A fatal microlight crash near Westport has been blamed on the pilot breaking Civil Aviation rules.
"It is considered that if Civil Aviation rules had been complied with, the accident would not have occurred," said the Civil Aviation Authority (CAA) report.
Pilot Roger Smith, 58, and his passenger Cole Ashby, 25, both of Westport, died on January 30 last year, when their microlight crashed at Carters Beach just minutes from Westport Airport.
The CAA investigation found Mr Smith, who had about 765 hours flying experience, took off in visibility conditions below the minimum required.
Conditions had further deteriorated to thick fog before the crash about an hour later. Mr Smith probably suffered from "spatial disorientation" after the microlight entered the fog in limited light, and lost control of the aircraft, the report said.
"Considering the environmental conditions and the approach of night, the pilot found himself in a situation that [neither] he nor the microlight was equipped for."
Mr Smith was not night or instrument rated. The microlight was not equipped for flying at night or in instrument meteorological conditions.
Mr Smith did not have a current microlight pilot certificate. His biennial flight review was about a year overdue. His certificate and membership validation had expired, the report said. His associated medical certificate and declaration could not be found.
Investigators found no mechanical defects with his Bantam B22s. It had a current flight permit and had passed its annual inspection four months before the crash.
CCTV footage at Westport Airport showed Mr Smith pumping fuel into his aircraft at 8.21pm on January 30, before the flight to look for deer.
The aircraft was last seen flying near Cape Foulwind about 9.10pm.
Several witnesses indicated the microlight was flying below the minimum allowable height of 500 feet. They said that Mr Smith would often fly low.
Witnesses in the Carters Beach area heard a loud bang about 9.20pm.
The microlight was reported overdue the next morning. The wreckage was found at 9.30am; Mr Ashby's body was inside and Mr Smith's body was about 1.5km away along the beach.
The area weather forecast that day was for mist, then fog, in the late evening with visibility reducing to 500m. Investigators could find no evidence Mr Smith had obtained the forecast or made a pre-flight plan.
Westport Airport's visibility was just 300m about the time of the crash. The cloud ceiling had reduced to 200 feet.
Visual flight rules require 1500m visibility and a 600-foot cloud ceiling in uncontrolled airspace at aerodromes.
The report said "spatial disorientation" was a well-known physical and mental phenomenon. It was a significant risk when a pilot pressed on into poor visibility with no instrument rating, lost visual clues, and failed to sense correctly his position or motion.
It could take less than three minutes for non-instrument rated pilots to lose control of their aircraft once all visual references disappeared.
Mr Smith's decision to continue the flight into adverse weather conditions was characteristic of 'get-there-itis', the report said. Research showed that pilots often flew into deteriorating weather to reach their destination.
The report said Mr Smith had come to CAA's attention in 2007, when it was alleged he flew at about 200 feet near Westport Airport and breached the airport's circuit procedure.
It was also alleged he operated a microlight without radio gear in a zone where pilots were required to broadcast their call sign, position and altitude every five minutes.
A CAA inspector subsequently discussed the concerns with Mr Smith and Mr Smith sought instruction on radio and circuit procedures at Westport Airport.
CAA was to "continue to monitor activity when travel plans allow" but the report found no evidence of any follow-up.
On the fatal flight, the microlight operated within the Westport mandatory broadcast zone. However, investigators found no evidence of a radio on board or of any radio broadcasts.
CAA said the investigation had highlighted discrepancies in the communication and exchange of safety information between aviation recreation organisations and CAA.
The Recreational Aircraft Association of New Zealand had highlighted the dangers of a visual flight rules pilot flying in instrument meteorological conditions, and spatial disorientation, in its May magazine.