Cruisair Metal Prop STC (The Other One)

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NC86786

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Hi, Everyone. Does anyone out there have a copy of SA1029WE? This isn't Dr. Solt's STC, but one by Kenneth Eddy Matthews of Poulsbo, WA. The difference is that Dr. Solt's STC calls for a 75" 1A170 McCauley, this one allows a 76". I have a 76" lying around, which I'd like to use, but Dr. Solt's STC precludes this.

If you have a copy of this one, I'd love to hear from you.

Thanks.
 
assuming your 76 inch prop needs to be repitched, couldn't the prop shop cut it down to match Dr Solt's STC? 25 years ago, I bought a right to Dr Solt's STC from Dr Solt (I recall he was a Dentist in Eastern Maryland) He told me the FAA went for a test ride with him with the prop-observed its flying characteristics and then and there issued the STC-no engineering studies, no vibration studies. Try that today! Good luck finding the other STC
 
A few years back Eddy Mathews widow was still alive and selling the stc for $25 . I believe she was still in Washington state Maybe an internet search could locate her? Larry lowenkron might know more about her location.If you find out about the stc please let us all know because many of us would like to buy a copy with the correct approval letter. Good Luck ;Grant
 
I found Joan Mathews' heir. He will dig out the STC and see if he wants to give me a copy or offer to sell me the right to use it. I'll post on this topic when I know how we'll proceed, so I can keep everyone in the loop.
 
I just got a phone call from the Mathews, saying they have applied to the FAA to transfer rights to the STC to Joan Mathews son and heir, Bob. I don't know how long it will take for the paperwork to clear, but I will let you all know when it does.
 
I was just looking through the Sensenich co. web site and came across a letter from 1954 saying that the company gave blanket approval to replace any previously approved Sensenich wood prop with an equivalent Sensenich metal prop.This was under miscellaneous documents.If I am reading this correctly, this eliminates the need for an STC to put a Sensenich metal prop on our Cruisairs. Could one of the Gurus look this up and see if I have a case of wishfull thinking or if it is true? Grant.
 
gjordan:

If it were only that easy. It would depend on the thinking of the A&P / IA that sign's it off. Franklin SL 72-2 dated March 1972 refers to Bellanca 14-13 FAA TCDS or STC's for approval. STC SA29EA list's a Sensenich 74DR-0-60.
The blanket letter you mention is good data for a field approval along with the data from an STC that is no longer available.
It shouldn't be that hard to get it approved.
The later model crankshaft in the 150's has a different flange dia. than the early ones.
I couldn't find the 74RA propeller in the Sensenich list of propellers they make or have made in the past. The TCDS gives you an out if you wanted to install a wood propeller as it says (any) wood propeller rated for the engine.
 
What got me looking through the Sensenich web site was my adventure in varnishing my prop.When I removed the spinner to do a good job of varnishing I had a real surprise. The prop bolts had no safety wire. There were also 2 different types of bolts. I am cleaning the plane up to get it ready to annual and I hope I dont find any more surprises.My real question is what are the correct prop bolts for a Franklin 150 with a Sensenich W74-RR66. I looked in my Bellanca manual and only could find numbers for Aeromatic bolts. Franklin manual didnt tell me anything more and a call to Sensenich hasnt gotten me anywhere yet. Maybe the bolts in it are approved but I cant find them in 43-13 . They are all drilled and 6 of them have CXS on the head. The other 2 have a triangle with a small dot in the center. I cant find either in 43-13 or in the Aircraft Spruce catalog. Any advice will be welcome. Thanks,Grant.
 
Grant, Piece of cake. Measure the thickness of the propeller hub at the flange, measure the thickness of the crush plate at the bolt holes-accurately. This should be the grip length. I like a thin steel washer under the bolt head. Go to a bolt guage or spec sheet to get your part number. You need a drilled head bolt - either an AN6 or AN76 series. Something like AN6H-45A is close. The point is, that after the prop is torqued correctly - 200 in/pounds, per Sensenich, there should be at least 2-3 threads showing in back of the inserts in back of the flange. The CXS is nothing more than a brand's headstamp. The triangle with a dot on the head, 'I think,' means magnetic particle inspection. That 66 prop is probably an OK cruiser, but not good for short field, high and hot conditions. Now, you could spare yourself all of the above by bolting a decent A E R O M A T I C and have the best of all worlds. Have fun, Dan
 
Thanks Dan,I will measure tonight and see what I can order. You are absolutely right about the prop being a cruiser, not a climber. I only have a couple of hours in the plane and it sure uses a lot of runway.It barely turns up to static and has a anemic climb rate. An Aeromatic will be in the not too distant future,but for now I just want to solve all of the little problems and get it through an annual . Thanks Again. Grant.
 
Drum roll, PLEASE!

I just got a phone call from Bob Matthews, who finally has gotten rights from the FAA to his mother's (and father's) STC. He's willing to sell you one for $125. If you're interested, his phone number is 360-697-6160.

I got tired of waiting and put my other prop on, with Dr. Solt's STC.

Mike
 
OK., all you folks, so eager to install one of the fixed pitch metal props................There is an RPM limitation when installed on the 150/165 Franklins. I don't have the exact figures in front of me; but I believe all operations, except transitional power, between 1950 and 2250 RPM are prohibited. It used to be that all aircraft with this combination had to have an advisory sticker posted on the instrument panel. Failure to abide by this restriction can result in a broken crankshaft. I'm so old that I've seen this, too. Can anyone else supply more info? Dan
 
Having had the Solt STC on a 14-13 (150 HP) I don't recall that it would ever run in that RPM range during normal operations.
 
The RPM limitation on Dr. Solt's McCauley STC is "Avoid continuous engine operation between 2100 and 2300 RPM". I seem to recall that the Sensenich STC has a narrower restricted band...maybe 2150 to 2250? Dr. Solt also had an STC for Sensenich props on Crusiairs, but I never saw it. I do have the data for the Mathews STC now, but do not have permission to use (install) it.

Larry
 
The Matthews STC is for the 165 hp engine with a 76 inch (Max and Min) dia McCauley 1A170-DM765 prop. The RPM limitations are "Avoid continuous engine operation between 2150 to 2250 RPM."

Dr. Solts STC is for the AIRCRAFT and does not specify the engine. It does say the prop dia is 75 inches and has the slightly bigger rpm restriction band.

Sorry about making this into two posts.
 
Curious that Stolt has that curious rpm restriction. Probably just guestimated and we are all test pilots. Stolt told me that the FAA taxied out with him. Had him run it up, then a brief flight while they watched the tach and then signed off on it. No science, no engineering, no vibration reports on the various stations of the prop etc. I would ask around and look into any other data from other aircraft with a similar prop/engine combo and make up my own limitations rather than adhering to Stolt's.
 
The problem is that some of these restricted ranges are in a power range that could be used in descent. When you add power, as in takeoff, the engine passes quickly through this range and you never experience the harmonic vibration. When you slowly reduce power, you will feel it. Franklin's later engines, that were designed to drive a constant speed propeller added the Houdaille Viscous Dampener to the starter gear to rid the engine of harmonic vibration. I believe this dampener can be added to the 150/165 series. Ask Greg Lucas or Don Maxfield about this. Dan
 
I may be hallucinating (being a child of the sixties), but I swear I can feel when my engine is in the restricted rpm without looking (sometimes). As I recall, when I put my McC on, I talked to both Sensenich and McC. and they talked about the harmonics. Charlie Hart also talked about it one year at OSH. He said that you won't feel anything before it comes apart (hence the reference to hallucinating), but I don't really want to exercise my Glider rating privileges in my Cruisair. Regarding Dan's comments about descents; definitely is something you have to be aware of, but it is more of an inconvenience than anything. It does force you to think ahead.

I did find Dr. Solt's Sensenich STC(SA29EA) The limits are for the M74DR prop on the 165 engine with:
static rpm limits of 2290 to 2340
60 in pitch
72 to 74 inch dia
continuous RPM avoid limits of 2150 to 2250
 
I read an article describing the process Beech went through in the mid 40's to figure out prop limitations, so that science was around then. The Stinson 108 had the 150 Franklin Engine 6A4-150-B31, -B3, or -B4 with an MacC prop or 74-76 inches (pitch not mentioned but static RPM defined) and they had a redline area of 2100 to 2300 RPM. They also had the 165 Franklin Engine 6A4-165-B3 or 6A4-165-B4 with an sensenich propof 74-76 inches (again no pitch but does have static rpm)but now a redline of 2100 to 2250 http://www.stinsonflyer.com/avtextsf/a-767.pdf has the details (read all the way to the bottom to see all the possible props and pick the one closest to an all metal sensenich) I might guess that Stinson might have put a bit more science into their recommendations than Stolt- Read the entire type certificate as they have info for wood props and 2-position props etc.
 
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