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Tamarack goes military

After a setback, active winglets go beyond Citations

Aerodynamic design is a complex subject, full of compromises and trade-offs. For example, if an airplane has too much drag, engine power must be increased to reach airspeed and range targets. But it’s not as simple as that.
Photography by Chris Rose
Photography by Chris Rose

A more powerful engine usually means extra weight and increased fuel consumption, which in turn requires more fuel capacity and its attendant weight. The tradeoff between power and weight can be a vicious cycle.

Another challenge comes when trying to improve a wing’s efficiency to achieve more lift. Increasing wing area is one way to do this, but this can mean a total wing redesign—and a lot more wing structure. Translation: more weight, and the risk of more tradeoff cycles.

Increasing wingspan is another way to boost lift and overall wing efficiency. The most common ways of doing this are to simply increase the wing’s area and span, or install winglets. Winglets “trick” the wing into thinking it’s longer than it really is. They do this by reducing wingtip vortices, those churning trails of disturbed air caused when low-pressure air coming from the top of a wing meets the higher-pressure air from beneath.

smartwing mods

Dubbed the “Performance Smartwing,” the Tamarack modification includes a four-foot wing extension on each wing, which allows the dual panels, plus a specially designed winglet. The flight test airplane is a 1979 A200 King Air, fitted out for military use under the C-12 designation. The flight test airplane has a preflight test unit mounted just below the pilot’s side window. Pressing a test button momentarily activates the active camber load alleviation surfaces. Unlike Tamarack’s Citation modification, the King Air has two load alleviation surfaces, each with its own pushrod. It’s a workhorse, not a showboat, as the worn, vintage power quadrant and instrument panel attest. Black and yellow stripes highlight the location of the two engine fire extinguisher T-handles.

Another way to improve aerodynamic efficiency and wing performance is to do both—extend the wing structure and install winglets. But once again, weight is a factor. There must be supporting structure for both the wing extensions and the winglets. Without it, the wing surfaces would flex under aerodynamic loads. Even more concerning is that the entire wing would flex at the wing root, where the wing attach points are, and test their limits. This would be especially concerning if the airplane’s cabin is heavily loaded. Flexing at the wing root would be greater. More fuel in the wing tanks would lessen this flexing, but this would compromise the amount of passenger/cargo weight you could carry. Zero fuel weight limitations, which define the weight you can carry in the cabin, are designed to minimize flexing. Any weight above ZFW must be fuel weight.

Tamarack Aerospace founder and CEO Nick Guida came up with a way to install winglets, extend wingspan, tame wing flexing, and increase ZFW. It uses its ATLAS (Active Technology Load Alleviation System) control surfaces—which look like mini-ailerons—to aerodynamically “turn off” the winglet’s contribution to wing lift. Should the airplane encounter changing loads or G-forces, the control surfaces symmetrically deflect and bending forces are eliminated. This way, the advantages of extra wingspan are retained, without any compromises owing to the weight of the wing extension, wing bending, or flexing at the wing root.

Since 2013, Sandpoint, Idaho-based Tamarack has installed more than 150 of its active winglet systems in the Cessna 525-series fleet (the Citations CJ, CJ1, CJ1+, M2, CJ2, CJ2+, CJ3 and CJ3+). The systems are installed at three “Transformation Centers,” located at the Sandpoint Airport; the Aiken Regional Airport in Aiken, South Carolina; and at the Oxford Airport in Kidlington, United Kingdom. Prices of the STCed modification run from $229,000 (for the CJ, CJ1/1+, and M2 models) to $269,000 (CJ2/2+) and $279,000 (CJ3/3+).

In Citations equipped with the Tamarack active winglet system, the company says that the performance advantages compared to stock Citations include, on average:

  • A 33-percent reduction in fuel burn.
  • A 25-percent increase in range.
  • An extra hour of endurance at maximum continuous power.
  • Better hot-and-high performance.
  • Lower stall, VMC, and VREF airspeeds.
  • Faster times to climb.
  • Shorter takeoff and landing distances.
  • Increased useful loads.
  • 5-percent increases in ZFW.

For all these benefits, Tamarack has encountered difficulties. In 2018 the company issued a mandatory service bulletin that improved product reliability and helped “neutralize the impact of system failures” through a trailing edge “centering upgrade.” A series of five incidents, and a fatal accident in Indiana, all occurred after uncommanded rolls. A National Transportation Safety Board (NTSB) investigation delved into the fatal accident and in a factual report found fault in the Tamarack’s active winglet control surface system. For a time, the Tamarack fleet was grounded by the FAA and the company entered voluntary bankruptcy. After a three-year delay, the NTSB’s final report named “asymmetric deployment of the left-wing load alleviation system for undetermined reasons” as the probable cause of the fatal accident. Tamarack disagreed, strongly suggesting that the airplane’s AHRS (attitude and heading reference system) could have malfunctioned, thus sending erroneous signals to the winglet system. Either way, the crash destroyed the airplane, leaving little in the way of evidence. The company also noted that there have been no roll-related accidents or incidents involving the active winglets since the 2019 airworthiness directive was issued. As this goes to press, a Tamarack official stated that the company will appeal the NTSB ruling (see “Winglet Maker Disputes NTSB Findings,”

By installing the Smartwing modification, times to climb should be reduced—the better to avoid exposure to low altitudes, where susceptibility to ground fire is greatest.
The latest news is that Tamarack is going after the defense market, starting with the King Air 200 and 350 series of airplanes. These King Airs are already used in intelligence, surveillance, and reconnaissance missions where loitering at altitude is a top attribute, but Tamarack has designed a new version of the ATLAS system. Now dubbed the “Performance Smartwing,” the King Air system comes with two active-camber load-alleviating control surfaces per wing, each one having its own actuating pushrod assembly. By installing the Smartwing modification, times to climb should be reduced—the better to avoid exposure to low altitudes, where susceptibility to ground fire is greatest. And high-altitude, low-airspeed loiter times should be five hours or more, and potentially double the stock airplanes’ four-hour typical endurance times.

The King Air’s mod is being developed in partnership with Dynamic Aviation of Bridgewater, Virginia. Dynamic has a large fleet of King Airs, and one of them—a 1979 King Air A200, fitted out as a military C–12—is being used in the flight test program, which has already begun. Guida says that the Smartwing mod would produce greater performance improvements to King Airs than those realized in ATLAS-equipped Citations. Maybe because it adds four feet to each wing’s span, or could have a new “shark fin”-looking winglet that Guida and Tamarack President Jacob Klinginsmith are pondering.

Once the military market is addressed, Tamarack’s next ambition is to offer the Smartwing mod to private King Air 350-series and 360 owners. Like the Citation mods, installations would be made at Tamarack’s three locations—but the price tags would be higher. Neither Guida nor Klinginsmith were prepared to elaborate.

In terms of scale and market penetration, the goal is an ambitious one: to mount a campaign to convince airline executives to install Tamarack’s active winglet systems in “certain very popular single-aisle airliners,” as Guida once put it. Those would be the Boeing 737 and Airbus A320. In view of the fuel economies and other aerodynamic efficiencies already demonstrated, it could be difficult for the airlines to ignore the sales pitches. Especially in these environmentally aware times. A Tamarack-equipped airplane filled with sustainable aviation fuel (SAF), burning less of it, and having reduced runway requirements in the bargain, is one way to help move us closer to net-zero carbon emissions goals.

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Thomas A. Horne

Thomas A. Horne

AOPA Pilot Editor at Large
AOPA Pilot Editor at Large Tom Horne has worked at AOPA since the early 1980s. He began flying in 1975 and has an airline transport pilot and flight instructor certificates. He’s flown everything from ultralights to Gulfstreams and ferried numerous piston airplanes across the Atlantic.

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