The FAA has issued a proposed airworthiness directive (AD) that would require owners of Cessna Citations modified with Tamarack Aerospace winglet systems to comply with a Tamarack service bulletin issued on April 19, 2023. The bulletin calls for installation of placards on the winglets’ Tamarack active camber surface (TACS) as well as a revision to the airplane flight manual (AFM) supplement.
Tamarack’s autonomous load alleviation system (Atlas) modifies CitationJet 525, 525A, and 525B models with winglets and the TACS, which actuate during flight to reduce the increased load on the wings caused by the winglets.
According to Tamarack president Jacob Klinginsmith, the company notified the FAA that during a periodic design review, it found an Atlas failure mode that would not be annunciated to the pilot. If one of a pair of opto-isolators in the Atlas control unit fails, this would prevent an enable signal from being sent to the TACS control unit, thus preventing the TACS from operating and not providing load alleviation for the winglets. If the TACS aren’t working, pilots need to reduce speed to prevent overloading of the wings and potential exceedance of the limit load.
“This is not something we’ve seen in the fleet,” Klinginsmith told AIN. Tamarack issued the service bulletins last year to warn pilots about this issue, but it is also working on a permanent fix. “We found this when we were reassessing our design during a periodic review,” he said. “This is Tamarack being proactive about safety. We’re constantly rolling in upgrades to the equipment, and we will be rolling this in too. But there is a lot of testing, qualification, and approval needed to make sure any change is robust. This is a good solution in the meantime.”
The service bulletin calls for adding an update to the AFM and installing placards on the TACS to help pilots see whether the TACS are working during night operations or to provide contrast if the TACS are painted a dark color.
Many of the nearly 200 Tamarack-upgraded CitationJets are already in compliance with the service bulletin and thus meet the requirements of the proposed AD, which would give owners 60 flight hours—or six months after the effective date of the AD—to comply. “We’re working with the fleet to get everyone upgraded,” Klinginsmith said.