NPAS 11 January 2020 Norwich 3am

The request was successful.

Dear National Police Air Service,

I would like understand why there was such significant helicopter noise caused by your
aircraft G-SUFK circling Norwich at 3am on 11 January 2020.

Yours faithfully,

James

Turner, Shaun, National Police Air Service

Classification: OFFICIAL

James Duez,

Many thanks for your email and I apologise on behalf of NPAS if you were disturbed by the noise.

In answer to your question.
The main source of sound from a helicopter comes from its rotor blades. Blades produce several types of sound. Some are due to air displacement (thickness noise); others (loading noise) are from forces acting on the air that flows around the blade—these are caused by lift and drag, for example. Other sounds come from aerodynamic shocks on the blade surface, or interactions with turbulent inflows of air.

Kind regards

Shaun Turner
Service Delivery and Operations Centre Manager
National Police Air Service

Web: www.npas.police.uk

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Dear Turner, Shaun,

Thank you for explaining how helicopter rotor blades make noise. My enquiry was not to elicit an explanation of the physics of noise compression but to respectfully enquire as to why such activity was warranted at 3am waking up a significant number of residents.

Yours sincerely,

James Duez

Turner, Shaun, National Police Air Service

I am out of the office until Monday 18th January 2021. For any urgent
enquiries please contact the NPAS Flight Duty Officer on 01274 645281.

I will have limited email access during this time.

Turner, Shaun, National Police Air Service

Classification: OFFICIAL

James,

Your question was why is so much noise generated by the aircraft, which I answered.
The aircraft was searching for a missing child.

Regards

Shaun Turner
Service Delivery and Operations Centre Manager
National Police Air Service
Web: www.npas.police.uk

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Dear Shaun,

Thank you.

Yours sincerely,

James Duez