Background
On September 22, 2016, at approximately 1820 Atlantic standard time, a Learjet 25D, registered as YV1738 in Venezuela, sustained substantial damage during a runway excursion while landing at Fernando Luis Ribas Dominicci Airport (TJIG) in San Juan, Puerto Rico. The aircraft was operated by WMG Techno-Logistic, C.A. under 14 CFR Part 91 as a business flight. The flight originated from Punta Cana, Dominican Republic (MDPC) at 1750 AST. The crew and one passenger were not injured.
Accident Sequence
The pilot reported that the runway appeared wet as they were cleared to land. Light rain was observed on the windshield, which intensified during the approach. After a smooth touchdown on runway 9, while decelerating through 80 to 90 knots, the airplane began to hydroplane. It departed the left side of the runway onto the grass. Crossing an intersecting taxiway, the left main landing gear collapsed, the aircraft rotated 180 degrees, and came to rest on the grass. The occupants evacuated the airplane and were met by first responders. The pilot stated there were no mechanical anomalies or malfunctions that would have prevented normal operation.
Aircraft Examination
An inspector from the Federal Aviation Administration examined the wreckage. The left main landing gear actuator support beam was structurally damaged. The left wing tip fuel tank exhibited scrapes on its lower side. Rudder control continuity was confirmed. Tire skid marks from all three landing gear were observed on the runway, leading to the aircraft's final position; the marks were white in color.
Runway 9 measured 5,539 feet in length and 100 feet in width. The asphalt surface was in good condition but was not grooved. Inspection of the main landing gear tires revealed that three of the four tires had no measurable tread remaining. The number 4 tire (right, outboard) had 1.17 mm of tread. All main tires were approved by the airplane manufacturer. The Goodyear aircraft tire maintenance manual states that tires should be removed when tread is worn to the base of any groove at any spot, or up to 1/8 of the tire circumference.
Weather and Conditions
At the time of the accident, weather conditions at TJIG included wind from 350 degrees at 8 knots, visibility of 2 statute miles in thunderstorms, an overcast ceiling at 2,000 feet, and an altimeter setting of 29.94 inches of mercury. A U.S. Customs agent reported heavy rain at the accident site. The passenger stated that there was 2 to 4 inches of water on both the taxiway and runway, describing the rain as profuse. Daytime visual meteorological conditions prevailed, and an instrument flight rules flight plan had been filed.