Not disagreeing about the VG's (as I mentioned earlier, they do improve boundary layer), but just as an observation:
The A-model has only 1-degree of wing washout to affect aileron control at low speed. Cessna increased the B-model to 3-degrees of washout to improve aileron control at low speeds (presumeably to go along with the low speeds afforded by the large flaps.) 170 Aileron control is discussed at some length by former Cessna test pilot Wm. Thompson in his book about the single-engine development of "Cessna, Wings for the World".
Sportsman STOL kit
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
I likewise won my vg's in a raffle. They look cool.
Here's where I found the differences. 1. Lift the plane off the ground at very low airspeed into ground effect and it doesn't feel mushy. 2. I measured best angle of climb performance before and after and found a slight improvement.
If I really need the slight additional performance they give me I've made a mistake already.
Here's where I found the differences. 1. Lift the plane off the ground at very low airspeed into ground effect and it doesn't feel mushy. 2. I measured best angle of climb performance before and after and found a slight improvement.
If I really need the slight additional performance they give me I've made a mistake already.
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Bruce Fenstermacher
- Posts: 10318
- Joined: Tue Apr 23, 2002 11:24 am
I agree with both statements but jestew might be missing the point of VGs. VGs do don't make your wing create more lift. They make the boundry layer stick to the wing surface at a higher angel of attack. Which means that the wing creates lift and your ailerons are more effective at a steeper angle of attack ie slower flight.jestew wrote:Here's where I found the differences. 1. Lift the plane off the ground at very low airspeed into ground effect and it doesn't feel mushy. 2. I measured best angle of climb performance before and after and found a slight improvement.
With VGs at takeoff you may be able to shorten you takeoff roll by pulling the aircraft into ground effect sooner and feel comfortable and in control but if you don't have a clear departure to lower your wing angle of attack and exellerate creating more lift to climb your in trouble.
I'm not sure but I think STOL kits that use a leading edge cuff change the airfoil which may create more lift at a slower speed.
My thoughts are if you want to takeoff and climb faster get a bigger engine. If you want to have better control while approaching slower get VGs.
In fact as I write this I realize besides the obvious installation differences the major difference between a STOL kit and VGs may be that STOL creats more lift slower whether in a climb or descent, VGs give more control (than stock) at slower speeds.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Last August, we all had an interesting discussion about go-arounds. I posted a comment that I feel is germane to this discussion. It's not one of my shortest comments, so I deleted most of it. (You can find the whole comment on an Aug 13 remark on flap useage during go-arounds. Click on my username, and select the topics I've commented on, and select the one that starts:
Putting my CFI-hat on here for just a moment.......
The 170B is only approved for takeoff (go-around) with 20-degrees or less flaps. Those are the only flap settings for which takeoff performance is plotted. .....
The part germane to this discussion is:
(While on this subject, the question is sometimes asked "Will VG's help?". My personal belief is "No." VG's, by lowering stalling speeds, make the float last longer and eat up runway. They also reduce braking effectiveness by reducing weight on the wheels. The argument that VG's will lower stalling speeds and therefore shorten landing distances is offset by the reluctance of most pilots to actually fly that slowly. Remember, the fastest way to slow an airplane is with it on the ground with brakes applied. And, VG's claimed ability to allow a slightly slower full-flaps approach speed then creates an even greater disparity between approach speed and an effective obstacle climb speed. In the event of a decision to go-around, the pilot would have even more airspeed to try to make up.)
I believe this opinion is in agreement with Bruce F.'s regarding whether VG's are more useful for approach/landing than for departure. Vg's do not improve L/D (they do not lower best climb speeds), so any perceived climb performance improvement is in the mind of the pilot...not a reality.
Putting my CFI-hat on here for just a moment.......
The 170B is only approved for takeoff (go-around) with 20-degrees or less flaps. Those are the only flap settings for which takeoff performance is plotted. .....
The part germane to this discussion is:
(While on this subject, the question is sometimes asked "Will VG's help?". My personal belief is "No." VG's, by lowering stalling speeds, make the float last longer and eat up runway. They also reduce braking effectiveness by reducing weight on the wheels. The argument that VG's will lower stalling speeds and therefore shorten landing distances is offset by the reluctance of most pilots to actually fly that slowly. Remember, the fastest way to slow an airplane is with it on the ground with brakes applied. And, VG's claimed ability to allow a slightly slower full-flaps approach speed then creates an even greater disparity between approach speed and an effective obstacle climb speed. In the event of a decision to go-around, the pilot would have even more airspeed to try to make up.)
I believe this opinion is in agreement with Bruce F.'s regarding whether VG's are more useful for approach/landing than for departure. Vg's do not improve L/D (they do not lower best climb speeds), so any perceived climb performance improvement is in the mind of the pilot...not a reality.
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Tracy Hood
- Posts: 1
- Joined: Wed Apr 30, 2003 7:02 pm
Sportsman Stol kit
I don't have any 170 time at all. But I do have around 1800 hours in a 140. The last 300 of those hours are with VGs. After flying with them I wouldn't fly without them. They are not for everybody though. What I noticed the most is I can pull it off the ground sooner with more control. It doesn't help my climb rate but there are times when you are hot and high that the little extra is nice to have. If you fly off of long strips there is no reason to have VG's. You will float if you don't slow your speed on landing but the same is true with flaps. My wife and I each have a 140 and fly and camp in the Idaho mountains in the summer. We appreciate any extra safety margins we can get. Our goal is to trade up to a couple of 170's hopefully next year. You guys have a great web site I have learned more about 170's than anywhere else.
VGs and STOL Kits
My 170A has both the HORTON STOL kit and VGs. There is a noticable difference in low speed performance over a stock 170. Slow speed elevator and aerilon control is significantly better helping in both takeoff and departure especially when the winds are messing with ya. It also seems to handle rough air better over a stock 170
In general, it will fly with the airspeed indicator bouncing around zero with the ability to maintain altitude and perform some low bank turns. In this condition I've seen GPS ground speeds as low as 25kts. The most noticable difference is that the tail comes up faster on takeoff. This helps when you are departing on State or FS maintained grass strips; not having to drag that tailwheel any longer than necessary sure helps reduce the takeoff roll.
On my last biannual the CFI pulled power and was certain that we could not make the runway in a standard 170. We did with no problem and had extra altitude to lose; the altitude was easly lost with the application of flaps after touch down was assured. The nice thing about the A model is that you can also slip it with full flaps.
With the slow speed control canyon turns are much shorter in radius, one can do a 180 turn in about a road width. It takes some practice, but they can be done with a much shorter radius than in a standard 170.
The mods don't significantly help climb performance. If you want increased rate of climb and Husky/Super Cub like take off distances you need additional HP.
In general, it will fly with the airspeed indicator bouncing around zero with the ability to maintain altitude and perform some low bank turns. In this condition I've seen GPS ground speeds as low as 25kts. The most noticable difference is that the tail comes up faster on takeoff. This helps when you are departing on State or FS maintained grass strips; not having to drag that tailwheel any longer than necessary sure helps reduce the takeoff roll.
On my last biannual the CFI pulled power and was certain that we could not make the runway in a standard 170. We did with no problem and had extra altitude to lose; the altitude was easly lost with the application of flaps after touch down was assured. The nice thing about the A model is that you can also slip it with full flaps.
With the slow speed control canyon turns are much shorter in radius, one can do a 180 turn in about a road width. It takes some practice, but they can be done with a much shorter radius than in a standard 170.
The mods don't significantly help climb performance. If you want increased rate of climb and Husky/Super Cub like take off distances you need additional HP.
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Bruce Fenstermacher
- Posts: 10318
- Joined: Tue Apr 23, 2002 11:24 am
George I'm guessing it was the VGs which are mounted one the elevator as part of the VG kit that changed the elevator efffectiveness and not the Hortons Stall Kit.
I also find it curious that either Horton or the VG STC allow the other modification since either would significantly change the aerodynamics over the stock wing.
I also find it curious that either Horton or the VG STC allow the other modification since either would significantly change the aerodynamics over the stock wing.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Most of the VG kits now permit installation (and are flight tested) on airplanes equipped with the most popular STOL kits. Micro, for example, has approvals for installations on Sportsman, Bush, Robertson and Horton equipped aircraft, at least on some models.
The Sportsman leading edge really is a nice addition. It is not light, as pointed out, and installation is labor intensive. I very much like the aerodynamics of what it does for the airplane, as opposed to what the VG's do for the airplane, which isn't much, at least in my limited experience, with my airplane, which has a stock wing.
The VG's on my airplane mellowed out the stall a little bit more (on a nice stalling airplane to start with) but I really don't see much change in stall speed. It will hang on a little longer in a deep stall with no pilot inputs, but that's about it. And, I'm a big believer in pilot participation during stall events in any case.
The Sportsman kits that I've flown do a very commendable job of really slowing the airplane down, and offer really solid performance at very high AOA.
I don't like the VG's on the 170, and were I to do it again, I wouldn't.
And, I didn't win them in a raffle.
One of these days, I'm going to slit my wrist on one of those miserable suckers on a rainy day when I slip while fueling, I'm afraid.
I'd install a Sportsman in a heartbeat. Look at the wing on a Cirrus. That leading edge is derived from the same NASA research that spawned the Sportsman kit. It works. The Robertson and Sportsman kits work well on Cessna wings. In my experience, the VG's work much better on Cubs and Scouts. The change in performance is very aircraft type specific on all of these things.
I decided to try the VG's because of price of installation (at $75 an hour shop rate), and have been dissapointed since. If it wasn't such a pain to take them off, I would.
Mike Vivion
The Sportsman leading edge really is a nice addition. It is not light, as pointed out, and installation is labor intensive. I very much like the aerodynamics of what it does for the airplane, as opposed to what the VG's do for the airplane, which isn't much, at least in my limited experience, with my airplane, which has a stock wing.
The VG's on my airplane mellowed out the stall a little bit more (on a nice stalling airplane to start with) but I really don't see much change in stall speed. It will hang on a little longer in a deep stall with no pilot inputs, but that's about it. And, I'm a big believer in pilot participation during stall events in any case.
The Sportsman kits that I've flown do a very commendable job of really slowing the airplane down, and offer really solid performance at very high AOA.
I don't like the VG's on the 170, and were I to do it again, I wouldn't.
And, I didn't win them in a raffle.
One of these days, I'm going to slit my wrist on one of those miserable suckers on a rainy day when I slip while fueling, I'm afraid.
I'd install a Sportsman in a heartbeat. Look at the wing on a Cirrus. That leading edge is derived from the same NASA research that spawned the Sportsman kit. It works. The Robertson and Sportsman kits work well on Cessna wings. In my experience, the VG's work much better on Cubs and Scouts. The change in performance is very aircraft type specific on all of these things.
I decided to try the VG's because of price of installation (at $75 an hour shop rate), and have been dissapointed since. If it wasn't such a pain to take them off, I would.
Mike Vivion
Im considering installing the sportsman on my stock '54 170B. Im thinking it will help my takeoff performance, if/when, I get my plane on floats. From what Ive read, the airfoil change is the primarily selling point for the added lift. I read an article, I think in water flying, that also discussed the STOL kits from the view point of added wing area. From what I have seen the Sportsman STOL adds a couple inches to the leading edge, mutiply that by the length of the wing and bingo added wing area/more lift.
Im still stuck on the cost. I had it priced installed by former a approved dealer/installer and was quoted 6K. Thats a big chunk of the cost of my airplane and 1/2 a set of floats.
Im thinking an 8042 prop is more bang for the buck.
Im still stuck on the cost. I had it priced installed by former a approved dealer/installer and was quoted 6K. Thats a big chunk of the cost of my airplane and 1/2 a set of floats.
Im thinking an 8042 prop is more bang for the buck.
Craig
Eagle River, AK
Eagle River, AK
Craig,
I'm with you on that one. Frankly, these are pretty decent flying airplanes in any case. Every little bit helps, but at what cost? That's where I choked, at the price of a Sportsman installed. Maybe you could get someone who would let you do the install under their supervision, but.... It isn't rocket science. We had it done on a 185 and the installation is pretty straightforward, just time consuming. Then you really need to paint it....
I'd go for the prop,
Mike
I'm with you on that one. Frankly, these are pretty decent flying airplanes in any case. Every little bit helps, but at what cost? That's where I choked, at the price of a Sportsman installed. Maybe you could get someone who would let you do the install under their supervision, but.... It isn't rocket science. We had it done on a 185 and the installation is pretty straightforward, just time consuming. Then you really need to paint it....
I'd go for the prop,
Mike