Flying a Drone at Dawn and Dusk in the UK

Dawn and Dusk in UK Aviation Context

In manned aviation, dawn and dusk are formally defined periods tied to sunrise, sunset, and twilight phases. For drone operations in the UK, the CAA does not impose separate rules for dawn or dusk — the same VLOS requirement that applies at midday applies at 05:00 or 20:30.

What makes dawn and dusk operationally distinct is the speed at which lighting conditions change. A flight that begins in adequate light may end in conditions where VLOS is compromised, or vice versa. This creates a planning requirement that does not exist during stable midday conditions.

Civil and Nautical Twilight

Understanding twilight phases helps you plan dawn and dusk flights:

• Civil twilight — the sun is between 0° and 6° below the horizon. Objects on the ground are generally visible without artificial lighting. This is the period immediately before sunrise and after sunset
• Nautical twilight — the sun is between 6° and 12° below the horizon. The horizon is still distinguishable, but ground objects become difficult to see. VLOS of a small drone is extremely challenging during this period
• Astronomical twilight — the sun is between 12° and 18° below the horizon. For practical drone purposes, this is effectively night

In the UK, civil twilight duration varies from roughly 30 minutes in winter to over 45 minutes in summer, with longer twilight periods at higher latitudes (Scotland experiences longer twilight than the south coast).

Challenges Specific to Dawn

Flying at dawn presents some unique considerations compared to dusk:

• Dew and condensation — overnight moisture may be present on your drone if it has been stored in a vehicle. Allow electronics to acclimatise before powering on
• Ground fog — radiation fog forms overnight and is often thickest around dawn. Even thin fog can destroy VLOS at moderate distances
• Bird activity — dawn is a peak period for bird movement. Be alert to bird strike risk, particularly near water, woodland edges, and agricultural land
• Human presence is lower — fewer uninvolved persons may be present, which can simplify operations but also means fewer observers in case of an incident

Challenges Specific to Dusk

Dusk operations carry their own considerations:

• Deteriorating conditions — unlike dawn where light improves, dusk means your operating window is closing. Plan to land well before conditions become marginal
• Thermal activity — on warm days, residual thermals can cause turbulence during the early dusk period as the ground cools unevenly
• Artificial lighting interference — streetlights, car headlights, and building lights can create confusing backgrounds against which your drone's lights may be harder to distinguish
• Human activity patterns — in urban and suburban areas, dusk coincides with people returning home, walking dogs, and using parks. Maintain awareness of your proximity to uninvolved persons

Preparation Checklist for Dawn and Dusk Flights

• Check sunrise/sunset times and twilight phases for your exact location and date
• Fit auxiliary lighting to your drone — even if you plan to fly during civil twilight, conditions can deteriorate faster than expected
• Conduct your pre-flight checks in adequate light — do not rush through checklists in darkness
• Set a hard cut-off time and stick to it. Decide before you fly at what point you will land, regardless of whether you have finished your planned operation
• Carry a torch and wear visible clothing if operating near paths, roads, or other people
• Brief any observers on the lighting signals of your drone so they can track it effectively