ICON Completes Spin Resistance Testing
ICON's A5 LSA in a recent spin resistance test flight.
By J. Mac McClellan, Director of Publications, EAA 747337
February 16, 2012 – ICON Aircraft announced that its A5 LSA amphibious single has passed the FAA's requirements for spin resistance under the FAR Part 23 certification standards. Because it is an LSA, the ICON does not need to meet Part 23 rules, but its makers say that it has.
The basic requirements for spin resistant certification is that the airplane fly through a 360 degree heading change - or for seven seconds, whichever comes first - with the elevator control in the full nose-up position throughout the turn. During the maneuver the airplane must remain under control and not fall off into a bank. And the maneuver must be demonstrated at the full CG range, at various power settings, and with a variety of rudder and aileron inputs, including crossed controls.
The key to ICON's success in spin resistance is the wing, which has cuffs on the outboard leading edge. The cuffs lower the angle of attack of the wing's outboard portion so that part of the wing continues to lift while the root area is stalled. That keeps the ailerons effective into the stall so the airplane remains under control.
The Columbia 300 - now Cessna - was certificated under the spin resistance rules several years ago. Of course, the most famous "spin proof" airplane in the U.S. was the Ercoupe developed in the 1930s. And a number of European singles - most famously the Rallye - will not spin.
The certification alternative to spin resistance for single-engine airplanes is to demonstrate a 360-degree heading change with control inputs that would most likely cause the airplane to enter a spin. After one turn with pro-spin controls applied, the airplane must recover from whatever happens before exceeding another 360 degree heading change.
ICON's original wing, which had no flaps, was replaced by the new cuffed wing, but because of the new wing's performance it requires flaps, which ICON has included to enhance low speed lift for takeoff and landing.
ICON says its A5 is the first airplane to "completely" meet the FAA spin resistance certification standards, a claim that is apparently based on the rudder pedal-limiting device the Columbia uses to meet the rule under certain conditions. The Columbia was approved under an FAA ELOS (equivalent level of safety) finding that means the FAA determined it met the intent of the spin resistant rules. The A5 met the rule without an ELOS. The Ercoupe, of course, was certified long before there was an FAA so it did not meet the rule.
During the stall testing, ICON says it made a number of modifications to the airplane as performance was measured and verified, which is totally normal during low-speed testing in any airplane. The most demanding maneuver was the last when test pilot Len Fox, flying with the CG at the aft limit, held full up elevator for seven seconds while applying rudder and ailerons to promote a spin. The A5 did not roll off in either direction, and responded immediately when normal control inputs were applied.
As is normal in low-speed flight testing, ICON installed a "spin chute" on the tail of the pusher single. If the airplane had entered an unrecoverable condition the test pilot would deploy the spin chute to force the nose down and stabilize the airplane for recovery.
ICON did not announce a schedule of when the A5 will enter production or when to expect first delivery, but said it "is working aggressively on production preparations." Clearing the stall- and spin-testing hurdle is certainly a major milestone in development of any airplane, and ICON is to be congratulated on its success. For more on ICON, click here.