operate an RPAS when icing conditions are observed, reported to exist, or likely along the route of flight unless the aircraft has de-icing or anti-icing equipment and equipment designed to detect icing.

(2) No pilot shall operate with frost, ice, or snow adhering to any part of the remotely piloted aircraft.

Most small/medium multirotors in the field lack certified ice protection. Therefore:

• Freezing rain, freezing drizzle, wet snow near 0 °C, and flight in supercooled cloud/fog are cancel conditions.
• Preflight: remove frost/ice/snow; never launch with a white crust on props or airframe “because it will blow off.”
• METAR/TAF cues: FZRA, FZDZ, FZFG, temperature near/below freezing with visible moisture.

Icing destroys lift/thrust, adds mass, unbalances props, and can kill motors—Chapter 5 physics, Section 6.3 regulation.

Site survey weather factors

CAR site-survey duties (paired with pre-flight information rules you study elsewhere) must include weather that affects this site:

1. Wind direction/speed/gusts relative to obstacles (mechanical turbulence, rotor zones).
2. Visibility and contrast along actual flight paths (not only zenith sky).
3. Cloud base / clear-of-cloud feasibility for planned altitudes.
4. Precipitation and moisture (electronics, lenses, icing).
5. Temperature vs manual limits and battery performance.
6. Trend — METAR vs previous METAR; TAF TEMPO/FM over the next 1–3 hours.
7. Local effects — lake fog, valley drainage wind, urban channeling, wildfire smoke.

Document go/no-go criteria before the client arrives so commercial pressure does not rewrite physics.

When to cancel (hard professional stops)

Canceling is a professional act. The Advanced exam and flight review both reward pilots who can say no with a regulation and a weather product citation.

Night weather considerations and CAR 901.39

Night VLOS is more weather-sensitive, not less:

• Contrast drops; haze and light fog hide the aircraft until it is too close.
• Depth perception worsens; distance judgment errors increase.
• Precipitation and moisture scatter light from the aircraft and from ground sources.

CAR 901.39 night flight requirements centre on proper position/anti-collision lighting so the RPA’s position can be determined. Lights do not:

• Authorize flight in fog that blocks VLOS,
• Replace cloud clearance common sense,
• Or waive 901.34 / 901.35.

TC AIM guidance reinforces: do not operate in fog if visibility is too poor for proper VLOS even if lights are fitted. Night-vision goggles, where discussed in rules, do not remove required lighting obligations for applicable RPA.

Night weather checklist:

1. Confirm 901.39 lighting serviceable and on as required.
2. Set stricter personal minima than daytime for vis and cloud.
3. Avoid moonless flight toward unlit backgrounds that swallow the aircraft silhouette.
4. Watch battery performance in cold night air separately from density altitude.
5. Brief visual observers on scan sectors and lost-link night procedures.

Putting services and minima together (workflow)

1. Day before: Read TAF + GFA context; pick provisional window.
2. Morning of: METAR/SPECI trend; FIC if complex.
3. On site: Eyes, wind meter if used, obstacle turbulence check, contrast check.
4. Apply 901.34: manuals + VLOS (and medium/BVLOS numeric rules if applicable).
5. Apply 901.35: no icing, no adhering contamination.
6. If night: 901.39 lighting + reduced weather tolerance.
7. Launch or cancel — then keep monitoring; weather is dynamic.

Bottom line: Aviation weather services give you shared situational awareness with the rest of the NAS. CAR 901.34 makes weather a legal gate for VLOS, medium distance, and BVLOS visibility/cloud. CAR 901.35 is an icing wall. CAR 901.39 lights the night but does not invent visibility. Advanced pilots cancel early for CB, lost VLOS, out-of-limit gusts, and freezing precip—and can explain why with a METAR line and a regulation number.