PHOENIX - A medical-helicopter crash in Tucson that killed three people likely was caused by a mechanic's mistake and the lack of an inspection and testing of his work, according to a recently released federal report.
The report by the National Transportation Safety Board, released last week, said the AS350 B3 Eurocopter had undergone maintenance over several days before the July 28, 2010, crash .
The report, the results of which were first reported by The Arizona Daily Star on Tuesday, says a contract mechanic likely only finger-tightened bolts, instead of using a torque wrench, when he was putting the engine back together. Maintenance personnel did not adequately inspect his work and the pilot who performed a post-maintenance check didn't follow the manufacturer's procedures, the report said.
The LifeNet helicopter left Marana and was en route to its home base in Douglas when it fell 600 feet in eight seconds, crashed into a backyard fence and burst into flames about six minutes after leaving the ground.
The crash was in a densely populated area of Tucson but no one on the ground was injured.
Killed were pilot Alexander Kelley, 61, flight nurse Parker Summons, 41, both of Tucson, and paramedic Brenda French, 28, of Safford.
The report does not specify whether Kelley was the pilot who improperly performed the post-maintenance check, or whether a different pilot performed it.
The check was supposed to take 30 to 45 minutes, but the pilot's check took just seven and a half minutes, the report said.
If a full check was done, the report said the problem that caused the crash likely would have been detected.
In addition, the contract mechanic who put the helicopter's engine back together "was serving as both mechanic and inspector, and he inspected his own work."
Craig Yale, vice president of corporate development for LifeNet Arizona's parent company -- Colorado-based Air Methods -- said Tuesday that LifeNet made important changes not long after the crash.
Those changes include requiring the company's own staff to inspect the work of any contracted mechanics, and requiring pilots to do full-length maintenance checks.
"This (crash) was several things compounded and some very good people lost their lives," Yale said. "We're going to continue to do everything we can to make sure this doesn't happen again."
He said before the Tucson crash, LifeNet assumed that third-party companies would double-check their own work, but that didn't happen.
"Our lesson learned from this is double check everything, even when the work is done by an outside contractor," he said.
The NTSB report also says that Kelley, who had 14,000 hours of flight experience, had no training flights for nearly a year before the crash.
Although Kelley was not required to undergo additional training during that time, the report said it "may have negatively impacted the pilot's ability to maintain proficiency."
"However, because the engine failed suddenly at low altitude over a congested area, more recent training may not have changed the outcome," the report said.
The report said Kelley likely was trying to get the chopper to an open intersection about 300 feet away from the crash site, but was unable to reach it because he had to maneuver over a row of 40-foot power lines -- a maneuver that depleted the engine and caused the helicopter's near-vertical plummet.
Nonscheduled 14 CFR Part 91: General Aviation
Accident occurred Wednesday, July 28, 2010 in Tucson, AZ
Probable Cause Approval Date: 05/03/2012
Aircraft: AMERICAN EUROCOPTER LLC AS 350 B3, registration: N509AM
Injuries: 3 Fatal.
An open roadway intersection was located about 300 feet beyond the accident site, in line with the helicopter’s flight path. It is likely that the pilot was attempting to make an autorotative approach to the open area; however, he was unable to reach it because he had to maneuver the helicopter over a row of 40-foot-tall power lines that crossed the helicopter’s flight path near the accident site. This maneuver depleted the rotor rpm, which, as reported by the witnesses, caused the helicopter’s descent to become near vertical before it impacted the concrete wall, which was across the street from the power lines.
The pilot had no training flights during the 317 days since his most recent 14 Code of Federal Regulations Part 135 check flight. The lack of recent autorotation training/practice, although not required, may have negatively impacted the pilot’s ability to maintain proficiency in engine failure emergency procedures and autorotations. However, because the engine failed suddenly at low altitude over a congested area, more recent training may not have changed the outcome.
External examination of the engine at the accident site revealed that the fuel inlet union that connected to the fuel injection manifold and provided fuel from the hyrdomechanical unit to the combustion section had become detached from the boss on the compressor case. The two attachment bolts and associated nuts were not present on the union flange nor were they located within the helicopter wreckage debris. Separation of the fuel inlet union from the fuel injection manifold interrupted the supply of fuel to the engine and resulted in a loss of engine power. Postaccident engine runs performed with an exemplar engine showed that, with loose attachment bolts and nuts, the union initially remained installed and fuel would not immediately leak. As the engine continued to operate, the loose nuts would progressively unscrew themselves from the bolts. With the bolts removed, the union would ultimately eject from the boss, and the engine would lose power due to fuel starvation.
The helicopter's engine had undergone maintenance over several days preceding the accident. The maintenance was related to fuel coking of the fuel injection manifold. The operator's mechanics removed the engine from the helicopter and separated the modules. Another engine with the identical problem was also undergoing the same maintenance procedure at the time. A repair station technician was contracted to complete the maintenance on both engines. The operator's mechanics and the repair station technician disassembled the accident engine and set it aside. They then performed the required maintenance on the other engine, before returning to complete the work on the accident engine. While working on the accident engine, the repair station technician disassembled module 3, replaced the fuel injection manifold, and then reassembled the engine. This work required that the fuel inlet union be removed and reinstalled. It is likely that the technician did not tighten the bolts and nuts securing the union with a torque wrench and only finger tightened them. The engine was reinstalled into the helicopter by the operator's maintenance personnel. The repair station technician was serving as both mechanic and inspector, and he inspected his own work. There were no procedures established by the operator or the repair station to ensure that the work performed by the technician was independently inspected. Further, although 14 Code of Federal Regulations 135.429, applicable to Part 135 operators using aircraft with 10 or more passenger seats, states, in part, “No person may perform a required inspection if that person performed the item of work required to be inspected,” there is no equivalent requirement for aircraft, such as the accident helicopter, with 9 or fewer passenger seats. An independent inspection of the work performed by the technician may have detected the improperly installed fuel inlet union.
In 2008, the Federal Aviation Administration (FAA) principal maintenance inspector (PMI) for the repair station removed the repair station's authorization to perform work at locations other than its primary fixed location. However, the Repair Station Manual was not updated to reflect this change, and the PMI did not follow up on the change, nor did he log the change in the FAA’s tracking system. The PMI was unaware that, in the year before the accident, the repair station had performed work for the operator at locations other than the repair station’s primary fixed location at least 19 times. The FAA's inadequate oversight of the repair station allowed the repair station to routinely perform maintenance at locations other than its primary fixed location even though this practice was not authorized.
The duty pilot performed a 7.5-minute abbreviated post maintenance check flight the evening before the accident. A full maintenance check flight conducted in accordance with the manufacturer's flight manual should, under normal conditions, take 30 to 45 minutes to complete. Had a full check flight been performed, it is likely that the union would have detached from the boss during the check flight. Because the helicopter would not have been operating near its maximum gross weight and the check flight would have been conducted over an open area, the pilot would have had greater opportunities for a successful autorotative landing.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The repair station technician did not properly install the fuel inlet union during reassembly of the engine; the operator’s maintenance personnel did not adequately inspect the technician's work; and the pilot who performed the post maintenance check flight did not follow the helicopter manufacturer's procedures. Also causal were the lack of requirements by the Federal Aviation Administration, the operator, and the repair station for an independent inspection of the work performed by the technician. A contributing factor was the inadequate oversight of the repair station by the Federal Aviation Administration, which resulted in the repair station performing recurring maintenance at the operator’s facilities without authorization.