In the interest of safety and continuous improvement, Tamarack offers the following discussion regarding the chain of events that resulted in the April 13, 2019 incident.

On April 13, 2019, an Active Winglet failure occurred in the UK, which initiated an uncommanded roll in-flight. No damage or injuries were sustained. After the subsequent investigation, we now understand that while an Active Winglet failure did occur, the pilot report contained inaccuracies that ultimately grounded the fleet for a short time.

After a safe landing without injury or damage, the startled pilot reported his Citation jet had rolled 90 degrees in one second. However, data taken from the Citation jet shortly after the incident shows that the aircraft actually rolled at about four degrees per second, which aligns with the Tamarack Active Winglet failure recovery procedure, provided to all customers. This information can be found here as well, supplemented with a video example of a simulated Active Winglet failure and roll-rate.

The Citation jet involved in the April 13, 2019 incident rolled, uncorrected by the pilot, for approximately 19 seconds. While it is unclear why the roll was unaddressed for this amount of time, the AAIB reports that the pilot was unfamiliar with the Active Winglet AFM Supplement, including Emergency procedures. The pilot had recently purchased the Citation jet and had not yet acquainted himself with the modification. This is unfortunate, as pilot safety is the first priority of flying, especially with modified aircraft; and pilot familiarity is required by EASA and US regulation. However, the correction procedures following Active Winglet failure are conventional (such as speed reduction), so the pilot was able to recover using typical techniques without memorizing the proper procedure.

There are additional complicating factors in this situation. Following the April 13, 2019 report, it was brought to Tamarack’ s attention that the pilot had experienced an Active Winglet failure in March 2019 as well but did not report the incident to Tamarack or to anyone else. The following month, when they experienced a second Active Winglet failure, they were still unfamiliar with the Active Winglet AFM Supplement and emergency mitigation procedures.

Tamarack continues to take pride in providing continuous product improvements to increase reliability and customer satisfaction.  In 2018, one year before the March 2019 and April 2019 incidents with the same plane, Tamarack Aerospace introduced a Service Bulletin that improved Active Winglet reliability, offering it to customers for free, and recommending that it be done within one year or 150 flight hours. The upgrade would have certainly prevented both above 2019 incidents - as discovered through an aircraft inspection in April 2019, with the cooperation of the pilot.

A month prior to the March 2019 and April 2019 incidents, Tamarack introduced a second Service Bulletin meant to reduce incident severity by aerodynamically mitigating Active Winglet malfunction. This was a product improvement offered to customers at Tamarack’s expense, and this particular pilot customer did request the service from Tamarack after the March 2019 incident. However, while pilot customer did possess the second Service Bulletin at the time of the April 2019 incident, he had not yet had these improvements installed.

When the customer originally bought this aircraft, in February 2019, the pre-buy inspection did not identify any outstanding Service Bulletins for the Active Winglets.  The pre-buy did confirm that the Active Winglet AFM Supplement was properly installed in the AFM. However, after the UK incident in April 2019, the AFM was not readily accessible to the pilot, but found at the rear of the aircraft rather than the flight deck. It was also found to be incomplete.

It is rare that a single error results in an incident, and this event was no exception. Thankfully, despite many missed opportunities to avoid both incidents, plus the pilot’s unfamiliarity with recovery procedures, the outcome of this event was injury-free and damage-free. The safety investigation process should include a thorough analysis of factors contributing to the outcome, with pilot safety being the first priority.

Tamarack is pleased to collaborate with the agencies who have evaluated the April 2019 event, including the UK AAIB and EASA. Continuing to find opportunities to make flight operations safer is an important factor of aviation culture. Tamarack has taken steps to improve the product, literature, and communications with our valued customers.

Tamarack also encourages all pilots to become familiar with the Airplane Flight Manual, and Supplements, before beginning any flight.

By July 2019, the fleet grounding was resolved for all aircraft equipped with Tamarack Active Winglets, as long as they had incorporated prior Service Bulletins. No new system upgrades were required.  The fleet of aircraft with Tamarack Active Winglets has grown to over 100 aircraft, representing about 40,000 flight hours with Active Winglets. The full UK AAIB Serious Incident Report can be found here.

Updated March 3, 2021

The AAIB report contains 2 Safety Recommendations addressed to Tamarack Aerospace Group. Our responses to these recommendations have been provided to AAIB directly and will be included on the European Safety Recommendation Information System (SRIS) and on the AAIB’s website, after review by AAIB. The response can be viewed here.

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