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20170811024769A

Accident · Substantial damage
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FAA accident report · Schweizer 269D · Long Beach, CA · August 11, 2017

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Date
August 11, 2017 · 16:00 local
Place
Long Beach, CA
Phase of flight
Ground/Ramp/Ma
Operating rules
General operating rules (Part 91)
Damage
Substantial damage
Aircraft
N2086N
Reported as
Schweizer 269D
Reported engine
Allison 250-C20 series
People aboard
1
Fatal injuries
0
Other injuries
0
N2086NRegistration cancelled May 17, 2018 · Schweizer 269DS/N 0008 · Built 1994Airframe modelSchweizer 269DEngine modelAllison 250-C20 seriesTurbo-prop

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry by N-number and event date, checked against the reported make and model; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

August 11, 2017 maintenance personnel were performing engine run to check out helicopter rotor transmission which was just installed following overhaul. As mainteance personnel increased engine RPM to approximately 80 % the helicopter began to bounce violently from side to side with extreme vibration, maintenance personnel immediately shut down the engine stopping the event. Upon exiting the helicopter after this event and inspecting it was discovered to be very violent and it is suspected to be a ground resonance event. 2 of the 3 rotor blade were disconnected from the lead/lag damper and folded against the remaining intact rotor blade which created and extreme out of balance/phase condition. Unrestrained rotor blade came in contact with the vertical stabilizer and tail boom, engine /transmission and rotor shaft mounts were bent and torn from supporting structure. Very substantial damage to helicopter airframe. Inspection of rotor damper did not reveal cause of seperation due to damage inducted during this event. This helicopter was in the process of an annual inspection and was not returned to service at the time of this event. Cause of suspected ground resonance condition was not able to be determined. Helicopter maintenance records were all reviewed and all maintenance, airworthiness directives are all current with exception of the maintenance being performed.

As the FAA filed it

AUGUST 11, 2017 MAINTENANCE PERSONNEL WERE PERFORMING ENGINE RUN TO CHECK OUT HELICOPTER ROTOR TRANSMISSION WHICH WAS JUST INSTALLED FOLLOWING OVERHAUL.AS MAINTEANCE PERSONNEL INCREASED ENGINE RPM TO APPROXIMATELY 80 % THE HELICOPTER BEGAN TO BOUNCE VIOLENTLY FROM SIDE TO SIDE WITH EXTREME VIBRATION, MAINTENANCE PERSONNEL IMMEDIATELY SHUT DOWN THE ENGINE STOPPING THE EVENT. UPON EXITING THE HELICOPTER AFTER THIS EVENT AND INSPECTING IT WAS DISCOVERED TO BE VERY VIOLENT AND IT IS SUSPECTED TO BE A GROUND RESONANCE EVENT. 2 OF THE 3 ROTOR BLADE WERE DISCONNECTED FROM THE LEAD/LAG DAMPER AND FOLDED AGAINST THE REMAINING INTACT ROTOR BLADE WHICH CREATED AND EXTREME OUT OF BALANCE/PHASE CONDITION. UNRESTRAINED ROTOR BLADE CAME IN CONTACT WITH THE VERTICAL STABILIZER AND TAIL BOOM, ENGINE /TRANSMISSION AND ROTOR SHAFT MOUNTS WERE BENT AND TORN FROM SUPPORTING STRUCTURE. VERY SUBSTANTIAL DAMAGE TO HELICOPTER AIRFRAME. INSPECTION OF ROTOR DAMPER DID NOT REVEAL CAUSE OF SEPERATION DUE TO DAMAGE INDUCTED DURING THIS EVENT. THIS HELICOPTER WAS IN THE PROCESS OF AN ANNUAL INSPECTION AND WAS NOT RETURNED TO SERVICE AT THE TIME OF THIS EVENT. CAUSE OF SUSPECTED GROUND RESONANCE CONDITION WAS NOT ABLE TO BE DETERMINED. HELICOPTER MAINTENANCE RECORDS WERE ALL REVIEWED AND ALL MAINTENANCE, AIRWORTHINESS DIRECTIVES ARE ALL CURRENT WITH EXCEPTION OF THE MAINTENANCE BEING PERFORMED.