As a follow up anyone have a contact at MT Straubing? Interested in talking about the 5 blade PA-46 prop while I am there. Sales email comes back with "I am away for 2 weeks". Not super helpful.
MT propeller consists of two companies: One doing development (which includes the sales function for new props) and one doing maintenance on/for existing props.
Having said that, I exchanged my previous 2-blade metal prop against a 3-blade MT composite prop three years ago and dealt exclusively with Wolfgang Sell who is the MD of the maintenance company. Found him to be quite helpful and responsive. He can be reached via phone +49-(0)9429-94090 or [email protected].
While you are in Straubing you might want to pay a visit to Rieger Pilotenservice which is the local maintenance shop and talk to either Wolfgang Rieger or Jan Schroeder. Some of their turbine customers already installed 5-blade MT props so you might get an additional view or maybe some further contacts.
Are you going to stay overnight in Straubing? If so, I can recommend the Hotel Asam which also has a very decent restaurant attached. When my plane is in for the annual I always spend two days at the maintenance shop to help and to learn and usually stay at the Asam.
did you get the "increased noise protection level" with your 3blade & T/O RPM reduction? What colour has the MT prop? thanx
I recently overhauled my 2 blade metal prop at MT, and I have nothing to complain about. They were helpful on the phone, and work was done within budget on time. I do speak german though.
I also asked about replacing the 2 blade metal prop with a 3 blade composite MT prop, and they advised against it, because cruise performance would suffer quite a bit (which seems to be true, according to a friend whose aeroclub did the conversion on a very similar aircraft)
did you get the "increased noise protection level" with your 3blade & T/O RPM reduction?
Yes, but for the higher noise level certificate it is also required that a Gomolzig exhaust system is installed in the plane (which mine had). Also, this only applies to the TB20 and not necessarily to other types of aircraft. It is also worth noting that MT have different 3-blade composite props certified, depending again on type of aircraft. Some are older designs.
What colour has the MT prop?
Mine is grey with fire-engine red tips but they produce the colouring of the prop according to the specification of the buyer. AFAIK, pretty much any combination (I saw a neon green MT prop with yellow tips on an aerobatic plane in Oshkosh once) can be orderered but going from what I see on ramps most people tend to pick white, black or grey as the base colour and some form of red for the tips.
As a follow up anyone have a contact at MT Straubing? Interested in talking about the 5 blade PA-46 prop while I am there. Sales email comes back with "I am away for 2 weeks". Not super helpful.
I only know the 4 blade PA-46 prop, but SebastianG (in this forum) who i met there three days ago just got the 4 new four blade prop, he can probably tell you all the details about the 5 blade version, and why he didn't get it!
I also asked about replacing the 2 blade metal prop with a 3 blade composite MT prop, and they advised against it, because cruise performance would suffer quite a bit (which seems to be true, according to a friend whose aeroclub did the conversion on a very similar aircraft)
At least for my combination of airframe, engine and prop I cannot confirm that. Cruise performance is exactly as before with a 2-blade metal prop.
But then, not all combinations of airframe, engine and prop might lead to the same result and some designs and STCs from MT date back a bit. They might have newer designs of props which could also go on additional airframes but never obtained STCs for them because of lack of demand and cost associated with obtaining the STC.
What is the cost of the TB20 4B prop, and what is the weight difference?
I can confirm that a 1980s TB20 with a 2B prop (and a fresh engine) does exactly the same cruise speed as mine with the 3B prop, for the same fuel flow, peak EGT, same rpm etc.
But a 3B prop looks better, and a 4B prop would look better still 
Thanks guys. I am just there for a meeting and then a couple of hours in the afternoon. I will try emailing Wolfgang. I think the 5 blade is just for turbines.
At least for my combination of airframe, engine and prop I cannot confirm that.
Yes of course this is very much airframe specific. Mine is a Piper Arrow. The reason why people did the 3 blade conversion was less noise. But I personally find the cost of ~7kts less cruise for the same fuel not so attractive.
There are IMO two reasons why the MT prop is less noisy than a metal prop:
it absorbs more of the vibration energy (but that is likely the reason why an overhaul is essentially a replacement)
it has less diameter, causing the prop tip speed to be farther below the speed of sound
But the lower diameter also causes a larger percentage of the propeller disc to be in the shadow of the cabin, which must cost efficiency.
A 3 blade prop will always be less efficient than an equally well designed 2 blade prop. But at least at the higher power spectrum, more blades are needed due to mechanical forces.
I once tried to calculate the prop efficiency for my aircraft. If my calculations are correct (bit of an if because due to lack of design data I needed to match models to POH data), the prop efficiency in cruise is in the 90s. So there's almost no way to gain in cruise, one can basically only loose. In climb it's in the 70s - that may be why climb performance of these alternate prop STC's is not materially different or even slightly better than the original prop.
