The pilot stated that on his second flight in the Rans S-6ES, he completed some basic maneuvers without incident and returned to the airport in Ozark, Arkansas.
Shortly after, he and a passenger boarded for a local flight.
The pilot completed an engine run-up with no anomalies noted, and then departed from the grass runway.
About 70 feet above ground level he felt a vibration and was unable to maintain altitude. The engine RPM and oil pressure decreased as the airspeed slowed.
The airplane collided with trees and then hit the ground.
The pilot and passenger suffered minor injuries, but were able to get out of the airplane before it burst into flames.
The pilot provided a summary of his post-accident engine examination, which revealed that the oil supply line to the propeller speed reduction unit was completely clogged with an unknown gray material. Also, the gear reduction drive was seized, lacked oil, and the bearings were covered in a dry, rusty powder.
It is likely that the loss of engine power was due to oil starvation of the propeller speed reduction unit.
Probable Cause: Oil starvation of the propeller speed reduction unit, which resulted in a total loss of engine power.
To download the final report. Click here. This will trigger a PDF download to your device.
This July 2023 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.
There is something that many seem to think is optional – maintenance. No comment here indicating when any serious maintenance was carried out
This pilot appears to have only flown the aircraft for 1 hour since buying it.
It is a 30+ year old aircraft with 1300+ hours on it. We don’t know what inspections and maintenance he did before flying it.? Obviously he missed the PSRU lube system.
This was a Subaru conversion with a PSRU. Careful attention has to be done to ensure the gearbox is properly lubricated and in good condition.
These auto engine conversions can be less reliable than certified engines, especially those with a custom prop reduction unit.
And, the engines were not designed to run continuously at 75% power.!
Yet the failure was due to the PSRU; not the Subaru engine…
YES.!! the weak part in these auto conversions is the PSRU, not properly designed to handle the power pulses from the engine.
I fly a Cessna 175B which has a geared, GO-300, 6 cylinder engine.
There is a torsion bar [ quill shaft], between the crankshaft and the gear box drive gear.
This twists to absorbs the power pulses and has worked well now for over 2,700 hours.!
Valve grinding compound? Liquid gasket seal? Thank God they lived to tell the tale.
Regards/J
The pilot made no mention of a preflight, other than run up. He had one hour in the aircraft prior, with . He may not have picked anything up on preflight, but you might think he’d mention something in his report in addition to the run up. He had 1 hr. in the last month (any a/c), total time 142 hrs. (all a/c). A good lesson to us all, whether you rent or own a plane, the more you get up close and personal to your aircraft, the better chance you may discover a subtle change. They are very lucky and blest they lived to tell the story.