G'day Alan,

nice video. It's interesting that you put the noise down to turbine noise. There's been a fair amount of research on this and I think it's reliable to say that the majority of the noise doesn't come from the turbine, instead coming from the rotors and the gearbox. The latter source is a major source of noise - and of crew hearing loss, a subject near to my own ageing ears! during those evolutions the main rotor would have been at high collective pitch/high angle of attack therefore adding to its contribution to the noise.

Here's a quote from the UK CAA, which doesn't however point to the gearbox:

"The noise “signature” of helicopters differs significantly from that of fixed wing aircraft. The noise comes more from the main and tail rotors - particularly from their tips - and proportionately less from the engines."

It would be interesting to calculate the angular velocity of the blade tips, using your estimate of 250RPM for the rotors. Tip speed is a major limitation of helicopter performance. The advancing blade tip speed is a combination of it's angular velocity and the speed of advance of the helicopter...

Nice post, thanks.

CA

Steve,

No sorry mate, I only took video.

Checking the raw video quality, it isn't that great... The resolution is only 640x480. No frames where you can recognise anyone. Here are a few of the better ones.

Did all turn out well for the patient?

Regards,

Alan

Hi Mate,

I was the winch operator on the helicopter, would you happen to have any still photo's of the job?

Cheers,

Steve.

LOL Alan, you know me too well... I didn't use the video footage, rather the audio. I was looking at the spectrogram in baudline last night. Can't remember the figure, about 250 RPM IIRC. I'll post a spectrogram later.

Cool. I'm surprised you haven't done a calculation of the heli's rotor speed given the frequency of the cameras frame rate. :)

-A.