Technicalities: EAA Contest Aims to Stop Stalls

Cash prizes have been big motivators in aviation. The first flights across the Atlantic, the first man-powered flight, the first flight into space by a nongovernmental program — to name a few — were brought about, or at the very least hurried along, by the lure of a big payday. Not to say that honor and accomplishment are not powerful motivators in themselves — but talent and courage are not necessarily diminished, and can be augmented, by a seasoning of avarice.

With this history in mind, the Experimental Aircraft Association will be offering an annual prize of $25,000, called the Founder’s Innovation Prize in honor of the late Paul Poberezny, “to solve the problem of fatal loss-of-control accidents in amateur-built aircraft through innovation.” Second- and third-place prizes will be $10,000 and $5,000.

“The contest is intentionally open-​ended,” the online announcement continues, “with the only stated goal to reduce fatalities from this type of accident in amateur-built aircraft dramatically over the next decade — 25 percent in the next five years, 50 percent in the next 10.” Innovations must be broadly applicable to existing airplanes; the point is to fix a problem, not to invent a new kind 
of airplane.

Loss of control, in general usage, covers a wide variety of events: turbulence, vertigo, vacuum-pump failure, incapacitation and so on. But the main cause of loss-of-control fatalities is the low-altitude stall-spin, and that is the target of the Founder’s Innovation Prize. It is a resilient antagonist that has taken countless lives since people first flew and has so far defied efforts to defeat it.

An imposing panel of judges has been assembled: designers Burt Rutan and Dick VanGrunsven, former astronaut Charlie Precourt, test pilot Dave Morss and flight instructor Rod Machado. Rutan and VanGrunsven both have dogs of a sort in the fight. The canard designs for amateur builders with which Rutan launched his public career were, in fact, designed to be characteristically incapable of stalling and spinning — that, apart from their dramatic, sweeping wings and futuristic looks, was their main selling point — and VanGrunsven’s RV series of designs, because they are the more popular types among homebuilts, are also among the types more frequently involved in stall-spin accidents.

According to an EAA spokesman, the rate of these accidents is about the same among amateur-built and certified aircraft, and EAA’s hope is that whatever innovations emerge from the contest will migrate as some others have, like composite construction, from one class to the other.

How frequent are these loss-of-control accidents? I searched the NTSB’s accident database covering the past five years, selecting fatal accidents that occurred in the approach phase. There were 37, with a somewhat larger number of victims. Of the 37, at least 10 involved something other than loss of control, such as collision with terrain or another airplane, or just plain inept piloting. Another search, covering the same period and all phases of flight, and identifying reports in which the phrase “loss of control” appeared, turned up 45. The same search, this time not limited to amateur-built airplanes, returned 245 fatal accidents. If the search string was “stall” rather than “loss of control,” the number rose to 342.

It’s difficult to bring a specific class of accidents into sharp focus, both because the search capabilities of the NTSB’s online accident database are limited and because different investigators may interpret evidence in different ways and couch their conclusions in different terms. Nevertheless, it’s clear that accidents involving loss of control of some kind or other are quite frequent, and insufficient airspeed plays a part in the majority of those. It’s also clear that amateur pilots in small airplanes do not have a monopoly on losing control; pilots of twins and turbines do it too.

It has ever been so, and many attempts have been made to create airplanes “characteristically incapable of spinning.” One strategy has been to limit elevator and rudder effectiveness. This was the route taken by the Ercoupe designed in the late 1930s by Fred Weick, who had formerly been an influential researcher at NACA. Despite Weick’s efforts, Ercoupes, which remained in production until 1970, had a poor safety record, apparently because some pilots felt so secure in them that they ignored airspeed, got behind the power curve, and mushed into the ground while hauling back on the control wheel as hard as they could.

Another approach has been the self-actuating leading-edge slat, which allows a wing to rear up to a vertiginous angle of attack before stalling. Helio Couriers had these and so did Socata Rallyes. When the wing approached what would normally be its stalling angle of attack, the slat would pop out with a bang; no pilot action was required. When the nose came down, the slat slid back into its retracted position, looking again like a normal leading edge. Slats add manufacturing complexity and cost, however, and do nothing to mitigate the problem of getting behind the power curve; in fact, they exacerbate it.

Angle of attack indicators are extremely valuable in the hands of pilots who know how to use them; but most low-altitude loss of control accidents seem to involve pilots losing their focus on speed, power and attitude, and it is not clear if an additional instrument will help them. The ubiquitous vane-type stall warning with its attention-grabbing blare, invented by Leonard Greene in 1944, was perhaps the greatest single step ever taken toward the prevention of stall-spin accidents. It is also the type of device that best matches the spirit of the EAA contest — simple, cheap and applicable to any airplane.

What has made low-speed loss of control such an intractable problem, in spite of all sorts of preventive and warning systems, is that it is not just one problem but several. To begin with, there is the physical setting in which these accidents often 
occur. The airplane is in the traffic pattern and, therefore, by definition low. The psychological setting is important as well. Flying in the traffic pattern involves maneuvering at low speeds while distracted by other things, like traffic, power, checklists, trim, landing gear and flaps.

Another complicating factor is the fading out of stick forces at low speed. As the airplane nears the stall, its resistance to further raising of the nose lessens, making it easier for an inattentive pilot to inadvertently pitch up into a stall. Some production airplanes are equipped with elevator downsprings to replace aerodynamic forces — but few, if any, homebuilts are, and the stick forces of most homebuilts are small to begin with. Underlying all this is the fact that when an airplane is close to stalling, it is also likely to be behind the power curve or in “the region of reversed command.” This is the situation in which induced drag — drag due to lift — has become large enough that a low-powered airplane cannot accelerate except by first descending.

I doubt that the low-speed loss-of-control problem can be made to disappear altogether. Seventy-five years worth of attempts to solve it by mechanical and aerodynamic devices have had limited effect. What we have in our era that our precursors did not is software, and I expect that many of the approaches taken by competitors for the EAA prize will be in that department. A poor man’s stick pusher? A personal HUD that clips to your sunglasses? A rapidly deploying airbag under the belly?

We’ll see. The deadline for submissions is July 1; the judging will be at AirVenture.