Date: 201606
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: Marginal
Weather elements / visibility: Rain; 7
Light: Night
Aircraft: Citation V/Ultra/Encore (C560)
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
ATC / advisory: CTAF ZZZ
Reporter organization: Air Taxi
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Time Pressure; Distraction; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Evacuated
Contributing factors: Weather; Procedure; Human Factors; Aircraft
Primary problem: Weather

Narrative: During the approach phase of the flight we were asked by approach if we wish to cancel now. We didn't cancel during the initial phase of getting vectors for the approach. When we were established on final we saw the approach lights in sight and plus we were making all of the necessary callouts (position reports) in going into a field (uncontrolled) after the tower closed operations for the day. So we switch over to approach and cancel our IFR and proceed in VFR since we had the field in site. After doing research with our [company manuals] this shouldn't have taken place this. Should have waited until we were on the ground safely. There was traffic behinds us so we made an immediate call to go around due to our incident so no more planes could land.At the time of approach the weather was legal to shoot the approach (ILS). The first weather was [wind] 120 at 4 kts 7 SM 900 few 4300 OVC 24/23 29.68. The second report was winds calm 400 few 2200 OVC. This was the last report before commencing the approach. During the approach the speed was on target (Vref) and on localizer and glide slope throughout the landing phase. During landing flare we touch down and started to hydroplane to the left and applied some brakes to the right to maintain center line. We slid off the runway and rested facing to the right. There was no injury to the crew nor passenger. We ran the emergency evacuation checklist and shutdown all systems.


Second narrative: Several hours after dark during our descent into our filed destination I was able to receive the local automated weather at the field. We decided to use the ILS approach. During our descent I picked up the weather once again when we were given a heading to fly to intercept the localizer. The weather reported winds calm 400 few 2200 overcast same altimeter setting. As we descended on glide path standard call outs were made. At roughly 900 MSL I called runway in sight. At that point the captain disengaged the auto pilot and continue the ILS approach. When runway was in sight and continued the approach we canceled our flight plan with approach. At this time I was under the impression that it was company's suggestion not to cancel an IFR flight plan operating under Part 135. Since the incident and reviewing procedures and regulations I now understand it is regulations that prevent the cancelation of an IFR flight plan not standard operations or procedures for the company. Throughout the approach I made standard call outs on airspeed; localizer; and glide path. Aircraft maintained a stable approach. As the aircraft was in the flair portion of the landing with the weather conditions rapidly changing with winds and heavy rain the Captain was trying to maintain centerline. As we touched down it felt like the aircraft was on ice as it felt the aircraft never made position ground traction on the right main wheel as that was the wing low with the correct crosswind control inputs at that time. The aircraft felt like it was drifting left as right rudder and control inputs were being made. The aircrafts left wheel entered the grass as the captain at that point was trying to maintain positive control. After the aircraft came to a stop off the side of the runway; the emergency checklist was ran. As soon as the engines were shut down I exited my seat to check on the passenger. The passenger was upright in his seat belted in and reported no injuries to me as I opened the cabin for him to exit.With tropical storms present in the areas throughout the season receiving 4-7 inches of rain I think it would be beneficial for airport ops to conduct runway condition reports hourly at uncontrolled fields.


Synopsis: CE-560 flight crew reported landing after a heavy rain. After touchdown the aircraft hydroplaned and exited the runway. The aircraft came to rest off the runway facing the opposite direction.