FAA AMOC Clears Tamarack-equipped Citations for Flight

Days after the European Union Aviation Safety Agency (EASA) lifted an emergency airworthiness directive (AD) on Cessna CitationJet models fitted with Tamarack Aerospace active load alleviation (Atlas) winglets, the FAA followed suit on July 10 with a path that will allow U.S. operators to resume flying.

The alternative method of compliance (AMOC) lifts restrictions of the FAA's AD on Textron Aviation Model 525, 525A, and 525B light jets that comply with EASA service bulletin (SB) 1480. That SB incorporates two previously issued Tamarack bulletins (SB1467 and SB1475) addressing the functionality of the active load-alleviation tabs—called Tamarack Active Camber Surfaces, or TACS—utilized to reduce aerodynamic loading on the winglets.

The AMOC marks a significant step forward for Tamarack, following allegations that TACS malfunctions could lead to inflight loss of control. “It's really satisfying to know our product has been validated by the authorities and the solutions we had available prior to the ADs have been accepted as their resolution,” company president Jacob Klinginsmith told AIN.

The comment period on the FAA’s May 25 AD closed shortly after the FAA approval of the AMOC, so the directive remained active until the process played out. According to Tamarack, 89 of 91 Atlas-equipped Citations worldwide already fulfilled the requirements of SB1480 at the time the AMOC was issued.

Also important to the company, which entered Chapter 11 bankruptcy in June, Klinginsmith noted Tamarack booked three deposits on new Atlas installations while the fleet was grounded, and those installations were to begin in July. “Our dealers are excited to get back to selling,” he added, “and owners have already sent us photos showing them flying again.”

The European Union Aviation Safety Agency (EASA) initially approved fixes incorporated in the two Tamarack Aerospace service bulletins to resolve the emergency airworthiness directive that required deactivating Tamarack's active load-alleviation system (Atlas) on Cessna CitationJets.

Unlike conventional winglets, Atlas uses TACS to counter increased aerodynamic loading. In restricting the use of the winglet system, the EASA emergency directive issued April 19 had cited "occurrences…in which Atlas appears to have malfunctioned, causing upset events where, in some cases, the pilots had difficulty to recover the airplane to safe flight."

The fixes cited by the FAA and EASA require that Atlas-equipped Model 525, 525A, and 525B aircraft comply with a new service bulletin (SB1480) that encompasses two prior Tamarack SBs. Released in April 2018, SB1467 requires installation of a revised TACS control unit (TCU) to resolve instances of uncommanded TACS movement, while SB1475, issued earlier this year, calls for installation of aerodynamic centering strips to force those surfaces back in trail in the event of a TCU fault.

"I offer my sincere thanks to our loyal and supportive customers. They have been our staunchest advocates despite the inconvenience and hardship of having the use of their aircraft restricted," said Tamarack founder and CEO Nicholas Guida after EASA approved the return to service of Atlas-equipped aircraft. 

At the time the EASA approval was granted, Klinginsmith praised the coordination between the European and U.S. regulatory agencies. "EASA and the FAA have been meeting regularly and we anticipate that the FAA will offer a solution to the limitations very shortly, in the spirit of the bilateral agreement in place between the agencies," he said.