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Helicopter type has history
[Times photo: Boysell Hosey]
Photos from the crash scene
© St. Petersburg Times, published April 26, 2000
The helicopter used by Bayflite is a model heavily favored by police and medical evacuation programs, despite a disturbing range of mechanical problems that have caused several fatal accidents.
While there is no evidence that any mechanical failure contributed to the crash of the Bayflite helicopter near the Gandy Bridge, investigators will have the service record of the German-built BK117 in mind as they examine the wreckage.
It is a record that includes 20 Federal Aviation airworthiness directives in the past 13 years, orders for mandatory changes to fix flaws that potentially endangered an aircraft.
|[Sources: Eurocopter, Bayfront Medical Center]
While it was not an official "grounding," most of the BK117s worldwide stopped flying for a time last summer when the Federal Aviation Administration and German officials issued emergency directives ordering the replacement of the aircrafts' tension torsion straps.
The straps are bundles of 12,000 tightly wound wires, sheathed in plastic, that hold the main rotor blades on the rotor hub.
The order followed a crash of a hospital-owned BK117 in Houston in July, an accident that also killed three people. The cause was the unraveling of the tension torsion strap.
In August 1998, a medical BK117 in Topeka, Kan., rolled over during an emergency landing required after the engine cowling and door blew off in flight. They hit the main rotor and the tail rotor, throwing them out of balance.
The NTSB found a design flaw in the cowling and door that allowed ground crews to think they were closed and locked when they weren't.
And in May 1997, one person died when a BK117 crashed in New York City. The tail boom, which holds the stabilizing rotor, broke because of fatigue cracking. Again, the FAA issued an emergency directive to inspect and replace defects in the tail.
The BK117's Lycoming engine has been plagued by turbine blade cracking which caused 12 crashed and three fatalities, though none of these accidents involved the BK117.
Nonetheless, its supporters love the helicopter.
"It has been a wonderful machine for us, very reliable," said Russ Spray, chief executive officer of Rocky Mountain Helicopters in Provo, Utah, a large supplier of medical air support services.
The chopper that crashed Tuesday was leased to Bayflite by Rocky Mountain Helicopters, and the pilot was an employee of that company.
Typically, the BK117 weighs 3,840 pounds empty and can carry nearly its own weight in fuel and passengers. It has a continuous cabin, which makes it spacious enough to serve as an air ambulance. And it has a cruising speed of about 160 mph. The manufacturer is Eurocopter Deutschland GmbH.
Spray said that helicopters which operate in salt water environments, such as the Tampa Bay and Houston areas, must be watched carefully for signs of unusual wear from salt in the air.
"This helicopter was washed daily, specifically for that reason," Spray said. "It was maintained meticulously."
Records indicate that is true.
Rocky Mountain Helicopters reported 96 service difficulty problems to the FAA in the past 10 years on the BK117 that carried the tail number N-428MB, the aircraft that crashed Tuesday. The problems included cracked rotors, oil leaks and parts worn or grooved beyond acceptable limits.
Most of the problems equate to an automobile owner taking his car to the shop because it is dripping oil on the garage floor or needs a new fan belt.
The high number of service difficulty problems reported on this BK117 does not necessarily mean it was a troubled aircraft, but could have been because of meticulous record keeping by the owners.