Propellers

[6643]

I get about 2100 with the 52. 48's are common on C85's. If there's anyone else around with one maybe you could borrow their prop and try it out. If you have a friend with an Ercoupe and A C85, they may have a 50. At your elevation, if you want to do any short field work, you might want to avoid the 52.

I used to fly out of a 1400' strip at 1650'MSL with obstructions at each end. It was a one way strip due to the slope, about 4%. If I was taking a passenger, I had to pick the right conditions. I'm guessing my prop is about equivalent to a 51. I had it pitched to 52 but the actual length is 70. I don't think any compensation in pitch was made due to the missing inch.

Oh, BTW, I can cruise at 2350 and 115 mph IAS. (At least that's what the instruments say...)

[8233]

I get about 2100 with the 52. 48's are common on C85's. If there's anyone else around with one maybe you could borrow their prop and try it out. If you have a friend with an Ercoupe and A C85, they may have a 50. At your elevation, if you want to do any short field work, you might want to avoid the 52.

I used to fly out of a 1400' strip at 1650'MSL with obstructions at each end. It was a one way strip due to the slope, about 4%. If I was taking a passenger, I had to pick the right conditions. I'm guessing my prop is about equivalent to a 51. I had it pitched to 52 but the actual length is 70. I don't think any compensation in pitch was made due to the missing inch.

Oh, BTW, I can cruise at 2350 and 115 mph IAS. (At least that's what the instruments say...)

I assume that's with a C-90 John? What does you TAS end up being?

[6643]

Yes, a C-90. TAS? Who knows... I flight plan for 110mph, but who's keeping track? I usually use about 2000 RPM for casual cow watching.

Everything you ever wanted to know about propellers, and more!

[8233]

Yes, a C-90. TAS? Who knows... I flight plan for 110mph, but who's keeping track? I usually use about 2000 RPM for casual cow watching.

Everything you ever wanted to know about propellers, and more!

I know what you mean. It was curiousity on my part to compare how my C-90 performs. I have a 44 inch Senseich 76AK-2 prop that is on the TCDS for the 85 but not the 90 although there are several examples where this prop is used with a 90 on other airplanes. Instead of replacing the prop, I paid a small fee to a DER who reviewed the data and gave me a field approval for using this prop. I believe it’s more of a climb prop and sits on the upper end of the static limits.

[8279]

This has been a great help. I appreciate everyone’s input! I’ve done a static check using a digital tach and am barely making spec on the high side. I have friends who have offered their propellers but so far not the right ones. I feel like I know a lot more about the issue mostly thanks to you fellas! I’m leaning toward a 50 because of the 5045’ field elevation? Anyway, thanks again for the input.

Boyd

[6643]

Fill in your location in your profile. You never know who might be near by! Taylorcrafts, Luscombes, Ercoupes, and plenty more, I'm sure, are commonly fitted with C85s and 7148 props.

[8279]

Wilco...thanks John

[5806]

I recently installed a BRAND NEW McCauley 1B90/CM7152 square tip and have been doing some testing. Here are the numbers using a digital tach.
Engine has about 500 hours total time.
Density altitude 1800'
2115 rpm static - cold
2135 rpm static - hot

78 mph indicated = 500'/min climb @ 2000' msl < 1/2 fuel
78 mph indicated = 420'/min climb @ 2000' msl > 3/4 fuel

2350 rpm = 109 mph indicated
WOT@3500' msl = 2445 rpm = 113 mph indicated.

[8279]

Thank you 5806...

[5765]

My original prop was red tagged for corrosion, so I was forced to buy a new McCauley prop for my 1948 Cessna 140 with C-90 engine.

After much debate (with myself), I settled on a 7152 configuration--in the middle of the specification pack. McCauley only manufactures the square tip prop these days, but at least they are available. With a long wait. And without the face of the hub painted unless you know to ask. (The skull cap spinner doesn't cover up the bare aluminum).

WOW!!! What a difference it made. My truly original 70-year old prop had been re-pitched to a 7154 according to the paperwork. All I can guess based on the performance of my airplane after installing the new prop is that the original (which I "overhauled" in 1999) was not even close to it's original shape. Why do I say that? Because I now have much better takeoff and climb performance (enough that I had to re-learn my take off technique) AND faster indicated cruise speed. No possible by the numbers, but entirely possible if the prop you are replacing is out of specification.