Originally Posted by
nowherespecial
minigundiplomat is well placed to answer this question but from my memory, the noise signature of a CH47 over the sea in still wind (ie as controlled as it gets) was assessed to be either 10nm or 15nm for planning purposes (ie at 10.1 or 15.1nm you would not hear anything). wind direction and speed can have a profound effect on the way the noise travels.
The sound is pretty hard to mask, but directionally it can be very difficult to pin down, particularly in undulating ground and of course, at fifty feet visual acquisition is often a late spot.
Originally Posted by
pulse1
I used to live on the Western edge of the Bournemouth Control Zone in a rural gap between two built up areas. We often had military helicopters flying through this gap, especially at night around 2300 and at low level with no lights. I am currently reading the book The Workhorse of Helmand and discovered that Chinooks there operate in pairs and I believe that the ones flying low over my house was one of a pair with only one lit up. Of course this increased the noise level and the awesome effect of a Chinook coming right over your house with no lights was impressive. The change in noise level as they passed over head seemed to increase the dramatic effect. I have now downsized to a place just over a mile away so I still hear them but it's hats not the same.
That's a great book, by the way.........
