Spatial Disorientation

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  • Topic: Sensory illusions in aviation, Aviator, Visual flight rules
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SPATIAL
DISORIENTATION
The Importance of Awareness in
Aviation

Shanal Perera
HES1915A - Human Performance and Limitations in Aviation

Introduction
One of general aviation's biggest killers - Spatial Disorientation (SD). It is the inability to correctly interpret aircraft attitude, altitude or airspeed in relation to the Earth or other points of reference. Any condition that does not allow the pilot to maintain natural visual references, such as clouds or terrain, can cause SD. Whilst pilots can compensate by learning to fly using cockpit instruments, a malfunction such as a vacuum failure, in less than desirable visual meteorological conditions (VMC) can also cause SD, with the same lethal results.

While some pilots are introduced to the concepts of SD during their flight training, general aviation pilots still have misunderstandings about what it is and how to deal with it. There is a misconception that the majority of pilots who suffer SD are junior in their career. In reality, however, the pilots who are most at risk are those that are quite senior, with 10 years of experience and over 1500 hours in the cockpit(Newman, Physiology of Orientation, 2012, slide 37). The estimated career incidence of SD is 90 to 100%. It is thought that a pilot has either been disorientated, or is about to be (Newman, Physiology of Orientation, 2012, slide 4).

Types of Spatial Disorientation
There are three different types of SD:
1. Unrecognised (Type I)
2. Recognised (Type II)
3. Incapacitating (Type III)
The type of SD which most commonly causes accidents is Unrecognised SD (Type I). It is particularly dangerous as the pilot is not aware that disorientation has occurred. Therefore, the pilot does not make any alterations to correct the situation and the aircraft crashes into terrain. Recognised SD is the most common form experienced by pilots. Unlike Type I SD, a pilot is able to recognise that there is a problem. However, it is important to note that whilst a pilot may acknowledge that there is an issue, he/she may not recognise it as SD. It may present itself as confusion. The pilot might recognise for example, a difference in what the cockpit instruments are showing versus what the pilot sees in the outside environment. This situation should alert the pilot that he/she is experiencing SD and that immediate corrections are to be made.

Incapacitating SD is the case where a pilot recognises that disorientation has occurred but enters a state of panic or is so overwhelmed by the situation that he/she freezes and is physically and/or mentally unable to make corrections.

Orientation Inputs
There are three sensory systems which provide us with the information to help us determine where we are and what position we are in. Orientation is provided by the eyes, proprioceptors and the vestibular system.

The visual system produces approximately 80% of the information for orientation. Without visual cues, a pilot is left with receiving only 20% of available information to the brain which can produce fatal results.

1

This is often the case when VFR pilots enter into IMC. This situation accounted for at least 83 accidents in the USA between 1994 and 2003 (AOPA Physiology No. 1, Page 4) .

Figure 1: Spatial Disorientation
Accidents by Pilot Certificate and
weather conditions

Source: ASF Accident Database (AOPA Physiology
No 1.)

The following is an example of what can happen if the receipt of visual information is limited. Following a fuel stop in Indiana, the VFR-rated pilot of a Cessna 210 on a cross-country from Amarillo, Texas, to Washington, DC, contacted Washington ARTCC and said, “…I seem to be lost…I was heading east into Manassas showing ah sixty miles out and all of a sudden these clouds just fogged in front of me on the mountains so I just turned around and just kind of circling right here above two pretty good sized towns.” The aircraft was given a transponder code and identified at 1511, and...
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