TRIALS which could end years of complaints about disturbances caused by a police spotter plane have been postponed again.

The trials to try to reduce the noise made by the aircraft, which were to have taken place last week, have been postponed until the middle of next month at the earliest, because of adverse weather conditions.

The delay has angered protestors, many of whom live at Middleton St George, near the aircraft's base at Teesside Airport.

They have accused police of complacency, saying the number of complaints about noise is much higher than they realise.

The trials of silencer equipment and redesigned propellers are being carried out by Isle of Wight aviation company Britten-Norman.

Some tests took place two years ago, but the company went into receivership before a rescue package turned it around and the tests were never completed.

Even if the trials are successful, it could be many more months before the new designs come onstream.

The data gathered from the trials has to be passed onto the Civil Aviation Authority for its approval.

Nigel Dunhill, manager of the North-East Air Support Unit, said: "We have been trying for about five years to get this noise reduction equipment fitted to the plane.

"The delays are frustrating for us as well and nobody is more concerned about the noise than we are.

"We don't get a lot of complaints, but they are taken seriously."

Mr Dunhill said the redesign involved a silencer being bolted on to the aircraft exhaust and changes to the three-bladed propellers.

Earlier this year, the Home Office gave the unit £250,000 to fund the modifications required. The rest of the money needed will be provided by Durham, Cleveland and Northumbria police, who all use the plane.

Middleton St George parish councillor John Sterling said: "The police have blamed the aviation company going bust and then they said the delays were down to financing. They are also under the misconception that there are not many complaints.

"But that is because we as a parish council discouraged residents from complaining in anticipation of the silencers being fitted."