The preliminary findings into the cause of the ultralight aircraft crash near Waihi on March 28 haven't confirmed pilot Rod Vaughan's assertion that a collision with a drone caused the crash.

The investigation has confirmed there was a catastrophic failure of the windscreen, and that no other aircraft systems were considered compromised or pertinent to the accident – there was no engine failure, or flight control issues.

The investigator has praised Rod Vaughan's handling of the incident saying that considering the extreme compromising of the aircraft; 'The pilot operated the aircraft considerably well to a safe landing area.”

The nest steps are for the CAA to contact the aircraft manufacturer to get technical information, and an area search will be carried out at the mine for any other possible evidence.

The CAA reminds operators of drones to remain within the height restrictions that are in place to ensure their safe operation around other aircraft.

Katikati resident Rod Vaughan was taking his son for a flight in the vicinity of the Waihi goldmine when the windshield failed.

"Without any warning a tornado of air was just racing inside the cockpit," says Rod, reported on Stuff by Matt Shand.

The force of the impact, and pressure of the wind, dislodged the two doors which dangled behind the aircraft still tethered to the airframe.

"I immediately looked to get the plane on the ground. We were about 1600 to 1700 feet at the time and we came down in about 30 seconds."

He flew the damaged aircraft towards a cleared corn paddock near Ford Rd.

"There was a hedge that I think I clipped on the way," says Rod.

The bumpy paddock put too much pressure on the front wheel. It buckled causing the plane to flip.

The Vaughans were able to walk away from the crash but not without injury.

His son was able to brace himself during the crash so suffered only bruising from the seatbelt. Rod cut his head in the crash.

The fact the window imploded in the manner it did left Rod with three theories.

"One would be a bird strike but we didn't see any bird activity in the area.

"The second would be a high velocity rifle shot but I think we can rule that out.

"Another option is a drone."

Vaughan hopes the Civil Aviation Authority conducts a thorough investigation into the incident but he admits the truth might never come out.

"I don't think someone is going to put their hand up and say, 'I am missing a drone and it was last seen flying near your aircraft'."

Vaughan says spotting a drone while flying is nearly impossible and the prevalence of drones is putting amateur airmen at risk.

"Kids can buy drones for $90 at the Warehouse.

"It's hard enough to spot a plane in the air which is why we rely on radio reports, but drone operators are not using radios."