Cherokee 140/160 prop pitch

[ircphoenix]

Hi everybody!

Fir those of you that don't know, I have the 160 HP stc'd engine in my Cherokee 140. I understand that it is pretty common to have the prop repitched to 60 degrees after that.

Now, when looking through my prop logs, I have not come across anything that suggests my prop was ever repitched to 60.

Is there a way to tell if repitching the prop is necessary or worthwhile?

 

[charlie]

It's 60 INCHES not degrees. With the 58" pitch prop the engine will turn pretty close to red line in climb and red line or above in level flight wide open. If you are operating out of a very short field or at high elevation the 60 is a better match. I actually pitched one of mine to 62" and it worked well. I owned a couple of these over the years and flew about 20 more! Charlie Melot Zephyr Engines

 

[Graueradler]

Do the Art Mattsen prop tip mod and repitch 4 inches, 2 for the HP increase that you already have and an additional 2 for the increase in prop efficiency. That is what I did and WOT straight and level remained red line. I don't know who has the prop tip STC now. Art is no longer with us. The mod is very simple. It bevels the prop tip front to back at 45 degrees. He compared it to putting the Hoener wing tip shape on the end of the prop. I now a person that copied it on an experimental ans saw about a 100 RPM increase in static RPM.

 

[ircphoenix]

Inches. Not degrees. Oops.

Is there any way to know if it is something I *should* do?

And for reference, I mainly operate from long paved runways. Home drome is 5000' and 110 MSL.

 

[Graueradler]

Nothing bad is going to happen if you do nothing. Your prop is pitched more toward take off and climb instead of cruise and you will need to pay more attention in power on descents not to exceed red line RPM. Your engine/prop combination will probably also be able to exceed red line wide open throttle straight and level.

 

[ircphoenix]

Nothing bad is going to happen if you do nothing. Your prop is pitched more toward take off and climb instead of cruise and you will need to pay more attention in power on descents not to exceed red line RPM. Your engine/prop combination will probably also be able to exceed red line wide open throttle straight and level.

I did catch myself with an unhappy tach when I first got the plane in a power on descent. Surprised the crap out of me. Never had to deal with that in the 172s I trained in.

 

[bluerooster]

Hi everybody!

Fir those of you that don't know, I have the 160 HP stc'd engine in my Cherokee 140. I understand that it is pretty common to have the prop repitched to 60 degrees after that.

Now, when looking through my prop logs, I have not come across anything that suggests my prop was ever repitched to 60.

Is there a way to tell if repitching the prop is necessary or worthwhile?

I would think that if pitched to meet static RPM requirements for 160 hp Cherokee you would be fine.

Static r.p.m. at maximum permission throttle setting not over 2425 r.p.m.,

not under 2325 r.p.m.

What does the STC paperwork say?

 

[tawood]

I'd vote for leaving it alone, because I'd be afraid of losing too much climb. My 140 has a powerflow , so even though it doesn't have the 160hp upgrade, I'm sure it's not just 150hp either. I notice I'm right at redline if I'm at level flight and full throttle (which I've only tried once at 7500 feet), and that is at about 125+ knots with only 10 gph. I still get a decent climb, even fully loaded. By myself, I get more than 500 fpm up to 7000 feet, while fully loaded I get 500 fpm up to 4000 on all but the hottest days.

 

[Frogs97]

I'd vote for leaving it alone, because I'd be afraid of losing too much climb. My 140 has a powerflow , so even though it doesn't have the 160hp upgrade, I'm sure it's not just 150hp either. I notice I'm right at redline if I'm at level flight and full throttle (which I've only tried once at 7500 feet), and that is at about 125+ knots with only 10 gph. I still get a decent climb, even fully loaded. By myself, I get more than 500 fpm up to 7000 feet, while fully loaded I get 500 fpm up to 4000 on all but the hottest days.

125kts or mph? I only get 105kts in my stock 140. I heard good things about the Powerflow, but are you really seeing an extra 20kts?

 

[tawood]

125kts or mph? I only get 105kts in my stock 140. I heard good things about the Powerflow, but are you really seeing an extra 20kts?

Yes 125 kts...but that's with a powerflow AND virtually every speed mod you can put on a Cherokee: wing tips, fairings, gap seals, etc.

I guess it's all relative, because I still consider my Cherokee a dog. It's my dog, and I love her, but a dog none the less.

 

[Graueradler]

125 kts on a 71 Cherokee 140/160 Flite Liner WOT S&L with prop tip mod, repitched prop, wing root VGs, gap seals, and wing tips.

 

[weilke]

Do the Art Mattsen prop tip mod and repitch 4 inches, 2 for the HP increase that you already have and an additional 2 for the increase in prop efficiency. That is what I did and WOT straight and level remained red line. I don't know who has the prop tip STC now. Art is no longer with us. The mod is very simple. It bevels the prop tip front to back at 45 degrees. He compared it to putting the Hoener wing tip shape on the end of the prop. I now a person that copied it on an experimental ans saw about a 100 RPM increase in static RPM.

How does that fit in with the manufacturers specs and maintenance manual?

 

[ircphoenix]

1 AMU per knot. Jesus.

I'm gonna have to double check my books tonight. I don't remember the STC saying anything about repitching the prop, but literally everywhere on the internet suggests that 90% of props in situations similar to mine get repitched following the upgrade.

With the prop's propensity to want to overrev, I think it wouldn't be a bad idea. Next time I fly (Thursday), I'm gonna check the static RPM and see where it's at.

 

[Graueradler]

How does that fit in with the manufacturers specs and maintenance manual?

The mod has an STC. After repitching, it is still within spec. on static RPM.

 

[ircphoenix]

So I'm reviving my own post.

Apparently my prop is stock 58. Repitched to 56, I'm assuming to get better climb out of it. Then the STC happened and they repitched to 58. So I guess I could go up to 60. But IIRC... total pitch change is 4 inches.

 

[tawood]

So I'm reviving my own post.

Apparently my prop is stock 58. Repitched to 56, I'm assuming to get better climb out of it. Then the STC happened and they repitched to 58. So I guess I could go up to 60. But IIRC... total pitch change is 4 inches.

I think, actually, that your prop is "done"...after that many pitch changes, I don't think you can do another.

 

[Ravioli]

Keep in mind that if you're going up to Big Bear or over to Phoenix often you'll want to pitch for Climb. You won't give up much cruise speed and climb is all about density altitude. Your sunny summer flying days are not Standard Temperature and Pressure but those mountains to your East don't change height often

 

[kgruber]

There is evidence that your Cherokee is actually faster with the 58" than a re-pitch to 60". More RPM=more power=faster speed

 

[bluerooster]

125kts or mph? I only get 105kts in my stock 140. I heard good things about the Powerflow, but are you really seeing an extra 20kts?

The powerflow in our '73 140, required a re-pitch to prevent exceeding max static RPM. No speed mods, except Horner wing tips. and I'd plan for 115kts at 2350 rpm. So I would think 125 with all the speed mods, is easilly doable.