ICAO Noise Test results RV-10

Michael Wellenzohn · #1 07-29-2014, 03:16 PM

This might not be of great concern of most RV-10 owners especially in the US but I consider this still an important environmental information for all the RV-10 owners.

My RV-10 has been built and accepted under Swiss regulations and one part of it is the noise measurement certificate. Landing tax are based mostly on MTOW plus a charge for the noise class your aircraft is in. So it was of great interest to achieve the lowest noise class.
https://s3-eu-irl-209-prod.digitalhu...b7Szq1b0tKrByU
As there was no data available about noise emission of an RV-10 I want to share my findings.

The main noise sources are the propeller and the engine noise via the exhaust system. As prop tip speed is one factor I decided to go with a smaller diameter 3-blade MT (MTV-12B/193-53) propeller. The next factor is of course RPM which I reduced to max 2500. It is quite common for GA aircraft in Germany or Switzerland to have RPM reduced to 2500 in order to meet the maximal allowed noise requirements. The next thing is the exhaust system/muffler. There are special mufflers available like Liese which are quite common to muffle the noise even further, however I needed my baseline first to make the call to install them or not and to be able to define its required dB reduction.
My RV-10 has the standard Vetterman 6-3 exhaust system and the above called 3-blade prop running max 2500 RPM. The test were conducted at MTOW 2700lb /1225kg.

ICAO Noise Measurement Test Scenario

ICAO Annex 16 Chapter 10
- Application accepted from 1988 onwards
One measurement point
take-off flight path with max. take-off power
Noise measured in dB(A)
https://s3-eu-irl-209-prod.digitalhu...jpA2gUHXvuH91k

The measurement crew on the ground takes a picture of the overflying aircraft to compare the logged overflight altitude reported from the aircraft with the measured results. At the same time it measures the noise. More factors are taken into consideration including wind, surrounding surface etc. I had to conduct 6 flights and the average noise values plus the correcting factors result in the final noise level in dB, which puts me in one of the noise categories mentioned above.

To make a long story short my RV-10 achieved 77.5 dB which falls under category D, which is the lowest available.
It is interesting to note that the only other RV-10, which went through the same test, is equipped with an two place Hartzell propeller (as well reduced to 2500 RPM) and Liese mufflers attached to the Vetterman exhaust pipes, achieved noise class C. Therefore it looks as if the propeller diameter and probably the tip form is a major contributor to noise. There might be other contributing factors such as sound insolation which might work as a reduction of resonance.

For all the builders who are building under a regulation where noise reduction is a topic I hope that might help to consider propeller choice besides looks, ground clearance and weight.

Michael
https://s3-eu-irl-209-prod.digitalhu...Akm9rBsvwX_mFc

RV10inOz · #2 07-29-2014, 05:58 PM

Did you not do a test at 2700 RPM?

If you can use 2700 RPM the benefits are twofold. More power and reduced stress on the engine.

I would be interested to know what the results are.

Michael Wellenzohn · #3 07-30-2014, 02:51 AM

Hello David
No I did not perform the test with 2700RPM as this would have put me outside of the acceptable noise class. It is not an option due to the noise restrictions.
I agree to the power increase however given the great performance of the -10 it's is no issue at all to get out of any airfield.
The table below shows T/O performance with 2500RPM, MTOW, flaps 1 (0 degress)
https://s3-eu-irl-209-prod.digitalhu...IWNn2_NHT-Ov3s
Regards
Michael

terrykohler · #4 07-30-2014, 04:26 AM

Michael:
First, very good job. I won't be surprised to see noise abatement requirements here moving in the direction that is standard for you. What is the difference between the various classes? For example, do they restrict the Class C aircraft from airports you can use, or is it more related to time of day operations or flight paths?
Terry, CFI
RV9A N323TP

Michael Wellenzohn · #5 07-30-2014, 05:32 AM

Hi Terry
No there are no restrictions I am aware of rather then increased landing fees. As far as I know only Germany and Switzerland ask for the noise certificate but I might be wrong.
Just an example from Augsburg (Germany)
They have four noise categories also A-D but in reverse order so D is the noisiest.

A 13.5€
B 22.10€
C 34€
D 47.50€

So the fees are more than 3.5 times higher if you are in the loudest category.

Regards
Michael

flyvans.com · #6 07-30-2014, 01:53 PM

michi,
congratulations again!

regarding requirements:
C and of course D are never an issue (other than landing fee difference).
but starting with class B and certainly A you get into trouble on many airports, either complete bans or time constraints. so you will want to achieve at least class C.

the perversion is in the ICAO system/calculation, as lightweight and overperforming aircraft are being punished, whereas heavy and absolutely loud aircraft are getting a lot of "credit". nothing against the 10, but it definitely profits from the rules compared to lighter aircraft.
having a high MTOM is definitely of advantage.

regards,
bernie

BlackhawkSP · #7 07-30-2014, 07:53 PM

The mere fact that there is such a scheme for any government to have an excuse to charge/tax you more for flying doesn't sit right with me. It's not like the noise exposure, duration, or distance from housing is that great/close, even in the most built up areas. I would do like you and test at the lowest noise possible, but afterwords I'd be at 2700 RPM any time I liked.

BobTurner · #8 07-30-2014, 08:10 PM

Quote:

Originally Posted by BlackhawkSP

The mere fact that there is such a scheme for any government to have an excuse to charge/tax you more for flying doesn't sit right with me. .

Well, welcome to the real world - here in the US.
True, I do not directly pay a noise charge/tax. But indirectly, I do.
Here at KLVK they maintain an 800 phone line for noise complaints. And they mail a letter to owners who violate the voluntary curfew (what does 'voluntary' mean??) this is all done to try to mollify a few people who bought houses in re-zoned (from agriculture to residential) property 3 miles off the end of the runway a few years ago. And how is this paid for? With the gas I buy, and the hangar rent I pay. Or maybe the federal taxes I pay. But one way or another I help pay.

blahphish · #9 07-31-2014, 09:06 AM

Thanks for this great info Michael and for starting this topic.

On long cross country trips I often think it would be nice not only for the people on the ground, but for the people in the cockpit if it were quieter. Perhaps even quiet enough to comfortably take off headphones at altitude. Do you have any data or comments on how much impact the muffler and/or prop has on cockpit noise? It sounds like perhaps the prop is the biggest contributor but I am curious to what degree the muffler helps at altitude.

Michael Wellenzohn · #10 07-31-2014, 01:22 PM

Good question I am planning to do a not so scientific noise measurement In my -10 and compare it with the other -10 here but I guess that will take a couple month. I am not sure if the external noise measured on the ground will directly correlate to the cabin noise. Anyway once I can get hold of a decent measuring device and find time I will write it up here.
Mike