Accident Overview
On January 24, 2020, at about 2054 Atlantic standard time, a Gulfstream G150 (registration N373ML) was substantially damaged during a runway excursion at Fernando Luis Ribas Dominicci Airport (TJIG) in San Juan, Puerto Rico. The two pilots and two passengers were not injured. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight Crew Report
The flight crew reported that as they approached the airport, they were aware of rain in the area and that the runway was wet. The pilot in command stated that the instrument approach to runway 09 was stabilized, on glide path, and on speed. The reference speed (Vref) was 122 knots, and touchdown occurred in the vicinity of the 1,000 ft markers at a speed close to Vref. Thrust reversers were deployed from touchdown until the speed reduced to 70 knots. The pilot then noticed standing water on the runway; as the airplane encountered the standing water, it yawed initially left, then right, and departed the runway. The pilot reported no mechanical malfunctions or failures that would have precluded normal operation.
Site Examination
Examination of the accident site by Federal Aviation Administration (FAA) and Puerto Rico Ports Authority (PRPA) personnel revealed that the airplane departed the runway near the last 1,000 ft of runway 09, impacted a chain-link fence, and sustained substantial damage to the right wing spar. A review of photographs provided by the PRPA showed that the ground air brakes were deployed and the flaps were at or near the fully extended position of 40°.
Weather Conditions
Weather observations at TJIG were reported only when the air traffic control tower was open (0700 to 1900). The last available observation at 1745 indicated rain showers in the vicinity to the southwest and northwest. According to the PRPA, heavy rain showers were over TJIG at the time of the accident. Records from a surface weather system at TJIG showed that at the time of the accident, the wind was from 336° at 1 knot. Automated observations at San Juan Luis Marin International Airport (TJSJ), about 5 miles east, reported rain showers to the west and southwest in the three hours preceding the accident. At 2056, conditions at TJSJ included light rain that began at 2015.
Runway Condition History
According to an FAA Inspector, there were numerous events between 2019 and 2020 during which aircraft experienced braking performance issues when the runway was contaminated with standing water due to poor drainage. On January 23, 2021 at 1808 (sic; likely a typo for 2020), a field condition report was issued in a NOTAM advising of wet runway conditions. The runway was observed to be 100% wet with a water depth of 1/8 inch or less. The NOTAM was effective until January 24, 2020 at 1808.
Landing Distance Data
The pilot reported a landing weight of 18,400 lbs. According to the airplane manufacturer’s landing distance data, for a landing weight of 18,400 lbs, the unfactored landing distance for a wet runway was 3,620 ft, and for a contaminated runway (standing water) it was 4,100 ft. The landing distance available for runway 09 (ungrooved) at TJIG was 5,126 ft. The airplane flight manual specifies that landing performance is obtained by descending at a steady sink rate corresponding to a 3° glide path at Vref airspeed down to 50 ft height, then retarding power levers to idle, and at touchdown initiating maximum continuous wheel braking until full stop.