RunRyder - F3C 2006 noise limit 87 dB

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Aerobatic FAI F3C Contest > F3C 2006 noise limit 87 dB

Four Stroker
Veteran
Location: Atlanta

Effective Jan. 1, 2006, the noise limit is 87 dB over grass. This is a big step from 92 dB. The new rule must reflect that someone in Japan can already meet this limit. What engine/muffler can achieve this ? Does it also involve gear noise suppression ? Blade noise in the wind can add a few dB also.

The average airplane at my local field is about 100 dB. Most of the heli's hover at about 90~92 dB. The one who makes the most noise wins.

09-03-2005 Over year old.

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

How is that limit to be measured ?

Wolfgang

09-03-2005 Over year old.

HOMEPAGE

Four Stroker
Veteran
Location: Atlanta

Head high hovering over grass from a distance of 3m. 89dB over asphalt or cement. Heli is rotated through 360 to find highest reading. This is not necessarily pointing at the muffler due to gear noise.

09-03-2005 Over year old.

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

Also, is that "A" scale or "C" scale measurement ?

Wolfgang

09-03-2005 Over year old.

HOMEPAGE

Four Stroker
Veteran
Location: Atlanta

dB(A)

09-03-2005 Over year old.

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

A few years ago, I did some testing and found that simply changing the muffler can hav a 4 db change in the sound pressure level. Went from 88db to 84db or something like that (at about 3M) on a 50 size. The quire muffler was an off brand from Great Lakes at the time.

Wolfgang

09-03-2005 Over year old.

HOMEPAGE

Four Stroker
Veteran
Location: Atlanta

We tested all of the local Heli's one day and got about 90 dB on all of them hovering. Long ago I tested heli's at a contest and found about 92~93 dB hovering ( 60 size days ).

There seems to room to fake it since there was no rule that I could find that said you had to compete at the same hover rpm that you were tested at. i.e. you could test at 1100 and hover in the contest at 1500.

The old YS90 four strokes could easily meet the 87 dB(A) but would not be competitive with the new 90's. Only about 2 HP.

A new wrinkle are the new Fuji big gas four strokes 25 and 34. There is no rule for gas four strokes in 2006.

09-03-2005 Over year old.

raptorheli2
Elite Veteran
Location: rip off britain and no changing it

the old "cheat switch" will be seeing more action than normal me thinks now.

. been about in planes for a while. trim a couple hundered rpm off the top with a throttle curve not going to 100% when your being judged.

cheers

www.waterfoothelis.com

09-03-2005 Over year old.

HOMEPAGE

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Aerobatic FAI F3C Contest > F3C 2006 noise limit 87 dB

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