Understanding Civil Twilight and Night Flight Rules
After Sunset, Before Sunrise
Fieldwork Foundations
Civil twilight is that transitional period when the sun has dipped just below the horizon but there’s still enough ambient light to see without artificial lighting.
It happens twice a day—right before sunrise and just after sunset—and it’s a crucial window for drone operations that straddle the line between day and night.
Under Part 107, civil twilight is defined as:
- 30 minutes before official sunrise
- 30 minutes after official sunset
These 30-minute buffers allow drone pilots to continue (or begin) operations without needing to meet the full requirements for night flight—as long as the drone is equipped with anti-collision lighting visible for at least 3 statute miles.
When does night officially begin for drone operations?
- Night begins 30 minutes after official sunset
- Night ends 30 minutes before official sunrise
Once you’re outside of civil twilight, you’ve entered official night conditions under FAA regulations.
At that point, in addition to having proper lighting, the Remote PIC must have completed the FAA’s night operations training module to legally operate.
This matters most when you’re planning golden hour missions or filming sunrise/sunset footage—because if you’re not tracking these time boundaries, you could unintentionally fly into night conditions without the proper clearance, equipment, or certification.
UAS Anti-Collision Lighting:
Night Flight Requirements
Strobe Light Requirement
For night operations, Part 107 requires your drone to have at least one anti-collision strobe light.
Dimming the Strobe Light for Safety
Under Part 107, the Remote PIC may reduce the intensity of the anti-collision strobe light if necessary for safety, but may not turn it off completely.
This flexibility is allowed when lighting conditions create visual interference or hazards.
Field Example: You’re conducting a night inspection of a metal bridge, and the strobe light is creating intense glare off the structure, making it difficult to see. To maintain safe and effective operations, you dim the strobe light to reduce the reflection—improving visibility while still complying with FAA rules.
Night Visibility: 3 Statute Miles
Drone pilots are allowed to fly during civil twilight and at night only if the drone is equipped with anti-collision lights that are visible for at least 3 statute miles.
This visibility requirement is designed to help other aircraft and observers see your drone. This reduces the risk of midair collisions and enhances safety during low-light operations.
Recognizing Visual Illusions in the Field
When you’re flying in low-light or high-fatigue conditions—like civil twilight or night—your eyes can play tricks on you. These illusions may seem minor, but they can affect your ability to judge distance, depth, and movement, leading to poor decision-making mid-flight.
As a Remote Pilot, it’s essential to recognize and manage these illusions before they influence your control or safety.
Here are five visual illusions the FAA wants every drone pilot to know:
1. Autokinesis (The “Floating Light” Effect)
What it feels like: A stationary light in the sky appears to drift or move on its own when you stare at it for too long in the dark.
Autokinesis makes stationary lights look like they’re moving.
Why it matters: You might think another aircraft is on a collision course or that your own drone is drifting.
Solution: Avoid staring at fixed lights for more than a few seconds—keep your eyes moving and use visual references.
2. Flicker Vertigo
What it feels like: Flicker Vertigo, or the strobe light effect, happens when pilots get disoriented from flickering lights, like those from propellers. Dizziness or nausea triggered by flashes of light—often from spinning propellers reflecting sun or strobe lights.
Why it matters: This can cause discomfort, disorientation, or even temporary loss of focus.
Flight tip: Wear a brimmed hat or polarized glasses during bright conditions and avoid standing in the path of your drone’s strobes.
3. False Horizon
What it feels like: False Horizon is when pilots get can’t distinguish where the real horizon is, especially in low light. It can disorient your sense of direction during flight. You misjudge which way is “up” due to sloping terrain, city lights, or cloud layers aligning oddly.
Why it matters: This can skew your sense of level flight and mislead orientation if you’re relying on visual cues.
Flight tip: Always rely on your drone’s horizon indicators or telemetry, especially when terrain or lighting gets weird.
4. Reversible Perspective Illusion
What it feels like:A moving light in the sky (like another aircraft) appears to be flying toward you—when it’s actually moving away, or vice versa.
Why it matters: Misjudging direction or speed could lead to a loss of separation or a right-of-way violation.
Flight tip: Watch for size and brightness changes—if a light stays constant in size and intensity, it may be on a collision path.
5. Night Myopia (Nighttime Nearsightedness)
What it feels like: Your eyes start focusing too close in low-light settings, causing distant objects to blur.
Why it matters: You may have trouble spotting obstacles or aircraft, especially small moving lights.
Flight tip: Keep your focus outward and use off-center viewing to help your eyes adjust properly at night.
