← All explained questions · Supplemental · XI — Night Operations

What technique improves your ability to see dim objects (like terrain or other aircraft) at night?

Choices

Stare directly at the object using central vision.
Direct gaze hides dim objects in the foveal blind spot at night.
✓ Use off-center (peripheral) vision.correct
look 5-10° to the side of the object so light falls on the rod cells, not the rod-poor fovea. The fovea (center of vision) has cones, which are great in daylight but poor in dim light. Rods (peripheral) handle low-light vision. Looking 5-10° off-axis places the dim object on rod-rich peripheral retina. Staring directly at it makes it disappear because the central blind spot (rod-poor area) is centered on your gaze.
Close one eye to dilate the pupil of the other.
Closing one eye reduces total vision and binocular depth perception.
Increase cockpit light brightness for contrast.
More cockpit light destroys dark adaptation.

Why

look 5-10° to the side of the object so light falls on the rod cells, not the rod-poor fovea. The fovea (center of vision) has cones, which are great in daylight but poor in dim light. Rods (peripheral) handle low-light vision. Looking 5-10° off-axis places the dim object on rod-rich peripheral retina. Staring directly at it makes it disappear because the central blind spot (rod-poor area) is centered on your gaze.

FAA source: PHAK Ch 17, AIM 8-1-6; PHAK Chapter 17 — Aeromedical Factors; AIM 8-1-6 Vision in Flightbrowse the reference library →

Covered in Supplemental · XI — Night Operations — study the lessons free, then practice with grading and mastery tracking.

Original study question written for this course — representative of FAA knowledge-test topics, not an actual current FAA exam question.