Young’s remains were recovered along with some of the wreckage, the pieces of which were no larger than “a small trash can,” in the words of the accident report. With the airplane almost completely destroyed, analysis of the engine and airframe was limited to a review of maintenance records and interviews with ground personnel. These things, along with the fact that Young had never indicated a problem and the airplane had performed as expected, strongly suggested that the problem was not mechanical. (Coincidentally, a few months after Young’s crash, a Missouri Air National Guard F-15C broke apart in flight, setting off a fleet-wide grounding of F-15s to investigate failing longerons.)
With the airplane’s flight data recorder also destroyed, investigators were limited to reconstructing the flight path using radar tracking data, videotapes of the other airplanes’ head-up displays (which project critical flight information on a transparent display above the instrument panel), and data from their flight recorders, in addition to the testimony of the other pilots. Investigators determined that Young’s airplane hit the water at an angle of 24 degrees at a speed of 630 mph.
The report says that Young’s helmet showed he was sitting head-up, indicating he was likely conscious at the time of impact. Analysis further suggested Young was looking up and slightly to the right, not at the ocean in front of him, at his head-up display, or at his instruments. His G-suit was not fully inflated, indicating that he was not pulling significant Gs to arrest his descent.
Increasingly, the evidence pointed to spatial disorientation.
As Young went from climb to descent in his final maneuver, he would have been susceptible to a somatogravic illusion making his dive angle seem much shallower than it actually was. He may, in fact, have thought he was inverted. The fact that his rate of descent increased significantly in the final seconds indicates that Young “may have even believed he was climbing in the final moments, although he was actually still descending,” the investigators’ report said.
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.
The Air Force commissioned a team, led by NASA and the Air Force Research Laboratory at Ohio’s Wright-Patterson Air Force Base, to develop an autopilot that engages when the pilot is unconscious or unaware that he is about to hit the ground. The Automatic Ground Collision Avoidance System— Auto-GCAS—evaluates a variety of factors (aircraft weight and performance, navigational information, terrain and elevation data) to constantly calculate the aircraft’s position, time before impact, and maneuver required to prevent an impact. When the system determines that the airplane is within 1.5 seconds of the point of no return and the pilot still has taken no action, it will take control and perform an automatic rescue maneuver. The system, developed and tested over the past two decades, is now ready for use with F-16 and F-22 fighters. The Department of Defense hopes the system will virtually eliminate “controlled flight into terrain” crashes due to spatial disorientation or G-induced loss of consciousness.
While Auto-GCAS will certainly help, says William Albery, a senior scientist at Wright-Patterson, it won’t completely eliminate spatial disorientation. Susceptibility to vertigo will continue, he says, as long as there are human pilots on airplanes, and even pilots not in airplanes—in several incidents, pilots who remotely fly aircraft have lost control due to vertigo. The only way to completely eliminate the problem, he says, is to develop fully automated aircraft.