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The Inverted Spin – Intermediate Acrobatics Part VII. “Points out the difference between an accidental spin and an inverted spin; and demonstrates the procedure of executing an inverted spin.”
US Navy flight training film MN-1325f.
Public domain film from the US Navy, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
A spin is a special category of stall resulting in autorotation about the vertical axis and a shallow, rotating, downward path. Spins can be entered intentionally or unintentionally, from any flight attitude if the aircraft has sufficient yaw while at the stall point. In a normal spin, the wing on the inside of the turn is stalled while the outside wing remains flying; it is possible for both wings to be stalled but the angle of attack of each wing, and consequently its lift and drag, will be different. Either situation causes the aircraft to autorotate (yaw) toward the stalled wing due to its higher drag and loss of lift. Spins are characterized by high angle of attack, an airspeed below the stall on at least one wing and a shallow descent. Recovery may require a specific and counterintuitive set of actions in order to avoid a crash.
A spin differs from a spiral dive in which neither wing is stalled and which is characterized by a low angle of attack and high airspeed. A spiral dive is not a type of spin because neither wing is stalled. In a spiral dive, the aircraft will respond conventionally to the pilot’s inputs to the flight controls and recovery from a spiral dive requires a different set of actions from those required to recover from a spin.
In the early years of flight, a spin was frequently referred to as a “tailspin”…
Entry and recovery
Some aircraft cannot be recovered from a spin using only their own flight control surfaces and must not be allowed to enter a spin under any circumstances…
Spin-entry procedures vary with the type and model of aircraft being flown but there are general procedures applicable to most aircraft. These include reducing power to idle and simultaneously raising the nose in order to induce an upright stall. Then, as the aircraft approaches stall, apply full rudder in the desired spin direction while holding full back-elevator pressure for an upright spin. Sometimes a roll input is applied in the direction opposite of the rudder (i.e., a cross-control).
If the aircraft manufacturer provides a specific procedure for spin recovery, that procedure must be used. Otherwise, to recover from an upright spin, the following generic procedure may be used: Power is first reduced to idle and the ailerons are neutralized. Then, full opposite rudder (that is, against the yaw) is added and held to counteract the spin rotation, and the elevator control is moved briskly forward to reduce the angle of attack below the critical angle. Depending on the airplane and the type of spin, the elevator action could be a minimal input before rotation ceases, or in other cases the elevator control may have to be moved to its full forward position to effect recovery from the upright spin. Once the rotation has stopped, the rudder must be neutralized and the airplane returned to level flight. This procedure is sometimes called PARE, for Power idle, Ailerons neutral, Rudder opposite the spin and held, and Elevator through neutral. The mnemonic “PARE” simply reinforces the tried-and-true NASA standard spin recovery actions—the very same actions first prescribed by NACA in 1936, verified by NASA during an intensive, decade-long spin test program overlapping the 1970s and ’80s, and repeatedly recommended by the FAA and implemented by the majority of test pilots during certification spin-testing of light airplanes.
Inverted spinning and erect or upright spinning are dynamically very similar and require essentially the same recovery process but use opposite elevator control. In an upright spin, both roll and yaw are in the same direction but that an inverted spin is composed of opposing roll and yaw. It is crucial that the yaw be countered to effect recovery. The visual field in a typical spin (as opposed to a flat spin) is heavily dominated by the perception of roll over yaw, which can lead to an incorrect and dangerous conclusion that a given inverted spin is actually an erect spin in the reverse yaw direction (leading to a recovery attempt in which pro-spin rudder is mistakenly applied and then further exacerbated by holding the incorrect elevator input)…
