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What Are Negative Factors Of Stol Kits?  
User currently offlineNovelist From United States of America, joined May 2009, 5 posts, RR: 0
Posted (5 years 4 months 5 days 6 hours ago) and read 29883 times:

A STOL kit on a Cessna 172 helps deter stalling and decreases takeoff and rollout runs. But does the kit hamper the plane's speed, climb rate, or ceiling?

16 replies: All unread, jump to last
 
User currently offlineNjxc500 From United States of America, joined Dec 2007, 243 posts, RR: 0
Reply 1, posted (5 years 4 months 5 days 5 hours ago) and read 29898 times:

I have read claims of 3-4 knots lower stall speed.

http://forums.piperowner.org/read/5/80476/page=2

As for negative effects, I don't know of any and a quick search didn't turn any up. I would imagine since the aerodynamics could be 20 or more years old, there are some places to make up wing efficiency without compromising top speed.

Good Luck


User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 2, posted (5 years 4 months 5 days 5 hours ago) and read 29895 times:

The biggest drawback I can think of is insurance. When you start talking STOL to insurance companies, they start to get nervous as to what you might be doing with it and will raise your rates accordingly.


Proud OOTSK member
User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1654 posts, RR: 1
Reply 3, posted (5 years 4 months 5 days 4 hours ago) and read 29886 times:

I have some experience with a STOL kitted Cessna and I can't say that the performance was worth the money spent. Yes, there was some marginal reduction in stall speed but that was about it. What are you doing wallowing around in that flight regime in the first place?

The best short landing device was installed at the Cessna factory in the form of the old 40 degree flaps. You could drop in over trees right on the arrival end of the runway and stop very short, or land very slowly on a soft or rough strip.

Since I had a lot of back country airport experience early in my flying history, I learned how to use the 40 degree flap setting safely. On the other hand, I wouldn't want to use them except as mechanically driven with a flap lever, never as the electrically operated flaps.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 4, posted (5 years 4 months 5 days 3 hours ago) and read 29875 times:

The only negative thing I can think of that a STOL kit does for the aircraft performance is reduce crosswind component on landing...

Quoting ThirtyEcho (Reply 3):
I have some experience with a STOL kitted Cessna and I can't say that the performance was worth the money spent.

I beg to differ. I have had experience in the same 172L, before and after Horton STOL Craft installation. After installation, you could get this plane airborne in much less runway and land using much less runway (assuming, of course, you were using STOL techniques...). If you weren't flying in the STOL regime, it performed pretty much like it did before conversion...

I remember watching my instructor do a STOL takeoff, solo, one cold and calm winter night in this bird. He was off in about 300 feet (the bird also had the Air Plains 180 Horsepower conversion with climb prop), and I can still see the path that those navigation lights cut through the sky in mind to this day  Smile



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineL-188 From United States of America, joined Jul 1999, 29802 posts, RR: 58
Reply 5, posted (5 years 3 months 3 weeks 4 days 4 hours ago) and read 29527 times:

Don Sheldon had a wreck with a new 185 with a STOL kit. His book says he refused to fly one after that.

The problem with any stol kit is that you are trading off performance in one area for another. The one thing these kits don't see to really address is control authority. If you are going to fly slower you are going to need to have larger surfaces to stick out in the breeze.



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 6, posted (5 years 3 months 3 weeks 4 days 3 hours ago) and read 29514 times:



Quoting L-188 (Reply 5):
The one thing these kits don't see to really address is control authority. If you are going to fly slower you are going to need to have larger surfaces to stick out in the breeze.

Hence the reason that the STOL kit manufacturers lower the max crosswind component on STOL-kitted aircraft  Wink



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineDiamondFlyer From United States of America, joined Oct 2008, 1565 posts, RR: 3
Reply 7, posted (5 years 3 months 3 weeks 4 days 3 hours ago) and read 29510 times:



Quoting KELPkid (Reply 6):
Hence the reason that the STOL kit manufacturers lower the max crosswind component on STOL-kitted aircraft

You mean the lower the maximum demonstrated crosswind? Most light aircraft have just a maximum demonstrated crosswind component, which is not a limitation. Just beyond that, and you're a test pilot

I flew a Horton STOL (I think it was Horton) Cessna 150M. Not sure that it really did anything, other than drop the stall speeds down a bit. Might take a couple knots off the top end as well, but on something like a 150, its really not worth the money, IMO.

-DiamondFlyer


User currently offlineSEPilot From United States of America, joined Dec 2006, 6955 posts, RR: 46
Reply 8, posted (5 years 3 months 3 weeks 3 days 19 hours ago) and read 29451 times:

A STOL kit will lower top and cruising speeds slightly; my 182 was a 1962 which was before Cessna adapted the modified drooped leading edge (which came from a STOL kit). I also had a fair amount of time on a newer 182 (a CAP plane) that had the drooped leading edge. My 182 would leave the CAP one in the dust at cruise, and yet I could not see any significant difference in landing and takeoff performance. The other primary airframe difference between the two was that my horizontal stabilizer was 10" shorter, which would also mean less drag. During the time I operated the airport I had a chance to fly a couple of other (newer) 182's; mine would outrun all of them by a considerable margin.


The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineKELPkid From United States of America, joined Nov 2005, 6407 posts, RR: 3
Reply 9, posted (5 years 3 months 3 weeks 3 days 18 hours ago) and read 29429 times:



Quoting DiamondFlyer (Reply 7):
I flew a Horton STOL (I think it was Horton) Cessna 150M. Not sure that it really did anything, other than drop the stall speeds down a bit. Might take a couple knots off the top end as well, but on something like a 150, its really not worth the money, IMO.

-DiamondFlyer

Read the STOL kit supplemental to the POH. To take advantage of the STOL kit, you have to follow the STOL kit manufacturer's recommended techniques on takeoff and landing. The Horton STOL craft kit is incredible, IMHO (well, in the 172 at least, that's where I have experienced it).



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineDiamondFlyer From United States of America, joined Oct 2008, 1565 posts, RR: 3
Reply 10, posted (5 years 3 months 3 weeks 3 days 17 hours ago) and read 29410 times:



Quoting KELPkid (Reply 9):

Read the STOL kit supplemental to the POH. To take advantage of the STOL kit, you have to follow the STOL kit manufacturer's recommended techniques on takeoff and landing. The Horton STOL craft kit is incredible, IMHO (well, in the 172 at least, that's where I have experienced it).

I flew the plane once, and had no non-STOL 150 time to compare it to. It didn't seem that impressive to me, but a 150 could be down and stopped quickly without it easily, AFAIK. Putting STOL on a 150 is kind of a waste of money.

-DiamondFlyer


User currently offlineGeotrash From United States of America, joined Jun 2001, 326 posts, RR: 0
Reply 11, posted (5 years 3 months 2 weeks 4 days 14 hours ago) and read 29075 times:



Quoting L-188 (Reply 5):
The one thing these kits don't see to really address is control authority. If you are going to fly slower you are going to need to have larger surfaces to stick out in the breeze.

I have a Horton STOL equipped 182 and just returned from a trip to Alaska from Denver and back. I also spend a fair amount of time flying in the Rockies here locally so perhaps I can add some color.

The stall fence on the Horton STOL kit provides enhanced control authority in the stall regime because it prevents the stall from progressing outboard of the fence, ensuring better airflow over the ailerons. The rudder is a non issue in cosswinds as the 182 has plenty of rudder to work with- at least I've never run out of rudder with mine in a crosswind.

Some other observations:
-Will liftoff in short field takeoff at 42 mph indicated airspeed. In non-STOL 182s I've flown it's closer to 50 mph.
-In slow flight to a stall it will not break into the stall if I hold the wings level, it simply descends in a nose high attitude
-To get a true break in the stall, I have to push forward on the yoke and then pull back abruptly to induce the stall
-Little roll tendency in the stall and less chance of an incipient spin due to better aileron authority
-Doesn't help much on landing because the sink rate increases below 60 mph in landing config to a level that makes touchdowns firmer that I like. Likely why the rudder authority is a non issue.
-Best estimate is a 3 mph loss in cruise speed with the kit vs. without

Happy with the results overall.

Dave


User currently offlineL-188 From United States of America, joined Jul 1999, 29802 posts, RR: 58
Reply 12, posted (5 years 3 months 2 weeks 4 days 5 hours ago) and read 29021 times:



Quoting Geotrash (Reply 11):
The stall fence on the Horton STOL kit provides enhanced control authority in the stall regime because it prevents the stall from progressing outboard of the fence, ensuring better airflow over the ailerons. The rudder is a non issue in

Agreed you can engineer "fixes" into the STOL kit that will work. But control authority is a design issue. If you have a kit that droops the ailerons with the flaps, it definately is an issue.

I think the most incredible example are the fences on the upper wing of the Wren conversion. They turn with the control inputs, interesting thing to see when it is running up on the ground.

But then you start to get into the question about mechanical complexity vs. costs.



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineIllini_152 From United States of America, joined Jan 2001, 1000 posts, RR: 2
Reply 13, posted (5 years 3 months 2 weeks 2 days 13 hours ago) and read 28901 times:

Best STOL kitted Cessna I flew was a 402B with the Robertson STOL kit. It replaced the split flaps with slotted Fowler flaps and drooped the ailerons (5 degrees IIRC) with takeoff flaps selected.

The slotted Fowler flaps increased the wing area enough to reduce Vmc by 25 knots, and Vyse by 20. The numbers escape my memory, but we'd rotate and climb out at the new Vyse (which was slower than Vmc in the normal aircraft) then at 500 feet we'd accelerate to normal enroute climb speed before retracting the flaps.

The 20+ knot reduction in rotation speed really helped the takeoff distances in that pig, especially when it was hot out at heavy weights (which they almost always were, hauling freight...)

After flap retraction the plane was a normal 402 again, and cruise performance didn't suffer. think we took a 100lb hit on the empty weight, and flap speeds were adjusted; takeoff/approach flap speed was increased, while landing flap speed was decreased, oh, and you couldn't extend the flaps with the main door open, as the bottom half of the clamshell interfered with the extension sequence. Good way to trash a flap and flap-motor doing that...



Happy contrails - I support B747Skipper and Jetguy
User currently offlineGeotrash From United States of America, joined Jun 2001, 326 posts, RR: 0
Reply 14, posted (5 years 3 months 2 weeks 2 days 4 hours ago) and read 28868 times:



Quoting L-188 (Reply 12):
Agreed you can engineer "fixes" into the STOL kit that will work. But control authority is a design issue. If you have a kit that droops the ailerons with the flaps, it definately is an issue.

I think the most incredible example are the fences on the upper wing of the Wren conversion. They turn with the control inputs, interesting thing to see when it is running up on the ground.

But then you start to get into the question about mechanical complexity vs. costs.

Agree on control authority. Less airspeed generally equals less authority, usually made worse in the stall regime by the progression of the stall toward the ailerons. The stall fence and also vortex generators I suppose are adequate mitigation in most cases.

Didn't know the wren had movable stall fences...sounds trouble-prone  Smile

Dave


User currently offlineGeotrash From United States of America, joined Jun 2001, 326 posts, RR: 0
Reply 15, posted (5 years 3 months 2 weeks 2 days 4 hours ago) and read 28867 times:



Quoting Illini_152 (Reply 13):
The slotted Fowler flaps increased the wing area enough to reduce Vmc by 25 knots, and Vyse by 20. The numbers escape my memory,

Wow! Impressive indeed. Makes for a much safer aircraft if an engine fails I should think.

Dave


User currently offlineL-188 From United States of America, joined Jul 1999, 29802 posts, RR: 58
Reply 16, posted (5 years 3 months 2 weeks 1 day 4 hours ago) and read 28801 times:



Quoting Geotrash (Reply 14):
Didn't know the wren had movable stall fences...sounds trouble-prone

When I first saw one running up and checking controls it was the weirdest thing to see.

Just wasn't expecting to see them move. Later I got a closer look at one, and you will see that all of them are just mounted the middle, they aren't riveted down.



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
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