Progressive Spin

T-34C OUT-OF-CONTROL FLIGHT

CHAPTER TWO

characterized by oscillations in pitch, roll, and yaw attitudes and rates. In an incipient spin, the

nose attitude will likely fluctuate from the horizon to the vertical (nose down), the yaw rate will

increase toward the Steady-State value, and the wings will rock about a nearly level attitude.

The incipient phase lasts approximately two turns. A pilot can usually identify an incipient spin

by noting stalled AOA, airspeed accelerating or decelerating towards a Steady-State Spin value,

and fully deflected turn needle. Visual indications are misleading and may lead to the false

impression of a Steady-State Spin.

Steady-State Spin motion is considered to be OCF because control input in any one of the

three axes does not affect an immediate response about that axis. To develop a Steady-State

Spin in the T-34C requires maintaining pro-spin control inputs during the incipient spin phase.

With such a dedicated effort required to develop a Steady-State Spin, one might conclude there is

no danger of developing one inadvertently. Unfortunately, this is not the case. There are several

documented instances (some resulting in mishaps) in which pilots have attempted to recover

from OCF in its earliest stages and because they used improper technique, forced the aircraft into

a spin. To identify a Steady-State Spin properly, the pilot must depend on certain cockpit

indications and avoid the natural instinct to rely on visual cues. For instance, hanging in the

straps while the aircraft is upside down and spinning around does not equate to an inverted spin.

Understanding of this extremely important point is somewhat obscured by the out-of-date notion

that a "good" pilot can always depend on visual cues to determine what is happening to his

aircraft. To really identify a Steady-State Erect Spin, one must note a stalled (pegged) AOA, a

steadied airspeed of 80 - 100 KIAS, and a fully deflected turn needle. Indications of an inverted

spin are 2 - 3 units AOA, zero airspeed, and a fully deflected turn needle. Any indications other

than these signify something other than a Steady-State Spin.

202. PROGRESSIVE SPIN

Discussion. This maneuver is introduced in order to familiarize the IUT with the OCF

characteristics and disorienting effects associated with a progressive spin, which results from a

misapplication of spin recovery control inputs. For example, a reversal of rudder direction

during a Steady-State Spin while maintaining full back stick will result in a progressive spin.

The progressive spin is characterized by an initial increase in nosedown pitch and spin rate,

followed by a rapid reversal in spin direction. The number of turns, which occur prior to spin

direction reversal, varies depending upon the initial spin direction and the location of the

aircraft's CG. Spins to the left typically reverse after fewer rotations and tend to be the more

intensely disorienting than spins initiated to the right. NATC flight departure investigations

revealed that reversals consistently occurred 1 1/3 - 1 1/4 turn after full opposite rudder was

applied. Because of the increased potential for disorientation, it is once again important to

emphasize, "The turn needle is the only reliable indicator of spin direction".

The reversal phase also involves the motion, which occurs between Steady-State Spins in

opposite directions and is similar to the incipient spin phase. The reversal phase continues for

approximately 3 turns following initial reversal of spin direction. Aircraft motions during this

phase become oscillatory and airspeed may go as high as 140 KIAS.

2-2 UNUSUAL ATTITUDES AND OUT-OF-CONTROL FLIGHT