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STOL kits and Vortex Generators

  • ROD KLEISS
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3 years 1 month ago #1172 by ROD KLEISS
Replied by ROD KLEISS on topic STOL kits and Vortex Generators
I know that I would surely appreciate an article on this subject Scott. After this thread conversation, I am back to thinking that I need to look at both STOL kits and VG's, but the question is what will be the bang for the buck? As Steve has mentioned, I should practice landings until I can hit 630' at full gross, but then the question of landing speed comes in. I feel that I can land at 60 knots easily when there is not too much gusting wind and the plane is light. The AOA meter is sometimes confusing. In general I follow its guidance but in landing it will sometimes start sounding long before anything is really a problem. This is not every time. So it leaves me confused with a predictable way to really gauge whether I am approaching a limit on landing. Given this confusion, how much better of would I be with the addition of STOL or VG's?

In general, I don't find much help on the ground with the avionics shop or the A&P. The shop is mainly interested in making sure that the equipment functions as designed. I have flown the stall speeds used for calibrating the AOA but that is not a easy-to-discern point in flying. Things get mushy. When am I really stalling. In my Cessna 150, it was pretty abrupt, but in this 172 nothing happens suddenly. I like that but how does one set up AOA in that case.

Of course, none of this is an immediate problem. I will continue to operate on the safe side until I can understand how to approach even slower landings, but I am now sure there is a path to discover here and these new tools will be valuable, if I can just figure out how to do it and what modification is best for the effort.

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3 years 1 month ago - 3 years 1 month ago #1171 by Scott Kinney
Replied by Scott Kinney on topic STOL kits and Vortex Generators
Rod,

I can't speak for a "which is better" but both the Sportsman and Horton STOL-equipped 172s I've flown do show marked improvement in slow-speed control. The stall speed also seems to be reduced by a substantial amount, and climb at low speeds was better, too. I don't know what the respective manufacturers claim but it's pretty neat to be able to fly rock-solid short finals at 45-50 knots, or to climb out steeply at those same speeds. If you are going to be flying in the backcountry, that can make a huge difference in where you can go.

As Jose and Steve pointed out, so much of good STOL operation isn't equipment -- it's technique. In the hands of a qualified pilot, even a stock O-300-powered 172 can get in and out of a lot of tight places. I see a lot of guys with 182s and a bunch of STOL mods who, when landing, burn up nearly every foot of my 3,000' home strip. Their equipment is capable of 400' landings, but the pilot sure ain't. A lot of people don't understand weight-adjusted approach speeds...they'll fly the same max-gross Vref regardless of loading, and then wonder why they float 1,000' and touch down at midfield even though they flared at the threshold. Hint - it's because you're ten or fifteen knots faster than you need to be.

I'll see if I can get an article on STOL kits into our editorial calendar for 2019. We haven't done one recently, and I bet others have the same questions as you do.

-Scott
Last edit: 3 years 1 month ago by Scott Kinney.

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3 years 1 month ago #1170 by STEVE ELLS
Replied by STEVE ELLS on topic STOL kits and Vortex Generators
You raise a good point about VGs and frosty wings. Removing the frost could be a headache. I recommend that you take a mountain flying course. A bunch show up when you Google Mountain Flying. I have not done one but I have heard very good things about McCall Mountain Canyon Flying. Lori MacNichol has been teaching mountain flying for a couple of decades and runs a good school.
Is your AOA calibrated? If it is that's one of the best max performance tools around.
I lived up in Alaska for 9 years and STOL kits were common, so it's pretty easy to believe that Alaska pilots are sold on adding one for better short field performance.
My only suggestion for learning the new technique is practice; lots of short field practice; refine your technique to hit your spot at the correct speed every time; and get to know how to maximize your airplane capabilities, such as operating with minimum fuel in order to wring the best performance out of your XP.
When you can hit a spot at your target speed you're way ahead of most flyers.

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  • ROD KLEISS
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3 years 1 month ago #1169 by ROD KLEISS
Replied by ROD KLEISS on topic STOL kits and Vortex Generators
Thanks for the reply Steve. I actually did the ISHAM upgrade this fall and then took my first cross country trip from Minneapolis to Portland, Oregon for Thanksgiving. It seems like a new plane with that added horsepower. I am getting better at hitting the numbers on landing, but I am interested in just getting as much good performance from this plane as possible without going overboard or adding non-essential gew-gaws akin to wearing copper bracelets for my health. I appreciate your comment on the VG's. My A&P has a couple of 172's and an XP. He has installed STOL kits on them and thinks highly of them. It seems to me that I should think very carefully before I go around changing the shape of my wing though. The VG's seem like a much simpler addition, but we got a bit of frost one morning on our cross country trip. It made me wonder how easy it would be to break or let loose a VG while I'm scraping frost off. (We didn't do that this trip. We put the plane in a hangar and melted the frost.)

I bought and read Sparky's book. It gave me a sense of what may be happening in the mountains, but his references are all about steam gauges. I have a complete glass cockpit with AOA meter. He didn't really address things that I would be expecting to see in my cockpit while I am in the mountains. I am thinking I will need to go somewhere for training this spring. I would appreciate any suggestions you might have for how to approach this new flying technique.

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3 years 1 month ago #1167 by STEVE ELLS
Replied by STEVE ELLS on topic STOL kits and Vortex Generators
Hi Rod;
Your XP is a pretty good performer. With the correct short field technique you should be able to achieve book numbers (which are usually pretty accurate) for landing and takeoff distances as long as you factor in atmospheric variables such as altitude and temperature.
If you are not seeing numbers comparable to the book numbers I recommend that you spend some time nailing approach speeds. According to the 1977 XP POH I have, a short field technique take off at 2550 pound, and 20 deg F will give a ground roll of 830 feet (1430 over a 50 foot obstacle) when the airplane is rotated at 56 KIAS.
Numbers for landing at 2550 pounds (MTOW) are touchdown at 63 KIAS and a ground roll of 630 feet (1285 feet over a 50 foot obstacle).
These numbers are bettered if the airplane is flown at lighter weights.
As Jose mentioned, the XP wing generates lift at pretty low speeds, often at speeds that seem too slow.
One of the best reference books for mountain flying--which includes short field techniques--is the "Mountain Flying Bible and Flight Operations Handbook" by Sparky Imeson. Amazon sells it. The FAA also has a Mountain Flying ebook publication listed on Amazon.
I installed VGs on my Comanche and on the S35 Bonanza I updated for AOPA and although some Bonanza experts told me it cost a couple of knots airspeed, I am a firm believer in them. My view is that if there ever comes a day when I need fly very as slow as possible--in the event of a total or partial power loss, for instance--in my Comanche the VGs will help me maintain control at very low speeds.
One mod that will make your XP perform better is the ISHAM engine upgrade which increases the engine horsepower to 210. It's a very simple modification.
I believe the best STOL kit is the Sportsman STOL which includes gap seals, a drooped leading edge cuff and wing tips. It's marketed by Stene of Polson, MT>
Here is a link to an article on the Hawk XP: www.cessnaflyer.org/flighttraining/item/...e-r172k-hawk-xp.html .
Practice your short field landings and take offs, and I think you'll find that all your XP needs for shorter strips is bigger tires.
Happy Flying

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  • JOSE LOPEZ DEL PUERTO
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3 years 2 months ago - 3 years 2 months ago #1132 by JOSE LOPEZ DEL PUERTO
Replied by JOSE LOPEZ DEL PUERTO on topic STOL kits and Vortex Generators

ROD KLEISS wrote: I'd just like to land slower and reduce my stall speeds without affecting performance.


Well... every aircraft manufacturer will love to cruise very fast and land very slow, but there is no free lunch in aerodynamics. Cessna has a reputation of good balance for multipurpose airplanes. One known fact is that stock SE Cessnas are usually landed too fast and they have good short field capability in the hands of qualified pilots. Unfortunately I am not one of them.
Last edit: 3 years 2 months ago by JOSE LOPEZ DEL PUERTO.

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