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Hi Bill,
I think your information is old on the MT Propeller. The MTV-14D ****195-30a that I have on my L4P when attached to a (TS)IO-550 or 520 has a TBO of 1800 hrs. per there website TBO variable propellers bulletin Feb. 10, 2003. Interesting that the engine has a TBO of 1600 hrs for TSIO.
I should also point out that this propeller is Certified on these engines by the FAA on the Malibu and other planes. This is the email form MT to me:
It is correct, that the MTV-14-( )/195-30a is FAA certified with different hubs on the Piper Malibu/Mirage. However, the STC is not ours, it is
owned by VK-Aircraft in St.Petersburg. The STC-No. is SA-01654-AT for the MIrage and SA-01542-AT for the Malibu with TSIO-520 and TSIO-550 engines.
The Propeller itself has FAA certification with TC/TCDS P3BO, hence is in compliance with FAR23.905 and we have also vibration approval for the TSIO-550
in the Lacair IV-P, so we are in compliance with FAR23.907. Please let me have your fax number and we can send you the statement. Hope, this will help to eliminate the fly-off time because it is an approved combination.
Best regards
Gerd R. Muehlbauer
President
MT-Propeller Entwicklung GmbH
I was able to show this 19 months ago for my fight test and only had to meet the 25 hrs rule for Certified engine/prop. combos.
Usually, the 4 bladed prop is at least 1 inch less in dia. than a 3 blade, giving it lower tip speeds. And some theories show that the pressure wave of one blade works better while following another blade more closely and the pressure is less per blade. That is why some feel the smaller dia. 4 blade is the same performance or better than a longer 3 blade. But we all know that ONE blade is the best.
I was told that same false information before I looked into it.
Best of Luck getting back into the air soon,
Jim Hergert
N6XE, "An Sex Y" L4P
4 Blades and Wingtits
I have no experience with props. I know that as you add engine H.P., you should increase the blade diameter to utilize the extra power. The limiting factor then becomes ground clearance for the blade tips. The compromise is to add blades. I know that Don Goetz used the first 4-blade prop on his Lancair IV but I think that he wanted his machine to look different. I asked him if he could quantify the differences between 3 and 4 blades on the same engine but he suddenly found something else to do.
The only differences between MT and Hartzell that I am aware of, is that the MT is a composite prop and requires a 400 hour overhaul instead of 500 for the Hartzell metal prop. I suspect that the MT might be a little cheaper, however I dont think that a 4-blade prop has ever been certified on the L-IV by the factory. This means that you would require a 40 hour test program instead of 25 hours.
Regards, Bill Hogarty
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