Thorp Air Command - T18.net

Interesting back and forth I had with Sensenich yesterday/today (starts at the bottom)

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Lee:

I am familiar with Santa Monica Propeller, but not Sandy?

I guess my main concern, certified aircraft or not (although, I do admit that I thought the Thorp T18 was certified?), is that the propeller 76EM is not suitable to be cutback, or pitched that highly and run on the O-360 engine. If further testing was done by Sandy, or Santa Monica Propeller, we can not support it.

Perhaps Ed Zercher, who worked here since the dawn of time (smile) but retired last year might be aware of it.

Happy flying!

Denise

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Denise,

Sorry, that was a misprint I meant Sandy Friezner, he has long been a respected propeller vibration engineer (he may have passed on). We are not talking about certified aircraft here so STC's and or type certificates do not apply.

I understand your position, look back and you will see that Sensenichs' official position was that the 76EM cut down to 68" was perfectly acceptable for engines up to the 0-320 back in the 70's/80's. As far as the 0-360 goes, you are correct, Sensenich did not approve that prop officially for use on that engine but as I said after the vibration analysis was done by Sandy Friezner at Specialized Testing Srevice and or Santa Monica Propeller numerous T-18's including Don Taylor's round Round the world T-18 (now hanging in the EAA museum) used this prop (in fact the exact prop dimensionally Dick originally contacted you about)

I won't take any more of you time, I do thank you for what I've already taken.

Sincerely,

Lee Walton

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Lee:

I stand my statement that using a 76EM8 series cutback 8

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Lee,

I have a Sensenich 76EM8-6-68 prop that came with a non -rotational survey from Specialized Testing Service in North Hollywood. It was done on Oct 10, 1983. Signed off by David J. Payne on behalf of Sanford Friezner who was the president of the company at the time. They suggested that the prop not be operated continuously between 2520 and 2719 rpm. The prop was originally purchased from Santa Monica propeller for $1320.00 and at that time it was twisted to 71" of pitch.(This was March 22, 1983) The previous owner of my plane had an 0-320 engine that was tired. Hence the pitch reduction. At that time according to my papers, Santa Monica Propeller was an authorized agent for sales and service of Sensenich props.

Let me know if you would like a scan of these.

Jim Mantyla

Thanks Jim!

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Lee,

I was thinking that we would not want to see Sensenich issue an AD on these props that have been working so well for so many years. Sounds like some one there is getting nervous or as you stated looking to sell more props.

Jim Mantyla

I think were ok Jim. Nearest I can tell it was just a missunderstanding. Besides, we're flying experimentals, they won't issue an AD on custom builts. My impression is that the girl I was going back and forth with was a lacking a little info. First, she thought the T-18 was a production aicraft, second she wasn't even aware that they cut down M76 props. The Faa considers the M76 an experimental prop anyhow so were already 'breaking the rules'.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Hello all,

Been running a the 76 Sensenich on and 0-290gpu and it has over 800 hours. Great peformer which stays right with the 0-320 and 0-360 ships. Prop was repitched from 68 to 73 pitch some time ago. We keep a close eye on it and don't push it much. Still cruises great around 160 to 170mph. Flat out at altitude it does 190mph. Should I dump the prop and go to wood?

Brent Schultz
N6CM
Corona Airport

There's nothing wrong with the M76 especially on an 0-290. From what I can tell the folks who worked with the T-18 group back in the 70's have long since retired and the new folks are only familiar with the new 70/72 models.

That being said, it's pretty much unanimous that the Aymar-DeMuth prop outperforms just about everything else out there. So if it's performance you're looking for then have at it. But if you're concerned about safety and the M76, fear not it's perfectly fine on the Thorp.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD