Lack of maintenance brings down Bonanza

Aircraft: Beech Bonanza. Injuries: 3 Fatal. Location: Daggett, Calif. Aircraft damage: Destroyed.

What reportedly happened: While in cruise flight, the pilot transmitted that he was in trouble because the airplane had experienced a propeller failure. The air traffic controller provided him 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 saw the airplane flying in a southwesterly direction about 500 feet AGL. As the airplane approached a set of suspended power lines, it pitched up 15°, increased altitude by 100 to 200 feet, yawed to the right, made two 360° turns, then hit the ground.

A post-accident 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.

Laboratory examination of the bearing 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 stress, resulting in a fatigue fracture of the connecting rod bolts.

During the investigation it was discovered that 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 time between overhaul be 1,500 hours or every 12 years.

Probable cause: A loss of engine power due to the separation of a connecting rod, and the pilot’s failure to maintain control during a sudden maneuver to avoid power lines during the descent, which resulted in an unrecoverable aerodynamic stall and subsequent spin. Contributing to the accident was noncompliance with the manufacturer-recommended engine overhaul schedule.

NTSB Identification: WPR12FA012

This October 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.



  1. vaughn S. Price says:

    amazing!! he had his emergency under control, then tries to go over power lines instead of under. He definitely would never do as a crop duster

  2. ManyDecadesGA says:

    While sad at the event of any accident, and especially any accident with injury or loss of life, it is a total “copout” and disservice to skilled and creative maintenance technicians and GA operators alike, to simply attribute an accident like this “to the accident was [in] noncompliance with the manufacturer-recommended engine overhaul schedule.” If in GA, the legal liability and politically driven replacement or overhaul recommendations of OEMS and vendors were always exactly followed, there would be no affordable GA left to fly. Instead, the key issue is preserving enough critical mass GA expertise and experience in the MX and FBO community, to be able to safely maintain these kinds of aircraft and powerplants, by not making FAA inspection requirements so misapplied and onerous for things that are non-issues, that resources get diverted into placebo or unneeded maintenance actions. That just causes diversion of scarce resources away from being devoted to the real factors that actually drive safety. So at least a part of the blame for accidents like this should likely reside squarely with failed and misguided regulatory policies, which in turn cause a shrinking, failing, macro GA maintenance capability, a consequence of inappropriate authority policies, criteria, and practices, in turn leading to unnecessarily high-priced maintenance and unwarranted inspections. This situation, coupled with liability driven and profit motive driven OEMs and engine manufacturers, with artificial “over-specification” of constraints, eventually leads to a counterproductive safety trend. What goes around, comes around. But then they just typically blame it on the pilot and the pilot’s mechanic, not acknowledging the bigger picture, and real fundamental systemic causes.

    • Guido Spaini says:

      I agree. And after many years of profiting of a closed and non evolutionary market, they are whining the market is shrinking, the numbers of pilots are declining. And now are running in the arms of Chinese capitalists to keep their profits, without any commitment in innovation.
      Don’t believe me? Then, how long is Lycoming et all keeping this big grass mowers engines going? How long are they going to keep this phallacy of “safety” to maintain the sales of inefficient polluting engines, while at the same time do not allow any competitors in?

Speak Your Mind