Noise Footprint

[Vfrpilotpb]

Where my office is situated we are under two very well used tracks for Helis, and light A/c going to and from Yorkshire into Lancashire as well as North south traffic also, during a normal day we see and hear many different types of Helis, from the large Ch47's right down to the small R22, now having more than a passing interest in this form of travel I nearly allways much like a child look up to see just what is passing.

I have noticed that with most helicopters I normally hear the noise around about 1/2 minutes before I actually see the copter, with the exception of the A109Power, this must rate as the noisiest Civilian machine that flies, one has just gone over with the noise footprint lasting a full 6 minutes from first hearing to last hearing, the only thing louder seems to be the Ch47.

Is it just one of those things and possibly due to geographical situations that I am assailed by the thrashing blades of this most noisey of Helis? or does anyone else hear the clattering Din from the A109 Power?

Peter R-B
Vfr

[212man]

The Bell 214ST must be about the noisiest civillian helicopter in the UK skies, I would have thought, it even gives the Chinook a run for its money. (Apologies to 214 drivers!)

[CRAZYBROADSWORD]

Tis a noisy machine however a bit of noise is not always a bad thing,was on our heli pad the other day at the up wind end putting some wheels on an R22,and when I looked up there was an EC120 stairing right at me in the hover and I did'nt hear a thing.

[Simon853]

I work in West London, about 1/2 mile from the Northolt RAF base and only a couple more miles from Denham. Noisiest machines I see regularly are Chinooks and (what I think are) EH-101s. Then of course there's the occasional Gazelle, the police Twin squirrel(?) and very occasionally a Bell 222 (G-NOIR out of Denham?) All are pure music to my ears. I really can't understand anybody who dislikes the sound of blades thumping air. (Heck, even the sound of a police helo hovering over my housing estate at 3 in the morning brings a smile to my face!)

Si

[Ian Corrigible]

Interesting that the noise maker should be a Power. IIRC, the original A109 had a reputation for a [TR-related?] footprint, but I thought the Power's redesigned composite blades were supposed to have helped the type beat ICAO limits ?

I/C

[John Eacott]

The noise reduction mod for the Power is a redesigned tail rotor, which significantly changes the noise profile, as well as lowering the EpNDb. A modified Power has a noise signature more akin a JetRanger without the two blade beat, as well as being some 6Db quieter on a 1000ft overflight.

When Sydney was to get a helipad, a lot of trials were done to allocate a landing allowance per type, based on the noise footprints. The A109 was the worst culprit of those tested, and one A109 landing equated to (IIRC) about 6 JetRanger landings

Peter,

Whilst the (unmodified) Power can be noisy, your assertion that it is heard for 6 minutes is remarkable, if it is at normal cruise speed (145kias). That means you would be listening to it for nearly 15 track miles: can I borrow your ears for my next audio assessment ?

[Vfrpilotpb]

John,

You would not like my ear tabs, too much Rugby when younger has left them looking rather like a knackered Tom Cats

Peter R-B

[Eurobolkow]

Must agree with John Eacott on this one, the new composite tail rotor blades make a significant difference to the noise signature of the type.

I think VFRPilot if you check the official certification figures you will find that the new version of the Power and the Grand are as quiet if not quieter than similar normal configuration tail rotor aircraft such as the 'Future Police Helicopter' aka the EC145 aka BK117!!!

[Vfrpilotpb]

Dont get me wrong, the noise is to my ears(bad as they are) pure music, as with any flying machine or big engine, but what I hear from the A109 is the massive Rotor noise, it almost sounds like constant blade slap,
I have just been looking at the 1:500 00 map of our area, the journey this particular A109 takes is from North East to South West when approaching my home base, the regular flight line takes this heli down the centre of a long natural valley with hills ranging from 1850ft down to my elevation of around 800ft , quite possibly this natural earth shape could be tunneling the sound and stopping it from any form of errosion, but yet non of the other Helis ever sound quite as loud, wth the exception of the Ch47.

The Lancashire ASu from Warton is positivly whisper quiet compared with this particular A109.

PeterR-B

[helicopter-redeye]

A109s and S76 series helicopters make the most noise footprint overhead HQ Redeye as well so its not just knackered ears and Lancashire landforms. 90 to 150 secs before overhead is a good average for hearing them coming

[John Eacott]

Peter,

The topography would certainly funnel the noise, you may just be in a position to cop the worst! Re the 109E, if it doesn't have the tail rotor upgrade, it will be horrendously noisy

Then again, the dear old Huey/205 can be considerably worse, especially since it wanders around at 70% of the speed of the 109, giving you that much more time to enjoy the Vietnam experience

Here's a photo of the new Power tail rotor blades, which do so much to lessen the noise impact:

[Vfrpilotpb]

Well would you believe it, about 1520 hrs Gmt today one of these Helis (A109) flew over at about 750ft going like stink on a heading that according to my map is exactly West to East, topography is pretty constant at about 800 ft with no obvious hills or troughs, footprint lasted a fewseconds longer than 3 min.

So I am begining to think the topography of the NE to SW flight line is giving me the increased and longer noise due to the shape of the local hills, and quite possibly the direction of the wind.

Will have to see what a still/calm day brings

John, thats some set of paddles, is the light grey strip stainless to help avoid the abrasion, and is that centre hub left like that or does it get covered ?


Peter R-B
Vfr

[Vfrpilotpb]

Just to add a little more to this thread,

The A109 that flies over my home/office at least four times per week, has now confounded my assumption of Geography being the culprit for channelling the huge blade beat noise well forward of the actual heli, on Tuesday this week(17th May) just here we had clear blue sky to the NE, with a slight Northeasterly wind of about 12 to 15 kts, pilling up on the westerly horizon was a deep low which was proceeding some very dark clouds with a base at about 4/6k ft this was comming in from the direction of the Irish sea and North wales, the landscape is nearly flat really untill North Wales.

I heard the obvious beat of the A109 at least 2 minutes before I saw the dot that was to prove to be the machine in question the noise became loud enough to feel that I was stood very near to the Heli, it was flying at about 2kft almost head on into the 12/15Knt wind above a reasonably flat landscape but under cloud cover as described, my estimate of his sound footprint was around 5 miles in front of the heli, but not engine noise it was main rotor noise/beat

When just a few degrees past my overhead position it was as if the engine and blades had stopped working, I could not hear the heli at all, at that point however the pilot had blue sky above him.

Sorry to bore you all with this but I feel that weather has more to do with channelling sound than geography!

Peter R-B
Vfr