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The NTSB has reversed its findings over a deadly 2018 Citation CJ2 crash, granting winglet maker Tamarack's petition and stating that the available evidence does not sufficiently conclude that the ATLAS system caused the crash.
The NTSB updated its docket for the Nov. 30, 2018 crash in Memphis, Indiana that killed three people, including Wayne Estopinal, founder of Louisville City FC professional soccer club, now including a response to Tamarack's petition for reconsideration from Feb. 26. The Citation was fitted with winglet modifications by Tamarack Aerospace Group, consisting of aluminum wing extension, composite winglets and a proprietary load alleviation system known as an Active Technology Load Alleviation System (ATLAS). The initial final report noted six pins in the modified wingtip extensions were curled and two pins were not aligned, which could have led to power disruption and triggered the rollout, but the report concluded that investigators could not determine when the pins had been bent. Family and representatives of the three victims sued Tamarack for its winglet system not having adequate warning or instructions and likely resulting in the disruption of power.RELATED STORIES:Tamarack settles with families of victims in 2018 deadly Citation CJ2 crashTamarack Aerospace Disputes NTSB Findings in Citation Jet Accident
The NTSB report found that an electrical failure in the system likely caused one of the control surfaces to deploy separately, which caused an uncommanded roll. The pilot was not aware of any supplementary procedures, according to the findings. Further, the procedures did not explain the significance of the system failure nor did they address the failure in all flight conditions. Nearly six months after the crash, the FAA grounded all Cessna planes equipped with ATLAS winglets, which lifted in the summer of 2019 after Tamarack found a fix to improve the safety and reliability. After the report, Tamarack sent a petition to the NTSB to reconsider its findings, claiming they were inconsistent with the degree and timing of the TACS deflection and the evidence described, which could be linked with the force of impact, not necessarily indicating the position in flight.
The NTSB issued its final report in May 2021 and this was challenged by Tamarack in November 2021. The settlement with Tamarack with the families and representatives of the victims was settled in February 2023. Now, nearly three years after the final report was issued and a petition filed, the NTSB has reversed its findings.
In a rare occurrence, the NTSB granted the petition. The response notes that Tamarack said the NTSB's final report contained "key erroneous findings" and "factual errors" and that the "cumulative effect of the errors is to clearly demonstrate that there is no evidence that Tamarack's ATLAS was in any way responsible for the November 30, 2018 accident," and the NTSB responded. The agency re-reviewed many of the photographs of the left TACS control linkage assemblies, including the witness mark on the bellcrank and hinge fitting. The NTSB said the reexamination confirmed that the witness mark on the bellcrank was consistent with the contact with the trailing-edge-up mechanical stop at 21 degrees, which was beyond the 20-degree soft-stop limit of the left TCU.
"Further, damage to the hinge fitting could only occur with significant travel beyond the TCU and bellcrank mechanical stop limits," the NTSB response said.
Tamarack asserted that the damage to the hinge fitting would only be possible if the overdeflection of the tACS was about 55 degrees, which is almost three times the 20-degree trailing-edge-up limit. The NTSB could not confirm with assertation but recognized that the TCU would not have been able to move the TACS to that position during normal operation.
The NTSB said that in May 2023 it compared the wear marks from a normal operation on an in-service actuator with those from the accident left TCU ran guide housing and it showed that the witness remarks on the accident TCU were different than normal wear marks. The witness marks on the bellcrank and hinge were outside of the normal range of travel and likely not consistent with the TACS position at the time of the initial impact, therefore there was insufficient evidence to assert Tamarack's assertion that the actuator was in an intermediate position at the time of the initial impact. The NTSB did agree that there was insufficient evidence to conclude that the left actuator was in the extended position at the time of the impact and that the ATLAS caused the left rolling movement and has revised its report.
The NTSB discussed the bent pins, noting that the additional information from impact load testing and dimensional analysis supported the possibility that the pins had bent during the impact. The agency did not that the additional information did not eliminate the possibility that the pins were bent during manufacture or maintenance since the status of the pins before the accident is unknown.
The original report noted a similar roll event involving another plane equipped with ATLAS. Tamarack said this reference to the UK event was misleading since the accident involved an ATLAS screw that had not been removed and replaced in accordance with a Service Bulletin. The NTSB opted to remove the statement from the report that said five previous uncommanded roll events had occurred on an ATLAS-equipped plane to ensure the analysis did not inadvertently imply that the cause of the uncommanded roll in the UK event was a factor in the 2018 crash or that a screw assembly issue affected the Citation.See the docket and revised reports here
The initial final report said the probable cause was the asymmetric deployment of the left-wing load alleviation system for undetermined reasons, resulting in an inflight upset from which the pilot was unable to recover. This has been altered to read, "the pilot's inability to regain airplane control after a left roll that began for reasons that could not be determined based on the available evidence."
In the NTSB's response, it said the petition for reconsideration was granted, "in part because the available evidence for this accident does not sufficiently show that the ATLAS was the cause of the in-flight upset from which the pilot was unable to recover. In addition, the factual and analysis sections of the report and the findings have been revised to reflect the information presented in the petition response sections addressing witness marks, TCU bent pins, and the UK uncommanded roll event."
Tamarack was hit with financial difficulty after the crash, according to the AOPA. The company filed for bankruptcy protection soon after the FAA grounding, continuing to produce and install active winglets and emerging from bankruptcy in 2021. Tamarack President Jacob Klinginsmith told the AOPA in a phone interview on Thursday that they were pleased with how the process worked and that they have, "high praise for the NTSB for looking at this objectively from an engineering perspective to make sure all the facts are correct."