Strothman v. Airbus Helicopters

On March 18, 2014, an Airbus Helicopters AS350 B2 with registration number N250FB crashed in Seattle, Wash., killing the pilot and one passenger, and injuring people on the ground. The helicopter was owned by and registered to Helicopters, Inc. and had been contracted by Seattle television station KOMO. The helicopter was leaving the KOMO helipad headed for the Renton Municipal Airport in Renton, Wash. The weather was clear and was not considered a factor in the crash.

The National Transportation Safety Board (NTSB) concluded that the likely cause of the crash was the pilot’s inability to maintain yaw control resulting from a loss of hydraulic pressure to the foot pedals. Yaw is the movement of an aircraft either to the left or right around a vertical axis, in the case of a helicopter around the rotor mast. The pilot controls this movement via hydraulic force by applying pressure on the foot pedals. The NTSB determined that the loss of pressure was likely related to the activation of the hydraulic test button during pre-takeoff checks.

Slack Davis Sanger (SDS) represented the family of Bill Strothman, the award-winning KOMO videographer who was killed in the accident.  During the discovery phase of the litigation, SDS attorneys developed facts and conclusions that are in harmony with the NTSB report, but go significantly beyond the NTSB findings. They include:

Airbus knew of the hydraulics problem.

Airbus was aware, prior to the Seattle 2014 crash, that its AS350 model helicopters were susceptible to inadvertent and premature liftoff while the pilot was completing pre-takeoff hydraulics checks. Airbus accident investigator Michel Martin acknowledged these events in his deposition. He and others at Airbus referred to these occurrences as “the phenomenon.” There was no evidence that Airbus’ investigators had tried to determine why these inadvertent and premature liftoffs were occurring. Airbus had conducted no tests or experiments to understand how the inadvertent liftoffs were associated with a loss of yaw control, what the root cause was, what affirmative steps could be taken to eliminate or mitigate the risk of these events, and how to best communicate corrective actions to prevent future events to AS350 owners, operators, and the pilot community.

Martin’s testimony lead to a reasonable conclusion that Airbus was content to “scapegoat” pilots rather than address the underlying safety issues.

Airbus knew of the risk of a pilot losing yaw control.

Airbus was aware that its AS350 helicopters were susceptible to inadequate hydraulic pressure to the foot pedal (yaw) controls and a loss of control during pre-takeoff hydraulics tests. The assumption was the pilot could compensate with increased foot pressure.  Airbus significantly understated the foot pedal forces pilots needed to use to stop yaw rotation once movement had begun.

The pilot did not anticipate liftoff.

The crash resulted from an unplanned, un-commanded liftoff during pre-takeoff hydraulics checks. This conclusion was soundly supported by the video surveillance of the flight, as well as SDS’s own flight testing and a review of similar occurrences. SDS determined that the most likely scenario was that the pilot had the power lever in a position capable of producing an inadvertent liftoff and likely left the hydraulic test button “engaged” or “on” while performing pre-takeoff checks. When the hydraulic test button is engaged, the hydraulic pressure is degraded, or drops, and only increases once the test button is disengaged or turned “off.”

The two-position test switch was an issue.

SDS further concluded that a significant contributing factor in AS350 B2 and B3 takeoff loss-of-control crashes, including the Seattle crash, was the use of a two-position, push-button switch to control the hydraulic test function. The two-position switch increased the risk that the pilot would not remember to disengage the switch during pre-takeoff checks, leaving the hydraulics in a degraded condition. SDS concluded this crash likely would not have occurred with a single-position switch that would have disengaged immediately after finger pressure was released and would have allowed the hydraulic system to quickly restore proper operating pressure.

This type of two-position switch was faulted in a fatal AS350 B3 crash in Frisco, Colo. in 2015.  An Airworthiness Directive (AD 2015-22-53) was issued following the Colorado crash for the B3 model. It required the replacement of all two-position switches with a single position switch to eliminate the risk that the pilot would not remember to deactivate the two-position switch during the pre-takeoff hydraulic checks.

No warning regarding power lever position pre-takeoff.

Airbus issued changes to the AS350 helicopter flight manual prior to the March 2014 crash specifying that the power lever should be positioned so that power did not exceed 67-70 percent. Stated simply, Airbus intended for pilots to conduct all pre-takeoff checks with the engine power at ground idle. Airbus had previously specified that pilots conduct pre-takeoff checks at flight power. The flight manual changes show that Airbus clearly knew that the higher power setting could cause the helicopter to lift off before takeoff was intended by the pilot.

However, Airbus helicopter owners, operators, and pilots were not told the reason for the reduced power setting change when the flight manual change was distributed. Worse, Airbus inserted no warning into the flight manual to alert pilots that conducting pre-takeoff checks at a power level higher than 67-70 percent could result in an unplanned liftoff and a loss of control with the attendant risks of serious injury or death.

A better design developed by Airbus preceded this crash.

The power lever mechanism of the accident helicopter could be moved easily from ground idle to flight power. Martin was asked why Airbus had not designed a mechanism to ensure that the power lever was in the proper position specified by Airbus until all pre-flight checks had been completed.  When asked why Airbus had not envisioned the simplicity of a detent or gate for the power lever to prevent pilots from inadvertently advancing the power lever to a position beyond ground idle, Martin ultimately acknowledged that Airbus had designed and approved a modification prior to the Seattle crash.

Airbus documents confirmed that the modification featured both ground idle and flight idle detents.  Obviously, this modification would greatly reduce, if not eliminate, the risk of the power lever being mispositioned during pre-takeoff checks. It represents a safer design of the engine power control mechanism, which would have prevented the pilot in the Seattle accident from inadvertently mispositioning the power lever before completing the pre-takeoff checks.  SDS attorneys found no references to the Airbus modification in the NTSB accident docket for this crash. E-mail exchanges obtained between the NTSB investigator in charge and Airbus elicited no response from Airbus alluding to the modification and its relevance to the accident sequence involving N250FB. SDS found no mention of the modification in any communications from Airbus to either the NTSB or the French investigative authorities. Further, SDS contacted several U.S. AS350 B2 operators and none of them recalled being notified of the modification or the service bulletin Airbus supposedly distributed about the modification. At least one operator independently inquired of Airbus and was told that the modification hardware was not available.

Conclusion

The independent findings and conclusions of Slack Davis Sanger were submitted to the NTSB Office of Aviation Safety.

As stated before, Slack Davis Sanger represented the family of Bill Strothman, the award-winning KOMO videographer who was killed in the accident.  In early 2020, the family settled their claims with Airbus for a confidential amount.

 

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