A fascinating mystery, and an equally engaging video (allegedly courtesy of NPR — though Radiolab is produced by WNYC and distributed by NPR, so… ? Just sayin’, give credit where credit’s due… Like the uncredited Nawlins’ music? But I digress…)

Regarding our sense of direction (or apparent lack thereof), I’m reminded of this interesting Wikipedia article I stumbled upon the other day, pointing out the many additional senses we possess beyond the basic five of sight, sound, smell, touch, & taste; senses such as balance/equilibrium, acceleration, pain, relative temperature, proprioception/kinesthetics… It’s not the most revolutionary of all revelations, nor one that most people probably couldn’t come up with on their own if asked to seriously consider the subject for a moment, but I nevertheless find it curious that we humans appear not to have any innate sense of direction (beyond the use of external reference points). It would just intuitively seem otherwise.

I presume, then, that tendencies similar to those illustrated in the video (spatial disorientation) are probably responsible for a lot of otherwise “mysterious” plane crashes that have occurred at times of low visibility (or possibly due to instrument malfunction) in such infamous places as the Bermuda Triangle and the like…

Once an aircraft enters conditions under which the pilot cannot see a distinct visual horizon, the drift in the inner ear continues uncorrected. Errors in the perceived rate of turn about any axis can build up at a rate of 0.2 to 0.3 degrees per second. If the pilot is not proficient in the use of gyroscopic flight instruments, these errors will build up to a point that control of the aircraft is lost, usually in a steep, diving turn known as a graveyard spiral. During the entire time, leading up to and well into the maneuver the pilot remains unaware that he is turning, believing that he is maintaining straight flight.

In a 1954 study, the Air Safety Foundation found that out of 20 non-instrument-rated subject pilots*, 19 of the 20 entered a graveyard spiral soon after entering simulated instrument conditions. The 20th pilot also lost control of his aircraft, but in another maneuver. The average time between onset of instrument conditions and loss of control was 178 seconds.

* Approximately 80% of the private pilots in the United States do not have an instrument rating, and therefore are prohibited from flying in conditions where instrument skills are required.

Pilots are susceptible to spatial disorientation during night flight over featureless terrain.

Featureless like water on a moonless or cloudy night?

How come that doesn’t come up more often after news-making small-craft Cessna crashes? Or perhaps it does, and the ambiguous phrase “human error” is simply more palatable than “graveyard spiral” and explaining to people that they don’t know how to walk (or fly) in a simple straight line…