Page 41 - Volume 17 Number 4

much like independent ailerons, whose purpose is to react with computer processor speed to damp maneuvering or turbulence loads. Called TACS (Tamarack Active Control Surfaces), these outboard surfaces move up or down to negate the winglet’s increase of effective aspect ratio, but only while the load exists, instantly stowing when no longer needed. The first application is under development for the Cirrus SR22, since Tamarack Aero was already providing modifications to Cirrus airplanes, but the technology is scalable for larger, high-perfor- mance aircraft and now is being STC’d for the CitationJet.We flew with Tamarack’s test crew in the company’s CJ while we were at last fall’s NBAA convention, when the airplane was still outfitted with flow tufting and strain gauges. Nick Guida, company president, showed us around N86LA, the test-bed aircraft; they intended for the added-on portions of the wing to be noticed, hence the active controls were painted in a bright orange-red. The sculpted winglets look very natural on the CJ’s normally truncated wingtip, adding some four feet of spanbut little or no drag.The only preflight action needed is to manually raise the surfaces during the walk-around, then watch them restore themselves tothe normal trailing position upon the application of power to the system. Because it’s a fail-passive design, it can’t cause control problems on its own. Should the system be inoperative, maximum speed in turbulence is simply reduced to prevent winglet stress.The prototype winglets were still being fine-tuned for optimal angle and chord, and their height will be increased on the larger CJ’s, Guida said. The CJ cabin was outfitted with a 40-channel data recorder connected to a plethora of strain gauges above and below the wings. Brian Willett, Tamarack’s demo pilot, ushered me into the cockpit for a quick flight to 15,000 feet, south and east from the Orlando Executive airport (KORL). It wasa good day for showing off the ATLAS (Active Technology Load Alleviation System) modification, because Hurricane Sandy, far to the north, was spewing gusty winds southward into central Florida.The Williams fanjets wound up dependably and the takeoff com- puter showed 2,300 feet of runway required for a 15-degree flap takeoff, with V1 at 98 knots and VRof 102. Once airborne and plowing through the chop, the CJ showed us 3,300 fpm, external warts and all.The chief advantage of the winglet system is to loft the little CJ to41,000 in just over 30 minutes, instead of a more typical 50+ minutes, thereby gaining range by entering an efficient cruise condi- tion earlier. On the way down to NBAA, the Tamarack crew refueled in Montgomery, Alabama and reportedly climbed back up to FL410 in 32 minutes.As we rode the bumps, we could see the red-painted TAC surfaces twitch to alleviate load, typically reactingin 100 milliseconds, Guida said. As soon as the strain no longer existed, the surfaces returned to trail. We coasted out near Kennedy Space Center, where Willett bent aroundin a 2-G turn to demonstrate a sustained deflection of the active flight controls. Sure enough, they remained in a tilted-up position as long as he held the load.Returning to KORL in a stepped descent, maneuvering around the traffic into Orlando International, we re-entered the turbulence and put the ATLAS to work smoothing the ride and negating the winglets’ added lift as needed. Bug speed was 102 for the visual into the setting sun for runway 25; Brian handled the sporting crosswind with con- summate Citation skill.“We expect to make significant inroads with Active Winglets in the coming year, and in a decade we expect they’ll be standard on most high end, fixed wing aircraft,” saysAPRIL 2013TWIN & TURBINE • 39