WPR23LA028 · Eclipse Aerospace Inc EA500

The accident was the first flight since the airplane had undergone maintenance, which was completed earlier in the day. After an uneventful flight, the pilots began configuring the airplane for landing on the runway, which had a 0.6% downslope, and according to automated weather reports from the airport a 4-knot tailwind. The pilot-in-command reported that the airplane touched down in the landing zone, just beyond the 1,000-ft markings, but that when he applied brake pressure, the airplane did not decelerate and started to drift to the left.

The co-pilot then began to also apply brake pressure, and with no significant deceleration and the runway end approaching, he called for the pilot to activate the “ALL INTERRUPT” switch, to which the pilot responded that he already had. The pilot stated that he was also applying full right pedal to try to steer the airplane back toward the runway centerline, but the airplane did not respond. It eventually departed the left side of the runway, crossed over the last two taxiways, and came to rest in a drainage culvert, resulting in substantial damage.

Review of ADS-B and recorded onboard data showed that, although the approach path was relatively stable, the airplane’s landing reference and touchdown speeds were about 20 knots above that recommended for its configuration and the runway conditions. Additionally, the data indicated that, at the time of touchdown, the tailwind had likely increased to about 10 knots.

Recorded acceleration data indicated that the airplane touched down about 1,300 ft from the runway threshold, consistent with the pilot’s statement; however, due to lift still being created by the airplane’s wings because of the excessive speed, braking action would have been limited. This was corroborated by the weight on wheels (WOW) sensors, which did not activate until the airplane had progressed 2,490 ft down the runway. At this point, the airplane would have had about 2,760 ft of the runway surface remaining, including the blast pad, along with a 500-ft level dirt runoff area. Although performance calculations indicated this would not have been enough runway surface to stop the airplane, extrapolations based on the deceleration data attained from multiple previous flights showed that, with operational brakes, the airplane may still have been able to stop on the 150-ft blast pad, assuming it had not departed the runway to the side.

Examination of the runway surface revealed indications of predominantly left tire marks starting just left of the runway centerline about 3,300 ft beyond the landing threshold. The marks continued for the remaining length of the runway, gradually veering left until crossing over a taxiway and becoming darker as they approached the drainage culvert.

Examination of the hydraulic brake system did not reveal any evidence of pre-accident failure; however, the right anti-skid brake system (ABS) wheel speed transducer (WST) showed evidence that it had not been properly aligned with the hub cap when the cap was installed following maintenance. Maintenance instructions stated that such a misalignment can damage the brake system and interfere with braking, and subsequent testing revealed that the WST was damaged and not functioning correctly.

Under this condition, the ABS would have assumed the right wheel was locked in a skid and released brake pressure, rendering the right brake inoperative. This would have resulted in the degraded brake performance reported by the pilot, and the airplane’s transition to the left side of the runway during the landing roll as observed.

The airplane’s emergency procedures stated that, should the brakes become ineffective, or the airplane pulls to one side, the pilot should press and hold the ALL INTERRUPT switch until braking action was restored. Activation of this switch with a failed WST would have disabled the ABS system and restored normal braking. Although the pilot stated that he used the switch as the airplane approached the end of the runway, the onboard data appeared to indicate that the last time it was used was during the approach, when the pilot briefly activated it to confirm that the yaw damper was off.

Verbatim NTSB analysis and probable cause from the NTSB dataset