Mechanical & Engine Failure · NTSB WPR12FA012
BEECH E33 — Daggett, CA
| Date | October 16, 2011 |
| Location | Daggett, CA |
| Aircraft | BEECH E33 |
| Purpose of flight | Personal |
| Conditions | Day · Visual Meteorological Cond |
| Phase / occurrence | Emergency descent Loss of control in flight |
| Pilot age | 35 |
| Pilot total time | 94 hrs · Student / very low time |
| Time in type | 21 hrs |
| Fatalities | 3 |
Probable cause
NTSB findings
- Aircraft-Aircraft power plant-Engine (reciprocating)-Recip engine power section-Failure - C
- Personnel issues-Task performance-Use of equip/info-Aircraft control-Pilot - C
- Aircraft-Aircraft handling/service-Maintenance/inspections-Scheduled maint checks-Not specified - F
What happened
While in cruise flight, the pilot transmitted that he was in trouble and thought the airplane had experienced a propeller failure. The air traffic controller provided the pilot with instructions to the nearest airport, which was about 21 miles away. The pilot radioed that he thought that he could make it and began a descent toward the airport. A witness near the accident site observed the airplane flying in a southwesterly direction about 500 feet above ground level. As the airplane approached a set of suspended power lines, it pitched up 15 degrees, increased altitude by 100 to 200 feet, yawed to the right, made two 360-degree rotations descending vertically, and impacted terrain, consistent with an aerodynamic stall/spin.
Postaccident examination of the engine revealed a 2-inch hole in the top of the crankcase between the Nos. 3 and 4 cylinders. The No. 1 piston connecting rod had separated from the crankshaft, bending the end cap flat with no thermal discoloration evident. Laboratory examination of the bearing insert half identified circumferential wear marks on the back side of the bearing insert. The wear marks on the backside of the intact insert, the lack of heat damage to the connecting rod journal, and the lack of heat damage to the connecting rod and end cap suggest that the bearing began to spin, which led to extrusion/ejection of half of the connecting rod bearing. Once the bearing was free, fragments of bearing material worked their way up between the piston and the cylinder wall causing damage to and embedding in the piston skirt. The increased clearances between the connecting rod end cap and connecting rod journal caused large stress amplitudes that resulted in a fatigue fracture of the connecting rod bolts.
In 1998, after 1,002 hours of operation, the engine was top overhauled. A top overhaul does not inspect or replace items inside the crankcase, such as the main bearings or connecting rod bearings. At the time of the accident, the engine had accumulated 2,601 hours. The engine manufacturer recommends that the time between overhaul be 1,500 hours or every 12 years.