Incident Details
On January 2, 2024, about 1710 central standard time, a Learjet 35A, registration N45MF, was substantially damaged when it overran the runway at San Marcos Regional Airport (HYI), San Marcos, Texas. The aircraft was operating under Title 14 Code of Federal Regulations Part 135 as an air medical transport flight. The two pilots and three passengers were not injured.
Flight History
The flight departed Albuquerque International Sunport Airport (ABQ), Albuquerque, New Mexico, about 1448 mountain standard time, with the captain as the pilot flying. The destination was San Marcos Regional Airport (HYI), Austin, Texas. En route, the crew checked weather using the Garmin 750 system and listened to the airport's Automatic Terminal Information Service (ATIS), which reported wind from 310° at 12 knots, gusts to 24 knots, visibility 9 miles, lightning in the vicinity, and an overcast ceiling at 900 ft.
Approach and Landing
The captain briefed the ILS 13 instrument approach but was informed by the approach controller that they were using the RNAV GPS approach to runway 8 or 35. After hearing a missed approach call, the captain requested the ILS approach to runway 13. After vectors, the captain intercepted the approach course. When checking in with HYI tower, the controller cleared them to land on runway 13. No updated weather was provided, and the crew did not request a wind check.
The captain reported breaking out of clouds about 500 ft above ground with poor visibility. The first officer (FO) called out sighting the runway end identifier lights, which the captain also saw. The captain flew to the runway, touched down, applied brakes, and deployed spoilers. Normal brake pressure produced no deceleration on the wet runway. Increased pressure also failed. The captain called "no brakes" and, seeing an overrun, veered left to avoid the localizer antenna. The aircraft departed the runway end into a grass field. The nose landing gear separated, causing substantial fuselage damage.
The FO reported that during approach, the captain had difficulty maintaining course alignment due to autopilot malfunction. The FO advised hand-flying. Later, the FO called out having the airport and precision approach path indicators in sight at "12 o'clock," stating landing was assured. The captain initially did not see the runway until the FO directed him. The captain then "abruptly chopped power and descended to land at a rapid pace." After touchdown, the FO perceived hydroplaning, and the aircraft ran off the runway. The FO stated a go-around should have been initiated.
Weather Information
At 1600 CST, about 70 minutes before the accident, the automated weather reporting facility recorded wind from 070° at 8 knots, visibility 10 miles, thunderstorms in the vicinity, and light rain. At 1706 CST, wind was from 310° at 12 knots gusting to 24 knots, visibility 9 miles, and an overcast ceiling at 900 ft.
Performance Analysis
Recorded data showed the aircraft had about 15 knots of tailwind and a descent rate exceeding 2,000 ft/min about 10 seconds before landing, reducing to 1,000 ft/min about 3 seconds before touchdown. Touchdown occurred at 124 knots calibrated airspeed about halfway down the 5,601-ft runway, with about 2,600 ft remaining. A performance study calculated the landing distance on a wet/contaminated runway as 4,550 ft. The calculated base landing reference speed was 119 knots, increased for half the gust factor to 125 knots. The manufacturer's flight manual lists a maximum tailwind component of 10 knots, so landing data could not be accurately calculated for the accident flight.
Operational Guidance
The flight's general operations manual defined a stabilized approach as a constant-angle, constant-rate descent profile ending near the touchdown point. It stated the flight should be stabilized by 1,000 ft above touchdown in instrument meteorological conditions, and that an unexpected sustained rate of descent greater than 1,000 fpm should prompt a missed approach.