by Andy Montague
Years ago stall-spin training was a requirement for even a private pilots’ license. Now, it is only required of flight instructor applicants with the CAA having rescinded the requirement on June 15th 1949, citing too many training accidents. Since then advocates for mandatory spin training have blamed the lack of such a requirement for the continued high rate of stall-spin accidents. In general aviation most occur in the base-to-final turn in the traffic pattern. In the ag- aviation sector, however, they are most likely to happen in the procedure turn-around and occasionally in non-working impromptu flight demonstrations. While the number of these accidents may vary from year to year they have one enduring characteristic: they are the deadliest of accidents that occur in ag-aviation. This is the one type of accident in which the survivability rate has not noticeably improved with the advent of modern aircraft. Some thought the use of GPS “allowing the use of race track patterns etc”, as opposed to “back-to-back” patterns might alleviate the stall-spin problem. However there doesn’t seem to be any discernable improvement.
Over the years stall-spin accidents have been addressed many times by the FAA, and the aviation press. Recently there has been an increase in the attention given these accidents as they affect ag-aviation. The PAASS program has an excellent video that addresses the problem, and at least one ag-plane manufacturer is installing placards warning against skidding turns. The attention that is being given to this & other safety concerns will most certainly be a positive influence; not only in terms of safety within the industry but also how ag-aviation is perceived in general.
Suppose we list & examine a few items, definitions & terms pertaining to stall-spin
training. The three coordination conditions are:
(a) Coordinated
(b) Slip
(c) Skid
Coordinated: The ball is centered, both wings stall simultaneously.
Slip: The ball is displaced toward the low wing in the turn; when the stall occurs
the top wing loses lift first. The plane rolls towards the wing’s level position.
Skid: The ball is displaced toward the high wing in the turn: when the stall occurs,
the bottom wing loses lift first. The plane rolls toward the inverted position.
Uncoordinated: Non-specific, either a slip or skid.
Prerequisite for a spin: A stall.
Spin: An aggravated stall.
Step on the ball: A term used to aid in achieving & maintaining coordination.
Cross-controlled: Rudder deflected for one direction of turn while ailerons are
deflected for the opposite direction, i.e. right rudder, left aileron. A plane can be
in any one of the three coordination conditions with the controls crossed. This
is a term that is overworked & often misused. It does not denote the coordination
status of the aircraft. Although a valuable & descriptive term when used properly
it quite often indicates a lack of subject knowledge when used in a catchall phrase,
i.e. “cross control stall”.
Stalling a heavily loaded plane “coordinated or otherwise” at low altitude is very
dangerous at best. However when stalling out of a slip the plane will pass through
wings level flight (altitude permitting) before things get real nasty. While a skidding
stall probably will be immediate disaster, many of these turn-around accidents
happen while pilots are in pursuit of quick turn times.
During recent table discussion, it was determined that ag aviation, despite the lack of mandatory spin training, has a large number of stall-spin knowledgeable members, including but not limited to some accomplished aerobatic pilots & air show performers. It was also noted that at any given time, we have a few “quick turn artists” within our ranks & interestingly, both attributes are rarely shared by the same individual.
One thing that we need to emphasize is, do not intentionally place any AG plane in a spin entry position at “any altitude” or “no coordination stalls”. If you haven’t been introduced to stall-spin situations or if it’s been awhile, locate a “capable & knowledgeable” instructor & spin-approved airplane & get some training. It’s fun & in terms of safety – it will be time & money well spent.
