On Dec. 1, 2000, a nonfatal helicopter accident in Rockport, Texas, became the first in a series of events that culminated recently in settlements of lawsuits involving the helicopter’s Rolls-Royce 250 engine. The accident occurred when the engine’s compressor adapter coupling failed, decoupling the compressor from the turbine.
In an accident on June 15, 2003, four people were killed during a tour flight over Volcanoes National Park in Hawaii when the same part failed, generating the lawsuits.
The manufacturer of the coupling, Extex, brought the failure of the Rockport accident coupling to the attention of Rolls-Royce and the FAA, yet according to Extex president Larry Shiembob both paid little attention to the coupling problem until the fatal Hawaii accident.
Extex is a PMA parts manufacturer, making FAA-approved replacement parts under FAR Part 21.303 parts manufacturer approval regulations, which permit non-original equipment manufacturers to replicate aircraft parts. Extex manufactured 660 of the PMA Rolls-Royce 250 couplings before it elected to stop making the part.
Under the PMA regulations, Extex had to prove to the FAA that it duplicated precisely the Rolls-Royce coupling, and in the FAA’s regulatory view there is no difference between the Extex and the Rolls-Royce part. Alcor Engine (now Timken Aerospace Components) made the same PMA coupling.
After the Rockport accident, the failed engine was sent to Dallas Airmotive, a Rolls-Royce-approved service center, for teardown. According to the NTSB, the Extex coupling had fractured, and it was sent to the NTSB Materials Laboratory in Washington, D.C. Examination revealed a fatigue fracture around nearly the entire circumference, originating in an area where the coupling suffered fretting damage. “The examination of the coupling,” the NTSB wrote in its accident report, “revealed fretting on the outer diameter surface where the impeller was press fit onto the adapter.”
The NTSB never consulted with Extex about the failure, Shiembob told AIN. “They never asked us to do anything,” he said. Extex engineers looked for other evidence of coupling problems. “We got a number back for fretting,” he said. Some had 20 hours in service, some as many as 2,000 hours. “Nowhere did we see any problems with metallurgy.
“The fretting started to bother us,” Shiembob said. So in an Aug. 28, 2001, letter to Stuart Mullan, Rolls-Royce president for helicopters, Extex asked to discuss the fretting problem with Rolls-Royce’s engineering department. “As you may be aware,” Shiembob wrote, “we have recalled a limited number of two Extex part numbers. The failure of these parts could result in a turbine decoupling and is obviously of concern to us.”
Shiembob explained that Extex did discuss with the FAA the possibility of an airworthiness directive, according to the letter, “but they see no need for such action because ‘Allison [Rolls-Royce] has said there is no chance for a turbine wheel burst.’ We do not like the idea of an AD but we want to be conservative and err on the side of safety. Consequently, we would like to discuss this issue in more detail with the appropriate R-R engineering people to better understand the comment that was relayed to us.”
The Extex letter said, “We are aware that R-R is investigating a fretting problem on 23039791 [couplings]. We have seen similar fretting on couplings and have forwarded pictures to Dallas Airmotive for inclusion in their report. We would welcome the opportunity to share this information directly with your engineers with the aim of identifying and hopefully resolving a potential problem before it becomes exacerbated.
“I recognize that we are competitors,” Shiembob concluded, “but hopefully we can work together in areas that affect aviation safety.” He asked that Rolls-Royce provide the name of an engineer Extex could work with.
Shiembob said that Extex never got a response. The company sent a copy of the letter to the FAA, which also did not respond.
In April 2002, Extex issued a service bulletin (T-069) calling for removal of a sharp edge on the impeller (a Rolls-Royce part) to which the coupling attaches. The FAA asked Extex to rescind the bulletin because the company had no authority to issue a service bulletin on a Rolls-Royce engine part.
Extex stopped selling the PMA couplings nearly a year before the fatal accident in June 2003. According to Shiembob, sale of the part amounted to hundreds of thousands of dollars in annual revenue.
Rolls-Royce kept selling its couplings, he added, even though its couplings were also failing. “We showed the FAA evidence of failures of Rolls-Royce parts,” he explained. Alcor continued selling its couplings, too. Attorney Richard Genter, who represented plaintiffs in the Hawaii lawsuits, told AIN that Alcor couplings have also failed prematurely.
The only move that Extex didn’t make was to recall every single one of its couplings. Shiembob said that given what he now knows, “We should have [issued a recall] because we got sued.” But Shiembob feels that lacking any input from Rolls-Royce, except for issuance of a service bulletin focused on proper impeller alignment, or any concern on the FAA’s part, Extex did the right thing. “There was no problem found in our workmanship and material,” he said. “We [took] some action. No one else did.”
In February 2004, Airworthiness Directive 2004-26-09 became effective, mandating early removal of Extex and Alcor couplings, and removal of Rolls-Royce couplings no later than March 2012.
According to Shiembob, the FAA gave each manufacturer the opportunity to determine when its couplings ought to be removed from service. “The FAA would have let us keep them in longer,” he said, but Extex chose the shorter interval to get the couplings off the engines. “It has to do with your willingness to accept risk,” he explained. “It’s what level of risk you are willing to subject the customer to.”
The recently settled lawsuits arose from the Volcanoes, Hawaii crash and were filed by family members of the three passengers and the tour company pilot killed in the crash. Rolls-Royce and Extex settled both lawsuits, while the tour company settled the passenger lawsuit. Settlement amounts were not disclosed.
Shiembob believes that the coupling problem is a result of a Rolls-Royce design issue and that this explains why all three manufacturers’ couplings have failed. A question that keeps coming up is whether Rolls-Royce is redesigning the shafting system to prevent fretting of the coupling, which seems to be suspected as causing premature coupling failure. “Why doesn’t the FAA take a leadership role?” he asked.
Rolls-Royce declined to comment about whether its engineers are working on a redesign of the model 250’s shafting system. “The litigation involving this matter has been settled,” a Rolls-Royce spokesman told AIN. “Rolls-Royce did not manufacture the engine part at issue in the case and was not responsible for it. The Federal Aviation Administration holds each part manufacturer responsible for what they sell in the marketplace.”
Meanwhile, a new lawsuit is now in the pre-discovery phase, filed on behalf of pilot Charlie Duke, who was injured and is a paraplegic after the Dec. 9, 2004, crash of an MD 500 helicopter due to failure of the compressor adapter coupling. In this case the coupling was manufactured by Rolls-Royce. This lawsuit’s defendants are Rolls-Royce and engine overhauler Standard Aero, which provided a rental engine to Duke’s employer, Aerial Solutions of Wilmington, N.C., according to Duke’s attorney Genter, who also represented the families in the Hawaii crash.
After the accident, Genter said, Aerial Solutions owner William Cox voluntarily grounded his remaining fleet of five MD 500s and found every engine’s coupling fretted. These, too, were Rolls-Royce couplings. According to the NTSB final report on the accident, “The engine examination revealed the Rolls-Royce-manufactured compressor adapter coupling, which had been installed approximately 414 hours earlier, had disconnected the compressor assembly from the turbine assembly as a result of fatigue cracking initiated by fretting on the pilot diameter.”
While the December 2004 crash accident report was approved and the probable cause issued in less than a year, as of Oct. 27, 2006, the final report from the June 2003 Hawaii accident remains incomplete. AIN asked the NTSB for an explanation of the delay. The investigator-in-charge for that accident told AIN that the report is on her list of projects to complete but could not give an estimate of when it would be done.