Aftermath: Three Blades, Minus One
The velocity is a kit-built composite four-seater. Similar in configuration to Burt Rutan’s VariEze and Long-EZ, it has a swept wing with tall upturned tips, a pusher propeller and a rectangular foreplane of high aspect ratio. The landing gear may be fixed or retractable. Triangular leading-edge extensions, or “strakes,” along the sides of the fuselage carry fuel. Typical engines are Lycomings of 180 to 300 hp.
In canard airplanes like this, both the wing and the foreplane contribute lift. In terms of pounds carried per square foot, the foreplane, though the smaller, is the harder-working of the two. The center of gravity is not located near the quarter-chord point of the wing, as it would be on a conventional airplane; instead, it lies between the two lifting surfaces, like a patient between two litter-bearers.
The reason the foreplane is more heavily loaded than the wing is that, in order to avoid driving the wing to its stalling angle of attack, the foreplane, which is the airplane’s pitch control, must stall first. Once the foreplane stalls, it cannot pitch the nose up further, and so in principle the wing is prevented from stalling. Airplanes of this type behave innocuously at full aft stick: The nose rhythmically rises and falls a few degrees as the foreplane stalls and unstalls, while the wing retains lift and perfect roll control. This is a great safety feature; it is the most powerful argument in favor of the canard configuration, and has probably saved a number of lives.
Still, every silver lining has its cloud. If the wing does manage to stall somehow or other, the airplane may enter a stable, flat, parachute-like descent with little or no forward speed. Recovery may be difficult or impossible. Wing stalls can occur if the CG is too far aft, or under certain conditions of violent maneuvering.
In the late 1980s, three well-publicized accidents of this type befell Velocities. Remarkably, only one was fatal. After those accidents, the Velocity’s wing was modified to increase its stall margin.
At the time, it was widely believed that the stable stall produced a very low rate of descent. This implied an unexpectedly high, in fact unprecedented, drag coefficient, and novel, semimagical vortices were posited to explain the new phenomenon; but ground tests, conducted by Rutan with an airplane set up vertically on the back of a truck, failed to produce them. In the end, it appeared most likely that the two pilots had survived because their airplanes fell into water, and the rounded undersides of the fuselages provided some shock absorption.
On a Saturday in May 2009, a pilot, who had bought his 200 hp Lycoming IO-360-powered Velocity from its builder and had flown it himself for perhaps 250 hours with a two-blade fixed-pitch propeller, was test-flying a newly installed three-blade constant-speed prop. He proceeded incrementally, beginning with a fast taxi down the runway. He then flew a circuit and landed, then flew two circuits and landed. After each step he returned to his hangar, presumably to make adjustments. On the third flight he circled the field once, outside the traffic pattern but within gliding distance. Just as he was turning onto the downwind leg for the second time, at about 2,000 feet agl, one blade separated from the brand-new propeller.
The loss of a prop blade, or part of one, is startling and disorienting. The engine vibrates so violently that the instrument panel becomes a blur. There is a danger that the engine may break away from the airplane — although that is less likely to happen when the blades are of the lightweight composite type, as these were, than with heavier aluminum blades. There is nothing to do but shut down the engine immediately, hope it stays attached to the airplane long enough to stop turning, and look for a place to land. So long as the engine does not fall free, the airplane should remain flyable.