Vortex Generators STC

Vortex Generators STC

<HTML>Just got off the horn with Micro AeroDynamics about their new STC for the C-150H. They claims an 8% reduction in stall speed if you install their little vortex generators on the leading edges and tail.  They say the climb rate is improved also. What you get is a pile of paper and a bag of little widgets that you glue on yourself with Lock-Tite. They say the whole job takes about 1 day without a mechanic. The price is $695.

So, does this STOL stuff work and is it worth the money?</HTML>

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Re: Vortex Generators STC

<HTML>William. I had an email conversation with  Dick  ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it )  who owns and operates  a C182, he installed the vortex generators you mention, he had said he loved them, seemed to work, even seemed to smooth those small bumps at cruise out a little........... BUT you will loose a little  top speed.
If you send your email I'll forward you his email to me regarding these.
John</HTML>

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Re: Vortex Generators STC

<HTML>You can't install the STC without a mechanic with Inspection Authority.
Why do you want to complicate your life and your airplane's airworthiness with these things?  The airplane will already get into strips so short you can't fly back out.  So what are they going to do for you?  Did they tell you how many of the little VG's can fall off and legally still fly?  Did they tell you how much trouble washing the plane is after you install them?  Did you ever hear of anyone who installed any expensive gadget on their plane and then publicly stated they were sorry they did it?  (Asking a pilot how he likes his plane or what he did to his plane, is like asking him how he feels about his wife/girlfriend when she's standing next to him.)
  I have received private letters from more than one owner who admitted privately that their airplane will not stop floating during landing, and will not stop effectively (they believed due to insufficient weight on the wheels) due to their VG installation.  Admittedly, they were both taildraggers, so perhaps a trike won't have quite so much difficulty skidding tires.   But if you can't fly back out of the place anyway, then why try to shorten the landing distance?   And the airplane I test-flew with them was a troublesome thing in gusty crosswinds because it wouldn't slow down sufficiently.  (Must prove the stall speed reduction claim, tho'.)   Most pilots will not actually use the lower stall speed effectively, anyway. 
  The claim that the lower stall speed will improve takeoff/climb rate is not worthy of the expense, in my opinion.  Climb rate is mostly the result of excess thrust and horsepower.   Since lift at lower speeds also increases both parasitic and induced drag, VG's won't change that horsepower ralationship significantly, if at all.
  I know my opinion won't sell magazines or aircraft mods, but I am convinced of it's validity.  Standing by for incoming hate-mail.</HTML>

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Re: Vortex Generators STC

<HTML>I fly photo flights with a 180HP 172M at 45 knots (lightly loaded) and am constantly being told to "hold it right there". Would VG's or the various leading edge mods allow slower flight and or a less radical AOA? 8% less wouldn't really be a lot......but better control feel and less AOA would be nice.

Thanks</HTML>

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Re: Vortex Generators STC

<HTML>I've wondered, if the stall speed goes down, shouldn't Va decrease as well?  So wouldn't that mean you can't fly as fast in heavier turbulence?

I must say that for a 150 or 152 or 172, or even 182, I wouldn't bother with this.

For a 210 or a Mooney or other super fast landing plane, I might (a Comanche too maybe, just 'cause they suck).  I'd also do it on a twin if it helped Vmca (rudder/stab VGs).  One of the other problems with low stall speed is bad crosswind performance (can't land at higher speeds).

Keep in mind the 172/150/152 VG kit was one of the last released.  Why?  Because nobody buys them!  The planes do everything well as they are...</HTML>

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Re: Vortex Generators STC

<HTML>I wasn't exactly hot to buy the kit - just wanted to perk up the forum.</HTML>

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Re: Vortex Generators STC

<HTML>"I'd also do it on a twin if it helped Vmca (rudder/stab VGs). "----
  Actually, Mark, the VG's are even LESS useful in a twin, in my opinion.  Think about this.  Each and every twin has a Vmca that is slower than their minimum climb speed.  Since a multi-engine pilot is primarily interested in a continuing ability to climb regardless of an engine failure on one side, then that pilot must ensure that he is never slower than the minimum climb speed (unless he wants to stop flying completely, such as just before touchdown.) 
  So, if Vxse or Vyse is faster than Vmc, ...then what possible use is an expensive device that makes Vmc,-- slower still?  (And what total silliness is it to be interested in stall speeds in a twin that stalls below it's Vmca or Vmcg?)</HTML>

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Re: Vortex Generators STC

<HTML>I've flown many hours of photo missions for the gov't and fixed camera mounts pose a problem with high angles of attack, such as you've found, Jim.  VG's may lower your stall speed, but they do so because they keep the boundary-layer air attached at higher angles of attack.  So they will not help, but will instead hurt your AOA situation with a fixed camera mount.   Leading edge devices do the same thing, so I don't think you'll get much relief there either.  (I suspect you're already doing it, but if not, then full flaps and higher rpm/power settings will give you the most stabil camera platform.  The gyroscopic effect of the prop will help stabilize the aircraft, and the full flaps will lower your AOA and therefore your camera angles.)  The new laser camera setups are almost oblivious to aircraft speeds in the 100 kt range, and make great photos day or night.  The gyro-stabilized models are the cat's meow!</HTML>

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Re: Vortex Generators STC

<HTML>"the VG's are even LESS useful in a twin"

umm...I disagree.  VGs are used fore of the 737 ailerons to
improve smooth airflow at low speeds, and are used (by the manufacturer) on the rudders of many other twins large and small to reduce Vmca.  They were even used by the ATR folks to supposedly reduce icing problems (the jury's still out on that).
they're also on the 737 tailcone fore of the vertical stab.  So I think for some applications not necessarily stall speed these may be very useful.

Without a wind tunnel and a test pilot, perhaps it's hard to tell though  :-]

I do agree that just lowering a twin's stall speed, perhaps making it lower than Vmca, by installing VGs could be perilous.  I certainly wouldn't want to be the test pilot...

Mark

P.S. there's lots of stuff on the web about this.  Not so much about the aplication to GA though (or it looks like marketing, not discussion).</HTML>

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Re: Vortex Generators STC

<HTML>I put them on my 1968 172I this spring and WOW!!  I love the results.  There was NO decrease in top end speed. Combined with my 180 HP conversion with 2 fat guys in the front and full fuel, I'm off the ground in less than 200 feet. It is much harder to stall now and it stalls below the lowest marking on the airspeed indicator.

I highly recomend them and if your in the vacinity of VCB the Nut Tree Airport in Northern CA I'll be more then happy to show you the results.  My wife and I installed mine in about 6 hours and had the local IA inspect/sign it off.  The kit is VERY complete, you need no other tools other than a step ladder.</HTML>

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Re: Vortex Generators STC

<HTML>Curt,

  How are crosswind landings now?  Do you notice any difference?  I'm maxed on crosswinds at 15 knots (usually in Oregon or at Hollister or Salinas) at 500 below gross.  I simply run out of rudder (unlike the piper where you run out of aileron).  Have you noticed any difference?  Was there a gross weight increase?

  A friend worked for redding aero and said they had the VG kits on their 402s, but mostly for the gross weight increase (there were VGs on the tail too helping Vmca, but I don't know how much).  For cargo operations, of course, they'll do anything to increase gross weight...

Mark</HTML>

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<HTML>Yes you do get better athority with the rudder but I haven't reached it's max yet so I don't know the limit.  I did get 200lb gross weight increase but I also have to limit my flap travel to 30 degrees if I wish to take advantage of this gross weight increase.

With this increase and full fuel I can carry 860lbs in the cabin.  Try that with a new 172.</HTML>

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Re: Vortex Generators STC

<HTML>Interested in the gross weight increase - is that part of the VG STC or something else - I have a 1969 172K and the gross weight increase seems attractive.

Thanks in advance

Ken Wanagas</HTML>

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<HTML>If they were as good as they claimed, wouldn't they have been standard equipment by now? Afterall, with the costs of a 172 in the 160's (and higher), whats a couple hundred more in VG's? Wouldn't Cessna want to be able to publish 200 Lbs more gross weight and lower stall?</HTML>

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<HTML>"the VG's are even LESS useful in a twin"

umm...I disagree. VGs are used fore of the 737 ailerons to
improve smooth airflow at low speeds, and are used (by the manufacturer) on the rudders of many other twins large and small to reduce Vmca. They were even used by the ATR folks to supposedly reduce icing problems (the jury's still out on that).
they're also on the 737 tailcone fore of the vertical stab. So I think for some applications not necessarily stall speed these may be very useful.

Without a wind tunnel and a test pilot, perhaps it's hard to tell though :-]

I do agree that just lowering a twin's stall speed, perhaps making it lower than Vmca, by installing VGs could be perilous. I certainly wouldn't want to be the test pilot...

Mark"
========
  Well, firstly, the examples Mark used are like comparing Apples to Oranges.  Those airplanes mentioned also have dual/triple electrical systems, life rafts, compressed air starter motors, hydraulically boosted flight controls, dual wheeled landing gears, APU's, and $400 tires.  Does that mean our lightplanes should also benefit from those encumbrances?  (Come to think of it, Airconditioning and Flight Attendants would be nice,...if you didn't have to pay for it.) 
  VG's were discovered many years ago as a "Band-Aid" fix to boundary layer seperation problems for jet aircraft at HIGH-SPEED,....not the low speed solutions they are promoted for with light aircraft.  At high Mach numbers the ailerons would lose effectiveness on the 707, and the early Lears, also on the later Hawkers.  737 rudders (and others) suffered also from such problems.   In order to allow those aircraft to go FASTER the VG's were installed.  If VG's would make a light plane go FASTER then I'd want them too!  But lightplanes already go slower than the average (even the above average) pilot can effectively utilize.  So why spend a couple Grand just to go slower than you already needed anyway?
Again, lowering Vmca in a modern light twin aircraft is like putting expensive sponges in the pockets of your bathing suit to make sure the suit stays wet in the water.  In blunt terms,  Vmca is a speed you never want to be below unless you're already on the ground.  Why make it slower? 
Example: The Cessna 402C has a Vmca of 80 kts.   But it's take off and climb (rotation) speed (from the Approved Flight Manual) is 92 kts.  It's Best rate of climb speed is 109 kts.  It's recommended approach speed is 95 kts.  It's manuevering speed is 150 kts.  It's minimum speed for transitioning from landing approach to go-around climb speed is 92 kts.  Even its minimum emergency climb obstacle clearance speed (Vx) is 84 kts!  Bottom line:  None of those speeds, except the Vmca speed is lowered by a VG installation.  All of those speeds are higher than the original un-modified Vmca.  Therefore, a pilot operating that aircraft in accordance with the FAA approved flight manual will never be as slow as it's factory-original Vmca (except possibly during high altitude flight training to get his multi-engine rating with a flight instructor, and a lowered Vmca in that type operation is not a safety enhancement, but instead potentially complicates and further endangers the aircraft should the pilot be so unfortunate as to actually suffer an engine failure during training.  It will be even more unlikely that he'll successfully recover the airplane.)  Now, ...why would anyone want to spend a couple thousand dollars to lower Vmca?  It's beyond me.  But a really accomplished salesman could probably persuade someone to do it.  (Sorry, COO.  I guess my honest opinions are just not always conducive to selling advertising space in the magazine.)</HTML>

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Re: Vortex Generators STC

<HTML>...I definitely agree with the addition of flight attendants...

...and the jet VGs are certainly for a totally different reason (near supersonic flight, etc.) but Redding Aero does like their 402 VGs and the weight increase.

  I must confess when I tried to land that 402 at the end of the night (light weight
with cool air) it refused to come out of the sky (floated) until we pulled all the power off, and we had to get mighty low and slow to land at the tiny airport SW of Crescent City.

  So I suppose some people can't live without 'em, but I can't personally even pull my 172 back into a wings-level stall with full forward CG, so I can imagine it would be very hard to get slow enough on final (using the elevator as rigged) to use the lowered stall speed for landing (at least without dangerously and illegally rerigging the elevator).  The whole discussion may require a PhD in aerophysicalitiness to conclude...

  I was also thinking that I landed at Troutdale one time in 35G40 and took off in 30G35.  I'm not sure you could even taxi in my 172 if it had VGs at that point. 

  Stories of Piper Cubs with people helping to walk the wings spring to mind...

  Perhaps a trip to Nut Tree is in order to experience them on a 172 instead of my blowing more hot air...hmmm

  I've only been there once for gas.  Do they have a nice restaurant? 


Mark</HTML>

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Re: Vortex Generators STC

<HTML>I've got several hundred hours in 402's with varying degrees of mods, including Vg's, RAM conversions,etc.  The gross wt increases are nothing but paperwork excercises.  Trust me.  The 402 won't get out of it's own way if it loses an engine, and that paperwork gross wt increase will simply provide more inertia when you hit the hill!  Don't fall for it.</HTML>

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Re: Vortex Generators STC

<HTML>I think Redding Aero would put a picture of Martha Stewart on one side of the plane and Rosanne Barr on the other if it came with an STC gross weight increase!   :-P

(and it would need one then)

Mark


Yeah, but what about STOL kits?  Any point in those?</HTML>

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Re: Vortex Generators STC

The Micro Aerodynamics VG kit turns the Cessna 310 from being a nasty little monster if too slow into a pussycat.  I've a number of hours in 310's with and without the VG kit.  There is no question I would install them if I had a twin cessna, but not sure on a 150.  I have flown a 150 with the Horton STOL, and other than it becomes pretty nasty in a strong crosswind, the takeoff performance is impressive.

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Re: Vortex Generators STC

Wow, what a discussion about VG's. I'm not sure Ive seen a debate this interesting, since we had the sprinkle or dunk discussion in sunday school last year.
I fly a Cessna T303 and it was a white-knuckle flyer on 1 engine to say the least. My A&P/AI installed the VG's on it and it changed (read improved) the plane's flight dynamics dramatically. The T303 had a tendancy of severe stalls with no warning and a dramatic nose over before the VG's. All of that went away after the VG's. I have had them on the plane for 18 months with about 120+ hours total time and have only lost "1" VG and that was due to a line boy dragging the fuel hose over it.
Maybe the T303 was an unusual candidate for the VG's, but damn, they work.....thanks Jim.

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Re: Vortex Generators STC

I thought the T303 came with VG's to fix some of the rudder and ice problems.  Also I was not aware of an STC for VG's for T303.
I thought the CR props and lower HP made the T303 a bunny single engine compared to all 300-400 with critical engines.

Thanks

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Re: Vortex Generators STC

I have flown several aircraft with VG's and without. 172's, 185's,super cubs, and 310's,402's,414's and a 421... with all these aircraft I could tell the difference in trying to land. they tend to want to stay flying when most planes without the VG's are way past their landing point. I fly a lot of short fields in Alaska.. The purpose of the VG's is to create a more uniform layer of air across the top of the wing. watch any air tunnel test and you can see the difference.. Also in the twins the gross weight increase is a huge difference especially if you are a 135 operation.. you would have to fly one to see the difference and be convinced.. I am not a believer in most speed mods though. people will spend thousands of dollars on fairings and gimmicks to gain a knott... so the manufacturer will tell you. again watching a wind tunnel test with and without VG's is proof. I tell my customers of course you will fly faster... you lightened up your wallet!! most pilots I know would gain their speed back by putting a bullseye on their slip indicator to keep the ball perfectly centered.. The VG's is the only mod I have on my aircraft.. I can think of several necessities that the manufacturers don't put on from the factory or didn't.. one is fueling steps.how about recessed fuel caps on all aircraft. did you know your nav/com antennas have 2+ pounds of drag per antenna depending on type...

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Re: Vortex Generators STC

I just installed VG's on my 1974 C-182P and have yet to fly it due to a TFR (Chicago area.....).  I am looking forward to seeing what the difference is.  I have been told that landing takes some adjustment since as was mentioned earlier, it wants to stay in the air.  The POH states a speed on final of 70-80 MPH.  I am curious if anyone has some insight as to what I can expect a new final speed to be.

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Re: Vortex Generators STC

I am (proud :-) part-owner and pilot of a T303.

> I thought the T303 came with VG's to fix some of
> the rudder and ice problems.
Yes, it does.

> Also I was not aware of an STC for VG's for T303.
Nor am I.  I would be interested to hear of one.  Not that I think we need them.  Our short field performance is excellent, thanks to fowler flaps...

> I thought the CR props and lower HP made the T303
> a bunny single engine compared to all 300-400 with
> critical engines.
It is.  At 65 knots, the T303 VMCA is close to it's clean stall speed.  The only VGs we have are on our vertical stabilizer, and the aircraft is easy as pie to fly on a single engine.  During difference training I really had to go overboard to get it to lose directional control in the yaw axis, and when it did, the attitude was ludicrous and the process was gradual.

I actually had to shut down my starboard engine in Feb 2010.  (Stuck cowl flap at FL200 led to very low oil temperature, resulting in unstable RPM).  I had no trouble descending through the ice and flying an ILS approach on one engine.

Yours,

Adam

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