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Aircraft Spins 101

by Sarina Houston 30. May 2014 22:31
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Photo: H. Rabb/Wikimedia
As mentioned in my previous article on stalls, accidents that occur due to stall/spin scenarios are more fatal than others. According to an AOPA study, stall/spin accidents have a fatality rate of about 28 percent, higher than the overall average fatality rate of 20 percent.

A spin occurs when an airplane stalls in an uncoordinated or aggravated state. If a recovery is not initiated after an uncoordinated stall occurs, the wing that is more stalled than the other will drop and the nose will follow into a spiraling descent. The aircraft will descend rapidly in a corkscrew motion.

According to the Jeppesen Private Pilot Manual, a small airplane will descend about 500 feet for each turn in a spin, so there's not much altitude or time available for a recovery in many cases. Considering stalls and spins often occur at low altitudes to begin with, it's clear why the fatality rate is higher for these accidents.

Stages of a Spin
The FAA has outlined three stages for spins in light aircraft: incipient, fully developed and recovery.

  • Incipient: The incipient phase of a spin is the stall and spin entry, up to about 2 turns in the spin.
  • Fully Developed: When the airspeed and rotation stabilize, the spin is considered fully developed.
  • Recovery: Recovery occurs when the pilot applies rudder and aileron inputs to counter the spin and the aircraft regains lift and control function. Once the inputs are initiated to stop the spin, the aircraft can usually recover in less than one spin.

Types of Spin

  • Erect Spin: Erect spins are the most common type of spin, occurring when the aircraft rolls and yaws in the same direction and the aircraft is upright and in a slightly nose-down attitude.
  • Inverted Spin: An inverted spin occurs when the aircraft spins upside down and yaw and roll occurs in opposite directions.
  • Flat Spin: Getting its name from the flat-like pitch attitude, the flat spin occurs when the aircraft spins at a level pitch attitude around the vertical axis as a result of a yawing motion alone. Flat spins are the most difficult to recover from (and just as difficult to enter in some aircraft!)

 

Spin Recovery
Spin recovery should be initiated at the first sign of a spin. Recovery procedures are specific to the aircraft flown and are found in the pilot operating handbook of each aircraft. In light aircraft, the spin recovery procedures follow a typical pattern and can be remembered by the common acronym PARE.

P - Power: The throttle should be moved to the idle position to reduce thrust.
A - Ailerons: Ailerons should be neutralized.
R - Rudder : Full opposite rudder input should be applied until the rotation is stopped. If the aircraft is rotating to the left, right rudder should be applied. Once the spinning stops, the rudder should be neutralized.
E - Elevator: Quick forward pressure should be applied to break the stall and gain airflow over the wings. Once the aircraft gains lift, back pressure should be applied gradually so as not to stall again.

Training aircraft are stable by design. They're meant to recover from unusual attitudes without much external control input from the pilot. A Cessna 172, for example, is actually somewhat difficult to perform an intentional spin in. But this doesn't mean that pilots of training aircraft are immune to spins.

While intentional spins are not always demonstrated during training, stall and spin awareness should always be emphasized with flight students. Many pilots tend to become confident in stall recovery, but all pilots would be wise to remain familiar with spin entry characteristics and recovery procedures for their specific aircraft.

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Aircraft Accidents | Flying | Sarina Houston



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