Real-world Ops: Tamarack Winglets Boost CJ Performance

 - March 1, 2022, 8:15 AM
The Cessna CitationJet's new Tamarack Aerospace active-camber winglets. (Photo: Matt Thurber/AIN)

The mission sounded simple: James Benham needed to fly from his home base in Bryan, Texas, to San Diego, where he was scheduled to give a presentation the following day. Fortunately, Benham doesn’t have to rely on the airlines because he owns and pilots a CitationJet.

Traveling by general aviation isn’t always ideal, however, and there usually are constraints that could affect such a trip or even make it impossible to complete without spending extra time at the destination.

In the original CitationJet, there is no way Benham could make it nonstop from his home in Bryan to San Diego with safe fuel reserves, unless the prevailing winds shifted 180 degrees to blow east to west. And on this particular day, Benham had already spent a few hours flying friends back from a vacation in Colorado, dropping them off in Tyler, Texas, before returning to Coulter Field in Bryan.

Benham’s original plan was to stay overnight at his home, then depart the next day, with me joining him in Bryan for the trip to San Diego. This would have worked fine if the weather had cooperated, even if it required an intermediate stop for fuel, which would have been the case for a stock CitationJet.

As it turned out, a line of storms was about to encroach on southern Texas, and the next day’s forecast for San Diego called for widespread low fog. Benham had to make a quick decision. Was it safer to fly to San Diego that evening and land there at night in good weather? Rather than risk the worsening weather forecasted for the next day and the consequent increase in pressure because there was less margin for error if the weather didn’t improve?

There was one other factor that helped Benham with his decision: his CitationJet is equipped with Tamarack Aerospace active-camber winglets. They improve performance such that he can easily make the Bryan-San Diego trip nonstop, thus eliminating the risk of the additional stop and dialing down the potential reduction in safety margin due to fatigue.

So the flight was on. Benham picked me up at my hotel in Bryan, and we went to the airport to prepare for the flight.

CitationJet with Tamarack winglets
Preparing for the flight to San Diego in the Tamarack-modified CitationJet. (Photo: Matt Thurber/AIN)

The Tamarack Treatment

A few months earlier, I had met Tamarack Aerospace founder and CEO Nick Guida at Benham’s hangar to join the CitationJet’s last flight before the modification. We needed to fly the jet from Bryan to Tamarack’s headquarters in Sandpoint, Idaho, where the modification would take place.

The Tamarack upgrade adds winglets and 6 feet 1 inch to the CitationJet’s wingspan, plus something extra to help ameliorate the effect of the winglets. While winglets by themselves improve efficiency by increasing the wing’s aspect ratio and allowing faster climb times to higher altitudes, that improvement comes at a price: a longer wing adds more load to the wing structure, especially during maneuvering and when encountering gusts.

Passive winglet mods add more structure to the wing to handle the extra loads, which adds weight and partially offsets some of the efficiency benefit. But Guida, an aerospace engineer, came up with a clever solution, a way to offload the extra loading when the load happens without adding more structure to the wing. Added structure, after all, is there all the time. Tamarack’s active technology load alleviation system (Atlas) active-camber surfaces (TACS) actuate only to counteract an extra load when it happens, and the rest of the time they sit passively, waiting for the next load to come along.

In actual operation, the TACS operate often because loads on wings constantly change, but the point is that they alleviate the extra loading caused by the addition of the winglets, in exchange for a little bit of weight and a lot of processing power needed to analyze and react to the extra loads.

The TACS themselves are small control surfaces mounted outboard of the ailerons next to the winglets, and they move up or down as needed to alleviate loads. TACS are independent and autonomous, not connected to flight controls or autopilot. If they fail, they are designed to fail passively in-trail so they have no effect on the wing. However, if they do fail, the pilot must fly at a slower speed to prevent possible structural damage from the loading caused by the winglets. Tamarack has demonstrated during flight testing that if a TACS fails and is fully actuated, the pilot can maintain control by slowing the aircraft and counteracting the roll induced by the failed TACS.

Unmodified CJ

Guida and I met at Benham’s hangar for the flight to Sandpoint, which was 1,408 nm away. While the weather wasn’t an issue, we found a problem that prevented us from flying at the unmodified CJ’s most efficient altitude for the whole flight. The CJ had an intermittent transponder problem, so we had to talk with ATC to get higher altitudes, which worked for the leg to Cheyenne, but after that, we stayed fairly low, FL290, on the leg to Sandpoint. Winds aloft were rather strong.

Typically, this CJ would need about 1,000 pounds more fuel than we could carry to make it to Sandpoint nonstop with the required reserves. While the CJ’s maximum altitude is FL410, unless temperatures are way below normal, the jet simply can’t climb directly to that altitude, further hindering efficiency. The modified CJ can climb to Fl410 directly in 32 minutes. However, even with the mod, making it nonstop on this trip wouldn’t be possible unless winds were strong and right on the tail.

CitationJet before Tamarack winglets
Pre-modification, on the way to Tamarack Aerospace's Sandpoint, Idaho, facility for winglet installation. (Photo: Matt Thurber/AIN)

The flight to Cheyenne took 3.2 hours at FL380, and the final leg to Sandpoint took another 2.5 hours. At FL380, the CJ’s Williams International FJ44-1A engines each burned 350 pph. We made it briefly to FL350 on the leg to Sandpoint, but continuing transponder problems forced us to fly lower, and much of the trip was at FL290, where fuel flow climbed to 510 pph.

Shortly after we arrived, the Tamarack crew pulled the CJ into the hangar for the fairly extensive modification.

Turning a CJ into one with Tamarack active winglets starts with removing the original wingtip, then installing the new winglet, which includes LED nav and strobe lights. Much of the 10-day job is taken up by painting the winglets and matching the original paint, with four days set aside to install the electronics and wiring, including the switch and indicator in the flight deck.

“The goal is to get the time down so people don’t have their airplanes gone too long,” Guida said.

As of late January, Tamarack had sold 150 winglet upgrades to owners of eight CJ variants from the CitationJet to the CJ3+. About 75 percent of installations are done at Sandpoint, with the rest at approved installation centers in Aiken, South Carolina, and Oxford, England. The winglet systems are approved in the U.S., Europe, Canada, Mexico, and Brazil.

Efficient CJ

To see the difference between the unmodified CJ and the Tamarack wingletted version, I returned to Texas to join Benham on the flight to San Diego.

It was apparent the evening that we left on the flight that the flexibility offered by the winglets means a lot to Benham. As mentioned, we were able to make the flight nonstop, eliminating the need to fuel up on the way and vastly increasing our margin of safety when considering the forecast inclement weather and the possibility of fatigue.

It’s only 1,064 nm from Bryan to San Diego’s Gillespie Field, but with headwinds flying westbound, we'd still have to stop for fuel in the unmodified CJ. With the Tamarack winglets, we were projected to land with well over 700 pounds of fuel, still leaving a decent reserve if we had to fly to an alternate like San Diego International Airport.

CitationJet with Tamarack winglets
Post-modification with Tamarack active-camber winglets. (Photo: Matt Thurber/AIN)

We were able to climb directly to FL410 where the engines each sipped 300 pounds of fuel per hour, pushing us along at 342 ktas, illustrating the benefits of being able to climb higher. The weather was perfect; the thunderstorms in Texas held off until we were well on our way, and we flew westbound into clear skies above a wispy carpet of clouds thousands of feet below.

After a smooth 3.5-hour flight, Benham eased the CJ onto Gillespie’s Runway 27R. While flight planning showed we would land with more than 700 pounds of fuel, in fact we still had nearly 1,000 pounds left, a comfortable margin.

The Owner-pilot

James Benham came to flying after launching a software company that now has offices in the U.S., Argentina, and South Africa and more than 250 employees. He made quick progress once he began flying, earning his private pilot license in 2018, then buying his first airplane, a Piper Arrow; he followed that with a turbocharged Piper Saratoga II in which he logged 220 hours in six months. The next step was a twin-engine Piper Seneca V, which he eventually sold so he could buy a refurbished Piper Aztec. “I am a multiengine guy,” he said, “and my goal was to get to multi as fast as possible.”

Among his flying friends, many owned Beechcraft King Airs, and Benham considered moving up to the twin turboprop for his typical flights, which range from 600 to 1,000 miles. He didn’t like the idea of having to fly through, instead of over, the weather, and the cruise speed of the smaller King Air models just wasn’t appealing. Insurance costs have risen, too, and he would be paying 30 to 40 percent more for coverage in a King Air, without a huge boost in performance.

So Benham embarked on finding a jet, looking at the Embraer Phenom 100 and 300, Pilatus PC-24, and the typically owner-flown CitationJets (all except the CJ4).

At more than $10 million, the PC-24 was out of the running, given that a used Phenom 100 or King Air 200 cost about $2 million (prices have risen since he was in the market). When comparing the King Air with a CJ, he said, the jet “is cheaper per mile and [faster].” He felt that handling an emergency like an engine failure in the CJ would be much easier as the engines are mounted closer to the centerline, unlike the wing-mounted engines on the King Air. Ultimately, the CJ’s “cabin sold me,” he recalled, and luckily he bought the airplane just before prices spiked after the pandemic took hold. He also liked that the CJ’s engines are well supported by Williams International’s Tap Blue cost-per-hour program. “Tap Blue is a godsend,” he said.

The CJ, Benham said, “is capable, fast, and you can’t beat the cost.”

However, after buying the CJ in October 2020, then getting type rated at LOFT in Carlsbad, California, in November, and flying the CJ for a bit, Benham became aware of some drawbacks. “I noticed when it got warm [outside], I had to watch the weight and balance. The climb rate was anemic at times. And turbulence was noticeable.”

Benham had heard about the Tamarack winglets during his search for the airplane, liked how they looked, and started calling other owners to ask about their experience. He met like-minded pilots after joining the Citation Jets Pilots Association and queried them about their experience with the winglets, also calling Tamarack president Jacob Klinginsmith for more information.

CitationJet with Tamarack winglets
Leveling off at FL410 on the flight to San Diego in the Tamarack-modified CitationJet, burning just 300 pph per engine. True airspeed eventually settled at 342 knots. (Photo: Matt Thurber/AIN)

What moved the needle on his decision to buy the roughly $200,000 Tamarack mod, however, was his wife: after a hot and turbulent trip from Texas to John Wayne Airport in Southern California, which required a stop in Tucson, “She said, ‘Buy the damn winglets,’” Benham recalled. And shortly afterward he booked the upgrade at Tamarack’s Sandpoint headquarters.

While the winglets eliminated those interim stops, which Benham and his family appreciate, the winglets also mitigate some turbulence effects, making flying more comfortable more of the time. The TACS react quickly to changes in wing loading, and turbulence causes gust loads on the wings, which the TACS mitigate.

Another benefit that Benham appreciates is the lower landing speed enabled by the longer wings. He has found that when flying at the same angle-of-attack on short final, reference landing speed is nine knots lower. Where he used to fly a Vref of 103 to 104 knots, now he is seeing 96 or 97, making for more comfortable margins on landing.

Climb rates are much better than before the winglet mod, especially in hotter-than-normal conditions, and the CJ can climb directly to FL410 instead of having to step-climb or even stop at FL370. During our flight to San Diego, passing 39,500 feet, the CJ was still climbing at 400 fpm, at ISA +10 degrees C. “That would be impossible in the [original] CJ unless you had half fuel on board,” Benham said.

“Tamarack added an hour to this airplane,” he said. “This trip would have [burned] more than 1,500 pounds of [extra] fuel if we had to stop."