Aircraft engine manufacturers recommend that owners overhaul their engines when the engines have accumulated a set number of flight hours. Depending on the make and model, the "Time Between Overhaul" ranges from 1200 to 2400 hours. No regulation requires the general aviation aircraft owner to comply with the manufacturer’s recommended TBO. As far as the FAA is concerned, the owner is free to operate the engine indefinitely, as long as a certified mechanic has signed off the engine as airworthy within the preceding 12 months. And given recent advances in engine diagnostic equipment, more and more owners are feeling comfortable "busting" TBO.
I wrote about the practice years ago, in a post entitled "Running Past TBO: Smart Economics or Owner Negligence?" The NTSB recently came down on the side of "owner negligence," at least in the case of a Cirrus engine that was operated past Teledyne Continental’s recommended 2000 hour TBO.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The inadequate servicing and maintenance of the engine and the airplane owner and maintenance personnel’s disregard of the manufacturer’s recommended engine overhaul schedule and service bulletins, which resulted in an in-flight internal failure and seizure of the engine.
In that case, the engine failed at 2978 hours. The NTSB also faulted the pilot for flying the aircraft with only 5 quarts of oil on board, instead of 6 quarts as recommended by the manufacturer.
Fortunately, no one was hurt. But an owner should think twice about running past TBO, regardless of whether an FAA-certified mechanic has pronounced the engine airworthy.