gilcon

My club is considering raising it's noise limit (for gas) from 98 @ 3M to something higher like 100 or maybe the current IMAC test which would equate to 102 @ 3M. Our current noise limit has been in place for over 20 years, but the current crop of flyers prefer gas and find it hard if not impossible to meet that limit with the 50cc size engines such as the BME 50 or Brison 3.2 with off-the-shelf components. We do have a new subdivision (4 years old) about a 1/4 mile off one end of the runway and had 1 unsubstantiated noise complaint last summer (none previous to that) while we have "cheated" on our 98 rule. What do you guys think, is that the right way to go or should we tough it out at 98 and be as good a neighbor as possible? BTW, I support the 98 and fly gas, but am in the minority. Thanks for your input. Oh, I almost forgot, a new certified noise meter has prompted this discussion.

NitroWoman

Sounds to me like if you have housing 1/4 mile away and you value keeping your field, the last thing you should be considering is raising your noise level limits. If the Gas guy's can't (or just don't want to) meet the limits, send them somewhere else.

JohnW

My Feedback: (6)

I gotta agree with NitroWoman, don't raise the limit if you have residential neighbors near by, esp if they are only 1/4 mile away. While you haven't had any serious complaints yet, all it takes is one complaint by the right person and your field is closed forever.

You're still going to be heard at 1/4 mile with the sould limits. However, if you do get complaints, you can at least show that your club enforces sound rules that were adopted by an national organization (IMAC.) This may help your case.

I too fly large (100cc +) gas, and my planes meet the IMAC 2003 sound limits. However, I have been told my plane has been heard on up lines as far away as two miles.

Three is no good reason that a BME or Brison 50 can't meet the IMAC sound requirements when stock 150cc engines can meet it. It might not be the engine, i.e., just need to reprop with a different brand, etc. However, many 50's at my field are a LOT louder than my stock DA100. I think it is because the mufflers on many 50's are very poorly designed. Maybe certain engine manufactures need a phone call letting them know their muffler needs work as it potentially could cause many fliers to loose flying sites, etc.

Cheers.

Lynx

98 @ 3m vs 103 @ 3m might not seem like much but that is a HUGE increase in volume, considering 3 decibels is a doubling of the acoustic power (Human ears don't register it as 'twice as loud' because we hear based on a log system not a linear one) Considering how loud 98 is in the first place.. =)

Divesplat

My Feedback: (7)

Gilcon. I think that trying to keep the noise down is a good thing and still a hotly debated issue.

believe you have your IMAC info incorrect though. The large props and gas exhaust noise cannot be measured and don't represent flying noise appropriately at 3M. Last I knew it was 98dB at 25ft, with the meter aimed directly at the prop arc, 25 setting 25inches(I think) off the ground. The Pattern method was to aim the dB Meter at an angle to the fuse of the plane, at 3M without any heigth requirement.

It may be worth going to the IMAC website and geting the accurate skinny on this.

Ed

gilcon

Divesplat,

Going back and checking the IMAC stuff, the 2003 limit is 96 pavement, 94 grass, @ 25'. It goes down 2 dba each year until the desired level is reached whatever that may be. I was wrong in my initial statement which should have been for pavement. The equivalent 3M reading would be 104 @ 3M (+ 8 dba going from 25' to 3M per their document) for comparison only. Thanks for the input.

Hall

Grommet

My Feedback: (1)

Divesplat

Why do you say that the larger props and engines cannot be measured at 3m? I'd like to understand more about that.....

Thanks

Mike