Tuesday, March 1, 2011
The Dangers of Spatial Disorientation
Learning how to keep situational awareness while flying at night and in instrument meteorological conditions (IMC) is important to all helicopter pilots, especially those who regularly use night vision goggles.
Recognizing spatial disorientation, especially when using night vision goggles (NVGs), is a key skillset that every pilot needs to learn. The effect of spatial disorientation when flying during daytime can be alarming and confusing. Spatial disorientation occurs when pilots lose their perception of direction and motion relative to the ground. It is especially likely to happen when a pilot flies into weather that eliminates visual references.
The AOPA Air Safety Foundation, in its safety advisory document on SD, lists three sensory systems that provide humans with the information that allows them maintain their equilibrium, balance and how they are oriented in relation to their surroundings: visually through the eyes; through the vestibular system (basically organs of the inner ear that sense position and balance); and the somatosensory system—nerves in the skin, muscles and joints that combine to provide extra information from gravity, other feelings etc.
In providing advice to pilots, the AOPA’s advice states:
“For the military, especially those now engaged in operations where there is a tactical advantage to moving forces at night, the use of night vision goggles has become the norm. But again the onset of spatial disorientation while using NVGs in this much more challenging environment can be rapid and terminal.”
The onset of night vision technology has increased the amount of time during a 24-hour day when operations can be conducted, particularly when there is a military necessity to ‘push the envelope’ in the face of the enemy. To conduct missions, especially low level and by helicopter in the dead of night, has tactically changed the way in which military forces can move and conduct operations around the battlefield. Some units, such as the U.S. Army’s 160th Special Operations Aviation Regiment (SOAR)—known as the Nightstalkers—have made this method of operating central to their ethos and reputation.
But in operational areas such as Afghanistan, where the climate is fierce, the geography harsh and unforgiving and the pace often relentless, the eroding nature of these combined factors—together with periods of red ilume (less than 10 millilux of ambient light), increase the strain of operating missions using NVGs. In military operations, the pressure is always on to get the job done, often in critical situations with marginal or worse conditions.
According to a study entitled “Interactions between brown-out accidents and night vision equipment in military aviation accidents,” by CW Johnson, PhD for the Department of Computing Science at University of Glasgow in Scotland, the “use of night vision equipment has been associated with several different forms of spatial disorientation,” especially during ‘brownout’ landings.
The study looked at U.S. Army Aviation accidents (from 2006–2008) that involved flight, flight-related, ground and UAS accidents. It focused on “the operational limitations of night vision technology [which] can be exacerbated during the brownout conditions that occur when visibility is reduced by airborne particles, typically from helicopter downwash.”
It is obvious that wearing additional equipment such as goggles and devices can have a direct result on the ability of airmen to operate through fatigue and reduced situational awareness. Problems with depth perception and orientation lead to mishaps involving night vision-aided flight.
In an analysis of the accident study, where assessors read through each of the accident reports (209 total through Class A-C over three years), “they found that approximately 43 percent of all spatial disorientation mishaps occurred during flights that used night vision equipment.”
Further, “an examination of the spatial disorientation accident rates per 100,000 flying hours revealed a significant difference between the rate for day flying and the rate for flight using night vision devices. The mean rate for daytime flight was 1.66 while the mean rate for flight with night vision devices was 9.00.” The conclusion they reached was that NVG operations “increased the risk of a spatial disorientation accident by almost five times.”
The report continues making an important clarification. Although around 50 percent of accidents involving U.S. Army Black Hawk helicopters occurred when the crew were wearing NVGs, the accident rate could well have been greater if NVGs had not been used. This comes back to the point that night flying is essentially a difficult business. The study refers to the Army Training Circular 1-210 “Aircrew Training Program Commander’s Guide to Individual and Crew Standardization,” and what recommendations it makes to crewmen training for NVG operations. After familiarizing themselves with the cockpit layout and emergency drills—including NVG failure—it recommends a further period of 10 hours of training in numerous areas including “night terrain interpretation’” and night tactical operations, including the impact of lighting.
However, the study makes the point that general training may not sufficiently make crewmen aware of “the broad range of visual illusions that complicate the operation” of NVGs, especially during desert operations. This includes false horizons created by the contrast in light and dark areas of sand, the lack of visual markers and references distorting height perception, and the sense that at slow speeds the aircraft has stopped moving when it is actually still travelling forwards.
Research is being conducted into technologies that will be able to assist the pilot once visual references have gone, especially during brownout landings.
The Defence Advanced Research Projects Agency (DARPA) is researching ‘see and remember’ type applications: a radar sensor for 3D scanning; an onboard database to store successive scans of a landing zone; synthetic vision techniques that will restore aircrew situational awareness; and the most ambitious—an ‘agile’ flight control system to enable a helicopter to land itself. But before these become reality, existing aircrews need good training to make use of proved Tactics, Techniques and Procedures (TTPs), and existing technology that can replicate dangerous situations.
There are companies that provide independent and integrated night vision training (INVT) packages. Austrian training specialist company AMST invited Rotor & Wing to attend its 2nd Spatial Disorientation & Night Vision Training Workshop in December last year and to learn about its Nightfox INVT package. The workshop brought together speakers and delegates from 20 countries. Dr. Bill Ercoline of Wyle Laboratories and AMST’s Squadron Leader (Ret.) Douglas Vine chaired the workshop and surfaced a number of points. They gave details of numbers of accidents and some of the reasons why the accidents occurred, such as pilots not being aware that they were disorientated or not being aware of the attitude of the aircraft.
Ercoline said that in many instances in the U.S. there was a loss of focus on training for spatial disorientation (with the exception of the U.S. Air Force) and it was not a part of the standard flight training program. Operationally too, there is little difference between night and day tactics which can, under certain circumstances, lead to the onset of spatial disorientation. Vine talked about AMST’s integrated night vision course for fast jet, transport or helicopter pilots runs for four-and-a-half days. “Over 30 courses have already been run by AMST,” he said.
|The Airfox control station with simulator in the background is demonstrated to delegates attending the AMST’s 2nd Spatial Disorientation & Night Vision Training Workshop. Photo by Andrew Drwiega|
Each course has a modular four-phase approach that can be flexed according to the needs of the students, whether ab-initio or as a refresher course for more experienced pilots. Course attendees initially use the Avior NTS laser projection system to plan and fly missions before moving on to the much more complex Airfox Basic and Advanced Spatial Disorientation (DISO-ASD) system.
Phase one of the training is basic and provides a foundational knowledge of NVGs together with an introduction to human factors such as fatigue and spatial disorientation, as well briefing the limitations of using NVGs.
On the practical side students are introduced to the Night Vision Terrain Board (NVTB) of the Nightfox system, the Avior NTS laser projection system and the Airfox Basic and Advanced Spatial Disorientation (DISO-ASD) system.
The Nightfox system covers subjects that include contrast texture gradients, reduction in light levels and angular shadowing effects. Students use their own NVGs throughout the training. It focuses on the following areas: showing risk of visual illusions and disorientation; techniques for tactical night flying and improved target acquisition; learning the problems of landing and flying close to build up areas; night flying in marginal weather conditions; and recognition of visual illusions at night (with and without NVGs).
The Airfox SD system simulates visual and vestibular illusions and is NVG-compatible. It features a high resolution, 120-degree field-of-view display and the database allows pilots to perform a full mission after their planning phase on the Avior NTS. These two systems are used in Phase Two for mission planning and refresher training.
Phases Three and Four are much more mission planning and execution based, and this is largely where experienced pilots tend to focus for re-familiarization. Ab-initio pilots would generally cover all four phases of the INVT program.
Vine also reminded delegates attending the workshop of the very important value of crew resource management (CRM). “Every crewmember in a visually responsive environment has a vote,” he said. Having visited different forces around the world, this writer knows the value of that under any training situation.
Many air forces are currently upgrading their helicopters from those with analog-based avionics to digital, and with a host of new and complex systems to master. This involves a cultural sea change in the way that many forces have operated in the past. From the traditional view that the pilot had flown a particular type of aircraft year-in, year-out and was the master of all he surveyed, to new system based aircraft that are complex and require the full participation of the entire crew. Good CRM which is based on a crew continually sharing information about what they are doing and what is happening outside the aircraft, can be a lifesaver in more ways than one. But it is especially useful in brownouts.
In summary, there is no catch-all cure for spatial disorientation other than continuous training both in and out of the cockpit, whether real or in a simulator. But it is important to prepare for the worst—especially the sudden on-set of instrument meteorological conditions (IMC).