February 16, 2012
By Jim Moore
Icon Aircraft has proved the A5 light sport will resist spins even in a protracted, cross-controlled stall. (The photo depicts the A5 configured for spin testing with requisite instrumentation and safety equipment, including tufts and the boom-mounted spin parachute at the rear of the aircraft, which was installed specifically for the spin-resistance testing and will not appear on production aircraft.)
With a splashy Hollywood debut, sports car styling, and features including folding wings and an amphibious design, the Icon A5 has already attracted plenty of attention, and advance orders. On Feb. 16, the company announced the A5 has marked a significant safety milestone: passing the full slate of tests required to establish optional “spin resistant” certification under 14 CFR Part 23.
As an LSA, Icon will not actually seek Part 23 certification for the A5, but the company opted to design the sporty amphib, and test it, to the rigorous FAA standard introduced in 1991 following extensive stall/spin research by NASA.
“The only well-established, industry-wide standard that’s out there is Part 23,” said Matthew Gionta, Icon Aircraft vice president of engineering.
Icon worked for months to design and analyze a wing configuration that would resist spinning out of a stall, and hired Len Fox, a former U.S. Navy pilot with nearly 40 years of experience in hundreds of aircraft, to test it. In a series of flights, Fox completed an increasingly challenging set of maneuvers required for Part 23 spin-resistance certification. Cycling through the various configurations of control surfaces, power settings, flaps, and landing gear, the center of gravity was progressively moved farther aft, to its aft limit.
Though the aircraft was equipped with a spin-recovery parachute, designed to stabilize a spinning aircraft and then be jettisoned to allow continuation of flight, the safety system was never deployed, Gionta said. The A5 on Dec. 8 completed the last in a series of hundreds of test cases: stalls induced in a variety of configurations and power settings.
The certification protocol requires 360 different test points, and “we flew significantly more than that through the development process,” Gionta said, adding the final number was “two or three times that.”
The final flight over the San Joaquin Valley near Bakersfield, Calif., on Dec. 8, 2011, included 24 of those attempts, each passed within the limits specified by Part 23, Gionta said.
Other aircraft makers have tried and failed to meet the spin-resistance standard, a complex aerodynamic challenge. Gionta said the cuffed wingtip, along with some proprietary design features on the wing, proved the keys to resisting the tendency to spin.
Stall/spins are disproportionately deadly, accounting for 10 percent of all GA accidents and 13.7 percent of fatal accidents, according to Air Safety Institute research. A detailed analysis of 465 fatal stall/spin accidents from 1991 to 2000 found that at least 80 percent of those accidents occurred at traffic pattern altitude, 1,000 feet agl or less.
Icon Aircraft CEO Kirk Hawkins said the company is extremely proud of what the designers, engineers, and test crews have accomplished.
“While creating a full-envelope spin-resistant airplane was extraordinarily difficult and took longer than we expected, it was absolutely the right thing to do for safety and is a game-changing innovation,” Hawkins said in a news release. “Delivering an aircraft that provides excellent control throughout the stall while being resistant to entering a spin dramatically raises the bar for light aircraft safety by decreasing the likelihood of inadvertent stall/spin loss of control by the pilot.”
Gionta said that while the A5 never spun, there were tests along the way that failed to meet the Part 23 spin resistance standard, and called for refinements to the design. Designers also changed course on a previous decision to produce the aircraft with no flaps, restoring wing flaps to improve takeoff performance on the water.
With an estimated final price of $139,000, the A5 has already attracted deposits from nearly 650 buyers, Gionta said, and factory production will ramp up later this year.
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