19981027034949A

On October 27, 1998, at 1456 eastern standard time, a Learjet 45 registered in the experimental category, N454LJ, was destroyed after a loss of control during landing roll and collision with a ground vehicle at the NASA Wallops Flight Facility (wal), Wallops Island, Virginia. The certificated airline transport pilot (ATP) was not injured. The ATP rated copilot and the Flight test engineer received minor injuries. There were no injuries on the ground. Visual meteorological conditions prevailed for the local test Flight that originated at wal, at 1449. No Flight plan had been filed for the Flight conducted under 14 CFR part 91. According to the pilot, the airplane and crew were involved in Flight test certification for a new nose wheel tire. For the test, the airplane was passed through a "pool" or "trough" of water on the runway at different speeds. The data was collected using video, still photography, and on-board diagnostic equipment. The airplane was loaded, configured, and operated inside and outside the weight-and-balance and performance envelopes of a Learjet 45 registered in the normal category. The pool was 30 feet wide, 200 feet long, formed with flexible ruber dikes, and contained 3/4 of an inch of standing water. Beginning the day prior to the accident, the crew had successfully completed 10 passes through the test pool. In a written statement, the pilot described the Flight prior to the accident. He further described adjustments made on final approach to reach the intended touchdown point; 1,000 feet beyond the approach end of runway 22. The pilot said: "initial alignment during rollout was uneventful. (Thrust reversers) were selected to, and maintained at, idle reverse until a point where I thought we needed to select maximum reverse to get full reverse thrust and enter the pool at target speed of 80 knots. As soon as the (thrust reversers) reached full reverse, the aircraft pulled to the right. Left rudder was input to realign the fuselage. "At pool arrival, the aircraft had almost re-aligned and I left left rudder and nose wheel steering in to attempt to drift the aircraft left a couple of feet, since it appeared the right mains were on the edge of the pool. The aircraft began a fishtail to the right (nose left) and I immediately input right rudder and stowed the (thrust reversers). I believe this arrested the fishtail, but a runway (left) side departure was evident." The pilot described the maneuvers necessary to avoid striking test participants, vehicles, and equipment along the left side of the runway after the airplane departed the pool. However, he was unable to prevent the right wing from striking an unmanned pickup truck parked on an intersecting runway. After collision with the truck, the wings separated from the airplane, the fuselage rolled inverted, and spilled fuel ignited. In a written statement, the co-pilot said: "the aircraft entered the trough with maximum thrust reversers selected. (I) gave a "mark" to specify trough entry. My impression was that the aircraft had a slight right drift at water entry. Immediately after entering the trough, the aircraft yawed left. While this yaw was apparent, (I) felt the aircraft was controllable. The aircraft corrected back to the right slightly then yawed hard left. At this point, (I) felt the aircraft was in an uncontrollable hydroplaning condition and that the aircraft was going to depart the runway." A review of videotape revealed that nose-left steering and left rudder inputs were evident just prior to pool entry. The nose wheel and rudder remained deflected as the airplane entered the pool. The airplane continued to yaw left as the tail "fishtailed" to the right. The airplane departed the left side of the runway, struck the vehicle, and came to rest inverted and on fire. The wreckage was examined at the scene on October 28, 1998, and all major components were accounted for at the scene. Examination of the runway and the test pool revealed the tire tracks from the accident run were still visible. The tire tracks revealed that upon pool entry, the left main gear and the nose gear tires tracked through the pool, while the right main gear tires tracked outside the pool. When questioned about the airworthiness of the airplane, both pilots stated there were no deficiencies with the airplane or its performance. The pilots further stated the emergency and crew coordination training each received from the united states military, NASA, and Learjet, along with the coordinated efforts of the crew, resulted in a successful egress from the burning wreckage. (.4)the Learjet was participating in water ingestion tests, which required multiple landing rolls through a diked pool on the runway. On one of the landing rolls, the airplane's left main landing gear and nose landing gear tracked through the pool, while the right main landing gear tracked outside the pool. The airplane veered to the left, departed the left side of the runway, and struck a pickup truck parked adjacent to the runway. The airplane came to rest inverted and on fire. Formal hazard identification and risk management procedures were not employed and no alignment cues were in place on the runway to facilitate pool entry alignment. Further, the accident truck, other vehicles, heavy equipment, and personnel were placed hundreds of feet inside the FAA recommended runway-safe and object-free areas during the test. (-23)IAD99FA008