What are the indications of a spiral?

The correct choice is linked to the signs that indicate a spiral, which typically involves a situation where an aircraft is in a descending tight turn, resulting in complex aerodynamic behavior. When an aircraft experiences increasing airspeed together with oscillatory motions, it suggests that the craft is in a potential spiral descent.

In this scenario, the steady increase in airspeed indicates that the aircraft is possibly in an uncoordinated turn, where the lift vector is not aligned with the flight path. This condition often leads to a spiraling descent, as the aircraft maintains a turning motion while losing altitude. Meanwhile, the oscillatory motions can be a result of the pilot's attempts to regain control, indicative of the instability typical in such situations.

The other options describe flight conditions that do not relate to the characteristics of a spiral. Steady altitude with low airspeed typically indicates level flight or a straight climb or descent. A constant descent rate with stable airspeed would indicate a straight glide path without the turbulent characteristics of a spiral. Finally, stable climb with fluctuating airspeed suggests control and stability rather than the chaotic motion seen in a spiral. Understanding these distinctions helps in recognizing the specific behavior and indications of flight maneuvers like a spiral.