The Auditor-General has identified operational issues with the New Zealand Air Force's new NH90 helicopters which cost $771 million.
Eight NH90s have been purchased for operations, with a ninth to be used for parts.
In her commentary in the Ministry of Defence's latest Major Projects Report, Auditor-General Lyn Provost says the Defence Force anticipates problems ensuring that the NH90s will do everything they were purchased for.
Ms Provost says the helicopters are prone to damage from debris drawn into the engines and screens will need to be fitted to the engines to mitigate this.
However, once this is done the aircraft will not be able to operate in snowy conditions.
Ms Provost says the Defence Force is working to ensure that the helicopters will be able to operate in various climatic conditions as intended.
She notes these problems will mean some of the helicopters will have to be taken out of rotation, which will affect crew training.
Des Ashton, head of acquisitions for the Defence Force, says the helicopters will be altered by German manufacturers to perform in snowy conditions.
The Chief of the Defence Force, Lieutenant-General Rhys Jones, says 16 countries are taking delivery of the helicopters, including some Scandinavian nations, and issues with their performance in snow have been quickly resolved.
The Defence Force says the helicopters will not be operational in New Zealand for another few years.