Sandpoint, Idaho-based Tamarack Aerospace announced June 7 that it voluntarily filed for Chapter 11 bankruptcy protection earlier in the month, a decision the company termed "a direct result" of recent Airworthiness Directives from the FAA and European Union Aviation Safety Agency (EASA) that have "effectively grounded" Cessna CitationJets, CJ1s, CJ2s, and CJ3s equipped with its active load-alleviation system (Atlas) winglets.

"The decision to enter Chapter 11 [reorganization] allows Tamarack to continue to operate and focus all activities on supporting the Atlas winglet customers and to support EASA and FAA as they consider the proposal for lifting the restrictions imposed by the ADs," the company stated, adding it expects bankruptcy to be "a temporary state.”

EASA issued an emergency AD in late April, stating "occurrences have been reported in which Atlas appears to have malfunctioned, causing upset events where, in some cases, the pilots had difficulty to recover the aeroplane to safe flight." The FAA followed suit May 24 and, unlike the EASA directive that included a mitigation path for continued flying of Atlas-equipped 525-series jets—using “speed tape” to secure the Tamarack Active Camber Surfaces (TACS) in neutral position—the agency prohibited further operation of 76 Atlas-equipped CJs in the U.S., outside of approved ferry flights, until a better alternative is identified.

"Use of speed tape was never a Tamarack solution, and in the course of harmonizing to the EASA directive, the FAA noted its use wasn’t acceptable," said Paul Hathaway, Tamarack’s vice president of marketing, in May. "However, we have over the past year issued two service bulletins at company expense to address potential TACS asymmetry, and those modifications have been submitted to both aviation authorities as an alternate means of compliance [AMOC] to resolve the directives."

Those upgrades involve replacement of a screw inside the TACS control unit (TCU) that could work free of its fastening structure and drive TACS movement, and installation of aerodynamic centering strips on those surfaces. The TCU repair bulletin was mandatory, with parts costs covered by Tamarack, while the centering-strip bulletin was optional; Tamarack has since made both bulletins mandatory and available at no charge.

According to the company, 73 percent of the installed fleet has been fitted with these upgrades. "Tamarack is committed to the safety of our fleet and our customers," company v-p and chief engineer Jacob Klinginsmith told AIN in early June. "We feel we've been proactive in reaching out to make sure our customers have the latest, best, and safest product and we'll continue to work closely with authorities to lift the restrictions on the fleet."

Klinginsmith also confirmed that Hathaway was laid off in early June as a cost-saving measure related to the Chapter 11 filing, along with company president Brian Cox.

TACS Role in European, U.S. Incidents Questioned

In one incident cited by EASA involving a CJ1+, pilot René Klumpes told AIN that while climbing through 3,000 feet, the Atlas failed and the jet “[entered] a steep turn to 90 degrees left bank angle and nose down with increasing speed.” 

Data downloaded from the incident showed that the bank reached 75 degrees in 18 seconds, and g load during the recovery was 2.6, according to information provided by Klumpes. Tamarack countered that aircraft had not received the service bulletin improvements, adding “there have been no reported incidents in those aircraft with the latest upgrades.” After disassembly, the TCU in Klumpes’s CJ1+ was found to have the loose screw problem, according to Tamarack.

The FAA directive noted five control-loss incidents involving Atlas-equipped aircraft reported to the agency and EASA. In one of those incidents, however, Atlas appears not to have been involved. A December 2018 incident was documented in a NASA Aviation Safety Reporting System (ASRS) narrative, in which the submitter responded to a callback from NASA. In the ASRS report, NASA wrote in the callback section, “On the reporter's aircraft, maintenance found the aileron trim actuator was out of tolerance. Once the actuator was replaced, the problem has not returned.”

The agency also cited the ongoing NTSB investigation into a November 2018 fatal accident in Indiana that involved an Atlas-equipped CJ2+ (N525EG) that had complied with the mandatory TCU service bulletin. Aircraft manufacturer Textron Aviation and engine OEM Williams International are listed as parties to that investigation, but Tamarack Aerospace is not.

“The NTSB investigation focuses on the role the Atlas may have played in the accident,” the FAA noted in its reasoning for the AD. AIN asked the FAA whether it was specifically told that the NTSB’s investigation is focusing on Atlas, but the agency had not responded by the time this was published. 

In April, an NTSB spokesperson told AIN the N525EG accident investigation “is still ongoing at this time. Only preliminary information is available.” In a subsequent interview, Hathaway stated the Board has not contacted the company regarding the accident. 

“We’ve offered our input and have been told it is not needed,” he told AIN in May. “I can’t definitively say the Board has ruled out Atlas [as causal to the accident] but we’ve been told by other agencies it would be highly unusual to have not been contacted if they believed the system was relevant to the investigation.”

Textron Aviation, manufacturer of the Cessna Model 525 series Citations, told AIN the company “has been notified of the FAA's airworthiness directive concerning light jets fitted with Tamarack Aerospace's supplemental type certificate for active load-alleviation system (ATLAS) winglets.  

“Textron Aviation understands that Tamarack Aerospace is working with the FAA to determine an approved engineering solution,” the company continued. “Safe operations of its aircraft are of the utmost importance to Textron Aviation, which will continue to closely monitor the situation to encourage a swift resolution and understanding of the impact this AD will have on a select number of owners and operators.”​

Textron Aviation was an installation center for Atlas winglets, although the company is no longer listed as such on the Tamarack website. Textron Aviation would not comment to AIN when the company stopped installing Atlas winglets.