Cirrus Down Jan 8 2016

[ArtVandelay]

  On 1/27/2016 at 2:54 PM, steingar said:

They aren't even that expensive, they'll lower your stall speed  good bit and make your airplane far more controllable into the stall, all without slowing you down.

Oh no, they slow you down, there is no free lunch, on a Cessna you'll lose 2 knots, on a Mooney probably 3-5 knots depending on the model.

[aviatoreb]

  On 1/27/2016 at 4:07 PM, teejayevans said:

Oh no, they slow you down, there is no free lunch, on a Cessna you'll lose 2 knots, on a Mooney probably 3-5 knots depending on the model.

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How do you know?  Is that based on eyeball estimates, or word of mouth or have you other source of real data?  Not criticizing I am really curious as to how reliable is this statement.

Edited January 27, 2016 by aviatoreb

[Bob_Belville]

They also are said to be dangerous, particularly on a low wing, when washing/waxing or just brushing by. Not deadly but the fins are sharp and can cut. My A&P installed a set on a Maule that he rebuilt recently. I don't think I'd like them on a Mooney. 

[Shadrach]

  On 1/27/2016 at 4:16 PM, aviatoreb said:

How do you know?  Is that based on eyeball estimates, or word of mouth or have you other source of real data?  Not criticizing I am really curious as to how reliable is this statement.

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VG's necessarily must cause some though usually minimal speed loss. How much would require testing the airframe before and after.  I would think the speed losses minimal at lower altitude cruise because of the low AOA at high IAS in cruise.  Up high, when cruising at lower IAS and higher AOA, the difference may be more evident. 

I think that Mooneys are plenty docile on the lower end of the spectrum if you're practiced at handling them there.  VGs would add some extra margin, but unless your hanging it on the prop like a bush pilot, I can see little to no benefit for the type of flying that I do...and my ASI sees the lowish side of 60MPH on short final more than most Mooney owners. 

Edited January 27, 2016 by Shadrach

[Shadrach]

  On 1/27/2016 at 3:53 PM, aviatoreb said:

I am a believer in gear up - if I ever need to make a forced landing on a highly unimproved surface, or water, then better to land on a smooth belly than with gear down which may cause you to flip.  This is controversial though since some will say that gear down allows for them to maybe rip away which is absorbing energy.

I added vortex generators to my airplane for exactly the reason you said.

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Given that you've added them, you should know more than anyone. Do you have before and after data?  

In an off airport landing, I would leave the gear up for water of tree tops, anything else and it's likely better to have them there to dissipate energy. 

Perhaps you just want to ensure the insurance company gets the airplane they deserve?

Edited January 27, 2016 by Shadrach

[aviatoreb]

  On 1/27/2016 at 4:53 PM, Shadrach said:

Given that you've added them, you should know more than anyone. Do you have before and after data?  

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I don't know.  I added them almost immediately when I purchased the plane 5 years ago - seemed like a good idea at the time.  SO I have no before data.

Could be they slow me down?  I dunno.  Supposedly they are claimed that they do not, and they sit under the boundary layer while in cruise.  I dunno.  I do have tks which also is supposed to slow me down - so do tks plus vgs slow me down more than tks alone?  I dunno.

They do make a significant different at slow speed I was able to feel immediately when I got them.

[ArtVandelay]

  On 1/27/2016 at 4:16 PM, aviatoreb said:

  On 1/27/2016 at 4:07 PM, teejayevans said:

8 minutes ago, teejayevans said: Oh no, they slow you down, there is no free lunch, on a Cessna you'll lose 2 knots, on a Mooney probably 3-5 knots depending on the model.

How do you know?  Is that based on eyeball estimates, or word of mouth or have you other source of real data?  Not criticizing I am really curious as to how reliable is this statement.

Wikipedia, tests were done. Remember parasitic drag increases exponentially, hence my estimate on the Mooney drag.

[ArtVandelay]

  On 1/27/2016 at 5:21 PM, aviatoreb said:

  On 1/27/2016 at 4:53 PM, Shadrach said:

Could be they slow me down?  I dunno.  Supposedly they are claimed that they do not, and they sit under the boundary layer while in cruise.  I dunno.  I do have tks which also is supposed to slow me down - so do tks plus vgs slow me down more than tks alone?  I dunno.

They do make a significant different at slow speed I was able to feel immediately when I got them.

My understanding is the laminar flow wings retain the boundary layer for most of the wing shape, so they may sit under the boundary layer for some airfoil shapes, but not others.

The worst place is the leading edge of a wing, hence TKS and wing mounted landing lights are especially bad in increasing drag.

I thought the vortex generators are mounted close to the leading edge, correct me if I'm wrong.

[Shadrach]

  On 1/27/2016 at 5:21 PM, aviatoreb said:

They do make a significant different at slow speed I was able to feel immediately when I got them.

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Do tell?  We have the same airframe, albeit yours has a heavier engine on the front.  What low speed ailments have they cured?  Was your previous plane a Mooney? I only ask, because I remember some of my first impressions transitioning to the Mooney. Looking back 10 years and 500hrs later, a lot of my assessments were based on what I was used to, not what the airplane was actually doing or capable of. My plane will drop the left wing if aggressively stalled at low speed. That's it's worst habit. It actually behaves more benignly in coordinated accelerated stalls, though I don't do them often.

Edited January 27, 2016 by Shadrach

[Shadrach]

  On 1/27/2016 at 5:54 PM, teejayevans said:

 

My understanding is the laminar flow wings retain the boundary layer for most of the wing shape, so they may sit under the boundary layer for some airfoil shapes, but not others.

The worst place is the leading edge of a wing, hence TKS and wing mounted landing lights are especially bad in increasing drag.

I thought the vortex generators are mounted close to the leading edge, correct me if I'm wrong.

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They are "closish" to the leading edge. They need to be placed in the area of the wing were airflow separates at stall AOA. As I am sure you know, the turbulent area of separation moves forward as AOA increases, until the wing stops flying. It's my understanding that VGs enable the boundary layer to adhere at AOAs where it would be separated without. 

Edited January 27, 2016 by Shadrach

[steingar]

  On 1/27/2016 at 3:23 PM, Shadrach said:

You are correct about the stall speed of your C vs a Cherokee. In fact, for a given weight, I'm pretty sure your bird will fly slower than a Cherokee. It's a glider compared to the piper. The issue is that people don't fly them slow. I know I come off like an airspeed evangelist, but the fact is you even see the pros recommending significantly more speed than is needed. A lot of Mooney pilots never Become comfortable flying them slow...ever.   With shoulder harnesses a horizontal impact at <60mph is very survivable, unless you hit a wall.

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We are in agreement.  And a  Mooney flies like a trainer once its dirtied up.  Anyone really worried about forced landings should 1. take good care of their engine and 2. practice slow flight.  The only time I ever tried to stall mine I couldn't even get it to break.  Keep everything coordinated and it will land just like a Skyhawk or Cherokee.  I think I'd lower the gear, mostly because I don't think I could get it down to flap speed clean.

[bonal]

  On 1/27/2016 at 6:11 PM, steingar said:

We are in agreement.  And a  Mooney flies like a trainer once its dirtied up.  Anyone really worried about forced landings should 1. take good care of their engine and 2. practice slow flight.  The only time I ever tried to stall mine I couldn't even get it to break.  Keep everything coordinated and it will land just like a Skyhawk or Cherokee.  I think I'd lower the gear, mostly because I don't think I could get it down to flap speed clean.

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I'm not sure that I would be too worried about causing damage to my flaps or the spar from dropping them at above speed since they are about to be torn to bits by the rough landing surface. not to start the flaps no flaps debate but if your going to ditch in water I would leave them up they could cause the nose to pitch down into the water same as trim works on a boat.  This discussion has caused me to increase my downward surveillance for best case off field choices. Something I already did but now with much more thought.

[aviatoreb]

  On 1/27/2016 at 4:47 PM, Shadrach said:

VG's necessarily must cause some though usually minimal speed loss. How much would require testing the airframe before and after.  I would think the speed losses minimal at lower altitude cruise because of the low AOA at high IAS in cruise.  Up high, when cruising at lower IAS and higher AOA, the difference may be more evident. 

I think that Mooneys are plenty docile on the lower end of the spectrum if you're practiced at handling them there.  VGs would add some extra margin, but unless your hanging it on the prop like a bush pilot, I can see little to no benefit for the type of flying that I do...and my ASI sees the lowish side of 60MPH on short final more than most Mooney owners. 

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I really don't think you can logic your way through subtle aerodynamic principles like VGs must necessarily cause speed loss as if it is an axiom or a theorem.

The company says it causes no loss of speed at cruise, and their argument is plausible.  They claim that they sit below the boundary layer of the flow over the wing at high speed - i.e., essentially in almost standing still air.  They claim they tested they cause no speed loss at cruise.  But at slow speed the boundary layer is supposedly thinner and the fins stick up into the air so they have effect at slow speed but none at high speed, so they say.

I am not sure I believe them that they have no effect at high speed.  But certainly we cannot make up numbers like 3-5 kts without testing.  Unfortunately I didn't test - I installed them immediately when I got the plane as sort of training wheels.  I moved from a Diamond DA40 - my former airplane to a much hotter Mooney rocket - I had 350 hrs and instrument, but I was intimidated just a bit at the time and my thinking was anything to slow down stall speed is a safety feature.  I still believe that.

But I have no before and after data - they have been on my airplane essentially for 5 years I have owned it.

This guy, Rogers, a professor of aeronautical engineering at USNA, who is a well respected GA enthusiast as well who publishes useful GA studies, tested VGs before and after on his Bonanza.  He noted cruise speed changes and made graphs of the changes for various speeds.  I would expect it to be roughly similar if not worse for a "laminar" flow wing mooney.

http://www.nar-associates.com/technical-flying/vortex/Vgs_stall_wide_screen.pdf

However, to complicate the issue, my tks system already is tripping the flow near the leading edge of the wing so I am already loosing some speed due to tks, and then it is not clear if even if a VG causes speed loss in a clean wing, if it causes further speed loss in a tks wing.

I like them though - they DO make for crisp handling right up to stall instead of that mushy washed out feeling. By comparison to book, it seems as if my stall speed is a tad slower too.  I really should have tested before and after but I wasn't ready when I had them installed. So I would love to hear from someone who did. In a Mooney.

[aviatoreb]

  On 1/27/2016 at 6:01 PM, Shadrach said:

They are "closish" to the leading edge. They need to be placed in the area of the wing were airflow separates at stall AOA. As I am sure you know, the turbulent area of separation moves forward as AOA increases, until the wing stops flying. It's my understanding that VGs enable the boundary layer to adhere at AOAs where it would be separated without. 

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I don't think that description of the way VGs work is correct.  Or how stall works with respect to AOA.  Where the flow separates from the wing creeps forward toward the front of the wing as the AOA increases.  In some sense, the wing is always stalling a little bit because the flow always separates somewhere a ways back on the wing - even at your highest speed cruise.  The amount of lift you get from the wing is mostly a function of how much area of the wing is in front of that point of separation - say half or 2/3 of the wing in high speed cruise.  AS you slow, and you aoa increases, less lift is generated, until the amount of lift generated - up force - is less than the weight of your plane - down force.  This is what is called the stall - when your lift is less than your weight, but interpreted as a point of separation, the wing is stalling a little bit at all speeds.  This is why you stall at a higher speed if heavy since it takes more lift force to carry the heavy airplane, so a relatively lower aoa when the point of flow separation is not as far forward, is the critical point where there is more weight than lift.

The VGs do something interesting to the flow. The add vorticity to the flow travelling down the surface of the wing.  And for some reason I do not know - I just take it as an experimental fact, energized flow, meaning flow with more vorticity, separates later (farther back) than flow with the same speed but no vorticity.  And further back means more lift force, for a given aoa.  So you can fly at a higher aoa.

The other thing is that the vorticity energized flow supposedly has an easier time staying attached as it travels back toward your control surfaces, in modern designed airplanes which are meant to have the root stall before the tips.

Vorticity by the way you can think of as a tornado - swirling wind tubes travelling backward.

Aerodynamic Engineering theory from a math prof - so I am not a real aeronautical engineer, I just play one on TV.

[C-GHIJ]

  On 1/23/2016 at 11:14 PM, MyNameIsNobody said:

Technically I think the rider failed more than the chute...and the harness.  That is a face plant vs. my face palm...

 

 

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  On 1/23/2016 at 6:17 PM, Marauder said:

What the heck. Chutes can fail.

 

Sent from my iPad using Tapatalk

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Hell she needs the Cirrus, I don't think I could get her in my Mooney!!!!!!  I give her points for her landing though.

[Shadrach]

  On 1/27/2016 at 11:52 PM, aviatoreb said:

I don't think that description of the way VGs work is correct.  Or how stall works with respect to AOA.  Where the flow separates from the wing creeps forward toward the front of the wing as the AOA increases.  In some sense, the wing is always stalling a little bit because the flow always separates somewhere a ways back on the wing - even at your highest speed cruise.  The amount of lift you get from the wing is mostly a function of how much area of the wing is in front of that point of separation - say half or 2/3 of the wing in high speed cruise.  AS you slow, and you aoa increases, less lift is generated, until the amount of lift generated - up force - is less than the weight of your plane - down force.  This is what is called the stall - when your lift is less than your weight, but interpreted as a point of separation, the wing is stalling a little bit at all speeds.  This is why you stall at a higher speed if heavy since it takes more lift force to carry the heavy airplane, so a relatively lower aoa when the point of flow separation is not as far forward, is the critical point where there is more weight than lift.

The VGs do something interesting to the flow. The add vorticity to the flow travelling down the surface of the wing.  And for some reason I do not know - I just take it as an experimental fact, energized flow, meaning flow with more vorticity, separates later (farther back) than flow with the same speed but no vorticity.  And further back means more lift force, for a given aoa.  So you can fly at a higher aoa.

The other thing is that the vorticity energized flow supposedly has an easier time staying attached as it travels back toward your control surfaces, in modern designed airplanes which are meant to have the root stall before the tips.

Vorticity by the way you can think of as a tornado - swirling wind tubes travelling backward.

Aerodynamic Engineering theory from a math prof - so I am not a real aeronautical engineer, I just play one on TV.

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You're muddying the waters with speed. Stall happens at critical AOA. It's the same no matter your weight...under gross, over gross and everything in between or your speed...20KIAS TO 220KIAS.   It always happens that the same AOA for a specific configuration. That is all. This is why the vane on our stall horn need not be adjusted for weight or speed or any of the other things that are related to stall but don't really serve much purpose for this part of the discussion.

If you watch a tufted laminar flow wing (or any wing for the that matter) you can watch the area of turbulence move forward. 

Note this picture of a tufted wing with VGs on the outer part of the wing. On the inner part of the wing, you can clearly see that the separation is moving towards the leading edge as the wing is flying at a higher AOA. On the outer part of the wing with VGs the boundary layer is still attached.

If you like your airplane better with VGs, who am I or anyone else to tell you otherwise? I am sure they improve the high AOA performance of the wing. I don't think the wing performs badly and so have never felt a need to improve it. If you think it cost you no speed, I'll take your word for it, congratulations on getting the proverbial "free lunch".

Tell you what, you should lend me your plane for a month and I'll give you a second opinion.

[DonMuncy]

  On 1/28/2016 at 4:11 AM, Shadrach said:

You're muddying the waters with speed. Stall happens at critical AOA. It's the same no matter your weight...under gross, over gross and everything in between or your speed...20KIAS TO 220KIAS.   It always happens that the same AOA for a specific configuration. That is all. This is why the vane on our stall horn need not be adjusted for weight or speed or any of the other things that are related to stall but don't really serve much purpose for this part of the discussion.

If you watch a tufted laminar flow wing (or any wing for the that matter) you can watch the area of turbulence move forward. 

Note this picture of a tufted wing with VGs on the outer part of the wing. On the inner part of the wing, you can clearly see that the separation is moving towards the leading edge as the wing is flying at a higher AOA. On the outer part of the wing with VGs the boundary layer is still attached.

If you like your airplane better with VGs, who am I or anyone else to tell you otherwise? I am sure they improve the high AOA performance of the wing. I don't think the wing performs badly and so have never felt a need to improve it. If you think it cost you no speed, I'll take your word for it, congratulations on getting the proverbial "free lunch".

Tell you what, you should lend me your plane for a month and I'll give you a second opinion.

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Stall happens at a given angle of attack for each specific plane. Does that critical AOA change when you attach VGs. Although I don't know, it would seem likely to me that it would.

[carusoam]

Cruising around at Rocket FL altitudes...

A Math Professor can make up for any lost airspeed due to friction caused by the VGs or TKS system.

- lowered stall speed. When you want it.

- lowered potential icing. When you need it.

- Next step: airbag seat belts for the Mid and short body Mooneys. This is a topic that has greater possibilities than the chute/Mooney retrofit project.

Well done, Erik!

-a-

[Shadrach]

  On 1/28/2016 at 4:53 AM, DonMuncy said:

Stall happens at a given angle of attack for each specific plane. Does that critical AOA change when you attach VGs. Although I don't know, it would seem likely to me that it would.

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VGs do allow the wing to continue to fly at a higher AOA. So yes critical AOA is raised.