Friday, March 18, 2011

Six For Safety: Illusions of Flying

Try your knowledge of aviation safety. This month: Illusions of Flying.




It's one thing to say you're going up for some spins. But it's a completely different scenario when you inadvertently wind up in a spin. According to an AOPA Safety Advisory from 2004 title Spatial Disorientation, disorientation results in a higher percentage of deaths compared to other accident categories -- over 90% in fact. With that, try completing this months short quiz based on a few flying scenarios that might challenge an unsuspecting VFR pilot. Answers and discussion can be found at the end of the quiz.


1) Traveling back from the Cape and heading southwest, after having crossed over KHPN and now just past the Hudson River, you begin your approach into KCDW. The day has been hazy but a beautiful sunset reigns supreme. However, there is a noticeable sloping cloud line off in the distance. As you move your attention back into the cockpit you check your location against the chart, confirm GPS settings and listen to ATIS. Resuming your outside scan, you are shocked to see KTEB off in the distance and straight ahead. What illusion might have caused you to inadvertently change your heading left of course?
a) An event horizon.
b) The leans.
c) A false horizon.
d) None of the above.

2) It's night time and your touch-and-go landings have been flawless. You decide to take a break and exit the pattern. Upon turning around for a 45 entry, you spot what you think is the the one and only ramp light at this non-towered airport. Strangely, the light keeps moving around. In an attempt to stay aligned, you start over-controlling the airplane. This type of illusion is known as?
a) Autokinesis
b) Autopilot oscillation.
c) Pilot oscillation.
d) Autocorrelation

3) It's a half-moon, night-approach into Orange County (KMGJ) and given the snow covered ground, the terrain is a dimly lit featureless moonscape. At a mile out and lined up for runway 03, the GPS TAWS alert goes off. You immediately pull up and add full power. What just happened?
a) You just entered the twilight zone.
b) You just experienced a dark hole approach.
c) You're still thinking about that crazy light from question 2.
d) You just experienced a black hole approach.

4) Forecasts are not perfect, and during this flight the cloud bases aren't quite at 3,500 feet as you realize it's gone completely haze gray and wet outside. Having entered the cloud while flying under VFR, you immediately commence a 180 degree turn. Upon leveling out on your reciprocal course, you feel the plane turning in the opposite direction. Instinctively, you reapply correction to the yoke. At the same time you notice you're loosing altitude and apply back pressure. You have just entered the initial stages of a....?
a) Inversion illusion.
b) Elevator illusion.
c) Graveyard spiral.
d )None of the above.

5) For no other reason that it's there, you decide to make an approach into Warwick (N72–2150'x28'). It looks like your flight path is too high so you cut the power to steepen the approach. Before you know it you are low and about to land short of the runway. This is type of illusion is known as:
a) Runway width illusion.
b) Terrain slop illusion.
c) Somatogravic illusion.
d) None of the above.

6) Flying at night, you keep noticing what appears to be a faint light just off to the right of the aircraft nose. However, when you look in that direction, the light disappears. This is caused by a “night blind spot” which is due to a lack of rods in an area of the eye known as the fovea.

True or False?
Answers and discussion:
1) The correct answer is c). In this scenario, the sloping cloud formation in the distance creates a false horizon for the VFR pilot. This phenomena can cause misalignment with the true horizon and result in a dangerous attitude. A sloping ridge or a line of lights (or stars) against a dark background can have a similar effect.

2) The correct answer is a). Though not completely understood, pilots who happen to focus on a stationary point of light against a featureless background may actually perceive movement. In not recognizing this situation for what it is, the pilot may inadvertently maneuver in reference to the light source -- either to maintain alignment with it or taking evasive maneuvers thinking it's another aircraft.

3) The correct answer is d). This scenario illustrates a featureless terrain illusion. Many pilots refer to it as if flying into a black hole since there are few, if any, visual references. Snow covered ground, water, and darkened terrain can induce this type of low approach scenario.

4) The correct answer is c). This scenario falls under the broader category known as vestibular illusions. Vestibular illusions are brought about by fluid movements in the semicircular canals of the ear. For example, given a prolonged stable and coordinated turn, our ears "reset" to a perceived non-motion environment. Upon leveling out of the turn, we sense motion, however, there is a lag in the fluids (as much as 20 seconds) before things settle down again. So even though straight and level, a pilot may sense they are still moving in a particular and sometimes opposite direction.

5) The correct answer is a). Warwick is a great example where runway width illusion can come into play, especially if you're used to flying into airports with 100 feet or more of runway width. It's a matter of perspective and what you're used to seeing when flying an approach. Just the opposite, a pilot that typically flies into a narrow-width runway may find they are high on approach into a wide runway environment.

6) The correct answer is True). Rods are an indispensable part of our visual system. Without them, we would see very little if anything at night. However, the eye is only so big and Rods compete with Cones (our daylight receptors) for space. Cones dominate the center of the eye providing crisp and precise visual representations of our surroundings. Also, Cones require strong light to be activated, thus they are essentially blind in dark environments. Since there is not a lot of space in the back of the eye, the Rods are essentially left to the outer field of vision away from the center of the eye. This explains why we can perceive objects at night, but that they tend to disappear when looked at directly.
FAA recommendations to counter and/or prevent disorientation:
  1. Understand the causes of these illusions and remain constantly alert for them. Take the opportunity to understand and then experience spatial disorientation illusions in a device such as a Barany chair, a Vertigon, or a Virtual Reality Spatial Disorientation Demonstrator.
  2. Always obtain and understand preflight weather briefings.
  3. Before flying in marginal visibility (less than 3 miles) or where a visible horizon is not evident such as flight over open water during the night, obtain training and maintain proficiency in airplane control by reference to instruments.
  4. Do not continue flight into adverse weather conditions or into dusk or darkness unless proficient in the use of flight instruments. If intending to fly at night, maintain night-flight currency and proficiency. Include cross-country and local operations at various airfields.
  5. Ensure that when outside visual references are used, they are reliable, fixed points on the Earth’s surface.
  6. Avoid sudden head movement, particularly during takeoffs, turns, and approaches to landing.
  7. Be physically tuned for flight into reduced visibility. That is, ensure proper rest, adequate diet, and, if flying at night, allow for night adaptation. Remember that illness, medication, alcohol, fatigue, sleep loss, and mild hypoxia are likely to increase susceptibility to spatial disorientation.
  8. Be physically tuned for flight into reduced visibility. That is, ensure proper rest, adequate diet, and, if flying at night, allow for night adaptation. Remember that illness, medication, alcohol, fatigue, sleep loss, and mild hypoxia are likely to increase susceptibility to spatial disorientation.
  9. Most importantly, become proficient in the use of flight instruments and rely upon them. Trust the instruments and disregard your sensory perceptions.
Safe flying!

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