On January 24, 2020, about 2054 Atlantic standard time, a Gulfstream G150, N373ML, was substantially damaged when it was involved in an accident at the Fernando Luis Ribas Dominicci Airport (TJIG), San Juan, Puerto Rico. The two pilots and two passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The flight crew reported that as they approached the airport, they were aware of rain in the area and that the runway was wet. According to the pilot in command, 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. The thrust reversers were deployed from touchdown until the speed reduced to 70 knots. The pilot then noticed standing water on the runway, and as the airplane encountered the standing water, it yawed initially to the left, then to the right, and departed the runway. The pilot further reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation.
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 revealed that the ground air brakes were deployed and the flaps were at or near the fully extended position of 40°.
Weather observations at TJIG were reported only when the air traffic control tower was open (0700 to 1900). The last available observation occurred at 1745, which indicated that rain showers were in the vicinity of the airport to the southwest and northwest. According to the PRPA, there were heavy rain showers over TJIG at the time of the accident. A review of records from a surface weather system at TJIG revealed that at the time of the accident, the wind was from 336° at 1 knot. Automated weather observations reported at the San Juan Luis Marin International Airport (TJSJ), located about 5 miles to the east of TJIG, included rain showers to the west and southwest in the 3 hours preceding the accident. At 2056, the conditions reported at TJSJ included light rain which began at 2015.
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, a field condition report was issued in a notice to airman (NOTAM) that advised of wet runway conditions. At that time 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.
The pilot reported a landing weight of 18,400 lbs. A review of the airplane manufacturer’s landing distance data revealed that at a landing weight of 18,400 lbs, the unfactored landing distance for a wet runway was 3,620 ft. The unfactored landing distance for a contaminated runway (standing water) was 4,100 ft. The landing distance available for runway 09 (ungrooved) at TJIG was 5,126 ft. According to the airplane flight manual, landing performance is obtained by:
1) Descend at steady sink rate, corresponding to 3° glide path, at Vref airspeed, down to 50 ft height, then retard power levers to idle. 2) At touch-down, initiate maximum continuous wheel braking. Continue brake application to full stop.