Monday, February 23, 2009

Intentional Spins

The intentional spinning of an airplane, for which the
spin maneuver is not specifically approved, is NOT
authorized by this handbook or by the Code of Federal
Regulations. The official sources for determining if the
for a specific airplane are:

  • Type Certificate Data Sheets or the Aircraft

  • The limitation section of the FAA-approved
    AFM/POH. The limitation sections may provide
    additional specific requirements for spin
    authorization, such as limiting gross weight, CG
    range, and amount of fuel.

  • On a placard located in clear view of the pilot in
    the airplane, NO ACROBATIC MANEUVERS
    placarded against spins, there is no assurance that
    recovery from a fully developed spin is possible.

There are occurrences involving airplanes wherein
spin restrictions are intentionally ignored by some
pilots. Despite the installation of placards prohibiting
intentional spins in these airplanes, a number of pilots,
and some flight instructors, attempt to justify the
maneuver, rationalizing that the spin restriction results
merely because of a "technicality" in the airworthiness

Some pilots reason that the airplane was spin tested
during its certification process and, therefore, no
problem should result from demonstrating or
practicing spins. However, those pilots overlook the
fact that a normal category airplane certification only
requires the airplane recover from a one-turn spin in
not more than one additional turn or 3 seconds,

whichever takes longer. This same test of controllability can also be used in certificating an airplane in the
Utility category (14 CFR section 23.221 (b)).

The point is that 360° of rotation (one-turn spin) does
not provide a stabilized spin. If the airplane's
controllability has not been explored by the
engineering test pilot beyond the certification
requirements, prolonged spins (inadvertent or
intentional) in that airplane place an operating pilot in
an unexplored flight situation. Recovery may be
difficult or impossible.

In 14 CFR part 23, "Airworthiness Standards: Normal,
Utility, Acrobatic, and Commuter Category
Airplanes," there are no requirements for investigation
of controllability in a true spinning condition for the
Normal category airplanes. The one-turn "margin of
safety" is essentially a check of the airplane's controllability in a delayed recovery from a stall. Therefore,
in airplanes placarded against spins there is absolutely
no assurance whatever that recovery from a fully
developed spin is possible under any circumstances
The pilot of an airplane placarded against intentional
spins should assume that the airplane may well become
uncontrollable in a spin.

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