Cessna 172 Horton STOL Technique

[Matthew Bourguignon]

Greetings, all!
We recently acquired a 1979 Cessna 172N with the Air Plains 180hp conversion and a Horton STOL kit including gates, tips and cuffs. It's the third addition to our rental fleet and despite being in pretty serious need of a paint job, it's proved popular with our students! I'm not sure what about it exactly, but I have also become pretty fond of it when I'm taking an aircraft from the fleet on a nonrev flight. What I'm wondering though is: what changes, if any, should I be making to my short and/or soft field takeoffs? I'm still using my usual technique: stick full aft until the nose wheel comes up, then hang out on the bleeding edge of the wheelie until the mains lift off, avoiding over-rotating while also avoiding re-settling the nose. Once she's up, pitch down to accelerate to Vx, then "follow Vx up", pitching up to hold Vx as she climbs out of ground effect and over the trees.

I took my family to lunch in this airplane two weeks ago. We went to one of our two favorite spots: GA2, a 2,400ft grass strip just south of ATL. As always, I did my W&B and performance calculations carefully. It was a hot day, with high DA, but everything was within the limits with which I'm comfortable and know I can fly, so we made the trip. We used a good bit more runway than I am used to, but that didn't surprise me since I flew the approach at normal speed instead of reducing it for the STOL kit. However, I couldn't tell if we had a shorter takeoff than what I'm used to. In any case, takeoff and landing were uneventful, but it did leave me wondering if I should be adjusting my technique.

Anybody who has STOL kit experience or similar setup experience, can you share your thoughts on technique?

Thank you!

 

[MRC01]

We recently acquired a 1979 Cessna 172N with the Air Plains 180hp conversion and a Horton STOL kit including gates, tips and cuffs. ... What I'm wondering though is: what changes, if any, should I be making to my short and/or soft field takeoffs? I'm still using my usual technique: stick full aft until the nose wheel comes up, then hang out on the bleeding edge of the wheelie until the mains lift off, avoiding over-rotating while also avoiding re-settling the nose. Once she's up, pitch down to accelerate to Vx, then "follow Vx up", pitching up to hold Vx as she climbs out of ground effect and over the trees.
...

That technique sounds more like soft field than short field, minimizing nose wheel weight at the expense of increasing induced drag during the takeoff roll. For short (not soft) field, I prefer to accelerate on the takeoff roll with stick neutral, which will have less drag. Then rotate at 55 kts (a bit faster/later than soft field), then the rest of the procedure is the same as yours: reduce pitch to accelerate to your desired speed (Vx or Vy) while in ground effect, then pitch to maintain that airspeed while climbing.

It's similar to your procedure, but for short field takeoffs on hard surface runways it starts out with stick neutral instead of full aft. Also with the 180 HP engine I use 10* of flaps if DA is below 5000'. And lean rich of peak power/RPM if DA is above 3000'.

This is with my 1980 172N with Penn Yann 180 HP STC, flaps limited to 30*, but with no STOL kit.

 

[Matthew Bourguignon]

That technique sounds more like soft field than short field, minimizing nose wheel weight at the expense of increasing induced drag during the takeoff roll. For short (not soft) field, I prefer to accelerate on the takeoff roll with stick neutral, which will have less drag. Then rotate at 55 kts (a bit faster/later than soft field), then the rest of the procedure is the same as yours: reduce pitch to accelerate to your desired speed (Vx or Vy) while in ground effect, then pitch to maintain that airspeed while climbing.

It's similar to your procedure, but for short field takeoffs on hard surface runways it starts out with stick neutral instead of full aft. Also with the 180 HP engine I use 10* of flaps if DA is below 5000'. And lean rich of peak power/RPM if DA is above 3000'.

This is with my 1980 172N with Penn Yann 180 HP STC, flaps limited to 30*, but with no STOL kit.

Due to GA2 being a grass strip, I have to use a combined Soft & Short technique.

We also have a Penn Yan conversion with no STOL kit. 1979 but otherwise almost your twin.

 

[MauleSkinner]

the only way to answer that question is to know how much runway you normally use, and if it’s not your normal runway and/or load weight, you need to be able to compare your performance with that of the book to be able to extrapolate the new condition.

Of course, soft field technique isn’t included in book data (and I’d be willing to bet wasn’t necessary,) so you’d have to have some form of “other reliable information” (or whatever the regulatory verbiage is.)

 

[MauleSkinner]

Due to GA2 being a grass strip, I have to use a combined Soft & Short technique.

No, you probably don’t.

 

[Matthew Bourguignon]

No, you probably don’t.

Well now you're addressing another question I've pondered: do I even need to apply a soft field technique? The field is typically dry, albeit bumpy. It's privately owned, and the airpark owner closes it whenever the runway condition is suboptimal.

 

[Gilbert Buettner]

Well now you're addressing another question I've pondered: do I even need to apply a soft field technique? The field is typically dry, albeit bumpy. It's privately owned, and the airpark owner closes it whenever the runway condition is suboptimal.

I like to use the soft field technique on bumpy grass, like we have at my home 'drome. There are some very smooth grass runways in our area where it clearly is not required or recommended. I wouldn't feel it necessary to climb at Vx unless there are obstacles... usually accelerate to Vy in ground effect.

Yes, combining short and soft field techniques is required sometime.

 

[MRC01]

Well now you're addressing another question I've pondered: do I even need to apply a soft field technique? The field is typically dry, albeit bumpy. It's privately owned, and the airpark owner closes it whenever the runway condition is suboptimal.

That's a great question. When it's a soft field that is also short, which limitation (soft or short) is more constraining?

The key difference in procedure is whether to make the ground roll with stick neutral, or full aft. Stick full aft during takeoff roll increases aerodynamic drag but reduces stress on the nose wheel - which also reduces ground roll drag on soft or rough terrain.

It seems to boil down to pilot's judgment on whether the terrain is soft/rough enough to cause enough ground roll drag and stress on the nose wheel that you will reduce that at the cost of increasing aerodynamic drag during the ground roll.

 

[Matthew Bourguignon]

I like to use the soft field technique on bumpy grass, like we have at my home 'drome. There are some very smooth grass runways in our area where it clearly is not required or recommended. I wouldn't feel it necessary to climb at Vx unless there are obstacles... usually accelerate to Vy in ground effect.

Yes, combining short and soft field techniques is required sometime.

See I too worry about beating the **** out of the nosewheel running down the bumpy grass.

 

[MRC01]

See I too worry about beating the **** out of the nosewheel running down the bumpy grass.

Who doesn't? I always use soft field method (stick full back during ground roll acceleration) on soft fields when the runway is long enough. It's nicer to the airplane.

 

[455 Bravo Uniform]

What’s your flap setting on takeoff? I use 20 deg in my STOL 182 for the quickest wheels up.

You didn’t ask about landings. Go figure out Vs indicated with various flap settings at altitude, then come back and land with 1.2 or 1.3x.

I am NOT a CFI.

 

[MauleSkinner]

See I too worry about beating the **** out of the nosewheel running down the bumpy grass.

that would be a rough field, not a soft field. It takes a little experience to figure out what’s rough enough to beat the **** out of the airplane instead of just normal bumps on an unpaved runway. Walk the strip…if you trip over stuff or worry about twisting an ankle, it’s rough.

 

[Matthew Bourguignon]

What’s your flap setting on takeoff? I use 20 deg in my STOL 182 for the quickest wheels up.

You didn’t ask about landings. Go figure out Vs indicated with various flap settings at altitude, then come back and land with 1.2 or 1.3x.

I am NOT a CFI.

I use 10 degrees per the book for soft/rough field. Clean wing for short field/paved.

 

[Matthew Bourguignon]

What’s your flap setting on takeoff? I use 20 deg in my STOL 182 for the quickest wheels up.

You didn’t ask about landings. Go figure out Vs indicated with various flap settings at altitude, then come back and land with 1.2 or 1.3x.

I am NOT a CFI.

You're right. I started typing out a paragraph for landings and then deleted it for being extraneous. Landings I'm doing fine with experimenting on my own. I've found her gross weight stall speed to be 29 KIAS. I'm not comfortable approaching at 37 knots (yet) so I've been playing with reducing my approach speed a couple of knots each time. Lowest so far was 45 KIAS. Felt very uncomfortable, sight picture looked all wrong, etc. Takes some getting used to. Total distance was about 1,000ft with 4-5 hundred of that going to the rollout.

 

[MRC01]

I use 10 degrees per the book for soft/rough field. Clean wing for short field/paved.

After the increase from 160 to 180 HP, you might benefit from 10* flaps also on short field paved. Try it and see.

 

[kyleb]

GA2 is bumpy, but not *that* rough. Nor is it particularly short. I'd use elevator to take some of the load off of the nosewheel, then climb at VY.

 

[Racerx]

I've found her gross weight stall speed to be 29 KIAS.

Do you mean max gross stall? Otherwise gross weight is kind of arbitrary.

I have a Cherokee with the Horton kit. Look at the stc docs and they make no claims other than pilot skill greatly affects the mod performance. I've heard claims that it lowers stall speed on the Cherokee by 10mph. I guess I'm just not that skilled...or paying close enough attention when it actually breaks. I don't change my approach speeds because of the kit.

I would not be teaching students any technique that's not in the poh/afm.

 

[WDD]

GA2 is one of my favorite fields. IMHO, yes, you need to use Soft Field nose up for both take off and landing - always. 10 degrees of flaps on take off, and you'll up before the half way point.

As long as you land uphill on 13, and take off downhill 31, you'll be fine - it's not that short.

BTW - Short Take off requires holding the brakes with full throttle and then rolling. On grass, you don't want to stop and then roll - just keep rolling from the ramp. As well, Soft Field landings don't use brakes, where as Short Field you have maximum braking.

FWIW - Out club has a 180 HP Skyhawk (no STOL kit). The only thing I can add is that with the extra HP the nose come up quicker than a regular 150 HP. Easy to pop the nose up more than you want.

 

[MauleSkinner]

I've found her gross weight stall speed to be 29 KIAS. I'm not comfortable approaching at 37 knots (yet) so…

I assume you converted to KCAS for the calculation?

 

[kath]

We've got a nearly-identically modded C-172L (Horton STOL + Air Plains 180HP). We love it!

I haven't changed anything really about my technique, for short field or soft, from what I was first taught. I mean, none of the reasons for those techniques (lightening the load on the nosegear, etc.) have changed, have they? Everything just happens at a slower speed.

 

[Stewartb]

Look on Youtube for Valdez STOL contest videos for this year and last. A 180hp 172 known as Green Bean won it all last year and placed 2nd (I think) this year. Against Cubs! Pretty impressive.

 

[idahoflier]

If I'm taking off from a short backcountry strip (< 2,000 ft) or if it's taller wet grass I'll use 10° flaps, otherwise it's flaps up...

 

[Stewartb]

Takeoffs at 20° will be shorter at all weights. 30° is even better if lightly loaded.

 

[Matthew Bourguignon]

Do you mean max gross stall? Otherwise gross weight is kind of arbitrary.

I have a Cherokee with the Horton kit. Look at the stc docs and they make no claims other than pilot skill greatly affects the mod performance. I've heard claims that it lowers stall speed on the Cherokee by 10mph. I guess I'm just not that skilled...or paying close enough attention when it actually breaks. I don't change my approach speeds because of the kit.

I would not be teaching students any technique that's not in the poh/afm.

Max gross, yes.

We use the airplane for instruction and we teach out of the POH and Air Plains AFM supplement. We do not teach any contrary numbers, but we do make students aware that the aircraft will float further and take longer to contact the runway due to the STOL kit. They adjust accordingly. For this reason, we aren’t sure if we will keep her in the instruction fleet long-term.

 

[Matthew Bourguignon]

I assume you converted to KCAS for the calculation?

No, I wasn’t comparing this to book numbers. I was going from a gauge reading to another gauge reading: “If 29 KIAS stall, then 37 KIAS approach.”

Again, I’m not about to dive right into flying that slowly anyway.

 

[Matthew Bourguignon]

Takeoffs at 20° will be shorter at all weights. 30° is even better if lightly loaded.

TWENTY degrees?! Seems like outright blasphemy!

 

[Matthew Bourguignon]

Based on some of the feedback here, it sounds like I’ve got a great excuse to spend a few hours beating up the pattern and experimenting with various flap settings and techniques. I can even stop for lunch at Barnstormers in the middle! Don’t know how I’ll factor out the performance penalty from a burger and onion rings though…

 

[MRC01]

... We use the airplane for instruction and we teach out of the POH and Air Plains AFM supplement. We do not teach any contrary numbers, but we do make students aware that the aircraft will float further and take longer to contact the runway due to the STOL kit. They adjust accordingly. For this reason, we aren’t sure if we will keep her in the instruction fleet long-term.

It could be useful for instruction to have an airplane that is harder to land when the student approach speed is too high. Being too fast on final approach is such a common mistake even among experienced pilots, and it is a contributing factor to incidents causing injuries and damage. It would be nice to wring that tendency out of students early in training.

Better yet, I'd say have them learn in a taildragger, but sadly, it seems those days are long gone.

 

[MauleSkinner]

Max gross, yes.

We use the airplane for instruction and we teach out of the POH and Air Plains AFM supplement. We do not teach any contrary numbers, but we do make students aware that the aircraft will float further and take longer to contact the runway due to the STOL kit. They adjust accordingly. For this reason, we aren’t sure if we will keep her in the instruction fleet long-term.

You should be teaching “contrary numbers.” The landing should be made to the same standard with respect to touchdown point on the runway, and additional float shouldn’t be acceptable.

No, I wasn’t comparing this to book numbers. I was going from a gauge reading to another gauge reading: “If 29 KIAS stall, then 37 KIAS approach.”

Again, I’m not about to dive right into flying that slowly anyway.

If you’re going to come up with the correct speeds, you need to convert to KCAS and back.

 

[Matthew Bourguignon]

It could be useful for instruction to have an airplane that is harder to land when the student approach speed is too high. Being too fast on final approach is such a common mistake even among experienced pilots, and it is a contributing factor to incidents causing injuries and damage. It would be nice to wring that tendency out of students early in training.

Better yet, I'd say have them learn in a taildragger, but sadly, it seems those days are long gone.

I would love that, but convincing an insurance company to cover a taildragger for instruction and rental would take a small miracle and a large fortune!

 

[Stewartb]

Anyone interested in STOL flying would benefit from reading “Contact Flying” by Jim Dulin. Especially where landings and takeoffs are discussed. His teaching comments pretty much sum up what most STOL guys do, and few I know have read it.

 

[MRC01]

No, I wasn’t comparing this to book numbers. I was going from a gauge reading to another gauge reading: “If 29 KIAS stall, then 37 KIAS approach.”
Again, I’m not about to dive right into flying that slowly anyway.

Come in that slow and you risk scraping the bottom of the tail tie-down ring...

 

[Stewartb]

Only if you come in too fast and try to bleed speed by adding pitch. A properly trimmed airplane flies in a normal attitude. Throttle controls the touchdown point.

 

[MRC01]

Only if you come in too fast and try to bleed speed by adding pitch. A properly trimmed airplane flies in a normal attitude. Throttle controls the touchdown point.

First, to clarify: Pitch attitude in level flight depends on airspeed. The slower you fly, the more AoA you need for level flight, which means more pitch angle or a higher attitude. Trim takes the pressure off the yoke/stick but it doesn't change the pitch attitude. Unlike trim, flaps can change the pitch attitude for a given airspeed. In the 172, flaps reduce the attitude for a given airspeed, so it's easier to scrape the tail tie-down ring with a flaps-up landing.

All that said, on approach you aren't in level flight, but descending, so the pitch attitude is less than it would be in level flight at that same airspeed. This sounds like the difference you mention, because if you come in too hot and bleed speed by adding pitch, you're in level flight which means more pitch attitude, compared to a steeper approach at that same slow airspeed, in which case you are constantly descending with less pitch attitude. But even then the pitch attitude will increase in the flare.

 

[Brad W]

Based on some of the feedback here, it sounds like I’ve got a great excuse to spend a few hours beating up the pattern and experimenting with various flap settings and techniques. I can even stop for lunch at Barnstormers in the middle! Don’t know how I’ll factor out the performance penalty from a burger and onion rings though…

a little nap should factor that variable out quite nicely.....

 

[Stewartb]

In a descent the relative wind comes from below the airplane, so the AOA is already increased from cruise. You can add power and raise the nose if you prefer to drag it in but with Cessna flaps they land just fine with low power settings without hitting the tail or the nose wheel. It's that old stabilized approach topic. Trim it for speed and control descent with power. That's how STOL is flown. The real difference is the good STOL guys are flying the final final at barely above stall, so with little margin for error. That's easier done with altitude to trade for airspeed, at least in real world conditions. Jim Dulin refers to it as the brisk walk rate of closure and it done properly the pilot won't ever look at the airspeed.

My Cub has LE slats and is capable of crazy high AOA with power on. Tail bumping is easy to do but is easily avoidable. What I describe above is SOP for my planes. There's no difference between a tail low wheel landing and what I describe for the 172.