A Cessna Citation was descending toward Fort Myers, Florida, on March 30 when the left-side winglet installed by Tamarack Aerospace departed the aircraft with discernible "jolts" followed by yaw and prompted an emergency landing in Tampa.
The NTSB preliminary report provides many details on the flight of a Cessna 525B that was "substantially damaged" when the left winglet departed the aircraft, along with the active control surface designed to automatically limit airframe loads that the winglet can create, during a cruise descent to Fort Myers, Florida.
The pilot was the sole occupant of the aircraft that departed Walnut Ridge Regional Airport in Arkansas, intending to land at Page Field in Fort Myers. Flight data posted by ADS-B Exchange show the aircraft was descending just west of the Florida coast near Tampa when the winglet left the aircraft, and follows the aircraft to its safe landing. Video of the emergency landing captured by a news helicopter showed a descent and landing not visually remarkable (except for the absence of one winglet), followed by prompt arrival of emergency vehicles alongside the aircraft.
The pilot reported no issues landing at Tampa International Airport in an interview with investigators, the NTSB report notes.
"Furthermore, he stated that there were no flight control anomalies, but that there was some 'binding' of the ailerons on final approach," the NTSB wrote. "He also added that he was in visual meteorological conditions at the time of the accident and the flight was 'smooth' until the 'big jolts.'"
Tamarack issued statements on the most recent incident March 30, following the local news coverage, and April 5, when it noted that 180 Cessna Citations have been retrofitted with the winglet and active control surface now branded Smartwing.
“We are obviously grateful that nobody was injured in this strange event. We’re supporting the NTSB investigation to learn what happened in the air that would have caused the winglet and wing extension to be ripped from the aircraft. The FAA certification and engineering process served this pilot very well because he was obviously able to control the airplane and make a very smooth approach and landing,” said Jacob Klinginsmith, president of Tamarack Aerospace, in a statement emailed on April 5. “During certification, we successfully flight tested a 'one winglet removed' scenario simulating a bird strike, lightning strike, wake turbulence or any other abnormal damage to the winglet, so we would expect the plane to handle as well as we saw in the video of this emergency landing. Congratulations to the pilot and thank you to the multiple upgraded aircraft [owners who] have benefitted from Tamarack technology in their operations (the pilot and owner don’t want to be identified at this time)."
The Citation that landed safely after winglet departure on March 30 was retrofitted with Tamarack's system in December, the NTSB preliminary report states. In February, the modules that control the active camber surface mounted just inboard of each winglet were replaced "as a result of fault alerts to the pilot during two separate fights. In each instance, the pilot opened and reset the circuit breaker to the system which cleared the faults, and subsequently landed the airplane without issue."
No further anomalies were reported following replacement of the control units, investigators noted.
"Postaccident examination of the airplane revealed that the left wing extension and the left aileron were substantially damaged. The left wing extension, winglet, and TACS [Tamarack Active Camber Surface] were all missing except for approximately 28 inches of the leading edge of the wing extension. The left aileron had an impact mark on the bottom side of the trailing outboard edge and was buckled and pressed up, with chipped paint."
The remaining components of what the NTSB still refers to as ATLAS (it was originally called the Active Technology Load Alleviation System) were examined and "no anomalies were noted," investigators wrote.
"The ATLAS main circuit breaker was not found in the open position. A (functional) built-in-test of the ATLAS system was performed, and no anomalies were noted. Following the test, the left wing TACS bellcrank that remained on the left wing was between the stops in an approximately neutral position, and the right wing TACS was found in a neutral position."
Tamarack disputed the NTSB's findings on the 2018 crash of another Cessna Citation equipped with Tamarack's winglets and automated control surfaces. Three people died when that Citation rolled over and plunged into the ground in Indiana, a crash that the NTSB determined was probably caused by a malfunction of Tamarack's system. Tamarack hotly disputed that conclusion and filed a petition for reconsideration within days. The NTSB final report, published in November 2021, remains unchanged.
NTSB investigators noted in that 2021 report five other incidents of uncommanded roll events reported by pilots of Tamarack-retrofitted Cessna Citations in 2018 and 2019. The NTSB investigation of the 2018 Indiana crash was still underway when the FAA in 2019 grounded all Citations with Tamarack winglets installed. Fewer than 100 aircraft were affected at the time, and updates to the system components (as required by the emergency airworthiness directive, as well as a manufacturer bulletin) were made to 91 aircraft, 76 of which were then registered in the United States.
The 2019 grounding of the Tamarack-fitted fleet was soon followed by the company seeking Chapter 11 bankruptcy protection. The company continued operations (and winglet installations), and emerged from Chapter 11 in 2021, an effort supported by customers and vendors who chipped in $1.95 million to keep the company afloat during the bankruptcy proceedings.
Tamarack has since adapted its fuel-saving system to other aircraft, with similar automated control surfaces installed to obviate the need to add structure to the wing to carry the increased aerodynamic loads that the winglets can create. Tamarack modified the system for Beechcraft King Airs, as well as the hybrid-electric Ampaire now in development. Company officials have said they hope to expand the winglet installations to commercial aircraft as well.