ERA21LA077

The flight crew performed an instrument landing system approach in heavy rain. The published unfactored landing distance, which assumes ideal conditions for airplane speed, flightpath, and maximum braking immediately after touchdown, was about 330 ft shorter than the landing distance available. The factored landing distance, which 1) provides a safety margin and 2) allows for some variance from the ideal conditions, was about 1,360 ft longer than the landing distance available. During the approach, when the airplane was about 50 ft above the runway, the airspeed was about 4 knots higher than the target speed. After touchdown, the pilot(s) began braking within 1-2 seconds; however, the brake pedals did not reach their maximum braking position until about 8 seconds after touchdown. The brake pedals remained in the maximum position for 3 seconds before the parking/emergency brake was applied. The parking brake activation, which is not protected by the anti-skid system, resulted in the locking of both main landing gear wheelsets, reducing braking performance significantly. As a consequence of the wheels locking, the anti-skid system was deactivated, as designed. The airplane departed the end of the runway at a speed of about 60 knots and sustained substantial damage.

On December 16, 2020, at 1419 eastern standard time, an Embraer EMB-500, N661EP, was substantially damaged when it overran the runway during landing at Jacksonville Executive Airport at Craig (CRG), Jacksonville, Florida. The pilot, copilot, and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 corporate flight. According to the pilot, he performed an instrument landing system approach to runway 32 at CRG. He landed in the touchdown zone at a speed of 100 knots. After the airplane slowed to 80 knots, he applied full manual braking, but the airplane “was not reducing speed for stop as expected.” As the airplane approached the departure end of the runway, he attempted to apply the emergency brake three times, with no response. As the airplane rolled into the grass, he attempted to activate the emergency brake again, with no response. He applied left rudder to avoid colliding with the approach lights. As the airplane came to a stop the right wing contacted the ground. The airplane sustained substantial damage to the right wing, a portion of the right main landing gear punctured the right wing near its root. The automated terminal information system (ATIS) information Kilo, issued at 1353 was tuned in on the airplane’s radio and recorded on the cockpit voice recorder at about 1355. The weather information included wind from 100° at 4 knots, visibility of ¾ mile, thunderstorms in the vicinity with heavy rains and mist, few clouds at 300 ft and an overcast layer at 4,000 ft. The 1418 weather conditions reported at CRG included wind from 250° at 3 knots, visibility ¼ statute mile, heavy rain in thunderstorms, and mist, and a broken cloud ceiling at 300 ft above ground level (AGL). The remarks section of the weather observation included a note indicating the previous 1-hour precipitation water equivalent was 0.32 inches. According to the airplane Quick Reference Handbook (QRH), for a gross weight of 9,500 lbs. (the appropriate next higher value in the landing data from the pilot’s reported value of 9,331 lbs.), the landing reference speed was 104 knots, and the unfactored wet runway landing distance required was 3,679 ft. Unfactored landing distances are not adjusted (or ‘factored’) for any safety margin additives and assume that several criteria are met during landing. According to the airplane flight manual (AFM) these criteria are): · Steady three degree angle approach at VREF in landing configuration · VREF airspeed maintained at runway threshold · Idle thrust established at runway threshold · Attitude maintained until MLG touchdown · Maximum brake applied immediately after MLG touchdown · Antiskid system operative The AFM further advises “If these performance techniques are not strictly used for a typical landing made during normal operations, the distances may be longer.” Additionally, the QRH lists factored landing distances, which are intended to provide a safety margin to the landingdistance required, as well as account for other variables such as the effects of temperature, increased approach speed, and reduced wheel braking. The factored wet runway landing distance in this case was 5,368 ft. Runway 32 at CRG is 4,008 x 100 ft with an asphalt surface that was not grooved. A review of the cockpit voice recorder revealed that the crew performed a standard approach briefing at 1358, shortly after tuning in the ATIS. At 1411, air traffic control (ATC) asked the crew if they wanted to try the approach, or instead hold due to heavy precipitation over the airfield. The crew advised that they would like to try the approach, and ATC cleared them for the ILS to runway 32. At 1413 the flight was cleared to land on runway 32, and the control tower advised that there was a broken cloud layer at 300 ft. The crew continued the approach and touched down at 1417:29. A review of data from the flight data recorder revealed that when the airplane was on approach about 50 ft above ground level, the airspeed was about 108 knots (groundspeed 107 kts). The touchdown occurred about 1,250 ft from the threshold of runway 32 at an airspeed (and groundspeed) of 100 knots. The brake pedals began to move 1-2 seconds after touchdown and increased until they reached 100 percent travel about 8 seconds after touchdown, at which time the airspeed and was 88 knots. About 11 seconds after touchdown at an airspeed of 81 knots, the parking brake was applied for 9 seconds, and the main landing gear wheels stopped rotating. After the parking brake was released, the right main landing gear began to rotate again, the brake pedal position reduced before increasing again, asymmetrically, with more pressure on the left pedal than the right. The airplane departed the end of runway within about 1 second of the parking brake release, at an airspeed of about 60 knots. The airplane was not equipped with thrust reversers or ground spoilers. Examination and testing of the brake control unit (BCU) was performed at the manufacturer’s facility and overseen remotely by NTSB investigators. A review of the data captured by the unit’s non-volatile memory revealed that one fault that pertained to the accident landing was recorded, “Lt whl not turning” (left main landing gear wheel not turning). This fault would cause the BCU to send an “Anti-Skid” fault annunciation to a display in the cockpit. This annunciation was captured by the flight data recorder and occurred just after the application of the emergency brake and locking of both main landing gear wheelsets, which disables the anti-skid system by design. Testing of the BCU revealed no anomalies that would have precluded normal operation.