7.18. Spatial Disorientation Demonstrations. The following maneuvers simulate three common types of spatial disorientation illusions. They reaffirm the requirement to rely on instruments during instrument flight instead of “seat-of-the-pants” sensations. These maneuvers will only be practiced with an IP on board and only conducted in VMC. (T-2) The purpose of these demonstrations is to help a student pilot understand the real threat of spatial disorientation and the importance of trusting flight instruments. See AFMAN 11-202V3, AFPAM 11-417, Orientation in Aviation, and FAA-H-8083-15B for further information.

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7.18.1. Leans. An illusion experienced because of aircraft motion about the longitudinal axis (roll) on the semi-circular canals. There are three phases – roll entry, roll sustainment, and roll- out. During roll sustainment, the pilot may no longer perceive the roll, and upon roll out to wings level, can have the sensation of a bank and turn in the opposite direction. This is commonly experienced while maneuvering or being vectored in the weather or at night and can be particularly problematic during sustained or slow rate turns.

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7.18.1.1. Demonstration. The PNF closes their eyes while the aircraft is in a straight- and-level attitude. PF executes a well-coordinated instrument steep turn, which the PNF should sense correctly with eyes closed. As the PF sustains the constant rate turn for approximately 15 seconds, the PNF should experience a ‘straight-and-level’ sensation. At roll-out to straight-and-level flight, the PNF should experience the illusion of roll in the opposite direction of the original bank.

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7.18.1.2. In the absence of a good instrument crosscheck, this may lead to re-entry into the original roll at often more severe bank angles to “feel” straight and level during instrument flight conditions.

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7.18.2. Coriolis Effect. An illusion experienced when more than one angular plane of motion is stimulated in the inner ear. This is usually accomplished through the simultaneous motion of the head and aircraft but in different planes, e.g., looking down at an approach plate or checklist during a turn in instrument flight conditions. The result can be a sense of motion in the form of tumbling or vertigo and loss of orientation awareness. Compensatory eye movements in the form of nystagmus may occur and make aircraft instrument recovery much more difficult.

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7.18.2.1. Demonstration. The PF executes a well-coordinated instrument steep turn while the PNF closes their eyes and rotates their head position from facing forward to facing downward towards their lap, then back to facing forward while the aircraft is banking or rolling out of bank. The PNF will experience the Coriolis illusion and have difficulty in distinguishing orientation even after the PNF re-opens their eyes and focuses on their instruments.

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7.18.2.2. This demonstrates the danger of not only excessive head movement during aircraft motion in instrument flight conditions but also difficulty in determining correct instrument recovery procedures due to the severity of the illusion.

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7.18.3. Pitch and Elevator Illusions. A false sensation of pitch created by the effects of acceleration on the otolith organs. During instrument flight conditions positive acceleration can lead to a sense of nose-up pitch while deceleration can result in a sensation of nose-down pitch. Normally associated with takeoff at night or in the weather, the combination of positive acceleration and pitch required for takeoff rotation can lead to a sense of over pitch and cause aggressive pitch-down control inputs to compensate. Go-arounds and missed approaches at night or in instrument conditions are also common scenarios where this illusion can result in inappropriate aircraft control inputs. Sudden climbs and dives or abrupt changes to climbs and dives such as sudden level-offs can lead to a sensation of excessive vertical motion or the continuation of a climb or dive, as if in an elevator, even after vertical motion has stopped.

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7.18.3.1. Demonstration. PF configures the aircraft normally for an instrument approach while the PNF closes their eyes. Once established at final approach speed, the PF executes a simulated missed approach using normal procedures, allowing the aircraft to accelerate to a normal climb speed. PNF should sense a pitch in excess of actual aircraft performance. After climbing approximately 1,000 feet, PF levels the aircraft at moderate rate (faster than what would be normally desired). The PNF should experience the sensation of continuing to climb (elevator illusion).

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7.18.3.2. The demonstration warns pilots of the tendency to compensate with a pitch-down response in degraded visual conditions.

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