DULUTH, MN–The Federal Aviation Administration has grounded Duluth-based Cirrus’ Vision Jets.
The FAA issued the Emergency Airworthiness Directive on Thursday.
According to the FAA, the grounding is in response to Cirrus’ reports of three incidents regarding its Model SF50 airplanes.
The incidents all involve “the stall warning and protection system (SWPS) or Electronic Stability & Protection (ESP) System engaging when not appropriate.”
“The SWPS or ESP systems may engage even when sufficient airspeed and proper angle of attack (AOA) exists for normal flight,” FAA officials wrote in their grounding directive.
The incidents were reported between November 2018 and April 2019.
Cirrus issued the following statement regarding the grounding:
In early April of this year, one of our company pilots experienced the engagement of the Stall Warning and Protection System when not appropriate during a flight at altitude. The pilot followed the published Airplane Flight Manual (AFM) procedures and landed the aircraft safely. Out of an abundance of caution, we immediately began working with the FAA and our internal teams to determine the root cause and began our operator communication process. With the benefit of detailed feedback from our company pilot about the April event, we were able to identify service histories that pointed to a probable similar occurrence in November. We proactively and quickly issued two Service Advisories and one mandatory Service Bulletin to ensure our operators were up to speed on the issue and to remind them of the proper Airplane Flight Manual (AFM) procedures to follow in case of an Angle of Attack (AOA) related issue. We then quickly identified the root cause as an AOA sensor hardware issue; this is not a software issue. In our aircraft, the stall warning and protection systems are immediately overridable by the pilot with the press of one red button that is on the control yoke. When this button is pressed, full and normal control is immediately available to the pilot without requiring any additional steps to restore normal flight control forces. Pilots are trained in this exact procedure and, in each of the isolated events, pilots followed the published Airplane Flight Manual (AFM) and training procedures, which resulted in immediate disengagement of the stall warning and protection systems allowing them full and normal control of the aircraft. No accidents or mishaps have resulted from this condition and each pilot landed their aircraft without incident.The design features that were included in the SF50 specifically intended to mitigate the hazards associated with this kind of malfunction all worked as expected. We issued Service Advisories on 8 April and 12 April, followed by our mandatory Service Bulletin on 16 April where we required each operator to replace their AOA hardware sensor. The FAA issued an AD on 18 April which required the same AOA sensor replacement as prescribed by our Service Bulletin. Our AOA hardware supplier is now producing corrected AOA hardware sensors which are beginning to ship to operators now. These new, corrected AOA hardware sensors will be installed on fielded aircraft and new aircraft deliveries. Although jet production continues, our top priority is returning aircraft in the field to service. There are 105 aircraft in the field. Deliveries began in December 2016.
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