Graveyard spiral

[2] Graveyard spirals are most common at night or in poor weather conditions where no horizon exists to provide visual correction for misleading inner-ear cues.

[3] Graveyard spirals are the result of several sensory illusions in aviation which may occur in actual or simulated IMC, when the pilot experiences spatial disorientation and loses awareness of the aircraft's attitude.

The pilot loses the ability to judge the orientation of their aircraft due to the brain's misperception of spatial cues.

Mechanical failure is often a result, but generally not a causal factor, as it is the pilot's sense of equilibrium which leads to the spiral dive.

Pulling back on the control yoke has the effect of tightening that circle and causing the airplane to lose altitude at an increasing rate, like water swirling in a drain or funnel.

In the ever-tightening, descending spiral the aircraft eventually exits the base of the clouds and/or hits the ground.

[4] However, entry to the graveyard spiral is a gradual event, which allows the pilot to mentally adjust to an incorrect standard of feeling level.

If the pilot fails to recognize the illusion and does not level the wings, the airplane will continue turning left and losing altitude.

[6] The solution is for the pilot to consciously override the brain's imperative to judge physical attitude on the basis of signals from the vestibular, and rely solely on the visual cues of horizon or of attitude instruments in the airplane, until the brain once again adjusts, and vestibular sensory input agrees with visual input.