Fa­tal Erie he­li­copter crash caused by ro­tor sys­tem fail­ure

The Denver Post - - DENVER & THE WEST - By Jesse Paul

The 2015 crash of a he­li­copter at the Erie air­port, which left two peo­ple dead, was caused by an in­flight break-up of the air­craft’s ro­tor sys­tem prompted by un­de­tected fa­tigue crack­ing, the Na­tional Trans­porta­tion Safety Board says.

Specif­i­cally, fed­eral in­ves­ti­ga­tors ze­roed in on the chop­per’s No. 2 main ro­tor spin­dle — an in­te­gral part of the ro­tor sys­tem that buoys the blades of the he­li­copter — as the pri­mary cul­prit.

In its fi­nal re­port on the crash, re­leased late last month, the NTSB also cited the En­strom 280FX’s design as a con­tribut­ing fac­tor to the he­li­copter’s crash.

He­li­copter flight in­struc­tor Alex Vi­ola, a 23year-old from Arkansas City, Kan., and stu­dent Amy Wood, 25, of Boul­der, died in the Jan. 26, 2015, crash. The he­li­copter was reg­is­tered to New Course Aviation Com­pany and op­er­ated by Moun­tain One He­li­copters, ac­cord­ing to the NTSB.

Moun­tain One He­li­copters said af­ter the crash that Vi­ola was an in­struc­tor for the com­pany and that Wood was work­ing on get­ting her pri­vate li­cense.

The NTSB said the he­li­copter — man­u­fac­tured in 1985 — was on fi­nal ap­proach to land when one of the chop­per’s three main ro­tor blades sep­a­rated, caus­ing the in-flight break up. A wit­ness told in­ves­ti­ga­tors she heard a loud “pop” be­fore see­ing the he­li­copter start to ro­tate as a blade came off the air­craft.

“Me­tal­lur­gi­cal anal­y­sis of the frac­tured spin­dle re­vealed sig­na­tures con­sis­tent with a fa­tigue crack ini­ti­at­ing from mul­ti­ple ori­gins that prop­a­gated across 92 per­cent of the spin­dle cross-sec­tion,” the re­port said. “The re­main­ing 8 per­cent of the frac­ture surface ex­hib­ited sig­na­tures con­sis­tent with over­load.”

Sim­i­lar fa­tigue cracks were also ob­served stem­ming from the thread roots on the he­li­copter’s No. 1 and No. 3 spin­dles, the NTSB found.

Be­fore the ac­ci­dent, the re­port said, the spin­dle was not con­sid­ered to be sub­ject to wear and was there­fore not reg­u­larly in­spected. Fed­eral in­ves­ti­ga­tors said there would have been a “low like­li­hood of the op­er­a­tor de­tect­ing the fa­tigue frac­ture within the spin­dle threads be­fore the ac­ci­dent.”

Since then, the Fed­eral Aviation Ad­min­is­tra­tion be­gan re­quir­ing in­spec­tion of spin­dles with 1,500 hours or more time in ser­vice and En­strom re­leased a di­rec­tive bul­letin to op­er­a­tors.

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