PC-12 flight crew reported experiencing an HYDR CAWS alert while in cruise flight resulting in the flight crew diverting to an alternate airport where they landed safely.
Synopsis
PC-12 flight crew reported experiencing an HYDR CAWS alert while in cruise flight resulting in the flight crew diverting to an alternate airport where they landed safely.
Narrative
HYDR Central Advisory & Warning System (CAWS) light illuminated during flight shortly after establishing cruise at flight level 200 from ZZZ1. Pilot flying called attention to the CAWS light and we executed the QRH checklist which was to pull the HYDR CONTROL circuit breaker. We then decided to divert to ZZZ because it was a towered field; priority handling services would be available; and the weather was considerably better. ATC vectored us onto course for the ILS approach to runway XX. Once we turned inbound on the final approach course; we executed the landing gear extension checklist. We slowed to 110 knots; moved the landing gear selector to the down position; waited 30 seconds; and pumped the landing gear extension pump handle twice to get to the gear to lock and indicate 3 green on the gear indication lights. We coordinated with ZZZ approach control and ZZZ tower to execute a low approach for the priority handling trucks to visually verify both the main gear and the nose gear was down. Once we received the visual confirmation from ZZZ tower frequency; we entered left traffic of runway for a normal visual pattern approach to landing. All checklists were completed as normal. Pilot monitoring executed checklists as requested and communicated with ATC as operations required. We landed with a 15 degree flap selected. The landing was safe and uneventful. Emergency vehicles were available upon landing; but not needed.
Second reporter narrative
HYDR Central Advisory & Warning System (CAWS) light illuminated during flight shortly after establishing cruise at flight level 200 from ZZZ1. The first officer called attention to the CAWS light and we executed the QRH checklist which was to pull the HYDR CONTROL circuit breaker. We then decided to divert to ZZZ because it was a towered field; priority handling services would be available; and the weather was considerably better. ATC vectored us onto course for the ILS approach to runway XX. Once we turned inbound on the final approach course; we executed the landing gear extension checklist. We slowed to 110 knots; moved the landing gear selector to the down position; waited 30 seconds; and pumped the landing gear extension pump handle twice to get to the gear to lock and indicate 3 green on the gear indication lights. We coordinated with ZZZ approach control and ZZZ tower to execute a low approach for the priority handling trucks to visually verify both the main gear and the nose gear was extended in the down position. Once we received the visual confirmation from ZZZ tower frequency; we entered left traffic of runway XX for a normal visual pattern approach to landing. All checklists were completed as normal. The first officer executed checklists as requested by me and communicated with ATC as operations required. We landed with 15 degrees flap selected. The landing was safe and uneventful. Emergency vehicles were available upon landing; but not needed. Suggestions: My guess for the cause of this failure was the extreme cold temperatures that the plane was subject to for 8+ hours. The temperature in ZZZ1 was mid 20's F to mid 30's F with wind gusting up to 50kts. Perhaps the hydraulics lines were too cold for too when the gear was cycled and caused a break/leak (if that was the cause of the failure). If this was the cause (undetermined); a mitigation may be to keep the plane in a hangar when similar conditions are present.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.