Defining Civil Twilight
Drone Flight Before or After Civil Twilight
Civil twilight is the time right after sunset or just before sunrise when the sun is below the horizon but there’s still enough light to see without artificial illumination.
Part 107 defines civil twilight as the period beginning 30 minutes leading up to official sunrise and begins again ending 30 minutes after official sunset.
Drone pilots should accurately calculate these times for their operational planning.
As civil twilight sets in, changes in ambient lighting can lead to visual illusions such as autokinesis, false horizons, and loss of depth perception.
UAS Anti-Collision Lighting at Night
Anti-collision lighting on drones helps other aircraft and people spot your drone, especially in low light or bad weather.
3 Statute Miles Visibility Rule:
Part 107 mandates these lights to prevent accidents and ensure safety during flights.
You can legally fly during civil twilight as long as your drone’s lights are visible for at least 3 statute miles.
Anti-Collision Strobe Lights: Quantity Mandates
For night operations, the regulations require that your UA be equipped with at least one strobe light to ensure visibility. This single strobe light should be sufficient to make the drone visible from a distance.
While having additional lights can improve visibility, the minimum requirement is one strobe light to comply with safety standards.
The remote PIC may reduce the intensity of, but may not extinguish, the anti-collision strobe light if they determine that, because of operating conditions, it would be in the interest of safety to do so.
Anti-Collision Strobe Lights: Dimming
The remote PIC may reduce the intensity of, but may not extinguish, the anti-collision strobe light if they determine that, because of operating conditions, it would be in the interest of safety to do so.
Example from in the field:
You’re inspecting a bridge at night with your drone. The strobe light reflects off the metal, making it hard to see clearly. You dim the anti-collision lights to reduce glare and inspect the bridge properly while staying safe and following the rules.
Visual Illusions
Anti-collision lighting on drones helps other aircraft and people spot your drone, especially in low light or bad weather.
Autokinesis:
Autokinesis makes stationary lights look like they’re moving, which can confuse drone pilots.
Staring at a far-off bright light (like the light from your drone) against a dark background can make it seem like the light is moving, even if it’s actually not.
To counter this, switch your focus between different distances. It helps your eyes adjust better to what’s around you. Furthermore, do not to stare at one thing for more than 10 minutes. It keeps your vision clear and helps avoid confusion.
Reversible Perspective
Reversible Perspective Illusion is when you can’t tell whether what you’re looking at is close or far away.
Pilots need to watch out for this because it can cause issues with your sense of distance and space while flying. By not staring at any one thing for too long, as well as using familiar landmarks, pilots stay on track and know exactly where they are.
Flicker Vertigo
Flicker Vertigo, or the strobe light effect, happens when pilots get disoriented from flickering lights, like those from propellers.
Be careful in lighting that makes flickering worse, like low sun angles.
False Horizon
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.
Practice Quiz
Study Guide
Defining Civil Twilight
Civil twilight is the time right after sunset or just before sunrise when the sun is below the horizon but there’s still enough light to see without artificial illumination.
During civil twilight, you can see pretty well, but it’s not fully dark yet, so it’s a good time for certain types of flights, like doing inspections or surveys.
Part 107 defines civil twilight as the period beginning 30 minutes before official sunrise and ending 30 minutes after official sunset. No that’s incorrect that would be all day. Drone pilots should accurately calculate these times for their operational planning.
As civil twilight sets in, changes in ambient lighting can lead to visual illusions such as autokinesis, false horizons, and loss of depth perception.
How to Legally Operate Your Drone at Night
According to Part 107, if you want to fly your drone at night, you need to meet two key requirements:
- FAA Night Training Module Completion:
- Make sure you’ve completed the night training module available on the FAA website. This training will cover the specific rules and procedures for operating your drone safely at night.
- Anti-Collision Lighting:
- Your drone must be equipped with anti-collision lighting visible for at least 3 statute miles and have a strobe light with a flash rate sufficient to avoid collisions.
Anti-Collision Lighting
Part 107 mandates these lights to prevent accidents and ensure safety during flights. You can fly during civil twilight, but only if your drone’s lights are visible for at least 3 miles.
Anti-collision lighting on drones helps other aircraft and people spot your drone, especially in low light or bad weather.
Strobe Lights: Dimming & Quantity Mandates
For night operations, the regulations require that your unmanned aircraft be equipped with at least one strobe light to ensure visibility. This single strobe light should be sufficient to make the drone visible from a distance.
While having additional lights can improve visibility, the minimum requirement is one strobe light to comply with safety standards.
The remote PIC may reduce the intensity of, but may not extinguish, the anti-collision strobe light if they determine that, because of operating conditions, it would be in the interest of safety to do so.
Example from in the field:
- You’re inspecting a bridge at night with your drone. The strobe light reflects off the metal, making it hard to see clearly. You dim the anti-collision lights to reduce glare and inspect the bridge properly while staying safe and following the rules.
Autokinesis
Autokinesis can make stationary lights look like they’re moving, which can confuse drone pilots.
Watch Out for Optical Illusions: Staring at a far-off bright light, like the light from your drone, against a dark background can make it seem like it’s moving, even if it’s actually not. This happens because your brain struggles to tell the difference.
Stay Sharp with Adaptive Focus: To counter this, switch your focus between different distances. It helps your eyes adjust better to what’s around you.
Don’t Stare Too Long: Try not to stare at one thing for more than 10 minutes. It keeps your vision clear and helps avoid confusion.
Reversible Perspective
Reversible Perspective Illusion is when you can’t tell whether what you’re looking at is close or far away. Pilots need to watch out for this because it can cause issues with your sense of distance and space while flying.
Stay Safe with Instruments: Check instruments often to keep track of where drones are in the sky.
Keep Moving: Don’t stare at one thing too long.
Use Landmarks: Using familiar landmarks helps pilots stay on track and know exactly where they are.
Flicker Vertigo
Flicker Vertigo, or the strobe light effect, happens when pilots get disoriented from flickering lights, like those from propellers.
Watch the Lighting: Be careful in lighting that makes flickering worse, like low sun angles. Adjust your flight path and position to handle it.
Don’t Stare Too Long: Try not to stare at flickering lights for too long. Take breaks, and make sure anyone watching knows it could be uncomfortable.
Change Your View: Shift your view to avoid staring straight at flickering lights. It helps pilots feel more comfortable and avoids vertigo.
False Horizon
False Horizon is when pilots get mixed up about where the real horizon is, especially in low light. It can disorient your sense of direction during flight.
Trust Your Instruments: Use your drone’s instruments, like the horizon indicator on the controller, to keep your bearings right.
Keep Looking Around: Scan the area consistently and use landmarks to double-check where the real horizon is.
Don’t Stare Too Long: Avoid staring at one thing for too long—it can make false horizon issues worse. Keep scanning around you to stay on track.
Quick Review
Practice Quiz
