From what we know, there have been five instances reported to the NTSB related to uncommanded roll in Citation 525 series aircraft equipped with the winglets - one was fatal. We don't know of any other crashes. all others were able to recover and land successfully. On at least one (in Europe) it appeared the operator had not complied with an earlier Service Bulletin (SB) issued by Tamarack, and several more SBs have been released by Tamarack. At least one SB was released after the fatal accident involving the CJ2. While we are not accident investigators, from the incident/accident reports in the US and Europe, they appear to be uncommanded deployment of at least one Tamarack Active Camber Surface (TACS). The TACS are the control surface located on the aft portion of the winglet wing extension to alleviate aerodynamic load. While not an 'aileron' we would expect that asymmetric deployment would initiate an uncommanded turn - similar to a runaway/abnormal aileron trim situation. The first action in any runaway trip/control situation is to disconnect the autopilot (and hold the AP/Trim disconnect swwitch), grasp the control wheel firmly... and reduce airspeed. You need to reduce airspeed to reduce the aerodynamic force on the uncommanded trim surface to gain control. On at least the fatal CJ2 accident the NTSB report does not indicate the pilot did that. The Tamarack AFM supplement specifically tells pilots to reduce the throttle and limit IAS to 160 kts when the system fails. I have had uncommanded trim failures in high performance aircraft - including Citations. I test fly a number of jets after maintenance before delivering them to my clients and in one instances the pitch trim failure was extreme and if I had not reduced my airspeed, I probably would not be writing this reply. We don't know, nor have the expertise to ascertain, if any pilot action could have saved the lives of the people in the CJ2. We do know that it is imperative for operators to comply with SBs, for pilots to be adequately trained and be proficient on emergencies. I do feel confident flying the jets with the winglets, and do just that several times a month, as well as I train and review the emergency procedures for myself and the pilots I train. This ended up being a longer reply than I intended, but hope it helps in some way - and perhaps initiates other questions.

Multiple aircraft have them and are flying fine. No definitive proof they have contributed to those accidents.

@@PersonalWings All aircraft fly fine until they don’t. We all accept a certain amount of risk. But this is extra risk solely to save a few bucks. I’ve flown in one of these and I’m not confident in the ability to regain control if it decides to go haywire at low altitude.