Mechanical & Engine Failure · NTSB CEN15FA424
BEECH S35 — Pagosa Springs, CO
| Date | September 25, 2015 |
| Location | Pagosa Springs, CO |
| Aircraft | BEECH S35 |
| Purpose of flight | Personal |
| Conditions | Day · Visual Meteorological Cond |
| Phase / occurrence | Emergency descent Collision with terr/obj (non-CFIT) |
| Pilot age | 70 |
| Pilot total time | 5,640 hrs · High time |
| Time in type | Unknown |
| Fatalities | 2 |
Probable cause
NTSB findings
- Aircraft-Aircraft power plant-Engine (reciprocating)-Recip engine power section-Failure - C
- Personnel issues-Task performance-Maintenance-Installation-Maintenance personnel - C
- Environmental issues-Physical environment-Object/animal/substance-Fence/fence post-Contributed to outcome
What happened
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.