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Horton STOL performance

PostPosted: Sat May 07, 2016 11:52 am
by flyingredyeti
Okay, so I've just spent a weekend with my future 170B, and her current owners (of which, I am now partially included). I don't have my tailwheel endorsement yet, so while I flew her back to the airport, one of the owners performed the landing. I was curious about how slow this bird could fly with the Horton STOL kit, so I was watching the speeds all the way down. The landing was long, as he held her off until he was comfortably lined up (in a stiff crosswind), and he dropped her in just after the stall horn sounded. I was amazed at the speed at which this occurred: 38mph.

I remarked upon this afterwards and it was pointed out that was done with no flaps (I missed this as I was fixed on the ASI), riding 3-up, with tanks just over half full! Can anyone dispute these numbers? Did I miss something, could it be the needle swung momentarily giving a false reading? I've read some posters here saying their ASI indicates zero with the Horton kit, but as I understand it this kit includes wing cuffs, which I do not see installed on this particular 170B

Is this performance too good to be true? It seems like it is, but what am I missing?

p.s. I realize I could simply take her up to ca. 3000' and get some stall & slow flight practice in, but I must wait until October before I get to fly in this iconic performer once again.

p.p.s This aircraft is also equipped with 180 horses' of pure Lycoming, so if the STOL performance I observed was not a fluke, she's going to be one bad-ass bird for my Alaska bush flying!

Re: Horton STOL performance

PostPosted: Sat May 07, 2016 12:20 pm
by Bruce Fenstermacher
It will be a nice aircraft. 38 mph no flaps is probably due to ASI inaccuracy at the angle of attack. No doubt the AC can fly slow.

Re: Horton STOL performance

PostPosted: Sat May 07, 2016 1:13 pm
by flyingredyeti
That's a possibility. Although, the pilot was able to float her in between 42 -45mph with no stall horn enunciation. On the other hand, given that the density altitude on that warm, Colorado day was 8500', the likelihood of these performance numbers being accurate is suspect.

Can any of you with experience with this configuration offer me some hard numbers here? I'm curious to hear your take on both stall speed & rotation speed.

One aside, what does the Horton leading edge look like? Is it as conspicuous as the Sportsman STOL, or does it rest more discreetly on the leading edge?

Thanks

Re: Horton STOL performance

PostPosted: Sat May 07, 2016 11:40 pm
by 170C
For either stc, look at the landing/taxi light lens. You will be able to see the original leading edge just aft of the new slightly drooped leading edge. Also look at the leading edge just outboard a couple of inches outboard from the windshield.
When flying very slow, especially with no flaps, the high angle of attack can/will cause the ASI to be inaccurate due to the angle of the pitot tube.
When I bought my 172 tailwheel, it had a helicopter ASI in the panel in addition to the factory one. I asked the owner why and he said that with that Horton stol that the plane would fly so slow that the factory one wouldn't even register! BS! Guess what the first thing to come out of the panel was. :roll:

Re: Horton STOL performance

PostPosted: Sun May 08, 2016 12:27 am
by c170b53
The cuff is the Horton stall kit, so if its there's one installed, its there. The kit also has two small fences on the L/E just on either side of the windscreen, the large fence on the top side of each wing, about mid wing plus gap seals for the ailerons.
As for slow speed, its slow but possibly the stall horn may also not be accurate.

Re: Horton STOL performance

PostPosted: Tue May 24, 2016 3:37 am
by nippaero
This shows the different leading edge cuff shapes. Looks like the Sportsman is much more pronounced than the Horton kit.

From http://www.floatsalaska.com/sportsmanstol.html

Re: Horton STOL performance

PostPosted: Tue May 24, 2016 1:37 pm
by 170C
This is the first time I have seen a claim by a STOL mfg that adding their product will increase both top speed and cruise speed. I have never had anyone tell me that their STOL modification resulted in additional speed. Most advertise slower landing speeds, increased control at slow speeds, shorter take off distance and shorter landing distance due to slower speeds.
My '56 172 has both a conventional gear conversion as well as a Horton STOL. I do not have flap gap seals. If removing the nose wheel and adding the STOL mod increased the top and cruise speed of my plane it must have been the slowest 172 inexistance 8O
And its green to boot which should have made it extra fast :mrgreen:

Re: Horton STOL performance

PostPosted: Tue May 24, 2016 2:58 pm
by edbooth
170C wrote:This is the first time I have seen a claim by a STOL mfg that adding their product will increase both top speed and cruise speed. I have never had anyone tell me that their STOL modification resulted in additional speed. Most advertise slower landing speeds, increased control at slow speeds, shorter take off distance and shorter landing distance due to slower speeds.
My '56 172 has both a conventional gear conversion as well as a Horton STOL. I do not have flap gap seals. If removing the nose wheel and adding the STOL mod increased the top and cruise speed of my plane it must have been the slowest 172 inexistance 8O
And its green to boot which should have made it extra fast :mrgreen:


Hey Frank, maybe your throttle cable is too short. :)

Re: Horton STOL performance

PostPosted: Tue May 24, 2016 6:31 pm
by 170C
Thanks Ed, now I know what the problem is :roll:

Re: Horton STOL performance

PostPosted: Tue May 24, 2016 10:35 pm
by c170b53
Frank, the gap seals I was referring to in the Horton kit are very small. If you have the flap gap seals then I would have thought thar you would have a speed increase over a wing without them.

Re: Horton STOL performance

PostPosted: Wed May 25, 2016 1:14 am
by 170C
Jim, my Horton aileron gap seals are small I guess. I didn't know there were different sizes. I just figured there was one size. It was on the plane when I bought it. As o said I don't have flap gap seals and based on what I have read here an other places I don't think I want them.
I was just surprised to see the listed increased speeds.
Hope all is well and you are making progress on your 170. Hoping to see you two in July.
Frank

Re: Horton STOL performance

PostPosted: Wed May 25, 2016 2:06 am
by c170b53
Sorry Frank mis-read your post, thought you had flap seals as a secret green speed ingredient.

Re: Horton STOL performance

PostPosted: Wed May 25, 2016 12:16 pm
by jlwild
flyingredyeti,

My 2nd and current 170B has the Bush STOL conversion. It was installed in 1983 and includes the leading edge cuffs, stall fences, aileron seals, and wing tips when I purchased the plane.

My first Cessna 170B, that I flew in Alaska between 1970 and 1972, "did not" have the STOL kit. I flew it hunting and fishing out of a few rough and tight spots. But, "not" as hard or short as those you see on Utube. I do not have any test data you are seeking, but I never noted any increased airspeed between the two planes. The big difference I saw was slower indicated landing AS and landing distance. Again this was a judgement call. Yes, the AS read can read below 40 MPH on short landings, with no stall horn warning, but as mentioned the readings are not correct due to high angle of attack. The advantage of the STOL kit, in my opinion, is more stabilized slow speed handling. Jim

Re: Horton STOL performance

PostPosted: Sat May 28, 2016 7:30 am
by flyingredyeti
Thanks Jim, that's helpful. I have heard that the cruise speed would be pretty limited by the aerodynamic profile of the plane, so I'm not surprised that you saw no difference. I would expect there to be a small difference though, as more horses allows for greater thrust yanking the high wings/drooped fuselage, fixed gear, etc. through the air. However, I guess I'll have to discover this for myself.

On the other hand, I would love to know what you're seeing in fuel consumption with this conversion. My future 170B has stock tanks, and I'd like to know how long I can go in cruise at 8500' with 36 gallons of useable fuel. Can you offer any feed back on this? Actually, numbers for any altitude/MAP/RPM configuration would be appreciated.

Thanks again!

-Joshua

p.s. I'm appreciate your confirming sub-40mph IAS with no stall horn. Despite previous comments, I was still skeptical about what I saw; although I'm still skeptical behind the reasoning behind it.

Re: Horton STOL performance

PostPosted: Sat May 28, 2016 7:43 am
by flyingredyeti
A follow-up here Jim, the above question is based on the presumption that you've an O-360 installed, as you said your bird has had the Bush conversion. Although I've been calling the STC on my (future) bird a Horton Stol, it is actually the Doyn Bush conversion and the STOL portion of the conversion looks similar to the Horton (I believe). Although, in digging deeper into the STC, there's a hint that it may actually be the Mid-American STOL kit that is included in the Bush conversion.

Is my ignorance revealing itself yet? I've got copies of the STC, I'm familiar with the power plant, and I understand the concepts behind the aerodynamic modifications. However, my knowledge of the difference between the variety of STOL kits available and their resultant performance is admittedly limited, hence this thread.