Pilot David Duncan was killed when the twin engine Cessna 310 crashed shortly after takeoff.
The NTSB report says the left engine was tested after the crash and it quit when the nut was loosened the same amount.
NTSB says anti-tamper putty around the nut was broken. The putty is used to indicate if a nut has been loosened — purposely or by causes like vibration.
The report says a mechanic removed the nut the day before the crash to replace a cylinder.
NTSB says the mechanic told investigators he tightened the nut to proper torque but didn't have anti-tamper putty to put around it.