FAA Commercial Pilot Airplane (CAX)Human Factors and ADMHard
A pilot scans the night sky for a distant, dimly lit tower obstruction. When looking directly at the tower's light, it seems to disappear, but it becomes visible again when the pilot looks slightly to the side. What technique explains why the light reappears with this scanning method?
- AAutokinesis compensation
- BOff-center viewing utilizing peripheral rod cells
- CDark adaptation reset
- DCentral vision utilizing foveal cone cells
Show answer & explanationAnswer & explanation
Correct answer: B. Off-center viewing utilizing peripheral rod cells
Rod cells, which are more sensitive in low light, are concentrated outside the fovea. Off-center (peripheral) viewing directs the dim light onto these rods, making faint objects visible at night, whereas looking directly at them uses cone-dominated central vision, which is less sensitive in darkness.
Why the other options are wrong
- A. Autokinesis is an illusion of a stationary light appearing to move, not a viewing technique for object detection.
- C. Dark adaptation refers to the eyes' gradual adjustment to darkness over time, not the immediate effect of shifting gaze.
- D. Central/foveal vision relies on cones, which require more light and are poor at detecting faint objects at night.
Off-Center (Peripheral) Viewing
A night-vision scanning technique in which a pilot looks slightly to the side of an object rather than directly at it to use the more light-sensitive rod cells in peripheral vision.
- Rods dominate peripheral vision and are more sensitive in low light
- Cones dominate central vision and require more light, causing a night blind spot when staring directly ahead
- Full dark adaptation takes approximately 30 minutes
Memory trick: Look beside it, not at it, to see it at night.