Helicopter noise as boiler approaches operating temp

[mike004]

Ideal Logic Max Heat boiler (heat only). Installed 18 months ago.
It is now making a loud "helicopter" noise during warm up to operating temperature.
Water temperature is set to 65 deg C. Switch on boiler, then at about 60 deg C the noise starts.
When boiler reaches the target temperature, the noise stops. Hot water circulates OK and everything is reasonably quiet.
Any ideas on the cause?

The boiler has a 10 year warranty, but the fine print mentions some noisy boiler causes, such as sludge, are exempt.
The annual service is due in July, is it OK to wait until then?

 

[evdamadiynot]

For the purpose of warranty Id get it checked and bring forward the service.

 

[mike004]

This turned out to be caused by a worn out pump. A replacement pump was fitted.