Similar crashes, different causes
| • | Scrutiny of 1st crash moves to lab analysis |
By Jan TenBruggencate
Advertiser Kaua'i Bureau
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LIHU'E, Kaua'i — What happened to pilot Donald Torres and his passengers aboard a Hughes 500 Inter-Island Helicopter tour flight Sunday has happened at least 16 other times to pilots and passengers of similar craft in the past 10 years.
There is the loud bang as pieces fly off the back of the copter. There is the sudden vibration in the controls. The helicopter starts to spin, and the pilot struggles to bring the crippled aircraft to the ground, as Donald Torres did at Ha'ena on Sunday.
In his case, the rotors clipped a tree, and the helicopter came down on its side, killing one passenger and injuring three others seriously.
In most such cases, if a pilot has a flat, clear landing spot, he or she has been able to bring the helicopter down without injury. If not, serious injuries or fatalities have resulted.
Sometimes, passengers have seen pieces of the tail section fly by the helicopter cockpit as the pilot struggled to bring it down.
In a 1997 case in Miloli'i on the Big Island, passengers saw chunks of the tail rotor spin by the cockpit before the helicopter crashed. Three people were seriously injured.
In a 1998 case in Oso, Wash., passengers saw the rear gearbox fly by the left side of the helicopter. That helicopter got down without injuries.
But while the effects of a catastrophic tail rotor failure are similar, the causes of the kind of failure that brought down Torres' helicopter N911VC have been all over the map.
An Advertiser review of crash reports for this model of aircraft found that of the 16 crashes in the past decade due to tail rotor failures, the cause of some has never been identified, but others were caused by such things as pieces of clothing blowing out of the cockpit into the tail rotor, cargo hitting the rotor, metal fatigue in critical parts, improper assembly, and even such things as improper disassembly and reinstallation of damaged parts.
NO BIRD COLLISIONS
None of the crashes of the helicopters alternatively known as Hughes or McDonnell Douglas 369s or 500s involved in-air collisions with birds — one of the causes suggested as possible in the Ha'ena crash.
National Transportation Safety Board air safety investigator Jim Silliman, who is investigating the Sunday crash, said some of those earlier crashes have led to Federal Aviation Administration directives to improve maintenance procedures. And he said he would be reviewing Inter-Island Helicopters' maintenance records to ensure they have complied with FAA Airworthiness Directives.
Could a bird have flown into the tail rotor of Torres' aircraft and caused the rotor and part of the gear box to break off, as Inter-Island vice president Ken D'Attilio suggested? It seems possible, said NTSB investigator Brian Rayner, who is the lead investigator in Thursday's Kaua'i helicopter crash of a Heli USA A-Star.
But in the 16 accidents reviewed by The Advertiser, that hasn't happened. There is no common thread among the causes of the accidents. In fact, the only theme is the result of a rotor failure: the loud noise, the vibration, the helicopter going into a spin as it loses tail control.
Two crashes were believed caused by things flying out off the cockpit and hitting the spinning rotors. One wreck of a helicopter flying with its door off showed the imprint of a brass zipper on the tail rotor blade — although nobody on board admitted losing a piece of clothing with a brass zipper.
LAUNDRY BAG CULPRIT
Another crashed chopper's rotor had bits of plastic from a plastic laundry bag that had held a pilot's clean shirt. He had not completely closed the cockpit door.
In a Big Island case, the metal strip on the leading edge of a rotor blade had come loose. A fishing boat's fish-spotting helicopter crashed into the ocean after the pilot took a rotor blade apart, reassembled it in violation of manufacturer's recommendations, and went flying.
Metal fatigue in the gearbox was blamed for one crash, and improper assembly of parts for another. In 2003 on O'ahu, a helicopter was hauling a load of ladders. The load shifted and a ladder hit the tail rotor. The helicopter crashed but without serious injury to anyone.
For the NTSB's Silliman, one of the problems is that the missing pieces of the helicopter are still missing — and that includes rotor blades that might carry evidence of any kind of impact. The blades, and other parts of the tail assembly, fell into the ocean off Ha'ena Point. Divers have been searching but in big surf, they have not yet found anything confirmed as coming from the helicopter. Silliman said divers recovered pieces of metal that initially were reported as helicopter parts, but they since have been determined not to be from the Inter-Island helicopter.
The helicopter was moved yesterday from its crash site on the lawn of the YMCA's Camp Naue to a hangar at Lihu'e Airport for detailed analysis.
Correction: One person was killed, three others seriously injured and the pilot slightly injured in Sunday's Inter-Island Helicopter tour flight crash. A previous version of this story incorrectly said that three people, including the pilot, were seriously injured.
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A HISTORY OF TAIL ROTOR PROBLEMS Previous accidents involving tail rotor damage or failure in various models of the Hughes 500/ MD500/ Hughes 369/ MD 369 helicopter. Date; place; model; helicopter tail number; injuries/deaths Feb. 11, 2007, Placida, Fla., MD 369FF, N819BP, nonfatal: "A big bang was heard from the helicopter. Immediately after, the helicopter started spinning, uncontrollable," and crashed. Oct. 14, 2005, Kahului Airport, Maui, MD 369D, N58267, nonfatal: "Tail rotor control rod failed about 6.5 inches forward of its aft attachment point ... control rod fractured." Jan. 21, 2005, Pahoa, Big Island, MD 369E, N142MK, nonfatal: "Sudden vibration in the tail rotor pedals followed immediately by a loud 'crack' or 'snap' and then an extremely loud banging noise and a sharp vibration ... the leading-edge abrasion strip debonded from one of the (tail rotor) blades." Sept. 10, 2004, Waynesboro, Ga., Hughes 369D, N5211R, nonfatal: "Both the pilot and passenger heard a 'pop' in the rear of the helicopter. The helicopter began to spin 'hard to the right' (and hit trees). Tail rotor assembly failed due to fatigue fracture in the input gearshaft in the tail rotor gearbox assembly, which resulted in a loss of tail rotor control." Dec. 17, 2003, Wahiawa, Hughes 369D, N1113L, nonfatal: Helicopter hauling load of ladders that slipped, allowing a ladder to strike tail rotor, which separated from helicopter. Helicopter crashed. July 21, 2003, British Columbia, Hughes 369D, C-FOHX, nonfatal: "Loss of tail rotor authority and subsequent forced landing." Aug. 7, 2002, Springfield, Mo., Hughes 369A, N98MP, two seriously hurt: Pilot: "I felt and heard a noise in the aircraft ... the aircraft immediately began to yaw to the right." NTSB: "Overload failure of the tail rotor transmission housing (gearbox) for undetermined reasons, which resulted in an inability to adequately control the aircraft." Oct. 7, 2000, Kernville, Calif., MD369E, N819CE, nonfatal: "First indication of trouble was a loud snap sound from the rear of the helicopter, followed by violent airframe vibrations. ... Examination of the helicopter revealed a torsional failure of the tail rotor drive. ... Leading-edge tail rotor blade damage was observed to both blades, with red and blue color and material transfers evident ... the material to be of a cellophane base ... (cause was) pilot's improper storage of personal items ... allowing a plastic garment bag to blow out and strike the tail rotor." Aug. 11, 2000, Cape Town, South Africa, Hughes 369HS, ZSHFE, nonfatal: "A loud bang was heard and felt, and anti-torque control was lost ... tail rotor and gearbox assembly was found about 2 kilometers (1.2 miles) from the helicopter landing site. The abrasion strips were missing from tail rotor blades, and drive fork bolt was fractured." July 2, 2000, Destin, Fla., Hughes 369D, N88MP, nonfatal: Pilot felt strong vibration "followed by a loud bang, and the aircraft yawed violently to the right, and the nose pitched down." Parts of tail missing, gearbox partly separated, due to excessive wear of some parts and improper maintenance. June 7, 1999, off fishing vessel, Pacific Ocean, Hughes 369HS, N4278M, nonfatal: Helicopter crashes into ocean after intense vibration and the separation of tail gear box and tail rotor assembly, after unapproved repair to tail rotor blade tip. Aug. 10, 1998, Oso, Wash., MD369D, N1096L, nonfatal: "At about 250 feet above the ground, the pilot-in-command heard a bang and saw the tail rotor gear box fly past the rotorcraft on the left side." Helicopter began spinning to the right before hitting the ground. Cause of failure undetermined June 16, 1998, off ship, Pacific Ocean, Hughes 369HS, N95MS, two fatalities: Pilot declared loss of control and hit ocean. He died. NTSB: "The improper shimming of the tail rotor driveshaft by maintenance personnel, which induced fatigue in the tail rotor driveshaft coupling, causing it to fail." Sept. 12, 1997, Brinkley, Ark., Hughes MDL-369HS, N107CW, nonfatal: Pilot flying with door off, heard bang and aircraft yawed to right. Tail rotor drive shaft separated. One tail rotor had indentations as from a zipper, and marks made by brass. No passengers reported losing any personal items. NTSB: "In-flight collision of the tail rotor blade with an object that had a brass zipper on it." Feb. 21, 1997, Miloli'i, Big Island, Hughes 369D, N505RM, three seriously injured: A loud bang, followed by shudder in tail rotor pedals, and "a passenger reported pieces of the tail rotor blades flying past the left side of the helicopter." Cause of failure undetermined.
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Reach Jan TenBruggencate at jant@honoluluadvertiser.com.
