STOL Landings

OkieAviator

OkieAviator

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OkieAviator
I'm looking for some tips from guys who have been flying planes with STOL kits. Specifically I have a Sportsman STOL on a 172 180 Conversion. I've put 15 hours on the plane and have been landing as I trained and that's full flaps, approach at 60-65 and continue with back pressure after touchdown.

My landings aren't like they were in the regular 172's I trained on. I'm not getting a stall horn, I float a lot and the plane seems to ride one wheel with the slightest crosswind, actually sometimes with no crosswind. It just seems a bit like controlled chaos until I slow enough to have true positive control of the aircraft.

I'm speculating that I'm going too fast, I have too much flaps (30 degrees) and the added wing area from the STOL kit and flaps is reducing my aileron control. Talked to my CFIs and none of them have flown a STOL plane.

I've done slow flight and stalls in it so I have a good idea on the speeds and actually I struggle to stall it: will drop about 600 fpm, regain lift stall drop 600 fpm.. over and over.

So back to my questions... Those with STOL planes are you coming in at a slower than normal airspeed or are you not using full flaps... or both? Watched some videos and the guy was doing 20 degrees flaps and coming in slow.

Thanks
 
What is the standard aircraft book speed for a power off stall and what speed are you stalling at with the STOL kit aircraft?

The STC that installed the STOL kit should have had revised approach speeds and amended that data in the manual. If you are floating and not landing, your approach speed is to fast.

1.2 to 1.3 x stall speed for approach.
As to flaps, what does the STC say. I would think normal full flaps and a slower approach speed.

How is it reducing aileron effectiveness?
 
The Robertson STOL STC amends the POH with new performance numbers.

Does the Sportsman? Do you have a copy of the STC and/or POH addendum?
 
No - you are not using "too much flap" and Yes - your speed is too high. You just need more practice to get it right.
 
We're experiencing the a similar challenge. Our new-to-us 172 has the STOL tips. All the rigging and trim is OCD perfect. As a result, the thing does not want to stop flying. I didn't think this would have as remarkable an effect, but it does. The three of us and two CFIs have noticed, so it's not in our head either.

The best thing you can do is math. See what indicated airspeed it actually stalls at in a landing configuration while out in the practice area. If it's anything like ours, it will probably be off the scale and you'll have to interpolate. I found it to be about 30 indicated.

Reference the POH to convert that indicated airspeed to Calibrated Airspeed (CAS). There is a table which you can interpolate the value from. In my case, 30 IAS converts to 40 CAS.

Multiply the CAS value by 1.3 to get your final approach CAS. In my case, 40 x 1.3 = 52 CAS. Again reference the conversion table in the POH to convert that CAS back to IAS. In my case, 52 CAS converts to 48 IAS. That is the new final approach speed for the given weight in a landing configuration.

Do the math for your aircraft as your weight. And fly the numbers the math leads you to. You'll probably find the float goes away. Don't forget to add 3kts if you will be turning, and to add half the gust factor.
 
On power off stall the IAS is 0 due to the Angle of Attack. So can't really get anything quantitative. If the Sportsman came with an addendum I don't have it nor can I find it in the documentation or online. The STC just talks about the master eligibility list which is also attached to it. Regardless it being a 180 conversion might reduce the accuracy as well.

Pedals2Paddles said:
We're experiencing the a similar challenge. Our new-to-us 172 has the STOL tips. All the rigging and trim is OCD perfect. As a result, the thing does not want to stop flying. I didn't think this would have as remarkable an effect, but it does. The three of us and two CFIs have noticed, so it's not in our head either.

The best thing you can do is math. See what indicated airspeed it actually stalls at in a landing configuration while out in the practice area. If it's anything like ours, it will probably be off the scale and you'll have to interpolate. I found it to be about 30 indicated.

Reference the POH to convert that indicated airspeed to Calibrated Airspeed (CAS). There is a table which you can interpolate the value from. In my case, 30 IAS converts to 40 CAS.

Multiply the CAS value by 1.3 to get your final approach CAS. In my case, 40 x 1.3 = 52 CAS. Again reference the conversion table in the POH to convert that CAS back to IAS. In my case, 52 CAS converts to 48 IAS. That is the new final approach speed for the given weight in a landing configuration.

Do the math for your aircraft as your weight. And fly the numbers the math leads you to. You'll probably find the float goes away. Don't forget to add 3kts if you will be turning, and to add half the gust factor.
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So you're still landing with 30 degrees or more flaps right?
 
Any float means you have too much energy coming into the flare and the plane isn't done flying yet.

One word of caution, is that if you are approaching and flaring at idle at a slow speed, some planes could use a little bit of power during flare to help raise the nose. For example, in a 7ECA Citabria I fly, at 65-70 you can flare at idle smoothly, but you will float. At 60mph, there is a lot less float, but the nose doesn't want to come up as authoritatively as you'd like unless you use a little bit of power. This is explained in the POH for that plane, but just something to keep in mind. Some Cherokees I flew liked a touch of power during the flare as well, but I don't remember that being in the POH.
 
I am not familiar with the Sportsman STC. However you don't mention how you are managing your power during the approach. It sounds like you are either two fast or carrying to much power.
My best guess is you may need to approach slower and carry a bit of power during the appoach up until sometime between the roundout to touch down. But it could be some other combination, will take some practice to figure out what works best.

Brian
 
brcase said:
I am not familiar with the Sportsman STC. However you don't mention how you are managing your power during the approach. It sounds like you are either two fast or carrying to much power.

My best guess is you may need to approach slower and carry a bit of power during the appoach up until sometime between the roundout to touch down. But it could be some other combination, will take some practice to figure out what works best.



Brian
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This. The power off approach with the Robertson at the slow speed it'll fly at, is very steep. Our ailerons come back up and are almost back to normal but not quite at full flap. The stall fences and cuff are more in play than the aileron droop at full flap. (At flap 20, the ailerons are a full span additional flap almost and that's a completely different feel.)

To make it a normal looking "flatter" approach, you have to get behind the power curve with significant power and then close the throttle to stick it on a spot.

The stall fences are extremely effective on ours. But the Sportsman doesn't have fences, so finding out how it behaves at altitude and then interpolating to final approach seems to be the only way to get it right, if the STC doesn't publish numbers.

In ours, indicated airspeed is down near zero in power on, full flap, level, slow flight. That's a little too far behind the power curve for a landing (for my tastes anyway) so I'll fly it a little faster, even shooting for a "STOL" landing and still be stopped in a few hundred feet without a headwind component, if I'm willing to eat up brakes for the practice.

Most of the time, you'll simply still be well within the "still flying" envelope for "normal" approaches, but slower than a non-STOL aircraft of the same type. You can aim for the edge of the runway and use the "float" to decay the airspeed to put you actually landing somewhere just past the numbers.

Try this next time you're out. Three stage flare...

Normal approach, aiming well early of your normal aiming point.

Normal flare to that aim point. Then hooooooold it off...

Second more shallow flare that'll reach to the point where the wing really starts to give up flying.

Once you do that a few times you'll be able to make it a fluid motion and know where the wing will give up at.

That's the best I can describe it. It'll land slower than you think it will. ;)

The above makes instrument approaches entertaining. Especially after the DPE pointed out our airplane "likes" 110 knots better than 90 knots.

Break out at 200', chop straight to idle, and immediate full flap... and hope you can run out of airspeed in time to land on the 1000' marker. LOL. You'll often float right over it if you don't add some slip to slow it down. :) :) :)
 
Slow flight practice will improve your familiarity with attitude, power requirements, indicated airspeeds, rates of descent, and feel of the airplane. STOL landings should use full flaps and minimum airspeed. Minimum airspeed is variable with power application. You need to get some help from an instructor or a friend who's proficient in STOL operations in a cuff equipped airplane.
 
Good landings are slow landings. Use full flaps unless you have a gusting crosswind. As others have noted, you are probably carrying too much speed on final.

Bob Gardner
 
When I installed flap gap seals,my 172 had to be slowed down ,so that it didn't float on landing.used full flaps. You have to get comfortable with the slower speed.
 
PilotRPI said:
... For example, in a 7ECA Citabria I fly, at 65-70 you can flare at idle smoothly, but you will float. At 60mph, there is a lot less float, but the nose doesn't want to come up as authoritatively as you'd like ...
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Part of that is also due to your trim setting. The more nose up trim you crank in the less nose-up elevator authority you have because the area of the trim tab has effectively been removed from the total elevator area in that position.
 
Flew for about an hour and a half this morning. Took the plane to 5500 and practiced pattern work down to 4500, did this about 4 times to really focus on speed and decent rate. I ended each pattern run with a power out and flare to see how long I could hold the altitude before impending stall. My results were at about 1300 RPM while cycling through the flaps at the normal segments I maintained 500 fpm decent rate at an approach speed of final leg approach speed of about 50-55. When flaring I could stop my decent and hold it there for about 8-10 seconds before my horn would sound and I felt an impending stall, IAS at this point was 0.

I went to a close by airport and did some approaches to get the feel with a decent crosswind component. After that I went back to my home port, put it all together and landing just past the numbers with almost no float, no shaking and an easy roll out. Not 100% what my airspeed was I think it was a solid 55 on roundout. I used WingX blackbox feature which showed a ground speed of 49 knots on touchdown, wind was reporting 200 @ 6 and was landing runway 17 not sure that means much though.
 
How's the plane feel?

You already spent a bunch of time on stalls and slow flight with the STOL kit?

I'd also do some low passes on a long uncontrolled strip, just try toehold the mains off 6" and see how slow you can get her.
 
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James331 said:
How's the plane feel?

You already spent a bunch of time on stalls and slow flight with the STOL kit?

I'd also do some low passes on a long uncontrolled strip, just try toehold the mains off 6" and see how slow you can get her.
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The descent was normal except at a slower air speed. So at one point on final I had to push more throttle in to halt my descent so I would get to the threshold. I'll have to just tighten up my pattern to accommodate the steeper angle. So instead of a mile final, maybe I do 3/4 of a mile. That will just take me practice to get a new sight picture. On touchdown the plane felt like my training 172s, a bit of a chirp and then slowly bring the nose wheel down.

I have about 16 hours in this plane over the last 2 months. I did an hour with a CFI in it, I did a number of solo flights where I went and did slow flight, stalls, ect. This was the first time I tried to correlate airspeed, rpms, vertical speed and IAS and do a practice approach at altitude.

I did some approaches at another airport but was about 20' up vs 6".
 
I "leveled up" today! Still a bit uneasy about winds even after my great landing last time I decided to give it a go today. On landing I had a headwind about 15 and a crosswind of about 9 and landed without a single issue. The headwind really make me feel like I was going slow and landed just past the numbers.

STOL planes are fantastic once you learn how to fly them!
 
Good, I have something to look forward to, because after 20 years I'm still learning!
 
OkieAviator said:
I "leveled up" today! Still a bit uneasy about winds even after my great landing last time I decided to give it a go today. On landing I had a headwind about 15 and a crosswind of about 9 and landed without a single issue. The headwind really make me feel like I was going slow and landed just past the numbers.

STOL planes are fantastic once you learn how to fly them!
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They are TONS of fun..!!!
 
What does the book say for approach speed? A normal 172 might be at 60kts.

I'd guess you would be below that, full flaps on a STOL airplane. It sounds like you are fast. A good short field approach is full flaps, just enough airspeed to have the energy to arrest your descent rate before touchdown
 
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I remember a story a bush pilot friend told me. He got cocky one day while talking to an old timer about STOL landings. He said he could easily touch down and stop in the first 300' of the local runway. The old timer looked at him with no expression and told him if he was any good he'd go practice on the last 300' of the runway.

400-500' on a big paved runway looks a lot different than 400-500' of dirt between two cut banks of a river. Find yourself an experienced pilot who's good in your airplane and beg him to show you what it'll do. Steep turns at MCA, face-bender canyon turns, short field ops, etc. You have a very capable airplane. Enjoy it!
 
I get spooked on 3000 foot runways. Will be a bit before I'm comfortable on anything shorter than 2000 feet. I'll keep working, learning and practicing, always the front part of the runway though...
 
An angle of attack indicator (or lift reserve indicator) would be a good companion to your STOL kit. It will tell you a lot more about how close you are to stalling than your airspeed indicator will.
 
OkieAviator said:
I get spooked on 3000 foot runways. Will be a bit before I'm comfortable on anything shorter than 2000 feet. I'll keep working, learning and practicing, always the front part of the runway though...
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Nothing wrong with being more cautious as the safety margin decreases.
 
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