I am a new 170 owner. My 52 170B came with two props, a cruse prop "76 54" and a climb prop "76 44". I am going to keep the climb prop on her but before installing it I found a "76 47". Which prop would be better? I am in alaska and do off airport landings. Is the 44 pitch going to be too much or should I buy the 47 pitch prop?
Thanks
Chad.
Climb prop
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Climb prop
52 170B With the Sportsman STOL and The 8042 prop.
Re: Climb prop
The 44" pitch sounds pretty thin, but there used to be a fellow up at Johnson Creek airport in Idaho who ran a 44" on a flat back straight tail C-172 with that pitch and said it was great for that part of the world, but lousy for long cross country flights.
BL
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Bruce Fenstermacher
- Posts: 10320
- Joined: Tue Apr 23, 2002 11:24 am
Re: Climb prop
Hi Chad.
It is not that easy IF you want to remain LEGAL without getting any further approval from the Feds.
First we are going to assume you have the stock C-145-2 or 0-300-A and you are talking about a McCauley 1A170 prop. Any other engine will change the prop, pitch and limits I'm about to talk about.
A standard prop is a 7653, climb is 7651 and cruise is 7655. Now the pitch of the prop isn't really a limit legally per the TCDS. What is is the static rpm the prop is allowed to turn. In this case for a land plane the static pitch can not be over 2330 and not under 2230. You will probably find a 7651 will give you 2330 and a 7655 with give you 2230. If you installed a 7649 you are likely to exceed the static RPM limits and it would be illegal by the TCDS alone but if you static RPM was 2330 you'd be good to go.
The static RPM for a Seaplane on a 170A or B according to the TCDS is not over 2525, not under 2300.
It is not an exact science but on this prop static RPM changes about 50 RPM with every two inches of pitch change. So I'd expect a 7649 to have a static RPM of about 2380, a 7647 to give 2430, a 7645 to give 2480 and that 7644 (only one degree difference) to give 2505 static RPM. So if you have a land plane (or while operating on land) your 7644 or a 7647 would be illegal but if you have a Seaplane both those props should give a legal static RPM.
One thing to watch. It is possible to underprop an airplane. In other words you can pitch a prop so flat it will take longer to pull the airplane to takeoff and climb speed than a prop with more pitch. If you have a land plane I'm pretty sure I a 7644 would be way under propped. I can't say because I've never operated a Seaplane but I might guess the 7647 may be better but you need to ask Seaplane people.
BTW if your going to buy a prop you might want to look into a STC for a longer prop. I think it is a 8042 or there abouts which seems pretty popular in AK.
It is not that easy IF you want to remain LEGAL without getting any further approval from the Feds.
First we are going to assume you have the stock C-145-2 or 0-300-A and you are talking about a McCauley 1A170 prop. Any other engine will change the prop, pitch and limits I'm about to talk about.
A standard prop is a 7653, climb is 7651 and cruise is 7655. Now the pitch of the prop isn't really a limit legally per the TCDS. What is is the static rpm the prop is allowed to turn. In this case for a land plane the static pitch can not be over 2330 and not under 2230. You will probably find a 7651 will give you 2330 and a 7655 with give you 2230. If you installed a 7649 you are likely to exceed the static RPM limits and it would be illegal by the TCDS alone but if you static RPM was 2330 you'd be good to go.
The static RPM for a Seaplane on a 170A or B according to the TCDS is not over 2525, not under 2300.
It is not an exact science but on this prop static RPM changes about 50 RPM with every two inches of pitch change. So I'd expect a 7649 to have a static RPM of about 2380, a 7647 to give 2430, a 7645 to give 2480 and that 7644 (only one degree difference) to give 2505 static RPM. So if you have a land plane (or while operating on land) your 7644 or a 7647 would be illegal but if you have a Seaplane both those props should give a legal static RPM.
One thing to watch. It is possible to underprop an airplane. In other words you can pitch a prop so flat it will take longer to pull the airplane to takeoff and climb speed than a prop with more pitch. If you have a land plane I'm pretty sure I a 7644 would be way under propped. I can't say because I've never operated a Seaplane but I might guess the 7647 may be better but you need to ask Seaplane people.
BTW if your going to buy a prop you might want to look into a STC for a longer prop. I think it is a 8042 or there abouts which seems pretty popular in AK.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Re: Climb prop
Bruce.
Thank you for that information. All of your assumptions were correct. I would think that is why the previous owner went to the 7654 that is on the plane now. I guess I will have to do some more looking. If anyone has a 8042 I would be very interested. I have herd of this prop and it does seem to be the ticket. I will also have to dig through the logs and see where this 7644 came from.
Thanks again!
Thank you for that information. All of your assumptions were correct. I would think that is why the previous owner went to the 7654 that is on the plane now. I guess I will have to do some more looking. If anyone has a 8042 I would be very interested. I have herd of this prop and it does seem to be the ticket. I will also have to dig through the logs and see where this 7644 came from.
Thanks again!
52 170B With the Sportsman STOL and The 8042 prop.
Re: Climb prop
I believe that if I had a 7644 prop, I'd give it a try before I invested in a 7647. I have a hunch that the 44 would be OK. Of course, being the confirmed bootlegger that I am, my choices generally severely conflict with the opinions of our more upstanding members. Hell, I'd try an eight foot Ham Standard if I thought it would work.
If the 44 is a little too thin, maybe it can be re-pitched for less than the price of a 47.
If the 44 is a little too thin, maybe it can be re-pitched for less than the price of a 47.
BL
Re: Climb prop
Thank you blueldr, I will use it and just back off the throttle while crusing. The 47 im looking at has 1500 hrs and never reconditioned. He wants 700$ not sure If I should pass on that. 
52 170B With the Sportsman STOL and The 8042 prop.
Re: Climb prop
Re-pitching costs about $250. I had it done last year from a 53 to a 51.
I was lucky as the shop is driving distance. No shipping.
I was lucky as the shop is driving distance. No shipping.
Re: Climb prop
I have seen prop "re-pitching" prices go all over the board. Shop around and get a firm price for the work to be done. Some shops insist on an overhaul whether or not it's needed.
BL
Re: Climb prop
The 76/49 on my 170A w/O-300 does a good job of keeping up with my neighbors 170B with the 180 hp Lycoming in climb out - I cruise at 100mph though...
1952 170B (with the sexy rounded tail)
Re: Climb prop
I had a prop repitched on my Aeronca and it cost $150. But that was in 1983.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
Re: Climb prop
I would be very happy with 100mph and good climb! Thank youfishdoc wrote:The 76/49 on my 170A w/O-300 does a good job of keeping up with my neighbors 170B with the 180 hp Lycoming in climb out - I cruise at 100mph though...
52 170B With the Sportsman STOL and The 8042 prop.
Re: Climb prop
If you want good climb and would be satisfied with 100 mph, then you want a seaplane prop set to 42 to 43 inch pitch. I have a McCauley 1A175/SFC8040* set to 43 inch pitch and see 100 IAS at 2500 rpm cruise and about 6.5 gph in my '52B. I've also got big wheels and poor paint so I'm not impressing anyone with my cruise speed. I'm told switching to the seaplane prop is the single biggest change you can make to your 170 to get it off the ground faster and climb better. And you can undo the mod by bolting your original prop back on if you are an "originality nut" and nobody needs to know you've been operating on the wild side. Do it, you will like it.
* edit - I've got the O-300D, which has a 6 bolt crank flange. You may have the 8 bolt flange, so make sure you get the right prop for your crank.
* edit - I've got the O-300D, which has a 6 bolt crank flange. You may have the 8 bolt flange, so make sure you get the right prop for your crank.
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IdahoPilot
- Posts: 90
- Joined: Sun Nov 06, 2011 1:40 am
Re: Climb prop
What kind of difference did that give you on rpm?bagarre wrote:Re-pitching costs about $250. I had it done last year from a 53 to a 51.
I was lucky as the shop is driving distance. No shipping.
Ken Nimer
1948 Cessna 170 Ragwing.
1948 Cessna 170 Ragwing.
Re: Climb prop
Going from a 53 to a 51 gave me an extra 50 or 75 RPM on static run-up. I never took accurate measurements before to compare to.
As far as performance, I notice the tail comes off the ground sooner.
But, since then, I've learned how to 'fly' the plane better. My take-offs are much better now due to technique..
I did notice a 5mph drop in airspeed. That puts me on the other side of the 120mph mark ( about 117MPH at 3,000 feet and 2550RPM).
That was very noticeable. By my ASI, I went from 123MPH to 117MPH flat level perfectly smooth days.
Now that I have a (slightly) better feel for the airplane, I plan to re-pitch back to 53 or maybe even 55 this year.
99% of my flying is my wife and I out of a 2,000 foot or longer strip at sea level. I don't need the flat prop for my missions.
FWIW, my propeller is a C172-EM7651. The blade profile is different from the original 170 prop and (Im told) the pitch doesnt directly correlate. There is a few threads on this forum about propeller differences and pitch.
-David
As far as performance, I notice the tail comes off the ground sooner.
But, since then, I've learned how to 'fly' the plane better. My take-offs are much better now due to technique..
I did notice a 5mph drop in airspeed. That puts me on the other side of the 120mph mark ( about 117MPH at 3,000 feet and 2550RPM).
That was very noticeable. By my ASI, I went from 123MPH to 117MPH flat level perfectly smooth days.
Now that I have a (slightly) better feel for the airplane, I plan to re-pitch back to 53 or maybe even 55 this year.
99% of my flying is my wife and I out of a 2,000 foot or longer strip at sea level. I don't need the flat prop for my missions.
FWIW, my propeller is a C172-EM7651. The blade profile is different from the original 170 prop and (Im told) the pitch doesnt directly correlate. There is a few threads on this forum about propeller differences and pitch.
-David