The NTSB believed that since the propeller had damage from rotation, that the engine must have had power. The whole flight was 58 seconds and my son achieved an altitude of about 250 feet. I've been told that the propeller will continue to spin after an engine failure. This could have caused the propeller damage as it hit the trees and ground. It was evident that he was making a controlled emergency landing according to my aviation lawyer, who is a very experienced pilot. The NTSB went to interview the mechanic of the airplane and he happened to be having surgery that day. No further followup as far as I know. The there is no mention of the maintenance logs in the NTSB report. We are fighting the defense to get those logs now. They are refusing to give them to us as they also were refusing to allow us to inspect the aircraft and engine. My lawyer says the NTSB can use whomever they want to help with the investigation. They can choose the manufacturer of the engine and there is nothing anyone can do about it. As it was obvious power turbine wheel failure to my expert investigator, something is not adding up. I don't know exactly who is responsible for everything in the report, but it needs to be reopened with this new evidence brought to light. Thank you for the information and your interest in this case.