Graveyard spiral
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In aviation, a graveyard spiral is a dangerous spiral dive entered accidentally by a pilot and of which the pilot is initially unaware.
Graveyard spirals typically occur in instrument meteorological conditions (IMC), when the pilot loses awareness of the aircraft's altitude and allows the aircraft to enter a gentle banking turn. A pilot who allows their plane to bank into a turn while under the mistaken impression that it is still flying parallel to the ground may do so at first because they are not able to see either the horizon in the distance or some land underneath them. Barriers to vision might be clouds, fog, darkness or dimly lit un-featured terrain such as ocean. Such a pilot might not realize their position even though instruments (indicators) in the plane on the panel (dashboard) clearly show the actual position. An inexperienced or incompetent pilot may be scared by the situation and might not check the indicating instruments in the aircraft or may actually assume them to be malfunctioning because the sense impression of straight and level flight is so strong. the impression given by the senses in that situation would be level but descending flight. This impression usually leads to the pilot "pulling up" or attempting to climb by pulling back on the controls. In a banking turn however the plane is at an angle and will be describing a large circle in the sky. Pulling back on the controls has the effect of making that circle smaller and causing the plane to descend as part of the lift being generated by the wings is directed sideways. Only when the turning circle gets very small will the passengers notice the unusual sensations. At that point the aircraft is describing a descending circle or spiral. Unable to correlate the conflicting sensory mis-impressions the pilot may become afflicted by a temporary case of vertigo during which the pilots mind and body are unable to judge their position. in such cases of vertigo the pilot may experience symptoms such as air sickness and an inability to sit up or orient their body with reference to the aircraft cabin. The pilot who needs at that point more than ever to orient their aircraft may appear to be intoxicated as they struggle to sit up or reach for the controls. In any case the ever tightening, descending spiral eventually leads to the ground. That is what is referred to by pilots as a graveyard spiral.
