The New Seaplane/Climb prop thread

[alaskan99669]

Here's a question for you other guys using the 80 inch. Mine runs smooth as glass above 2400. It gets rough to varying intensity below that down to about 1700. Any similar experiences?

My 80/43 is smooth at all RPM's. I run quite often around 2250-2350 to enjoy the scenery and it's just as smooth as 2450.

[alaskan99669]

I have been searching the old posts and beating my head over what prop to put on the airplane to increase climb perf. ...buy a 3500 dollar 8042...

For about the same price you can install the Sportsman STOL kit. Here's some of their claims:
Max. Angle of Climb Speed: 64(stock) 45 (STOL)
Distance to Clear 50' Object: 1625'(stock) 820' (STOL)


http://www.steneaviation.com/sportsman.html

[Metal Master]

I bought the STC from Kenmore for the 8040 what ever propeller and the 8043 prop from AC prop in Seattle last year for our flights into Idaho back country this last summer. My partner and I did a bunch of before and after comparison flights between OAT density altitude before and after the change. I will not post that information here or elsewhere. However I did find that on climb out from Auburn airport that I was not making 2700 RPM although the climb rate was significantly greater. With the amount of baggage we carried into Idaho I would not want to be without the 8043 prop. When my partner later flew back to Montana to visit family and later to California we changed back to the 76 inch propeller. The cruise difference was significant over distances flown. For short flights I would not worry about changing back & forth and go with what ever prop was on unless I had to fly weight into a high density altitude airport. In level cruise I could if I wanted to push the engine over red line RPM with the 8043. Of course we never let that happen. All pitches of prop were available when I bought the 8043 and I figured by going with that particular prop pitch the likelihood of re-pitching either up or down was reduced to one re-pitch if we thought we needed to do so. The performance is just where we like it and have not chosen to re-pitch the prop.

[denalipilot]

Metal Master- Would you venture an estimate of how much less runway you need with the 8043, all other conditions being equal? Maybe in terms of a rough percentage? My '52 B model came with the 76" prop, and I often wish I had more STOL capability on the shorter runways and frozen lakes around my area. I tend to carry an ample survival kit, wing and engine covers, preheater, snowshoes, tool kit... It seems to add up pretty quickly and so I have been looking into the 80" prop at my upcoming annual. Thanks to all the contributors on this thread, the comments have been most helpful. Lastly, is there some way I can tell what my current 76" prop is pitched at?

-Denali Pilot

[Robert Eilers]

I like the idea of the Sportsman STOL kit, or even the Horton for that matter versus prop and engine upgrades. Reviewing the performance figures for the Sportsman STOL kit it seems to me that I might get the takeoff and climb performance needed for Idaho adventures and maintain a reasonable cruise. I am exploring the Sportsman with Harry Dellicker - Porterville.

[flyguy]

F their claims: Max. Angle of Climb Speed: 64(stock) 45 (STOL) Distance to Clear 50' Object: 1625'(stock) 820' (STOL)

I knew a fellow who had this wonderful Robertson STOL kit put on his 172. He bragged about all the wonderful things (he was told) it would do. I had a 1200' airstrip at my house and invited him to come and STOL me. My strip was grass and mowed fairly close. My 170 handled it just fine but that day his S(LOL)TOL 172 used all the grass and some of the over-run just to land! It was then that the reality hit home to him that some folks will stretch the figures to sell stuff but when it is vital to have those performance figures meet the need they fall short. I offered to carry one of his pax back to his home field, just 10 miles down the river, and he accepted.

I am very skeptical of manufacturers claims to those kinds of numbers. I know that you can increase the plane's attitude (angle of attack) without much benefit in fpm (altitude) gain. What good does that do. Slow maneuvering speed is already one of the assets of our 170s so the several thousand dollars if STOL mods isn't going to give you as much short field performance as changing from a 55" or 53" to a 40" pitch whether on a 76" or 80" blade. The 80" is a more efficient performer because of more working surface.

Here is the crux of the matter - If your forte is going somewhere as quickly as you can then speed, ie higher pitch, is important. A 40" pitch goes forward about 12" less distance per rev as that 53". It will not perform out exactly in practice as in theory but all things being equal here are the theoretical numbers for the different pitches @ 2700rpm.

A 55" = 140mph,
A 53" = 135
A 50" = 127
A 48" = 122 and
A 40" = 102
Lesser rpm of course is lesser mph.

The take-off distances aren't as easy to predict but there probably are charts somewhere could give that info. Interpolate figures for a 53" at "standard" and you will be in the ball park. Now go with both the 40" and a STOL kit and add 60 HP and you can climb straight up! but still go 102 mph

[GAHorn]

... Lastly, is there some way I can tell what my current 76" prop is pitched at?

-Denali Pilot

Yes, you can measure the angle at various stations along the blade and compare them to the specifications in the propeller manual for that model prop... or, if it's not been altered, you can look at the hub of the prop and read what is stamped there. (A 7653 would be a 76" diameter prop, with a 53" pitch.)

[AR Dave]

Plenty of very experienced 170 owners will tell you that the STOL Kits are NOT the way to go on a 170. If you do go with a STOL, please come back and share with others who might be mislead.

Kelly Mahon (Part 135 Idaho Mtns.) who a lot of us respect, concerning this subject, had this to say. He worked with the 80” prop and 8.50 tires.

Remember that for the price of VG’s or STOL Kits you can get the same performance increase by buying gas with that money and learning your airplane. Most of the time people talk about how they can now do something that THEY couldn’t before, more times than not it was a speed that was already attainable and the high dollar item gave them the confidence to try.

[jrenwick]

I hope people don't let themselves be intimidated by a statement like that. My 170 has a Horton STOL kit installed by a previous owner in Alaska, and an O-300. I assume it's an expensive mod, and it adds weight. I wouldn't add this stuff if I had a stock 170. But it is interesting to fly with, because it lowers the stall speeds significantly, and I believe it really shortens the takeoff roll and increases the rate of climb after takeoff.

It also makes the 170 a real challenge to land. The wing doesn't seem to want to stop flying, so it's very easy to bounce. This has forced me to become a much better pilot than I would have been otherwise. You really have to have your height above the runway and descent rate under control as you land. (I have a friend with a stock 170 who's also an excellent pilot with a lot of 170 hours. When he tried to land my 170, he thought he'd forgotten how to fly!) I can land my 170 gracefully most of the time now, and that feels like a nice accomplishment.

Anyway, I think the Horton kit is nice to have if you didn't have to pay for it and you don't mind the weight penalty. For most people, that would probably mean don't bother!

[alaskan99669]

Plenty of very experienced 170 owners will tell you that the STOL Kits are NOT the way to go on a 170. If you do go with a STOL, please come back and share with others who might be mislead.

Kelly Mahon (Part 135 Idaho Mtns.) had this to say...

Remember that for the price of VG’s or STOL Kits you can get the same performance increase by buying gas with that money and learning your airplane. Most of the time people talk about how they can now do something that THEY couldn’t before, more times than not it was a speed that was already attainable and the high dollar item gave them the confidence to try.

I know I only have a little over 200 hours in my 170, but I don't think any more hours trying will make it fly at 50 MPH on floats. Right now I can force it off the water at 50 but it sinks back down and skips across the lake until I can get 55 MPH. If the Sprortman will get me off the lake at 45 MPH, then I think that is money well spent. The kit is $2000. I'm still trying to nail down the cost of labor, but if it's not too outrageous I'll get back with next summer on the benefits (if any??).

[pdb]

I know I only have a little over 200 hours in my 170, but I don't think any more hours trying will make it fly at 50 MPH on floats. Right now I can force it off the water at 50 but it sinks back down and skips across the lake until I can get 55 MPH. If the Sprortman will get me off the lake at 45 MPH, then I think that is money well spent. The kit is $2000. I'm still trying to nail down the cost of labor, but if it's not too outrageous I'll get back with next summer on the benefits (if any??).

Corey:

I have a O-300a with VGs an 80-42 on my '53 170B and am based at Merrill. Let's meet sometime and fly my 170 side by side with yours. I also have a flight recorder that's coupled to a GPS so we can get real data absent the bs factor. (It will record position, speed, r/c at 4 second intervals for the entire flight.) We can do a series of take offs , climbs, and stalls to see what differences there might be and report back to the crowd.

Are there any stock, Horton, or Sportsmen equipped pilots who would want to meet as well?

[GAHorn]

[quote... We can do a series of take offs , climbs, and stalls to see what differences there might be and report back to the crowd.

Are there any stock, Horton, or Sportsmen equipped pilots who would want to meet as well?

Make certain both aircraft weight exactly the same and have similar wind components.

[jrenwick]

One thing I forgot to mention about the Horton (STOL-Craft) mod, and some may think it's pretty important: you lose the utility category of the C170. It requires placards: "This airplane must be operated as a normal category airplane in compliance with the Airplane Flight Manual." And "No acrobatic maneuvers including spins approved." And "Both tanks on for takeoff and landing."

Now go the AFM, Note 1: "The following maneuvers are approved for operation in the Utility Category only...: Chandelle....Steep Turn....Lazy Eight....All Stalls....Spins...."

So I come to the goofy conclusion that you aren't legal to do stalls, steep turns, etc., in a STOL-Craft equipped 170. I'm not sure how to resolve that, except through the whole river-in-Egypt thing.

[Robert Eilers]

I just heard back from a great aircraft maintenance shop in Salinas regarding a cost estimate for installing the Hortol STOL kit. The estimate, including the price of the kit, was just over $6,000. I think I will take the advice stated earlier and spend money on gas learning how to get the best performance from the aircraft as is. I have to admit, the stock 170B even with the standard prop, does very well. I was really just looking for an increase in climb performance. Good planning, sensible W&B and environmental considerations will do just fine.

[c170b53]

I too have the Horton and I think John is correct with regards to landing. I think the biggest factor being overlooked here (George is gonna love this),
a 170 with the Horton isn't as pretty as the original.