Army Aviation has a problem with spatial disorientation while operating in degraded visual environments. Historically, approximately 20 percent of all Class A and B mishaps have been attributed directly to spatial disorientation or loss of situational awareness in DVE, but the issue remains far from solution.
Here are some recent numbers: During fiscal 2013, two of eight Class A accidents were caused by loss of orientation in DVE; five of 18 in fiscal 2012; two of 14 in fiscal 2011; and eight of 21 in fiscal 2010. Over the past several years, the trend for losses due to DVE-related orientation miscues matches exactly the trend Army Aviation has experienced since the U.S. Army Combat Readiness/Safety Center established a consolidated accident database in 1972. Simply put, we as an institution have made no progress, either in enhanced training methods or with technical solutions, in reducing accident rates associated with this loss factor.
Two definitions are important in understanding the significance of this loss rate. The first is "spatial disorientation," defined as an aviator failing to sense correctly the position, motion or attitude of his or her aircraft, or him or herself, within the fixed coordinate system provided by the earth's surface and gravitational vertical. The second term is "degraded visual environment," defined as reduced visibility of potentially varying degree, wherein situational awareness and aircraft control cannot be maintained as comprehensively as in normal visual meteorological conditions, potentially leading to loss.
Unfortunately, the full implications of spatial disorientation on a pilot's standard mission profile are poorly understood by Army rotary wing aviators. Common perceptions of spatial disorientation are the well-known visual and somatogyral/somatogravic illusions taught in flight school to prepare students to operate in instrument meteorological conditions. Loss of spatial orientation in rotary wing aircraft, however, is very different from what we commonly think. The U.S. Army Aviation Research Laboratory noted in their 1995 report "Spatial Disorientation: A Survey of U.S. Army Helicopter Accidents 1987--1992" that, regarding spatial disorientation:
"Well known causes certainly exist, but do not appear to be predominant. For example, brownout, whiteout or inadvertent entry to IMC account for only 25 percent of the SD accidents. By contrast, aircrew distraction was thought to play a part in 44 percent of SD accidents, while misjudgment of clearance to the ground or a terrestrial obstacle was thought to play a part in 65 percent. The typical picture is less one of a classical illusion or an environmental problem than one of hard-pressed aircrew, flying a systems intensive aircraft under NVD, failing to detect a dangerous flight path …
"Other textbook conditions, such as flicker vertigo or illusions due to downwash, proved almost nonexistent in our accident database. Similarly, there were no obvious cases of vestibular illusions, although we cannot by any means rule out low grade vestibular disturbances. By comparison, the role of poor visual cues was highlighted by the relationship between SD and night flight and by the high percentage of accidents in which the inadequacies of NVDs were considered to have played a part."
It is worth emphasizing "hard-pressed aircrew … failing to detect a dangerous flight path" while faced with internal and external distractions and crew coordination challenges. In this context, USACRC/Safety Center accident statistics, in particular those occurring during the past 12 years of conflict, clearly show the depth of our problem. We recognized all this more than 20 years ago, but we are still struggling with the same issues today. We know poor visual cues negatively affect a pilot's sense of position and motion and contribute to a disproportionate number of rotary wing accidents, which leads to the topic of DVE.
Spatial disorientation and DVE are linked. While spatial disorientation is what happens to the pilot, degraded visual environment is the condition of reduced visibility in which the loss of orientation occurs. Think of it as a "what happens" and "where it happens" interrelationship. With that said, DVE is an intentionally broad definition that, in essence, covers any restriction to visibility: smoke, rain, night, dust, haze, brownout, whiteout, etc. The restriction to visibility could be induced by the weather, lack of illumination at night, or even a helicopter's own rotor wash with the recirculation of dust or snow during brownout and whiteout.
Identifying the where-it-happens aspect is critically important, and trending information from the past 12 years of Class A and B mishaps shows that operating in DVE accounts for 24 percent of the Army's flight accidents. Not surprisingly, this figure is roughly in line with the 20 percent historical loss rate for spatial disorientation. Since the initiation of Operation Enduring Freedom and Operation Iraqi Freedom, 88 of the total 367 Class A and B accidents have involved DVE. Of those mishaps, 67 percent occurred in combat, 52 percent happened during the landing phase of flight, and 57 percent involved brownout conditions. Recall the nature of spatial disorientation mishaps defined by USAARL as the hard-pressed aircrew with internal and external distractions failing to recognize a dangerous flight path, and one can clearly see the relationship between DVE and disorientation.
The real question is how we move forward to break the continued cycle of 20 percent annual losses attributed to spatial disorientation and DVE. When examined objectively, it is a three-step process. The first step is education; all Army aviators must be informed that losses due to spatial disorientation/DVE in the mission profiles we normally fly is completely different from our typical idea of classic illusions. The second step is training; we should update our aviation training programs of instruction to target how rotary wing pilots normally experience spatial disorientation (dark, dusty, in the landing profile, while task saturated), followed by both training in simulators and live in the aircraft. Lastly, the aviation enterprise needs to field a technical solution to increase situational awareness while operating in DVE. An ongoing, significant research effort seeks to improve aircraft handling qualities through digital flight controls, sensor systems able to penetrate obscurants, and improved symbology that effectively presents position and orientation information to pilots. Until technical solutions are ready, however, commanders must rely on education, training and good risk decisions to reduce spatial disorientation accidents.