Prop strike yesterday (and propeller specific noise level)

Well, we got a massive spanner in the works now.

We received the new noise certificate and guess what: According to the Swiss CAA, this prop is the loudest on the planet, the airplane is put into the highest allowable noise class and therefore can’t use a majority of airfields anymore who ban class A.

This after the test flight where we noticed that with this prop we can talk inside the plane without headsets and the people on the ground said it was very quiet on take off and on the one go around we did.

I hope it’s an error but I doubt it. It was classified by Annex 10 iso Annex 6 and apparently with reference to some EASA listing.

To say I am furious is putting it mildly. If this is what it is, the airplane will need to get sold outside the country, particularly outside Germany and Switzerland, who appear the only ones who care about noise certificates.

So if someone here is interested in a well equipped C Mooney with 3 blade Hartzell Prop (2.5 hours) and an engine which is just back from the shop at 600 hours with a new crankcase, fresh annual and ARC, you can let me know.

Airborne_Again wrote:

Why can’t you just put a 2-blade prop on it again? Another question is why the shop choose to install a 3-blade prop without consulting you? Or did they?

Ok. Thank you, I fully understand the situation now. Fact is, I was naive, stupid and it is all my fault.

After the prop strike, the maintenance organisation contacted Hartzell for a replacement prop. We were given a possible delivery date in February (was June in the end) for the 3 blade prop, 2 blade no delivery date was given, it was listed as not available.

So like a total amateur I concluded that a 3 blade prop is anyway better because it is quieter, so let’s take the one we can get the airplane going the fastest. This opinion was also voiced by the maintenance who then ordered the prop nor did the European Hartzell Dealer think it necessary to say something.

Nobody thought of checking with the FOCA or EASA. Again, my fault entirely. So I am now loaded with a prop I can’t use. I can also not afford to wait for a new 2 blade one which probably will cause another 9-12 months delay. By then the airplane will have disintegrated from disuse.

So now it is clear: The 3 blade prop on paper is much louder than the 2 blade or rather it is certified under a different Annex(10 iso 6) where it is right at the top. The noise classes go after the simple DBa, they don’t care about the Annex. So the 2 blade was at 74.2, the 3 blade is at 85.4. It appears the noise classification by the BAZL is simply taking the numbers, disregarding the certification base. Only like this is it possible that a much quieter prop is declared double as loud.

This clearly means we can’t use it. It precludes any training use and with Noise class A the airplane is banned from most airfields. This may well mean the end of my involvement in aviation. For good.

Graham wrote:

Could you move to France?

The airplane can. It is for sale now.

172driver wrote:

I cannot image for one second that EASA (or anyone else, for that matter) has tested all airframe / powerplant / prop combinations.

Apparently yes, these are test results, provided by the manufacturer together with the STC. So they are from the US, where of course nobody cares about noise.

The main thing is: Noise certification within ICAO Annex 16 has changed some years ago, where noise was certified with a fly by technique, according to Chapter 6. The new certification according to Chapter 10 records the noise at take off power, which naturally is much louder.

Consequently, under Chapter 10 a plane has to be much quieter to achieve the same noise certificate than under Chapter 6.

Switzerland has a national noise certification for the purpose of charging punitive noise surcharges, classified from A to D. I have not been able to find out exactly how they are issued vs the different chapters, but the fact is that this combination of airframe-prop is basically at the very maximum ICAO chapter 10 allows, so therefore it can “just” receive a noise certificate, but will be restricted in operation. Noise class A in Switzerland means quite a few restrictions such as no training, lots of airfields prohibit class A airplanes from visiting and of course you get massive noise surcharges on top of the landing fees where they are allowed.

The list published by EASA defining all the noise certificates available is binding and non-negotiable, even though to the naked ear the 3-blade prop is audibly quieter than the old 2 blade, the certification base is set in concrete.

The mistake which now de facto lost me my airplane is that neither me, nor the maintenance organisation nor the propeller dealer looked this up before we ordered the new prop, but we ordered it purely on availability and with the misguided opinion that a 3 blade prop is quieter than a 2 blade. Well, wrong. I will have to now negotiate to return the new prop to the dealer and somehow source a 2nd hand 2 blade prop identical to the one we lost in the accident.

Failing that, the airplane will be sold off to a country with less strict noise restrictions. In Switzerland, this airplane is practically worth nothing anymore.

Fact is, we will miss another flying season and the airplane remains grounded for the forseeable future, as Hartzell can not deliver any 2 blade props. So the best variant will be to sell it off to the highest bidder somewhere outside Switzerland and Germany. If anybody here is interested in a Mooney with a brand new prop, engine with new crankcase and 650 hours since OH, full IFR then drop me a PM. I am open to offers for a very fast sale.

eurogaguest1980 wrote:

If you feel the classification is not accurate, you can re-test.

AFAIK you can not overrule a chapter 10 certification with a chapter 6 testflight. But we will have to find out. I guess this will be food for lawyers now if I don’t run out of money before that.

Thanks @RobertL18C

they were as shocked as I was. Whom I really blame is the propeller dealer, who has to be knowledgable in these things. They knew what model airplane it was for and they should have said something. Other than that, what you don’t read yourself is your own fault. I am mainly furious at myself.

I’ll leave what ever registration the plane gets to whomever buys it.