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ASN Wikibase Occurrence # 179890
Last updated: 19 January 2020
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Date:25-SEP-2015
Time:11:26
Type:Silhouette image of generic BE35 model; specific model in this crash may look slightly different
Beechcraft S35 Bonanza
Owner/operator:Private
Registration: N193Q
C/n / msn: D-7708
Fatalities:Fatalities: 2 / Occupants: 2
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:Archuleta County South of Pagosa Springs, CO -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Private
Departure airport:Durango, CO (DRO)
Destination airport:Pagosa Springs, CO (PSO)
Investigating agency: NTSB
Narrative:
On the day before an air race competition, the accident pilot and another pilot decided to execute a practice circuit of the race course in their airplanes. As the two airplanes entered the course, the accident airplane was behind the other airplane. After they passed the first course waypoint, the accident pilot radioed the other pilot and stated that his airplane’s engine had lost power and that the airplane was going down. No further communications were heard from the accident airplane. Witnesses observed white smoke coming from the underside of the airplane before they lost sight of it. Examination of the accident site indicated that the pilot was attempting to land on a gravel road when the airplane impacted a steel pole adjacent to the road and traveled about 200 yards before coming to rest inverted. Examination of the engine showed that the No. 6 connecting rod failed due to oil starvation. The oil starvation resulted from movement of the No. 4 main crankshaft bearing to a position where it blocked the oil transfer passage to the No. 6 connecting rod. The engine thru-bolts were improperly torqued by unknown maintenance personnel, and this allowed the No. 4 main bearing movement to occur. In addition, disassembly of the engine revealed that unapproved pistons had been installed. However, the unapproved pistons were not related to the engine failure.

Probable Cause: Improper engine assembly by unknown maintenance personnel, which resulted in the failure of the No. 6 connecting rod due to oil starvation from the shifting of the crankshaft's No. 4 main bearing.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20150925X72014&key=1


Revision history:

Date/timeContributorUpdates
25-Sep-2015 20:21 Geno Added
26-Sep-2015 13:42 Geno Updated [Total fatalities, Total occupants, Other fatalities, Source, Damage, Narrative]
28-Sep-2015 18:15 Geno Updated [Aircraft type, Registration, Cn, Operator, Source, Damage]
30-Sep-2015 20:45 Geno Updated [Time, Phase, Nature, Departure airport, Destination airport, Source, Narrative]
01-Oct-2015 04:04 Anon. Updated [Source]
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
01-Dec-2017 15:27 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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