Photo above: HAI/Mark Bennett
Learn how to recognize and avoid spatial disorientation.
Helicopter Safety Enhancement (H-SE) 127A, Recognizing and Training Degraded Visual Environment (DVE) Conditions Conducive to Spatial Disorientation (SD), was established in 2017 after previous US Helicopter Safety Team (USHST) research identified and categorized the leading causes of helicopter fatal accidents and developed safety enhancements to address them. A team comprising a small but dedicated group of industry professionals was formed to lead this H-SE.
To tackle the challenge of recognizing and recovering from spatial disorientation (SD), the H-SE team examined related accidents and conducted an industrywide survey. Feedback to survey questions about pilot experience with spatial disorientation indicated a gap in both the fundamental understanding of the concept of SD and a pilot’s ability to recognize the conditions conducive to SD. Further investigation of related accidents highlighted the complexity, confusion, and unique environment that encounters with SD cause.
Our analysis also prompted a focus on developing techniques for better decision-making, emphasizing research the National EMS Pilots Association had conducted with Enroute Decision Points (renamed Enroute Decision Triggers) to identify improved methods of training and techniques to recover from and prevent possible SD encounters. These techniques are summarized below.
Effective risk mitigation begins during the planning phase, including the planning and briefing of the flight. During the planning phase, pilots should identify and brief their Enroute Decision Triggers (EDTs). EDTs are those conditions that, when encountered, trigger a predetermined decision (due to weather, degraded visibility, etc.). These EDTs can include airspeed, altitude, or divergence from the planned route.
The H-SE team opted to provide examples of conditions that may be used to create an EDT (depending on the situation) rather than recommend specific parameters that must be used (see Spatial Disorientation Induced by a Degraded Visual Environment: Training and Decision-Making Solutions, Helicopter Safety Enhancement No. 127A, Output No. 2). The predetermined decisions depend on pilot and equipment capabilities. Examples include:
- Land the aircraft
- Commit to instruments
- Turn to KNOWN good weather conditions.
While most pilots agree that decreasing visibility is a cause for concern and can lead to an in-flight emergency, most pilots don’t treat this emergency the same as emergencies caused by aircraft systems. For example, a pilot experiencing a WARNING light for an engine fire or a CAUTION light for transmission pressure wouldn’t second-guess the rotorcraft flying manual and contemplate alternate courses of action.
However, research is teeming with examples of pilots who continued into degraded visibility—flights that should have generated an internal CAUTION or WARNING light inside the pilot and a corresponding in-flight emergency response. By establishing and briefing EDTs during the preflight planning phase, a pilot is more likely to make a better in-flight decision, taking early action as he or she would in response to any other aircraft flight manual emergency.
Historically, aviation accident research highlights the importance of more effective training. Survey data confirmed this finding for spatial disorientation, as well, but it also indicated a general misunderstanding of the physiological impact of spatial disorientation.
Many of the survey respondents who believed they had experienced SD went on to describe illusions rather than spatial disorientation. This finding underscored a fundamental misunderstanding of what true spatial disorientation encompasses, making recognition of the phenomenon more challenging.
A comprehensive pilot training program should include an academic focus on understanding the mental and physical responses to encountering spatial disorientation. Aircraft training can be conducted in simulators or in aircraft. Limitations associated with each type of training should be well understood, as they do exist, and certain outside factors (such as ops specs, simulator cost and availability, certification, and so on) may preclude one approach versus the other.
Simulators are good at re-creating low-visibility conditions and for teaching basic maneuvers and instrument flying, as well as generally representing rotorcraft handling qualities at a fairly high level. While simulators provide excellent visual illusions, however, most lack the range of motion required to create vestibular illusions (according to the FAA, it takes 20 seconds of acceleration to create vestibular illusions).
The importance of combining visual and vestibular illusions is critical in degraded visual environment–induced SD training. The addition of visibility simulation systems to in-aircraft training offers variable control of in-aircraft visibility, providing the critical capability of re-creating both visual and vestibular illusions.
Simulator and in-aircraft training should be scenario based and include decision-making as well as allow full spatial disorientation to develop. As with all training conducted (whether simulator or in-aircraft), safety has to be considered first and foremost.
Historically, recovery from spatial disorientation is often lumped in with unusual attitude recovery. Although the techniques can be similar, the visual and vestibular disorientation experienced in SD lead to an overwhelming confusion in the brain that is not the same as the Coriolis effect, in which pilots can feel as though they’re pitching, yawing, and rolling simultaneously. SD brain confusion should be introduced during the training phase, but spatial disorientation is unique for each individual, during each encounter.
Each aircraft provides a slightly different set of variables during recovery, including stability augmentation systems, trim systems, and autopilot variants. Despite the many differences in aircraft, a combination of power, attitude, and balance (PAB) can be employed. Pilots who encounter SD should:
- Power: set power that will allow for a normal climb rate; care must be taken not to induce a rapid climb rate that can further disrupt the pilot’s vestibular system
- Attitude: level the wings, place the nose on the horizon
- Balance: place and keep the aircraft in trim.
This combination of actions minimizes the instrument scan.
In summary, better decision-making during every phase of flight is critical to avoid conditions conducive to spatial disorientation. Training should include scenarios emphasizing techniques to improve both aeronautical decision-making and the ability to recognize the onset of and recovery from visual and vestibular illusions.
H-SE 127A outlines these intervention strategies and provides a list of resources for pilots to consult to develop better knowledge and appreciation of the dangers posed by low-visibility conditions leading to spatial disorientation.