There was a fatal accident involving an Aero Commander 500S here in West Oz in 1986, whereby the engines were run up for a number of hours, by an engineer, as part of ground testing for onboard survey equipment.
Those testing hours were not recorded, as only flight time was required to be recorded.
The PIC had previously fully-fuelled the aircraft without taking it out. Upon returning to it, he presumed it was still full of motion lotion, as no flying time had been recorded.
The fuel gauges were inoperative, and he failed to physically check the quantity of fuel in the tanks.
He took off and ran out of motion lotion a short time thereafter, resulting in a crash into heavily timbered terrain, with resulting fatalities and total destruction of the aircraft.
Investigation: 198600131 - Aero Commander 500S, 2km North of Canning Dam WA, 27 February 1986
This would be an example of engine hours and airframe hours being out of sync after a lengthy period of operation, where ground testing with engine running is incurred.