Accident Kolb MARK III N213,
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ASN Wikibase Occurrence # 289533
 
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Date:Thursday 17 February 2011
Time:15:30 LT
Type:Kolb MARK III
Owner/operator:Batchelder Ellery D Jr
Registration: N213
MSN: M3-248
Total airframe hrs:177 hours
Engine model:Rotax 582
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Stetson, Maine -   United States of America
Phase: En route
Nature:Private
Departure airport:Old Town Airport, ME (OLD/KOLD)
Destination airport:Dexter, ME (1BO)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot was in cruise flight at 1,500 feet over a heavily wooded area when the airplane began to vibrate violently before sustaining a total loss of engine power. The pilot made a forced landing and the airplane collided with trees and the ground. The pilot stated that, about 30 flight hours before this accident, the airplane experienced a similar severe vibration in flight. He shut down the engine and made a successful forced landing to a nearby airport. Examination of the airplane revealed that a triangle-shaped aluminum plate on the rear of the propeller hub had cracked. The pilot installed a new propeller hub and the original propeller blades about 7 months before the accident and began flying again without any vibrations. The total hours on the propeller blades are unknown.

A postaccident examination at the accident site revealed that both carburetors had separated from the engine assembly and were hanging by their fuel lines and throttle cables. One composite propeller blade was delaminated with a large section missing. The remaining two propeller blades appeared to be intact without comparable or crash-related damage. The carburetor detachment likely caused the final engine failure and this separation was likely a consequence of the severe vibration.

Metallurgical examination of the propeller blades identified that separation of a portion of blade No. 1 initiated as a transverse fracture, originating near the trailing edge of the blade. The transverse fracture was progressive in nature, with the crack propagating in some combination of fatigue and/or stress rupture under continually applied loads. Blade No. 2 also exhibited a pattern of parallel transverse cracks on its aft side. Blade No. 3 was also visibly damaged, with significant delamination or disbonding of the woven carbon-fiber composite skin from the forward side of the blade, along with delamination at the trailing edge. Blade No. 3 also exhibited a pattern of parallel transverse cracks on its aft side. This damage was consistent with bending of the tip of the blade forward under air loading.

Probable Cause: The in-flight failure of the No. 1 composite propeller blade due to fatigue, which resulted in a violent vibration, loss of engine power, and a subsequent forced landing to unsuitable terrain.

Accident investigation:
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Investigating agency: NTSB
Report number: ERA11LA150
Status: Investigation completed
Duration: 1 year
Download report: Final report

Sources:

NTSB ERA11LA150

Location

Revision history:

Date/timeContributorUpdates
05-Oct-2022 14:59 ASN Update Bot Added

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