Accident Zenith Zodiac CH-601 XL-B N610TT,
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ASN Wikibase Occurrence # 194564
 
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Date:Friday 31 March 2017
Time:16:55
Type:Silhouette image of generic CH60 model; specific model in this crash may look slightly different    
Zenith Zodiac CH-601 XL-B
Owner/operator:Private
Registration: N610TT
MSN: 6-7884
Year of manufacture:2012
Total airframe hrs:129 hours
Engine model:OTT 3250
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Columbia Gorge Regional/The Dalles Municipal Airport (KDLS), Dallespor -   United States of America
Phase: Landing
Nature:Private
Departure airport:The Dalles, OR (DLS)
Destination airport:The Dalles, OR (DLS)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The commercial pilot, who was also the owner/builder of the experimental amateur-built airplane, reported that, after departure and while climbing through 3,500 ft mean sea level, he heard the engine sound abruptly change and observed a loss of rpm and higher-than-normal exhaust gas temperature readings. The pilot turned back toward the airport and attempted to troubleshoot the problem; however, the airplane continued to produce less power than expected. The pilot established a normal traffic pattern for the runway. After turning to final, the airplane started descending and had insufficient power to reach the runway. The airplane subsequently impacted terrain short of the runway.

Postaccident examination of the airplane revealed that all six propeller bolts that held the propeller hub to the drive hub were fractured. Further examination of the bolts revealed that the fracture surfaces all exhibited similar features consistent with reverse bending fatigue, likely from not fitting tightly into the propeller hub holes. The pilot reported that he had converted the engine and that, given its unique conversion, the bolts that were typically used to connect the propeller hub to the drive hub were too short; therefore, he chose to use the bolts that were on the hub at the time of the accident. Given the condition of the bolts and the pilot's statement, it is likely the bolts did not fit tightly in the propeller hub holes, which led to their failure due to reverse bending fatigue.

Probable Cause: A partial loss of engine power due to the reverse bending fatigue failure of the propeller hub bolts, which resulted from the bolts not fitting tightly into the propeller hub holes. Also causal was the pilot's decision to use improper bolts for this type of installation/operation.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR17LA082
Status: Investigation completed
Duration: 8 months
Download report: Final report

Sources:

NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N610TT

Location

Revision history:

Date/timeContributorUpdates
04-Apr-2017 22:36 Geno Added
16-Dec-2017 14:54 ASN Update Bot Updated [Time, Operator, Nature, Departure airport, Destination airport, Source, Narrative]
16-Dec-2017 17:05 harro Updated [Aircraft type, Source, Narrative]

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