Three Blade Prop

[mvivion]

Eric,

Actually, the original STC's for the 180 hp engine in the 170 called for a 74 inch Hartzell.

There is now an stc available from Hartzell for an 80 inch prop, equipped with a harmonic damper assy from a Piper Seneca I. This prop is NOT legal at 82 inches, EXCEPT on the engines with mass balanced cranks.

The 80 inch prop works well on the 170, but its heavy. The damper alone weighs 10 pounds.

Mike V

[AR Dave]

'53 C170B with a Lyc 0360, and a Hartzell 80" I was showing a hair over 1500fpm climb out at 80 mph

This brings up a question that I've been theorizing on. Did you have the 80" on before the conversion? What pitch?
Probably no one else would have a need to try this, but I'm curious if anyone can raise their tail, brakes on, full throttle, just before take off roll? What kind of lift or control does a climb prop give elevators and flaps, that the cruise prop doesn't? Pull for takeoff?

[mvivion]

AR Dave,

He's referring to an 80 inch Hartzell constant speed prop (specifically an HC2YR 8477-4, I believe).

Yes, I can lift the tail on my airplane with thrust by holding brakes, though its not something I do regularly, cause that big prop cost so much.

One of the problems with these prop discussions is people tend to mix their metaphors so to speak, and aren't clear which type prop is being referenced.

To the best of my knowledge, all of the 170 conversions with the Lycoming O360 require a constant speed prop, though someone may have gotten a fixed pitch field approved, I suppose. Can't imagine why they'd want to, but....

Mike Vivion

[AR Dave]

I was playing around with U turn takeoffs, one wheel full aileron takeoffs, and decided to try a takeoff with the tail raised, the other day. Do you think the 8043 is getting any extra lift under the flaps from the prop?

[zero.one.victor]

While most of the 360 Lyc 170's I've seen have c/s prop, I have seen one or two with fixed pitch. As per their ad in The 170 News, DelAir's conversion can use either c/s or fixed. Also, I believe XPMods' IO-360 Cont STC allows for either a c/s or fixed pitch.
I'm not arguing either for or against, but I can see some advantage to a fixed prop in both lower cost & lighter weight. Whether these are enough to counter the performance advantage(s) of a c/s, I can't say.
I was looking at a Stinson 108 the other day which had a Lycoming O-540 and a fixed pitch prop. Looks like the whole works coulda come right off the Piper Pawnee 235 tow-plane I was eyeballing recently. Maybe they know something we don't......

Eric

[Boiler Bill]

I sold a 170B with the six cylinder engine (stock motor) 145 in it. Then bought a 170B also a 1952 with the Avcon 180 h.p engine and Hartzel constant speed prop for about $2,500. more than what I sold my other plane for.

The noise was without a doubt louder. The vibration was the same, very smooth. Power was a major improvment for the northwest mountain area. Previous owner claimed 8 gallons per hour, Im guessing closer to 10 gallons per hour.

I would say the conversion cost is not worth the money, Just buy the best 180 you can find. I was lucky and found one in my neighbor hood that a guy had for 30 years and had to sell it.

[Joe Moilanen]

Hi Bill, I'll be faced with that dillemma when my 145 reaches TBO. I've got a 8043 pitch right now and don't have any problem getting out of my 650' strip down her south of you.

Joe in Longview, WA

[jon s blocker]

I have followed this conversation, because I like to hear the comments of others on these subjects. I have a '53 C170B with a Del Air conversion, Hartzell "80 C/S with dampener, Javelin aux tank. I used to own a '50 C170A. I liked flying the A model better, But I like the flaps and power plant on the B, I now have. I have flown several C180s and prefer my plane to the 180. I like the fact that you can handle the 170 much easier on the ground by yourself. The 180 feels like a truck in the air compared to the 170. The engine in mine is smooth. I don't know if it is because of the dampner, but other than the start-up and shut-down shudder, it is very smooth. The 180 is faster, but burns 3 gph more. I can carry anything I can stuff in the 170, not quite as much as the 180, but everything I have ever needed to haul. I can get off and land in a shorter distance than any stock 180 I have flown with. (185s are another story). Maintanance cost is less in the 170, and not much more than with the 170 with the 145s in them. I think a fixed pitch is good for targeted tasks, but the c/s prop gives you full power, (limited to 5 mins.), that you won't get out of a fixed pitch unless you give up your airspeed and raise your gph. Would I convert with an 0360 again, you bet. Would I trade for a 180, nope. Would love to have an IO-360, but THEN I would be looking for that 180. JMHO Jon

[Dave Clark]

So Jon, how is a comparably equipped 170 with a Lycoming cheaper in maintenance costs than a 180? The only thing I have more of to maintain now on my 180 vs. my 170 is more radios. To me they're the same and all would depend on the individual airplane condition.

[GAHorn]

The 4 cyl Lyc. would have 4 less sparkplugs.

[blueldr]

When it comes to three bladed props;

1. About 65% say they run smoother.

2. About 100% think they look "COOL",

[jon s blocker]

Dave, I was referring not only to the engine, but the total aircraft, which I found to be more expensive at annual time. The aircraft is slightly more complex and around here, the mechanics tend to charge more for maintenance on the 180 compared to the 170s. And yes George 2 more plugs . Also more cylinders, cowl flaps, articulating seats, etc., The time spent on annuals is generally longer and thus more maintenance and cost. But like I said, JMHO. Don't get me wrong, I LIKE 180s, but I can fly cheaper in my 170 and it meets all my requirements for fun general aviation. Jon

[jon s blocker]

Just a clarification, 2 plugs PER CYLINDER. Sorry George. Jon

[Watkinsnv]

That write up on a three bladed 170 years ago had a turbo IO-320 in it. He went on to say that the engine was cheaper to buy, cheaper to fly and out performed the O-360 at alt. Lance

[blueldr]

When you compare props on "Big Engined" C-170s, there is another problem that may occur. I flew my Continental IO-360 for the first year with a 76-60 fixed pitch prop. My problem was oil temperature. Everything was fine until I throttled back to 2400 or so for cruise. Apparently the throttle setting (manifold pressure) at a reasonable cruise RPM precluded a big enough "fire in the boiler" to keep the oil temperature up. It would slowly decay down to about 135 degrees. After I changed to CS prop, I could bring the RPM down to about 2100 and bring the manifold pressure up for the necessary power and the oil temperature then became normal.

However, I have a friend with that engine and a fixed pitch prop that he has flown for twenty years or so and has apparently never had a problem.

Go figure!

I readily admit that the CS prop has definite performance advantages, but the fixed pitch is lighter,simpler, cheaper , and requires less maintenance.
And they hardly ever have a AD. If your operations can be handled with a fixed pitch, I think they are the way to go.