New Zealand transport investigators have warned pilots worldwide not to rely on a back-up instrument check system after it misled two Air Nelson pilots.
The Bombardier Dash-8 311's nose wheel collapsed during landing at Blenheim airport in 2010 after the aircraft had been diverted from Nelson due to bad weather.
Three crew and 46 passengers were on board. No one was injured and there was minimal damage to the plane.
A Transport Accident Investigation Commission review released on Thursday report found that debris in the gear's hydraulic fluid prevented the nose landing gear from extending.
It says the primary alert system told the pilots that there was a problem, but a second system said there wasn't. The pilots also ignored a warning horn and alarm, which they thought were faulty.
The commission's investigator, Peter Williams, says pilots need to believe the alerts and the crew could have asked someone in the air tower to try to see if the landing gear was down and safe.
Mr Williams told Radio New Zealand's Checkpoint programme on Thursday that pilots globally have been warned that the system is unreliable.
"There's cautions in relation to how you use it in the checklist, limitations of it and there is work taking place in Canada to improve the reliability of that system."
The back-up check system used on aircraft is being upgraded, he says.
