Spin-Resistance at ICON Aircraft Raising the Bar for Light Aircraft Safety
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Spin-Resistance at ICON Aircraft Raising the Bar for Light Aircraft Safety recognized spin-test pilot Len Fox to put the aircraft through i ts spin-resistance testing regimen. Fox has nearly 40 years of experience and has flown almost 200 aircraft types. He was a United States Naval Aviator for 20 years, flying 17 military types including F-15, F-16, and FA-18. He has completed spin testing for 25 different types, which made him ideally suited for spin-resistance testing of the A5. The FAA Part 23 spin-resistance standards require tests across the range of configurations and center-of-gravity (CG) locations that the aircraft will fly with, and the tests become progressively more difficult as the CG moves aft. For each configuration, the aircraft must successfully complete five different maneuvers ranging from a relatively mild wings level or coordinated turning stall to an aggressive abused input (uncoordinated with full deflection of elevator, full rudder, and full aileron input opposite to rudder), which must be held for seven seconds without a spin initiating. With all configurations and permutations, the A5 was subjected to over 360 test cases. During the testing process, the A5 was continuously optimized. As the tests became more difficult, it became necessary to make a variety of aerodynamic changes, which were iteratively flight tested. After several weeks of iterations and testing, the A5 finally passed its last and most difficult test, the 7-second “abused controls” or “pro spin” test (control inputs of rudder and aileron that would promote a spin) at aft CG. It was a momentous day at ICON, representing the successful completion of the riskiest and most technically ambitious part of the entire development program. When ICON Aircraft VP of Engineering Matthew Gionta and COO Steen Strand called the entire company together to announce the news, a spontaneous celebration erupted in a moment of elation, a reflection of the extraordinary challenges and risks the team had taken on to achieve such an ambitious goal. This photo of the completed and installed spin-resistant wing clearly shows the cuff on the outboard panel of the wing. “I’m incredibly proud of our engineering and fabrication team,” said ICON Aircraft CEO Kirk Hawkins. “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. 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. This is especially important at low altitude where the majority of sport flying will occur. This is just another example of ICON going above and beyond the call of duty to deliver not only the world’s coolest sport plane, but also one of the world’s safest.” (CLOCKWISE FROM LEFT) The A5 as equipped for spin-resistance testing with yarn tufts, spin parachute, and GoPro cameras used for data collection. ICON ground crew looks on as the A5 performs its spin-resistance tests. Their purpose is to recover the spin parachute and/or pilot in the event of a deployment. Fortunately, the parachute never needed to be deployed. The installed boom-mounted spin parachute References and Image credits: http://www.aopa.org/asf/publications/10nall.pdf http://www.airspacemag.com/flight-today/cit-bour que.html?c=y&page=5 http://www.aopa.org/asf/ntsb/stall_spin.html http://www.nasa.gov/centers/langley/news/researc hernews/rn_halloffame.html http://www.nasm.si.edu/images/collections/media/ full/A19790677000CP04.jpg Joseph R. Chambers, Concept to Reality, NASA SP 2003-4529 (2003) The wing cuff is a discontinuity on the leading edge of the wing that separates it into two distinct parts that have different airfoils. The outboard panel of the wing has a drooped leading edge, which allows it to continue generating lift after the inboard panel has stalled. This gives the A5 a progressive stall, which is a significant contributor to spin resistance. Ailerons are located on the outboard panel of the wing, which continues to fly even while the rest of the wing is stalled. This ensures that the pilot maintains roll control during a stall. Control authority was not limited in any axis to achieve spin resistance. Wing flaps provide additional lift at low speeds and are particularly valuable during water takeoffs. A spin-resistant airplane must demonstrate that it is resistant to entering spins with the flaps both up and down. 4. Planing Wing Tips The wing tips have flat surfaces on the bottom to ensure that the wings skim along the surface of the water during extreme or unintentional water maneuvering. They also provide hydrostatic stability when the aircraft is not in forward motion. [generic comment about wing tips as the relate to spin resistance such as “they do not meaningfully impact spin resistance”] Tufts of yarn taped to the wing show how the air is flowing over the wing at any given time. This is especially important as the plane sta

History of Spin Resistance A spin is a dangerous combination of a stall and yaw. Spins occur when a stalled aircraft experiences too great a yaw rate, which can be the result of an incorrect rudder input or a pre-existing yawing moment as would occur if an airplane is stalled while performing an uncoordinated turn. During the ensuing spin, an aircraft rapidly loses altitude as it rotates about its spin axis, driven by an asymmetric stall condition between the two wings. The pilot often loses the ability to control the aircraft because of disorientation or loss of control authority, making...

History of Spin Resistance A spin is a dangerous combination of a stall and yaw. Spins occur when a stalled aircraft experiences too great a yaw rate, which can be the result of an incorrect rudder input or a pre-existing yawing moment as would occur if an airplane is stalled while performing an uncoordinated turn. During the ensuing spin, an aircraft rapidly loses altitude as it rotates about its spin axis, driven by an asymmetric stall condition between the two wings. The pilot often loses the ability to control the aircraft because of disorientation or loss of control authority, making...