AviationBanter - View Single Post - Spinner strobing as a "Bird Strike Countermeasure"

**Mxsmanic** · December 5th 07, 05:41 PM posted to rec.aviation.piloting,rec.aviation.homebuilt

writes:

There's a well-known phenomenon that can incapacitate pilots. A
propeller spinning so that it cuts through the sun's glare and causes
a stroboscopic effect on the pilot's eyes can result in confusion. A
frequency of less than between 25 and 55 Hz, depending on the
individual, can cause dizziness or nausea. It's called "flicker
vertigo" and the fact that it happens tells me that the human eyeball
(or at least the visual cortex) does have a frequency function of some
sort. 25 Hz on a two-blade prop would be 750 RPM and 55 would be 1650.
Some tests have found that frequencies as low as four to 20 Hz will
induce it rapidly.

It is probably more a consequence of intermittent photic stimulation, the same
phenomenon that can trigger seizures in susceptible individuals. As I recall,
the bulk of the response is outside the visual cortex.