VG installation with STOL kit

[GAHorn]

Has it occured to anyone that ...if a wing.... or aileron....or flap.... (etc) ...loses efficiency of effect as airspeed slows.... that the exact same loss of effectiveness occurs with VG's as well? It's only an opinion, but I feel that VGs are like a lot of other mods that owners perform on their airplanes.....once the money is spent.... it was a great expenditure!

Perhaps if I operated in the outback or flew customers out for salmon fishing in Idaho or Alaska I'd feel different....but I'd still go for the horsepower first, before I'd do STOL or VGs. If I were looking to buy serious cushion for survival.... I'd buy a 406 ELT, CO-detector, and survival gear before I did those mods! (Think about THAT...if you're considering spending a little extra cash on VG's.) Then I'd get a 185/206, Super Cub or, what the heck, Turbine-Beaver!
Each person must make those decisions for themselves. I hope my comments are taken in context with the type of flying that I do...not what others might do.

[canav8]

Has it occured to anyone that ...if a wing.... or aileron....or flap.... (etc) ...loses efficiency of effect as airspeed slows.... that the exact same loss of effectiveness occurs with VG's as well? It's only an opinion, but I feel that VGs are like a lot of other mods that owners perform on their airplanes.....once the money is spent.... it was a great expenditure!

Perhaps if I operated in the outback or flew customers out for salmon fishing in Idaho or Alaska I'd feel different....but I'd still go for the horsepower first, before I'd do STOL or VGs. If I were looking to buy serious cushion for survival.... I'd buy a 406 ELT, CO-detector, and survival gear before I did those mods! (Think about THAT...if you're considering spending a little extra cash on VG's.) Then I'd get a 185/206, Super Cub or, what the heck, Turbine-Beaver!
Each person must make those decisions for themselves. I hope my comments are taken in context with the type of flying that I do...not what others might do.

They are George. That was exactly my point. I believe that morphing an aircraft to special needs catagory has significant limitations. That was the reason for my post. I never want to hear a guy installed VG's to stretch a glide to the crash site. DOug

[Bruce Fenstermacher]

So George the VGs installed on twin engine aircraft rudders to increase the effectiveness of the rudder doesn't work? VGs are installed in lots of other places on lots of airplanes to correct or improve airflow over the surface for many reasons. Surely you've flown many planes with them George. I'm sure you don't think they are there just to increase the cost of the plane.

VGs work by swirling the air passing over the wing causing the boundary layer to stick to the airfoil longer through a stall. The effect is slower stall speed and better aileron control at that speed.

[buzzlatka]

I'm thinking VG's could help me in this scenario. More horsepower would really help but that costs a lot. Scenario, strip in California 1200 ft long with big trees at one end and a levy and sailboat mast at the other. Can land no problem, getting out requires that the airplane is light or the air cold. I would like to be able to fly out a little heavier. This is not an outback strip where I need survival gear, this is within 40 miles of San Francisco.


Takeoff
http://vimeo.com/7911101

Land
http://vimeo.com/7911054

better view of strip
http://vimeo.com/7911128


Forgive the video quality, had to use and iphone, weight was an issue and all...

Anyone know how to embed these things?

[cmsusllc]

For what it's worth George, flying the flat lands of Texas and flying in the Northwest where summertime means heading into the Cascades or Rockies for some R&R is what we live for. Improving the preformance really helps with the pucker factor in some of these places. I use book numbers for the 170 and don't push past them. That's my safety cushion even though I have the O-360 conversion. I have a friend that had a 53B with the same Avcon conversion ( identical planes ) but had the sportsman stall kit installed. It made a big difference when compared to mine, quicker off and shorter on with a steeper climb, which was enough to convince me that I want one when I can afford it. Then he installed a set of VG's .
His report was that the stol kit made it fly slower and the VG's gave it excellant control at the slower speeds. I have talked with others that have done similar things to there 170'S, 180's, and 185's and if you fly in the mountains as I do they all simply say "DO IT". Also in visiting with Lori MacNichol of McCall Mountain Canyon Flying Seminars she suggested the VG's on my plane would alow the comfert level to fly most of the Idaho back strips.
And further - as to your next suggestion, yea a 180 might be better but the 170 is a lot more fun to fly and my hourly cost is about half what my friends spend on their 180's and I don't need the load capacity.
Sheese, You flatlanders just don't understand.
Scott ..... 53B

[hilltop170]

I think Vg effectiveness depends mostly on the wing design. On a Super Cub with a big fat high lift high drag wing, it makes a big, easy to measure difference. I'm not sure how much difference it makes on a Cessna wing, I have never seen any before and after numbers from anyone. All I have ever personally heard (and I ask every pilot I talk to who has put VGs on their planes if they took before and after data and what difference did they see), is "It made a big difference" in this or that but never with any data to back it up. I'm skeptical until I see some real data.

On my old Super Cub, the indicated stall speed with full flaps went down from 42mph to 20mph after VGs. Not actual airspeed, indicated. It had a helicopter airspeed indicator with the 40mph mark at the 3 o'clock position and plenty of low speed resolution. The VGs made it possible to fly a stable approach at 40mph indicated instead of stalling at 42mph indicated. That made a big difference on floats, wheels, or skis.

Also, before the VGs, flying formation with an identical Super Cub with VGs, my plane would stall while the other Cub could do 30 degree banks and slow fly well below my minimum controllable airspeed. After VGs we could fly side by side down to stall with the same performance. They work on a Cub wing.

I have not heard of anyone who has taken good before and after numbers with a Cessna or flown next to another identical Cessna to compare performance with and without VGs. I think I'll save my money until I see something.

[Bruce Fenstermacher]

Richard you are another I'm sorry never got to fly my 170 with the VGs. (Dam it more sellers remorse.)

I attempted to take data before and after installation of my VGs. The problem is you wouldn't believe the after data to be accurate. After all how fast would I really be flying when the airspeed indicator is indicating 0. I know I'm still moving forward but the angle of attack is that steep. And while it is in that attitude I was able to steer about the sky comfortably with ailerons only. One issue with flying this slow is rate of decent. I saw nearly 800ft a minute with the nose up while performing turns about the sky. Yes you could set up and ride it to the ground like an elevator.

The key to VG's is you will never fly as slow as you are able on approach but you will find yourself flying slower than without because you are more comfortable doing so. I found myself flying approachs 10mph slower and never realizing it. Others with 170 experiance did the same. I could fly them slower if I tried but it wasn't natural.

I wouldn't say VGs improve climb other than to say if you are more comfortable at a steeper angle of attack you are more likely to fly that angle and that might improve your climb rate.

As Richard said VGs have a more profound effect on an thicker airfoil like a Cub and that only makes sense. But they also improve control in slow flight on a Cessna 170 airfoil. What more can I say. I've had them and flown with them for lots of hours on a Cessna 170. They work and I'd buy them and install them in a heart beat if I was operating in an environment that demanded pushing the envelope of slow flight.

I personally would buy and fly VGs before I put on a cuff on an airplane only because of the simplicity of installation and lower cost. I think VGs give you some of the same advantages a cuff does at slow speed but not all. And I think a cuff alone can't give some advantages the VGs do.

If I was flying in a more critical environment I'd probably like a cuff with VGs for the approach and more power for departure.

[jrenwick]

....
Each person must make those decisions for themselves. I hope my comments are taken in context with the type of flying that I do...not what others might do.

George, if that's truly what you mean, you should probably add that qualification as needed when you issue an opinion. Yes, at times I've had to ignore your opinion because you seem to be advising a back-country pilot as if he did most of his flying in Texas.

Best Regards,

John

[GAHorn]

So George the VGs installed on twin engine aircraft rudders to increase the effectiveness of the rudder doesn't work? VGs are installed in lots of other places on lots of airplanes to correct or improve airflow over the surface for many reasons. Surely you've flown many planes with them George. I'm sure you don't think they are there just to increase the cost of the plane.

VGs work by swirling the air passing over the wing causing the boundary layer to stick to the airfoil longer through a stall. The effect is slower stall speed and better aileron control at that speed.

Lowering stall speeds on a twin......That is probably the WORST reason to install VG's. (Yes I have flown them.) Here's why it's a lousy idea: One never wants to fly a twin (or any multi) below it's single-engine-climb speed, because once below that speed, the loss of an virtually engine guarantees the loss of the airplane. On twins...stall speed is ALWAYS below Vmc and Vxse/Vyse.....therefore a prudent pilot will not normally fly there. Therefore adding VGs to that airplane truly is like Tits on a Boar Hog.

Some of the jets I fly have VGs, but they are for the purpose of preventing boundary-layer separation at HIGH speed...not to lower stall or improve low-speed control.

The intent of VGs on a multi-engine's vertical stab is to improve low-speed effectiveness of the rudder in an effort to lower Vmc. ... but remember, .... Vmc is well-below any single-engine ability to climb or even maintain altitude...so no multi-engine pilot is going to be operating that slow unless he's willing to risk the loss of the airplane. So, in my view, adding VG's for slow speed control of a twin is the silliest mod of all.......Doh! (At least with a single that particluar consideration is not an issue.)

[GAHorn]

[...George, if that's truly what you mean, you should probably add that qualification as needed when you issue an opinion. Yes, at times I've had to ignore your opinion because you seem to be advising a back-country pilot as if he did most of his flying in Texas.

Best Regards,

John

What part of...

... In my opinion ...

.... wasn't clear?

If qualification of every opinion were made in these forums..... the internet would run completely out of ink!

( It's your wallet....Feel free to disregard my opinions anytime.)

[jrenwick]

George, it wasn't the "opinion" part that I was talking about. It was "...in context with the type of flying that I do...not what others might do." In this instance you were responding to a pilot in western Montana, which is mountainous and close to the famous Idaho back country. Now we understand you were advising him as if he did most of his flying in Texas! I had already figured that out, but thanks for the clarification.

This discussion should start with the premise that we're talking about a mountain flying situation, where anything that can increase rate of climb, such as a STOL kit, VGs (do they?) and bigger engines would be desirable. For many, a larger engine on a 170 isn't an option, so it becomes a discussion about the other things that might help.

Best Regards (I really mean it!),

John

[Bruce Fenstermacher]

Has it occured to anyone that ...if a wing.... or aileron....or flap.... (etc) ...loses efficiency of effect as airspeed slows.... that the exact same loss of effectiveness occurs with VG's as well? It's only an opinion, but I feel that VGs are like a lot of other mods that owners perform on their airplanes.....once the money is spent.... it was a great expenditure!

Has it occured to you George that properly placed VGs change the rate and timing of the loss of efficiency of the wing, aileron or flap as angle of attack is increased and airspeed slowed the effect felt being increasing control and lowered stall speed? The VGs you are familer with hold the boundry layer to the airfoil at high speed by their design and placement. The VGs design and placement we are talking about hold the boundry layer to the airfoil at high angles of attack and slow speed.

[GAHorn]

I'm not arguing how VGs work, which is a well-known effect.

My opinion is with regard to their relative value versus realized performance gains. The question most often posed is not by those who actually "work" their airplanes and is similar to "are they worth the expenditure versus the expected performance gains". I only wish to point out that dollar-per-mph they are very expensive, their cost of maintenance is not free, and that the aircraft requirements for legal preflight-status is affected. (Most installations have limits on the number and location of missing units for dispatch, and all of them are susceptible to damage and increased trouble for things as simple as a wash-job. Anyone who has torn a shirt, ripped an armpit, or fallen on one will not soon forget it.)

Did I mention they are ugly?

Otherwise I like them very much.

(Caveat: Bruce's short field landing demonstration at Petit Jean argues-well for VG's. Unfortunately there's not been a comparison with an unequipped airplane alongside his, nor was there a takeoff demo, and it's unknown how much of that demo is related to his logged hover-time.)

[hilltop170]

To me, the value of any wing modification is not how much does it improve performance when the plane is empty but when it is at max weight. The C-170 and C-180 have essentially the same wing.

My C-180 has flown all over Alaska operating off tundra, beaches, glaciers, mountains, and even a paved strip or two on wheels and retractable wheel skis. It was stock for the first 13 years I owned it. Then a O-520 P-Ponk engine and 86" prop was installed. That made more difference in take off reduction, climb, and cruise than I ever imagined. It will take off shorter than it can land at any weight and that was my justification for the big engine. Stall fences were added which had a fairly good effect on indicated stall speed. It flew like that another 10 years with stock wings, again all over Alaska. It did everything I wanted it to do with no problem. It would operate at gross weight out of 700'. Most Alaska flying is close to sea level except of course in the mountains.

Then about 4 years ago a Sportsman cuff and Wing-X 18" wing extensions were added to each wing. It added some weight and slowed the plane down in cruise but when the plane is loaded, it is much more solid on approach and the pitch attitude/nose height/ability to see over the nose limits how much pitch attitude to carry, not airspeed. It allowed approaches at 50mph indicated with solid control where before the plane would stall at 50mph indicated and I would carry 60mph indicated. That was the improvement I was looking for and it is there.

Those changes made definite and subtle differences in performance but nowhere near the difference the added horsepower made. The big engine is all about take off, climb, and cruise. The wing mods are all about slowing the plane down and more control. They work well together.

I don't know how much slower VGs would make the plane fly if they were added, if any, or if I would even be willing to fly it any slower. I don't know, but that was the original question MontanaBird asked to start this conversation. If VGs would pitch the nose down on approach it would be nice but I never heard that claim.

VGs on the Cub and wing mods on the C-180 did the same thing by different methods, slowed down approach and touchdown speed while improving control. There has to be a point of deminishing returns though. I would like to hear from or fly beside someone who has done all the mods to see for myself.

Along the way I took data with the various configurations to compare what actually changed with each one. The plots below are self explanatory and were all made in steady-state flight holding constant power, indicated airspeed, and altitude.

[Bruce Fenstermacher]

It is my opinion that th biggest bang for the buck if you want to improve the slow speed control of your 170 it is VGs. Yes they can be a pain if you wash your plane and you have to watch them fueling. You have to lose 5 VGs and it doesn't matter where, to render a 170 unairworthy. This was never a problem for me in 8 years of VG ownership. Most of the VGs that came off I knocked of with the fuel hose. I never lost any from under the elevator which is a surprise. They may be ugly but that fit my plane and since I only washed it when it rained so that was not a problem either. BTW it takes seconds to re-glue them back on. Loosing VGs was just not an issue.

I would suspect that much the same performance in slow flight can be gained with a leading edge cuff and stall fences at a higher cost. They may improve climb because the wing creates more lift at less of an AOA than a stock wing with VGs. They are easier to wash and hopefully they won't come off and need to be re-glued or your REALLY in trouble.

I think having both mods would be the ultimate wing configuration short of a total wing redesign for slow flight but adding either mod to the other probably won't show as much a change in flight characteristics as either one mod did alone.

To be clear VGs will not increase lift except the pilot will feel more comfortable flying at a higher AOA and therefor more lift might be created. VGs will not allow a lower nose profile while in decent. In fact above 60 mph with the nose down I can't say I even knew I had VGs installed.