Prop Survey

[Andy Metzka]

Just wondering what most people are running for propellers? Any preference for McCauley or Sensenich? Are you satisfied with what is on the plane or have a wish list for something different?
I live in flat country and like grass strips- currently running a Sensenich 74 56 because that was on the plane when I bought it.

[Bruce Fenstermacher]

Most 170s have a McCauley. I have the McCauley and the Sensenich. I run the McCauley. I have run the Sensenich just to see the difference and to be honest couldn't really tell if there was. If the performance numbers in the Owners Handbook didn't tell me the Sensenich performance was ever so slightly less, I'd never know it and be telling you they are the same.

Because most of the numbers in the handbook are for the McCauley, and I like to compare my performance with others it is nice to have what everyone else has. I also want every advantage, even if it is only perception cause I can't tell the difference. So I run the McCauley.

If I needed a prop, I'd be looking for another McCauley but if I found a Sensenich at a good price I wouldn't pass it up.

If you think you will see a performance gain replacing your Sensinech, you will be disappointed and it will be the worst money you spent.

[bagarre]

+1
The differences in the props are at the academic level unless every meteorological condition is exactly the same.
Before thinking about swapping props, I'd think about repitching the one you have.

And this is coming from a guy trying to sell a McCauley at the moment

[48RagwingPilot]

McCauley 1C172MDM7653

I'm happy with it but would like to try an 80/42 just for grins. Unfortunately, I don't think that prop is approved for ragwings.

[n2582d]

... would like to try an 80/42 just for grins. Unfortunately, I don't think that prop is approved for ragwings.

Anyone know if Wick Air is still around?

[48RagwingPilot]

Just got off the phone with Aaron @Wick Air in Palmer, AK. They sell an STC for the 80/42 prop that covers the '48 C170 land plane. Cost is $250.

[Andy Metzka]

[quote]Hi Andy, do you have a 6 or 8 bolt crank?[quote]

Mine is an 8 bolt. Flew it today- at 2000 feet wide open- tach showed 2700rpm. GPS average 2 directions was 115 knots.

I was contemplating a 76 53 McCauley a friend has for short field performance, but am wondering how likely it would be to overspeed the engine or how much cruise would be lost. I normally only run it around 2300 because I am just flying for fun.

[bagarre]

Hi Andy,
Lots of variables in that question. Might be worth searching the forum for propeller performance, repitching, tachometer accuracy.. There's quite a few threads and topics out there.

Is your static run up ok?
The TCDS gives us a static run up rpm numbers to use for each prop. If it falls into that range, you're ok.
Making redline at 2000ft WOT is about what mine does with an EM7651 (6 bolt crank) depending on density altitude that will give me about 117mph indicated.

Before I repitched I was an EM7653 and similar conditions would show 122mph on the dial.

All ASIs and Tachs are not equal in there readings tho so we cant compare your numbers to mine directly. You'll want a digital hand held tack to verify yours. If possible take it for a flight and check it at each 100 rpm increment. Mine was easily off my 100 RPMS at some reading. Some over, some under. Bought a new tach to resolve that.

The 8 bolt is a DM vs my EM. The DM has a thicker blade profile but I thought a DM7653 was standard with a7655 being cruie and 7651 being climb. The differences in each being about 5mph and 100 feet of climb.

The 8042 mentioned is the seaplane prop and WILL make a difference on short field. Your cruise will be about 95mph tho.

On another note, I would think about running a higher cruise RPM for the engines sake. Lower RPMS seem to not do well at annual time compression checks. When I started cruising at 2550, my low cylinder numbers went away and plugs seemed to run cleaner. Whole other topic and lots of opinions there too but worth reading up on.

In the end, swapping a prop is easy. You might want to bolt it on and take it around the patch and compare your numbers. That would be the best way to tell but I think the difference will be subtle and only noticeable by needle deflection difference.
Would love to get the direct comparison tho.

[Bruce Fenstermacher]

Andy,

The Sensenich M74DR 74/56 you have is nearly the same as a McCauley 1A170 76/53. The McCauley would not be a climb prop in comparison to yours.

You will see little difference. The numbers you give with the prop I would expect from a McCauley 1A170 76/53.

And no the McCauley will not overspeed any more than the Sensenich.

[blueldr]

48RagwingPilot,
If they will give you a prop with that $250 STC, I would think it was a good deal. However, if I wanted to see how well it worked, Id put one on and try it.
In my experience, I have not seen many inspectors running around with a tape measure checking the length of C-170 props

[48RagwingPilot]

BL,

I would dearly love to try out an 80/42 before buying, so am making inquiries as best I can. Hopefully, a pirep to follow. Thx.

[Andy Metzka]

Thanks for all the replies! For now I will likely just run what I have. Maybe if the weather warms up I may see if we could swap props for a check. The 170 pretty much does what I want- especially after flying a 120 for 16 years. ( a 120/140 is pretty economical to own and operate- less than 5 gallons an hour of mogas)

Also- an interesting thought about running at low rpm. I will have to find those threads and read them! I just do that because I enjoy being in the air and rarely go any distance to speak of. Kinda like riding the Harley- the ride is fun without a particular destination...

[Joe Moilanen]

BL,

I would dearly love to try out an 80/42 before buying, so am making inquiries as best I can. Hopefully, a pirep to follow. Thx.

I live just south of you in Longview, WA if you want to try out my 80/43.

Joe

[blueldr]

48RagwingPilot,

That's a very generous offer from Joe Moilanen. I doubt you'll find any other as good.

[cessna170bdriver]

... I was contemplating a 76 53 McCauley a friend has for short field performance, but am wondering how likely it would be to overspeed the engine or how much cruise would be lost. I normally only run it around 2300 because I am just flying for fun.

A 76/53 McCauley is definitely NOT for short field performance. In the McCauley model 1A170 on a 170' the 53 pitch is considered standard, 51 is climb, and 55 is cruise. My 53 made my airplane a little bit of a ground lover, and higher density altitude takeoffs could really get your attention, but it gave me a good honest 105 knots up to about 7-8000 feet, and would turn around 2600 at full throttle at that altitude.

If I was still in California (based at 4000 MSL), I would have considered an 80/42 to replace the original-to-the-airplane 76/53 damaged beyond repair in St Louis. But now that I'm a flatlander again, I think I'll be happy with the 76/53 I found, especially since I rarely carry more than two souls, and generally gross under 2000lb.