Propeller pitch question

kgassert

kgassert

New member
Hello,

Today I had the pleasure of removing a perfectly performing cylinder (78/80) from my Franklin 165 because the helicoil backed out as I was removing a spark plug. The cylinder will be on the way to Greg tomorrow. Anyway my question is this. It has been a long time since this propeller has been looked at , probably not since it was installed in 1987. I figure now that the engine is down might be a good time to send this prop to the shop. It is a McCauley 1A170 M7161. I get pretty good cruise at about 150MPH indicated but I am not too impressed with the climb or length of run for takeoff. I would be willing to give up 5 to 10 MPH of cruise to get better climb. How many inches of pitch do you guys think would be best to take out of this prop.

Thanks,
Kevin'
 
Kevin,

If you look at the TCDS for the propeller, I believe that it shows a max dia of 76 and a min of 74. Of course on the TDCS for the aircraft the McCauley is not listed but other props are to be max dia of 74 with a minimum of 72.5. Diameter is the first thing that I would look at, you are indicating that yours is a 71 in with a pitch of 61. Maybe your STC or field approval of the prop indicates a smaller diameter. Just a suggestion maybe look at a 74 dia with 54-56 for pitch. We might have a prop off of a Stinson that you might be able to try.

Dan Schultz
937-603-2459 cell
 
Dan,

Sorry, I meant to say 7561 so it is 75". It was installed under the Stolts STC that specifies 75" so I guess I need to stay with that length but it does not specify a pitch so I thought I would get this one overhauled and remove a couple inches off it but not sure how many.

Thanks,
kevin
 
Before you do anything. Verify the RPMs you are getting with a digital tach checker. This is a little hand held device, far more accurate than most mechanical tachs. Can you get 2800 rpm full throttle, level flight at about 3000' msl, after about 20-seconds? What do you get for takeoff? Generally, 1" of pitch change equals 100rpm change Dan
 
7561, 75 is diameter, 61 is the pitch in inches. Like Dan said, I'd make only one inch change.
Kent
 
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