PC-12
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; Flight Crew Landed As Precaution; Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
The incident occurred during an otherwise uneventful reposition flight from ZZZ - ZZZ1. The PIC was acting as Pilot Monitoring; and the FO as Pilot Flying. The filed altitude was FL200; but the flight had requested and received FL220 approximately 45 minutes to an hour prior to the incident to escape some moderate turbulence.  At the time of the incident; the conditions were IMC with intermittent patches of VMC; light turbulence; and trace to light icing at about -23 deg C. The aircraft was on the western edge of the occluded segment of a frontal low. The first indication was the De-Ice Boots CAS. The FO remained Pilot Flying; and PIC attempted to troubleshoot the problem with the QRH. In addition; the QRH checklist was cross checked by the FO. Unfortunately; the problem did not reset; so the crew determined that it was not safe to remain in icing conditions without wing De-ice capability. The crew then examined alternates; eventually deciding on ZZZ2 due to the availability of a runway greater than 10;000 feet in length; its position behind (west) the front; and the prevailing conditions of unrestricted visibility and a 900 foot ceiling. The PM then informed ARTCC of the need to divert and received a vector for the ILS XX. During the descent; the PM calculated the required landing distance for the Flaps 0 deg Boot Fail scenario; the approach was set up and briefed; and the appropriate checklists were run. Due to the failure of the De-ice Boots; some mixed icing on the leading edge; clear runback ice on inside third of the upper surface; and rime on the underside of the airfoil accumulated during descent and approach.  The crew monitored the accumulation visually and by referencing the trim indicators to ensure that abnormal force was not required to control the aircraft. The approach and landing was conducted at Flaps 0 deg and in accordance with procedure for landing with inoperative boots.
PC-12 Captain reported an uneventful mechanical diversion due to Ice & Rain Protection system malfunction during icing conditions.