WPR23LA028

Maintenance personnel’s failure to properly align the right brake wheel speed transducer, which rendered the right wheel brake ineffective during landing, and the pilot’s subsequent failure to follow the correct procedures to restore braking action during the landing roll. Contributing to the accident was the pilot’s failure to attain the proper approach and landing speed, which resulted in the airplane landing excessively fast.

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.

Runway 22L was examined for evidence of tire transfer marks. The first identified mark was from the left tire, just left of the runway centerline about 3,300 ft beyond the landing threshold. The mark continued for the remaining length of the runway, gradually veering left until it crossed over the side stripe at taxiway D2. Three distinct wheel marks were then evident as they crossed over a grass area and through taxiway D1. As the marks continued across the taxiway, the left tire track became distinctly darker, continuing beyond the taxiway and into a drainage culvert at the end of the runway. The airplane came to rest in a 6-ft-deep drainage culvert 115 ft beyond the end of runway 22L and about 180 ft left of the runway centerline. The airplane sustained damage to the nose structure and both flaps. The nose and right main landing gear assemblies had partially collapsed into their respective wheel wells. Both the nose wheel and the left wheel and brake assembly had broken away from their respective trunnions, and the nose tire had separated from its rim. There was no evidence of heat discoloration or fluid/oil contamination to the brake pads or disks, all of which displayed normal wear and had friction surface life remaining. There was no evidence of pre-accident brake line damage. The right brake was functionally tested with brake pedal application and was operational; impact damage prevented a similar assessment of the left brake system. The left tire had worn down to between 1/32nd and 1/8th inch tread depth; the right tire appeared relatively new with ¼ inch tread depth remaining. Both tire contact surfaces and side walls exhibited diagonal and longitudinal scratches and scuffs, and no bald spots were evident. The left and right tire pressures were 82 and 86 psi, respectively. On November 3, 2022, about 1915 mountain standard time, an Eclipse Aerospace EA500, N150NE, was substantially damaged when it was involved in an accident in Mesa, Arizona. The pilot and co-pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations part 91 post-maintenance positioning flight. The airplane underwent maintenance at a facility at Henderson Executive Airport (HND), Henderson, Nevada. The maintenance was completed on the day of the accident, and the accident flight was the first flight after the airplane was returned to service. The work performed included the completion of the 24-month/300-hour airframe inspection. Both pilots reported that the brakes appeared to operate during preflight and taxi operations, although due to rain and the airplane not being equipped with windshield wipers, they were traveling relatively slowly during the taxi. The pilot reported that, after an uneventful flight, he and the co-pilot began configuring the airplane for the landing on runway 22L at Falcon Field Airport (KFFZ), Mesa, Arizona. After slowing the airplane and configuring the flaps and landing gear, they were cleared to land. He reported that, as part of the before-landing checklist, he confirmed that the ABS was armed and pressed the ALL INTERRUPT switch to ensure the yaw damper was off. He reported that the airplane touched down in the landing zone just beyond the 1,000 ft markings, but 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; however, 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 towards 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. The airplane was equipped with an integrated diagnostic storage unit (DSU) capable of recording GPS position along with engine and airframe parameters at various intervals. Neither control surface positions (except flaps), nor parameters regarding brake application or brake pressure were recorded. The airplane was not equipped (nor was it required to be equipped) with a flight data recorder or cockpit voice recorder. Brake System Operation The braking system was conventional and consisted of brake master cylinders coupled to the toe brakes and connected via hydraulic lines to brake calipers on each main landing gear. Each caliper contained five hydraulic pistons, which pressed pads against a single disk. There are no brake boosters or other pressure assist systems, and the airplane was not equipped with thrust reversers or spoilers for use in landing. The ABS system consisted of a brake controller (DECU), a left and right brake control module (BCM), and WST fitted to each the wheel axle. Although the airplane was equipped with WOW sensors, they were not interfaced with or used by the braking system. Aircraft ground speed (derived from GPS data) and wheel speed are used by the DECU to determine the difference between wheel speed and aircraft speed. If the DECU senses a skid, it commands the BCM to release brake pressure until the wheel speed matches the GPS speed. Both BCM’s operate independently of each other. Each BCM contains a series of hydraulic valves and a motorized pump. The modules are fitted in the feed line from the master cylinder to the calipers on each side. The WST within the wheel axle has a keyed tab, which engages with a slotted drive adapter mounted inside the hub cap. The ABS system does not activate during normal ground and flight operations and is disabled during low-speed taxi. When the brakes are applied and ground speed is above 15 kts, the BCM activates and provides pressure (charge) to the pressure side of the module through activation of the motorized pump. This motor operation may be heard in the cabin, but does not indicate that the ABS is active. Once the brakes are applied during landing or taxi and a skid is detected, brake pressure is directed back to the master cylinders and released from the brake caliper to the wheel, allowing the tire to regain its speed. The BCM will stop pushing against the master cylinder(s) and brake pressure will be restored once the wheel is accelerated above the skid threshold by runway friction. The cycle will repeat for as long as the pilot applies brake pressure beyond that required to skid the tire. The airplane was equipped with a model of WST that used an adhesive to bond its input shaft to the drive bore. This type of transducer was the subject of Eclipse Aerospace Service Bulletin (SB) 550-32-005, Rev B, which was intended to ensure that the drive shaft was adequately bonded to the bore and could not be pulled out. The bulletin provided instructions for inspection, test, and repair (if necessary) of the transducer. There was no reference in either the airplane’s maintenance logbooks or Eclipse Aerospace service records to indicate the service bulletin had been complied with on the accident airplane. The airplane was used in both Part 91 and Part 135 operations, and compliance with the service bulletin was not mandatory. Later revisions of the WST used a keyed rather than bonded shaft. Damage to the landing gear prevented an accurate assessment of the WOW switch rigging and operation. An ABS indicator is included on the left side of the instrument panel. It provides status of the system (ARMED or INOP). The INOP indicator illuminates when any of the following faults are detected: GPS ground speed is out of range (< 0kts or >500kts) or unavailable, wheel speed is out of range (>200kts) or unavailable, the controller power is low, the controller Built-in-Test (BIT) has failed, or the ABS BCM solenoid control line is in open circuit. There are no annunciators that signal if the ABS is actively operating during a ski