Vertigo (Spatial Disorientation)

Here are a few interesting paragraphs that are from the September 2008 issue of the Smithsonian's Air & Space.

Despite the best training and technology, why do pilots still die from not knowing which end is up?

On June 26, 2007, while on a training exercise off the Oregon coast, Major Gregory D. Young of the Air National Guard flew his F-15A fighter into the Pacific Ocean. The $32 million aircraft was destroyed and the pilot killed. There was no distress call, no attempt to eject, and no apparent aircraft malfunction. Young, 34, had 2,300 hours of flight time, more than 750 hours of it in F-15s.
As investigators sifted through the wreckage—what little was left—colleagues, family, and friends were left to wonder: What caused Young to guide his airplane right into the ocean at more than 600 mph? The answer, revealed in an investigative report two months later, was both profoundly unsettling and all too familiar. Young, in the prosaic terminology of the report, “experienced unrecognized (Type 1) spatial disorientation (SD), which caused him to misperceive his attitude, altitude, and airspeed. As a result, [he] was clearly unaware of his position and impacted the water.”

A U.S. Air Force review of 633 crashes between 1980 and 1989 showed that spatial disorientation was a factor in 13 percent, resulting in 115 deaths. Among crashes of high-performance aircraft, the rate was higher: 25 to 30 percent. A U.S. Navy study found that in contrast to general aviation accidents, a majority of accidents in high-performance aircraft occurred in daylight and in visual flight conditions. The pilots were an average of 30 years old, with 10 years in the cockpit and 1,500 hours of pilot-in-command or instructor time, and in the prior three months they had flown an average of 25 times—all of which shows that no amount of expertise, training, or experience immunizes against spatial disorientation.

Spatial disorientation is so insidious, and the sensations it creates so compelling, that unless you suspect you have a problem, you would never know there is one.

In addition to primary flight data (attitude, airspeed, altitude, heading), the head-up displays in military cockpits provide the pilot a continuous view of what is directly in front of the aircraft. Displays also project flight information on the helmet visor so the pilot’s head is free to move. Three-dimensional “highway in the sky” displays give a pilot’s-eye view of the terrain and project a path to follow. Today’s pilots can maintain a level of situational awareness that their predecessors never dreamed of.

But when it comes to countering spatial disorientation, the new displays create their own problems, says Bill Ercoline, a scientist at California-based Wyle Laboratories who provides human factors research for the Air Force Research Laboratory at Brooks City-Base in Texas. Studies of unusual attitude recovery using head-up displays found that HUDs can actually interfere with recovery. The field of view is narrow, the manufacturers use symbols that are not universal, and the nature of the displays is not intuitive; compounding all that, there’s simply too much information to process. “It’s like drinking through a fire hose—it’s just difficult to get the right gulp,” Ercoline says. With so many more systems to manage and monitor, pilots end up devoting less time to actually flying.