Tamarack Aerospace Group is challenging the National Transportation Safety Board’s (NTSB) determination of a 2018 fatal accident involving a Cessna CitationJet CJ2+, calling on the NTSB to reopen the investigation in order to “reconsider and modify its findings” that Tamarack’s winglet design contributed to the accident.
Tamarack petitioned the NTSB on January 3, noting the agency made “erroneous findings that are unsupported by the factual record, inconsistent with engineering principles or proven to be physically impossible.”
Active Winglets At Issue
The aircraft was equipped with Tamarack active winglets consisting of the Tamarack Aerospace Group’s active technology load alleviation system (ATLAS), which operated independently of other airplane systems.
The system included the installation of Tamarack active camber surfaces (TACS), which are aerodynamic control surfaces mounted on the wing extensions that either hold their position in trail with the wing or symmetrically deploy trailing edge up or trailing edge down to alleviate structural loads. The TACS are actuated by the TACS control units (TCUs) and are not controlled by the pilot.
What Happened
Shortly after takeoff in instrument meteorological conditions, the pilot activated the autopilot during the initial climb to the assigned altitude. A few seconds later, the aircraft entered an uncommanded roll. At 30 degrees of bank, the autopilot uncoupled and the aircraft continued to roll while simultaneously entering a dive the pilot could not recover from.
Tamarack contends the active winglets installed on the CJ2+ did not cause or contribute to the accident and demonstrates that the autopilot disconnected for unknown reasons prior to reaching its internal disconnect criteria.
The Details
According to the NTSB report, on November 30, 2018, the Citation 525A with one pilot and two passengers took off from Clark Regional Airport (KJVY), Jeffersonville, Indiana, en route to Chicago Midway International Airport (KMDW), in Chicago, Illinois.
IMC prevailed, and the pilot was on an IFR flight plan. According to data provided by the aircraft’s automatic dependent surveillance-broadcast (ADS-B), the airplane climbed to an altitude of about 1,400 feet then turned left to the assigned fix and continued to climb.
The pilot contacted air traffic control and was assigned 10,000 feet. The pilot activated the autopilot and selected the assigned altitude. As the aircraft passed through 3,000 feet, it began rolling to the left at a rate of approximately 5 degrees per second.
After the onset of the roll, the airplane maintained airspeed of about 240 knots and continued to climb for 12 seconds. When the airplane reached about 30 degrees of left bank, the autopilot disconnected accompanied by an aural alert. The autopilot was designed to automatically disconnect at 45 degrees of bank.
One second later, the cockpit voice recorder (CVR) recorded a statement by the pilot consistent with surprise, likely made in response to the autopilot disconnect or the bank angle. The NTSB surmised that based on the pilot’s reaction, the roll to the left was uncommanded.
Both the climb and the bank angle continued until an altitude of about 6,100 feet, then the aircraft entered a rapid descent and the bank angle increased to near 90 degrees.
The CVR picked up the airplane’s enhanced ground proximity warning system, announcing eight “bank angle” annunciations and one “overspeed warning” annunciation.
“The NTSB needs to take a step back and get back to basics.”
John Goglia, a member of the NTSB from 1995 to 2004
About 23 seconds after the autopilot disconnected, the pilot made a mayday call, shouting that he was “…in an emergency descent unable to gain control of the aircraft.” At the final ADS-B data point, the airplane was at an altitude of about 1,000 feet, at an airspeed of about 380 knots, and in a 53-degree left bank. The airplane impacted terrain in a wooded area about 8.5 miles northwest of the departure airport. The total time from the beginning of the uncommanded roll to impact was about 35 seconds.
In the final report, the NTSB cited the probable cause of the accident as “the asymmetric deployment of the left wing load alleviation system for undetermined reasons, which resulted in an in-flight upset from which the pilot was not able to recover.”
Tamarack takes issue with the NSTB’s findings, saying in particular that the NTSB suggested that the devices moved in a manner that is physically impossible, and the witness marks found on the wreckage were caused by impact damage.
Tamarack presented this information to the NTSB. However, the manufacturer alleges that the board did not consider the information, instead releasing the probable cause of the accident four days later.
The petition also questions the NTSB’s inability to determine the experience level of the pilot in command. The pilot had an airline transport pilot certificate and a Cessna 525 type rating, but as the pilot’s logbook was not located, the pilot’s experience could not be determined.
By failing to locate his logbook, Tamarack suggests that the NTSB did not follow its own published recommended procedures used on all aircraft accidents.
John Goglia, a member of the NTSB from 1995 to 2004, is critical of the NTSB’s handling on the investigation, in particular the refusal of the NTSB to accept engineering information from Tamarack prior to publishing the probable cause, calling it “a lack of attention to detail.”
“The NTSB needs to take a step back and get back to basics,” he said, adding that NTSB appeared not to follow agency procedures during the nearly three-year investigation.
Goglia referred to some of the NTSB’s questions as “shallow,” not just in this investigation but in others, saying that because of this, the agency often does not get all the information needed.
