The investigation into last year’s fatal crash of a 1965 Carson Helicopter Sikorsky S-61N is beginning to take on the tenor of a high-stakes suspense novel. Although an official probable cause has yet to be issued, the reams of documents released to date by the NTSB, and a preemptory rebuttal from Carson and its lawyers contained in those documents, are rife with suggestions of document irregularities, post-crash evidence tampering, bureaucratic intransigence and cover-ups.
The 35,000-hour helicopter crashed on August 5 last year while lifting off from Iron #44, a 6,000-foot-msl helispot on the Buckhorn Fire in the Shasta-Trinity National Forest, 15 miles northwest of Junction City, Calif. The helicopter was en route to the firebase at Weaverville, Calif. The NTSB preliminary report states that the helicopter experienced a loss of power to the main rotor during takeoff initial climb, and subsequently crashed into trees and terrain at 7:41 p.m. local time.
Witnesses on the ground said the helicopter labored to gain altitude before sinking and clipping trees. The helicopter came to rest on its side and was immediately engulfed in flames. The wreckage burned until the next morning. Nine of the 13 aboard were killed, including the PIC and a U.S. Forest Service (USFS) check pilot. The SIC and three firefighters survived. Carson had acquired the helicopter from Canada’s CHC in 2007. The family of one of the dead firefighters filed the first lawsuit two weeks later.
In the weeks following the crash, investigators discovered that the records for the six other Carson S-61s under contract to the USFS understated their weights and that those erroneous lighter weights were reported on forms used to obtain the contracts. The USFS subsequently suspended its contracts with Carson in October 2008 and terminated them a month later “for cause.”
Carson acknowledged that the helicopters exceeded the weights submitted to the USFS during the bidding process due to an inadvertent error, but said even if they were heavier, they still fell within USFS guidelines. It also claimed the firm the USFS hired to reweigh the helicopters used improper procedures and the NTSB effectively counted the weight of added components, such as seats and a sideview Plexiglas bubble, twice, and asserted that both errors combined exaggerated the overweight condition by more than 800 pounds.
The USFS also alleges that Carson’s flight manuals contained improperly modified performance charts that could lead pilots to believe the helicopters had more available power than they actually did. For a time it was thought that a disgruntled former employee, who had threatened various forms of retribution, could have been responsible for propagating the mislabeled chart in the flight manual. Carson’s attorneys discount this theory as speculative.
Carson denies that either error contributed to the crash and points out that the crash helicopter made three successful runs from the helispot with heavier loads and in significantly higher temperatures immediately before the crash.
Alleged Evidence Tampering
Rather, Carson wants the NTSB to focus on the role a contaminated pressure release valve in the fuel control unit played as the cause of the engine power loss that contributed to the crash. In a July 10, 2009 letter to NTSB Office of Aviation Safety director Thomas Haueter, Carson president Frank Carson wrote to complain about “possible tampering and destruction of evidence relating to the fuel-control units (FCUs) from the accident aircraft” and “the disregard of substantive factual information related to the fuel control units and contamination that was found that would have resulted in a loss of engine power.” Carson warned, “These issues are critical not only to understanding” what caused the crash but also to preventing “a similar event” if “corrective actions are not immediately forthcoming.”
Carson points the finger of blame squarely at Columbia Helicopters, the company that serviced the fuel-control units. Columbia operates the only authorized commercial overhaul facility for FCUs for the engines on the accident helicopter, the GE CT58. Carson wrote, “The post-crash conduct of Columbia, which may involve tampering with and destruction of evidence related to these units, must be fully investigated, not simply handled ‘internally’ by the NTSB.”
The engines and the FCUs were sent to Columbia for post-crash analysis on August 13-14 and a preliminary examination suggested a loss of power in one engine. The FCUs remained in Columbia’s sole possession until shipped to the NTSB on August 18. During an inspection of the FCUs at the NTSB August 28, Carson alleged that the FCUs had been placed in boxes rather than the original evidence bags and that key components present during the initial inspection were missing. Carson also alleges that additional parts, not present during the initial inspection, were added and that other parts had been switched between the two FCUs.
The NTSB Materials Lab report on the components revealed a significant amount of scoring of, and contaminants in, the pressure regulating valve (PRV) of both FCUs, particularly the number-two unit. Contaminants in an FCU’s PRV can cause it to stick and the engine it serves to lose power. A Transport Canada investigation of a Hayes Helicopter S-61N crash in 2002 faulted a sticking PRV as a contributor to that crash.
The NTSB investigated Carson’s allegations regarding possible tampering with the FCUs and determined “it cannot be definitively established whether the smaller parts reported as missing were actually present on August 15  at Columbia Helicopters’ facility.” It concluded, “the condition upon receipt of the main fuel control units and condition of received parts were not in a significant different condition from that which existed at the conclusion of the teardown on Aug. 15, 2008.”
On September 15 this year the NTSB opened the public docket on the investigation, including the Operations Group chairman’s factual report; however, a final probable cause has yet to be issued. Columbia and Carson are co-defendants in wrongful-death suits being brought by families of seven of the crash victims. Columbia is also suing Carson for indemnity to recover legal fees accrued while defendant to third-party lawsuits in California, Connecticut and Oregon.