Vortex Generators

[Guest Mike261]

Anyone have VG's on a J model? I looked online for some data but didn't have much luck. I'm interested to see what the actual takeoff and landing distances are as i may have to get in and out of a 2000 foot paved runway at about sea level on the regular, and loading and density altitude will no doubt be factors at some point. 

i would also like any input i can get from those who regularly operate out of 2000 foot runways.

and...what if any other STOL improvements are there for the j model, wing tips etc.

 

Mike

 

[Hank]

VGs on a mooney? I'm sure someone, somewhere, has done it.

I used to fly my C in and out of a 2000' grass strip. One end was clear, there was a hump big enough to throw you in the air around 55-60 mph when departing towards the clear end, and it curved slightly to the right, following the river.

My rule was always land & depart over the clear end when able, as a cement plant's gravel pile was at the other end.

I also never went there heavy. Two people and half tanks was my limit. Fortunately, my 3000' home field was only 8 nm away, but it was always a fun trip. That was one of the few times I regularly used Full Flaps to land, then stood on the brakes and to take off with Takeoff flaps.

Watch your float on landing. Speed control is critical. Grass will slow you down faster (and impede your takeoff more), but not when you're 3' high in ground effect. You can raise flaps and sit right down, though; did that once floating past midfield, didn't even need to brake to stop.

Be careful of field condition, watch out if recent rain or heavy rain in the past few days. Walk the strip and see how well it drains. Learn when they mow, the day after is very different from the day before. Dew is slippery in the morning, freshly cut grass is slippery, freshly cut grass that has been dewed on will make your language impolite when you look at your prop, gear and belly. Frosty grass is very slippery . . .

But it's not a problem, just be prepared and fly in exactly on speed. VGs are not required for this, and I think their effect would be minimal on a laminar flow wing anyway.

EDIT--reread, you're going to a 2000' paved field. Shouldn't be a problem, just don't try it at gross until you get comfortable. Look in the Video forum, there's a video there going into 2W2 in an F, 1840 x 30. If memory serves, that field has a Mooney Service Center.

Happy flying!

[Will W]

Your best STOL kid on a J model is a 3 bladed prop.  VG just slow you down because they create drag (the lift that's created to prevent boundary layer separation also creates drag).  Yes, you can fly slower before you get boundary layer separation... but you are doing it at a larger cost of a slower cruise speed.  Do you have any obstacles on the departure or arrival or can you be in ground effect before you get to the pavement?  This helps your takeoff which you can take off and get into ground effect like on a soft field takeoff.

[cliffy]

Speed control on short final and obstacles on final will be your controlling factors.

I can always get stopped by 1500' in my D/C (2 pax, lighter fuel) at my home field at 4300 MSL (DA's 0f +6000')

Can't get it off too well in 2000' at that that DA but I'm near gross at T/O most times.

You at Sea Level shouldn't have a problem if your speed is under control.

Remember, a go around can be the correct answer to the question- "can I do this?"

[Seth]

Erik, don't you have VG's on your Rocket?

 

The MSC you are thinking about Hank is Freeway - W00.  They have a 2400 x 40 paved strip with tall trees on one end and power lines on the other and all Mooney's of all varieties fly in there to the MSC.  Many are based on the field.  That's where I learned to fly a Mooney.

 

You don't need VG's to operate out of a 2000 foot strip, just accepting a reduced safety margin and be on your game.  On takeoffs, use ground effect to build speed if it's hot out before climbing out of ground effect.  Use takeoff flaps.  When landing, do not come in fast, fly the numbers and you should be fine.  If worried or need to get your skills up to par, practice at a longer field and keep practicing until you are turning off by a certain taxiway.  Then go to a shorter field and do the same thing.  Maybe start at a 4000 foot field, turn off by halfway.  Then go to a 3000 foot field and turnoff by half way.  Then go to a 2500 foot filed and come to a complete stop on the runway (or mid field turnoff), and then you'll know you can easily get into that 2000 foot field.

 

-Seth

[LANCECASPER]

Don't ruin the beauty and function of that laminar flow wing with VG's. It will handle slow flight just fine with good instruction and practice.

[KSMooniac]

Put in an AOA indicator instead.

Sent from my VS985 4G using Tapatalk

[carl]

micro aerodynamics

 

"Reduced STALL SPEED 8%! • Reduced Approach Speed • Much Better Roll Rate • Improved Ailerons • Lighter Elevator Forces • Improved Characteristics • Improved Controllability • FAA STC Approved • Easy One Day Installation • Kit Price $1450 plus S&H"

 

The first lear jet I saw had vortex generators ,so I have always wanted them. Never got them .

[M20F]

I find vortex generators handy if you need to cut your hand on something......

[Shadrach]

2000ft is no biggie. If you want VGs, cool. However, the plane does not need them for a 2000ft strip.

[Guest Mike261]

thanks for the replies. I don't really want VG's per se...was curious what the gain is. i read the little available info on line but could only find speed data, no rollout data. i don't like the aesthetic of the VG's at all, and it seems that the disruption to the airflow is detrimental to cruise performance may not be worth the tradeoff.

[M016576]

Put in an AOA indicator instead.

Sent from my VS985 4G using Tapatalk

Best post of this thread! Great advice for short takeoffs as well as short field landings.

[M016576]

micro aerodynamics

"Reduced STALL SPEED 8%! • Reduced Approach Speed • Much Better Roll Rate • Improved Ailerons • Lighter Elevator Forces • Improved Characteristics • Improved Controllability • FAA STC Approved • Easy One Day Installation • Kit Price $1450 plus S&H"

The first lear jet I saw had vortex generators ,so I have always wanted them. Never got them .

They forgot "reduced top speed"

[Piloto]

2000ft runway fields do not have a control tower and many may not even have a windsock. At night even with a windsock is hard to tell wind direction from it. Landing into the wind on 2000ft runways is a must. To insure that I am landing into the wind (specially at night) I do this procedure:

Approach the runway end I feel is the probable one with a head wind.

Check the ground speed is lower than the airspeed at about 3nm from the end

If the ground speed is lower I go ahead and land.

If the ground speed is higher I side step to the downwind and land at the opposite end.

On a good short field landing the stall alarm will come up just before touchdown. Practice for this.

José

[aviatoreb]

They forgot "reduced top speed"

 

How do you know?

[aviatoreb]

Put in an AOA indicator instead.

Sent from my VS985 4G using Tapatalk

 

I put both VGs and an AOA.

[Shadrach]

How do you know?

 

What's your experience with them? Are they the "free lunch" that most installers claim?

[aviatoreb]

What's your experience with them? Are they the "free lunch" that most installers claim?

 

I don't know....  I had them installed during the first weeks of ownership before I did any speed testing.  The plane was still too new to me and still a handful drawing too much attention then to thinking about a flight-test engineering run.  

 

Mine is a tad slow compared to book - but I also have tks.  And no smooth belly - that probably makes no difference.  A tad slow compared to book is still very fast.   So I am not the one who can tell you before and after effect speed wise- and even so, I think before and after speed wise would be different depending on if an airplane has tks or not - since TKS already disrupted the smooth flow a bit so even if the vgs disrupt flow at cruise in a clean wing, maybe they have no further effect on flow that is already slightly disrupted in a tks wing.

 

Theory is that they sit just below the boundary layer at cruise speed so they have no effect to speed.  The peek out just above boundary layer that is a bit shallower at slow speeds - when you need them.

 

I can say they work - I stall slower than book and I have none of that wishy-washy soft airplane feeling - I have crisp controls even slow.

 

Besides I consider any tool that allows you to land a bit slower to be a good thing and a safety thing, from the engineering perspective I think it is just cool manipulating air flow like that, so they tickle my fancy looking out at the wing and thinking about the physics of what they do - so call me a geek and I won't deny it.

[Houman]

I don't know....  I had them installed during the first weeks of ownership before I did any speed testing.  The plane was still too new to me and still a handful drawing too much attention then to thinking about a flight-test engineering run.  

 

Mine is a tad slow compared to book - but I also have tks.  And no smooth belly - that probably makes no difference.  A tad slow compared to book is still very fast.   So I am not the one who can tell you before and after effect speed wise- and even so, I think before and after speed wise would be different depending on if an airplane has tks or not - since TKS already disrupted the smooth flow a bit so even if the vgs disrupt flow at cruise in a clean wing, maybe they have no further effect on flow that is already slightly disrupted in a tks wing.

 

Theory is that they sit just below the boundary layer at cruise speed so they have no effect to speed.  The peek out just above boundary layer that is a bit shallower at slow speeds - when you need them.

 

I can say they work - I stall slower than book and I have none of that wishy-washy soft airplane feeling - I have crisp controls even slow.

 

Besides I consider any tool that allows you to land a bit slower to be a good thing and a safety thing, from the engineering perspective I think it is just cool manipulating air flow like that, so they tickle my fancy looking out at the wing and thinking about the physics of what they do - so call me a geek and I won't deny it.

Erik, you are a geek lol, we all are geeks on the engineering side of things, fascinated by our machines. I would take your TKS and VG's anyday, but AOA is the next item on my list, unfortuntely convincing my 10 000 hour ex-ATP aircraft partner that only flies 10h in a year to pay half is another thing...

[Oscar Avalle]

Erik, you are a geek lol, we all are geeks on the engineering side of things, fascinated by our machines. I would take your TKS and VG's anyday, but AOA is the next item on my list, unfortuntely convincing my 10 000 hour ex-ATP aircraft partner that only flies 10h in a year to pay half is another thing...

I have VG and the AOA installed on my M20C. The plane has always been a bit slower than book... but may be it is because I have a three blade prop. However, I have to say that with the VGs the plane handles extremely well in low speeds and helps me with my landings on short unprepared runways (grass). In this context the AOA is also great. Do I miss the 2 or 3 knots that I may have lost... Not really. 

[aviatoreb]

Erik, you are a geek lol, we all are geeks on the engineering side of things, fascinated by our machines.

 

 

Yup!  Takes on to know one....

[ryoder]

I hate how vortex generators look. I just couldn't do that to my wing. I enjoy waxing the smooth surface and seeing it shine. Those things kill it for me.

[aviatoreb]

I hate how vortex generators look. I just couldn't do that to my wing. I enjoy waxing the smooth surface and seeing it shine. Those things kill it for me.

 

To each his own - love how vortex generators look.  They speak of the engineering creativity it takes to manipulate the flow.

[M016576]

How do you know?

Fair enough question. Aerodynamics (to a lesser extent physics) is the answer, but, at the speeds we're traveling (compressibility of air type speeds), probably is fairly irrelevant.

Two types of flow, laminar and turbulent.

As the researchers explain, an object's boundary layer starts out as laminar, or smooth and orderly. As the object continues to fly through the air, small disturbances create instabilities and, above a critical value, the laminar flow regime transitions to a turbulent one. The transition can easily result in an order of magnitude increase in skin-friction (part of parasitic) drag on an aircraft.

Parasitic drag is inversely preportional to induced drag.

The thing is, turbulent flow adheres to a wing much longer (and better) than laminar flow... Which is why VG's drastically increase high AOA performance and slow speed maneuvering... But the price you pay is an increase in skin friction drag across the wing. Particularly when we're talking about a "laminar flow wing" design. But really it's probably only 2-3 KTAS in practice at our speeds. Not really significant for every day usage. But that's part of the reason why you don't see VG's on fighter jets.

Edit: those numbers IRT mooneys are just a guess on my part based on the VG size and position.

Double edit: after trolling a "c-word" brand .org, it seems the "expert consensus" says 1-2 KTAS loss of top speed for a C-140 or C-172. Cleaning the wings seems to be of more concern for those guys, though!

Triple edit: The TKS install on my missile certainly doesn't let it hit book numbers.., but last weekend I was flying down in the lowlands (Seattle), and had to depart ifr due to cloud layers- they (atc) held me down at 4k for what seemed like FOREVER- I had let the missile stay making full power expecting the follow on climb that didn't come for 20 miles... Anyway, ROP, 2650RPM at 4K I was seeing 182KTAS. Sweet!!!! Fuel burn? 20GPH ish.... Not so sweet, I should have leaned it out to 16ish or so, but I was expecting that climb.... Have I mentioned how much better I like VFR flying?

[LANCECASPER]

The most effective thing that VG's do is remove $1500-$2000 from your wallet which decreases your sink rate on short final.