Laminar Flow Wing - How does it work?

[Cpt_Kirk]

I've been wanting to fly a Mooney for quite some time now and have been doing quite a bit of research on just about every aspect of it but one question remains: how exactly does it's laminar flow wing produce lift?

I've got a ton of time in Piper/Cessna/Beech products and you can hold the nose wheel up and let the aircraft fly off the ground.

With a Laminar flow wing, that same act can be fatal (see Farrell's Ice Cream incident back in 1972).

Does it fly purely off of aerodynamic deflection? I've noticed that the take offs on YouTube seem to be fairly flat or with quick rotation with no aft wheel movement until Vr.

I know about a laminar flow wing's positive qualities and how it's the holy grail of aviation, but no idea how it gets an airplane into the air.

There's no differential pressure...

Help!

 

[Capt. Geoffrey Thorpe]

The difference is that the maximum thickness is further aft to avoid the increase in pressure that you get as the flow slows down and the overall shape is designed to minimize the "adverse pressure gradient" - the inevitable increase in pressure as you get to the trailing edge.

This does not result in a loss of differential pressure, does not eliminate the downwash, and does not eliminate circulation. The airfoil works just like any other.

I know nothing about the ice cream incident or what might have caused it.

What makes you think there is "no differential pressure"?

 

[Dan Thomas]

What makes you think there is "no differential pressure"?

Maybe confusing laminar with symmetrical?

Dan

 

[hindsight2020]

Mr. Thorpe summed it up quite nicely. The biggest detraction is that the laminar airfoil detaches the flow easier and quicker, thus its gradient between flying one moment and ungracefully wingrocking to earth on another is quite steep compared to a dirty wing. That is why many of the more advanced laminar airfoils out there include vortex generators to keep the churning of the air at a level that preserves some semblance of attachment during high AOA.

As far as 'aerodynamic deflection' you seem to be confusing concepts; what you seem to be pointing at is symmetrical airfoil versus non-symmetrical airfoil. That doesn't have as much to do with it. You can have laminar and turbulent airfoils in both flavors. There's nothing endemically laminar about a symmetrical airfoil or vice versa.

 

[Cpt_Kirk]

The difference is that the maximum thickness is further aft to avoid the increase in pressure that you get as the flow slows down and the overall shape is designed to minimize the "adverse pressure gradient" - the inevitable increase in pressure as you get to the trailing edge.

This does not result in a loss of differential pressure, does not eliminate the downwash, and does not eliminate circulation. The airfoil works just like any other.

I know nothing about the ice cream incident or what might have caused it.

What makes you think there is "no differential pressure"?

Maybe it's just not as easy to see as some others..

The accident was an F-86 that prematurely rotated and kept an extremely high AoA trying to fly it off the ground. It never got up and crashed into an ice cream parlor killing a bunch of kids.

Maybe confusing laminar with symmetrical?

Dan

I believe I am.

Mr. Thorpe summed it up quite nicely. The biggest detraction is that the laminar airfoil detaches the flow easier and quicker, thus its gradient between flying one moment and ungracefully wingrocking to earth on another is quite steep compared to a dirty wing. That is why many of the more advanced laminar airfoils out there include vortex generators to keep the churning of the air at a level that preserves some semblance of attachment during high AOA.

As far as 'aerodynamic deflection' you seem to be confusing concepts; what you seem to be pointing at is symmetrical airfoil versus non-symmetrical airfoil. That doesn't have as much to do with it. You can have laminar and turbulent airfoils in both flavors. There's nothing endemically laminar about a symmetrical airfoil or vice versa.

I think I'm getting it.. I might just need some flight time in order to answer the questions I have. I guess I just don't "see" the physics behind it as I do with other airfoils.

Thanks everyone for the responses so far.

 

[Capt. Geoffrey Thorpe]

I think I'm getting it.. I might just need some flight time in order to answer the questions I have. I guess I just don't "see" the physics behind it as I do with other airfoils.

Thanks everyone for the responses so far.

Part of the problem is that so many "explanations" involve thing with flat bottoms and curved tops that it is easy to believe that somehow this configuration has something to do with lift.

Take a look at a Cherokee next time you are at the airport. The bottom has almost as much curve as the top. Did the designers eff up? Is a Cherokee 6 essentially a 2 place airplane because of the curve on the bottom creating a "low pressure" and reducing lift? Or, is the "theory" of flats and curves total ****?

No, No, and Yes.

Camber (curvature of the line that runs through the center of the airfoil) helps increase lift at any particular angle of attack and can let you get to a higher angle of attack, but symmetrical airfoils (no camber) work just the same as any other.

 

[Pilawt]

Despite the fact that a "laminar" airfoil looks nearly symmetrical in cross-section, it produces lift when there is a positive angle of attack. A sheet of plywood produces lift at a positive angle of attack, too.

Laminar airfoils do have advantages in lower drag, but mostly at higher airspeeds. The P-51 was one of the early applications of this type of airfoil. In the speed range of typical piston light airplanes, though, the advantage is minimal. http://www.allstar.fiu.edu/aero/wing31.htm Moreover, slight airfoil contour imperfections caused by the thin metal skins and wide rib spacing of smaller light airplanes often defeats any aerodynamic benefit the laminar airfoil might offer.

The main reason that the Mooney and other (mostly low-wing) light airplanes have laminar airfoils is for interior packaging. A "laminar" wing has its maximum thickness -- and therefore its main spar -- further aft. That allows the designer to stow the main spar carry-through out of the way under the rear seat. By contrast, a Beech Bonanza does not have a laminar wing, and its spar carry-through goes under the front seats, interfering with rear-seat passengers' legroom.

The only high-wing Cessnas that have laminar airfoils are the C-177 Cardinal and (1967 and later) C-210 Centurion. Why? They are also the only cantilever high-wing Cessnas. A spar carry-through must pass through the cabin ceiling, and only laminar wings would allow the carry-through to go behind the heads of the front-seat occupants, instead of severely limiting front-seat headroom.

One characteristic of "laminar" airfoils is that drag increases much more rapidly at higher angles of attack. This is noticeable if the pilot attempts to rotate too early on takeoff; drag rises sharply and, if the airplane is at all underpowered, the takeoff becomes unduly sluggish, or in extreme cases, impossible. The sharp leading edge can also lead to more abrupt stalls.

As a result, the airfoils of several laminar-flow light airplanes were modified with more rounded leading edges, resulting in less drag at higher angles of attack, gentler stall characteristics, and little, if any, loss of cruising speed. Examples include the Cessna 177B Cardinal and 177RG Cardinal RG; Grumman-American AA-1A (and all Grumman two- and four-seaters thereafter); and the outer panels of the taper-winged Piper PA-28 and PA-32 series.

I know nothing about the ice cream incident or what might have caused it.

The reference is to the Canadair F-86 that went into the Farrells Ice Cream Parlor off the end of the departure runway at Sacramento Executive in 1972:

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=66685&key=0
http://en.wikipedia.org/wiki/1972_Sacramento_Canadair_Sabre_accident

 

[LDJones]

After 12 years of owning a M20C and flying almost ever model in the line-up (E,F,J,K,M,R&S), I'm happy to report that I doubt you'll find them dramatically different to fly than what you've flown so far.

 

[tonycondon]

Laminar airfoils do have advantages in lower drag, but mostly at higher airspeeds.

Uh, why has basically every competition sailplane since about 1955 sported a laminar flow airfoil then?

 

[Pilawt]

Uh, why has basically every competition sailplane since about 1955 sported a laminar flow airfoil then?

Everyone knows, Tony, sailplanes are better-designed and better-built.

Seriously, given the inherent aerodynamic imperfections of a powered lightplane's wing (e.g., rivets, oilcanning skins, various appurtenances, low aspect ratio, etc.) a sub-200-knot lightplane wouldn't be significantly faster with 6-series airfoil than with a NACA 24000, all else being equal. In wind tunnel and flight tests during development of the Bonanza, Beech found the difference between the airfoils "scarcely measurable" in this speed range. They stayed with the 24000 series wing, as did Cessna for the hotrod 310.

 

[mondtster]

After 12 years of owning a M20C and flying almost ever model in the line-up (E,F,J,K,M,R&S), I'm happy to report that I doubt you'll find them dramatically different to fly than what you've flown so far.

Agreed, I don't think Mooneys really fly any different than anything else. They fly like an airplane.

 

[Cpt_Kirk]

Part of the problem is that so many "explanations" involve thing with flat bottoms and curved tops that it is easy to believe that somehow this configuration has something to do with lift.

Take a look at a Cherokee next time you are at the airport. The bottom has almost as much curve as the top. Did the designers eff up? Is a Cherokee 6 essentially a 2 place airplane because of the curve on the bottom creating a "low pressure" and reducing lift? Or, is the "theory" of flats and curves total ****?

No, No, and Yes.

Camber (curvature of the line that runs through the center of the airfoil) helps increase lift at any particular angle of attack and can let you get to a higher angle of attack, but symmetrical airfoils (no camber) work just the same as any other.

I think this has helped me out the most.

I found a website that seems to be getting me in the right direction. I'm glad someone can come out and say the "Jack & Jill" explanation is all BS.

http://www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html

I guess this is going to be the hardest part of the CFI course for me - finding the line between the correct information and then what the FAA wants me to teach.

Despite the fact that a "laminar" airfoil looks nearly symmetrical in cross-section, it produces lift when there is a positive angle of attack. A sheet of plywood produces lift at a positive angle of attack, too.

Laminar airfoils do have advantages in lower drag, but mostly at higher airspeeds. The P-51 was one of the early applications of this type of airfoil. In the speed range of typical piston light airplanes, though, the advantage is minimal. http://www.allstar.fiu.edu/aero/wing31.htm Moreover, slight airfoil contour imperfections caused by the thin metal skins and wide rib spacing of smaller light airplanes often defeats any aerodynamic benefit the laminar airfoil might offer.

The main reason that the Mooney and other (mostly low-wing) light airplanes have laminar airfoils is for interior packaging. A "laminar" wing has its maximum thickness -- and therefore its main spar -- further aft. That allows the designer to stow the main spar carry-through out of the way under the rear seat. By contrast, a Beech Bonanza does not have a laminar wing, and its spar carry-through goes under the front seats, interfering with rear-seat passengers' legroom.

The only high-wing Cessnas that have laminar airfoils are the C-177 Cardinal and (1967 and later) C-210 Centurion. Why? They are also the only cantilever high-wing Cessnas. A spar carry-through must pass through the cabin ceiling, and only laminar wings would allow the carry-through to go behind the heads of the front-seat occupants, instead of severely limiting front-seat headroom.

One characteristic of "laminar" airfoils is that drag increases much more rapidly at higher angles of attack. This is noticeable if the pilot attempts to rotate too early on takeoff; drag rises sharply and, if the airplane is at all underpowered, the takeoff becomes unduly sluggish, or in extreme cases, impossible. The sharp leading edge can also lead to more abrupt stalls.

As a result, the airfoils of several laminar-flow light airplanes were modified with more rounded leading edges, resulting in less drag at higher angles of attack, gentler stall characteristics, and little, if any, loss of cruising speed. Examples include the Cessna 177B Cardinal and 177RG Cardinal RG; Grumman-American AA-1A (and all Grumman two- and four-seaters thereafter); and the outer panels of the taper-winged Piper PA-28 and PA-32 series.

The reference is to the Canadair F-86 that went into the Farrells Ice Cream Parlor off the end of the departure runway at Sacramento Executive in 1972:

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=66685&key=0
http://en.wikipedia.org/wiki/1972_Sacramento_Canadair_Sabre_accident

I see. I've flown a Cardinal and didn't notice too much of a difference. I didn't really know to look..

After 12 years of owning a M20C and flying almost ever model in the line-up (E,F,J,K,M,R&S), I'm happy to report that I doubt you'll find them dramatically different to fly than what you've flown so far.

Except for the speed control.

I HAVE to understand how something works in its entirety in order for me to get the most out of the airplane. That's the ultimate goal for me - to be able to exercise an aircraft to all of its limits (but not beyond), to get the most performance out of it.

 

[LDJones]

I think this has helped me out the most.

I found a website that seems to be getting me in the right direction. I'm glad someone can come out and say the "Jack & Jill" explanation is all BS.

http://www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html

I guess this is going to be the hardest part of the CFI course for me - finding the line between the correct information and then what the FAA wants me to teach.

....

Except for the speed control.

I read the NASA links....so if I am to take my cues from NASA, our response to questions on what creates lift should be "It's really complex and has many factors that not even NASA can explain in terms we'd understand. It just does."

Yes, speed control is very important in Mooneys, but I teach it is important in EVERY aircraft one flys if you want to get maximum utility and safety out of it.

 

[Pilawt]

When I instructed (a long time ago, in a galaxy far, far away) I would tell my students whatever was the FAA spiel du jour on aerodynamics, then I would suggest they buy a copy of Stick and Rudder. Yes, S&R grossly oversimplifies aerodynamics, but it is possible for a student to have his head so full of aerodynamic theory that it interferes with learning to communicate with the airplane in flight.

One of the most difficult students I had ("difficult" only in the learning sense; he was a very nice guy) was an aeronautical engineer for McDonnell Douglas across the field. He had been involved in the design of the DC-10 wing, but he had a heckuva time getting any feel for the Cherokee at all. He recognized that he was trying to fly the book instead of the airplane.

 

[Cpt_Kirk]

I read the NASA links....so if I am to take my cues from NASA, our response to questions on what creates lift should be "It's really complex and has many factors that not even NASA can explain in terms we'd understand. It just does."

Yes, speed control is very important in Mooneys, but I teach it is important in EVERY aircraft one flys if you want to get maximum utility and safety out of it.

I got: lift is a force generated by turning a moving fluid. Simply put, as far as I understand, if the fluids direction after coming into direct contact with an airfoil is a change from its original direction, aerodynamic force is exerted of the airfoil. Lift and drag both are the result of the aerodynamic force.

I just wish there was a simple, FAA-approved, and correct way of describing lift.

When I instructed (a long time ago, in a galaxy far, far away) I would tell my students whatever was the FAA spiel du jour on aerodynamics, then I would suggest they buy a copy of Stick and Rudder. Yes, S&R grossly oversimplifies aerodynamics, but it is possible for a student to have his head so full of aerodynamic theory that it interferes with learning to communicate with the airplane in flight.

One of the most difficult students I had ("difficult" only in the learning sense; he was a very nice guy) was an aeronautical engineer for McDonnell Douglas across the field. He had been involved in the design of the DC-10 wing, but he had a heckuva time getting any feel for the Cherokee at all. He recognized that he was trying to fly the book instead of the airplane.

I've heard horror stories of aeronautical engineers trying to fly an aircraft.

I can fly one easily by feel and sound. I feel more in tune with the ship.

My trouble here is a morality issue. I want the student to know the correct information while being able to use and understand it for a checkride while convincing the examiner that he knows what he's talking about.

I've read parts of stick and rudder. It was getting too redundant and I couldn't finish it.

 

[Dan Thomas]

Yes, S&R grossly oversimplifies aerodynamics, but it is possible for a student to have his head so full of aerodynamic theory that it interferes with learning to communicate with the airplane in flight.

A gross oversimplification is still better than many students absorb anymore. Witness the silly accidents due to accelerated stalls; these guys have been taught, or weren't paying attention, to angle of attack theory.

Dan

 

[GeorgeC]

http://www.av8n.com/how/

You're welcome

I think this has helped me out the most.

I found a website that seems to be getting me in the right direction. I'm glad someone can come out and say the "Jack & Jill" explanation is all BS.

http://www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html

 

[Bill Watson]

I only have about 15 or 20 hours in a Mooney 20C. I also have 1000+ in 2 high performance sailplanes with laminar flow airfoils. I am not an engineer. My observations and understanding:

- Laminar airfoils can offer lower drag or higher L/D ratios. The higher performance comes with a price and some tradeoffs.

- Achieving laminar flow for some portion of the airfoil requires precise control/manufacture of the airfoil profile and surface smoothness. Impossible with a fabric wing, difficult with wood, challenging with thinner sheet aluminum, easier with composite surfaces. Round headed rivets, aluminum sheet edges and even rain will act as turbulators and will tend to defeat laminar flow.

- The high point of laminar airfoils tend to be further back than non-laminar because it is easier to maintain laminar flow when airfoil thickness is increasing than when it is decreasing. I think Cessna and others may have taken advantage of this structurally but I'm thinking that they tried laminar for performance, that is, speed.

- The design of 'good' laminar airfoils is computer intensive. Therefore, modern airfoil designs are significantly 'better' than older ones. Better designs tend to be insensitive to dirt, bugs, water droplets and minor manufacturing defects. They handle angle of attack changes smoothly and generally fly without any surprises. In an older sailplane with an early laminar airfoil design, I once experienced a stall during a smooth pull-up when the wing suddenly encountered rain. That was a surprise. Later that same day I ended up taking a tow on a short runway, behind a weak towplane with wet wings and found that my takeoff was significantly delayed. That was also a surprise.

- The Mooney 20C I flew had a very distinct change in performance at around 80 or 85 mph (it was one or the other but can't remember which). One can fly a perfectly satisfactory approach at or above that speed without a problem. But once below that speed (with me and a CFI and half fuel) the approach noticeably steepens. One can fly a perfectly satisfactory approach at or below that speed. Since it'svery predictable and straight forward to compensate for, it's very useful for short field and obstructed field approaches. However, going into the flare above this speed can result in some float. What I noted in particular was how distinct the change in performance was and I'm pretty sure it was the result of a transition from laminar flow to non-laminar.

- During takeoff and climbout in the 20C, I noted the same sort of behavior. It doesn't exactly jump off the ground and kind of wallowed until the gear came up and the plane accelerated a bit. I didn't note the airspeed as carefully as I did on approach but there was the distinct feeling of "getting up on the step" at a certain speed during the initial climbout. Did I say that I REALLY liked the Mooney because of that beautiful high aspect ratio wing and the way it performed with so little HP?

 

[Hank S]

The Owner's Manual for my M20C says to keep it on the ground, then at 65-75 mph to "yank" it in the air then relax some of the back pressure. I use 70 mph normally, or 75 if loaded heavy or in gusty winds. It took a while to get used to, but it's now second nature. Run along the ground [grass or pavement], rotate firmly, relax a little, gear up and climb out.

Laminar flow creates less drag, which can then allow for either more speed or less fuel burn. Turbulent flow is caused simply by angle of attack. I've not noticed a magical speed at which performance increases or decreases. My target rolling wings-level on final is 85 mph, and I slow as I descend aiming for 75 mph on short final, which I decrease by 5 mph for every 300 lbs below gross weight.

Speed control is important because the landing gear are short, putting you well into ground effect. The laminar flow wing does not create a lot of drag to slow you down close to the ground, and giving too much elevator will increase altitude. Two people and half tanks should be at 70 mph over the numbers with the throttle already at idle. If you're faster than that, be prepared to float as she doesn't create mountains of low-speed drag like a Cessna's fat wind. Just hold off and let the speed come down in a thousand feet or so; if you flare at 80, hope you're at a field long enough for an ILS or you'll have a training opportunity for "go around" followed by another, hopefully slower, landing attempt.

 

[Henning]

I've been wanting to fly a Mooney for quite some time now and have been doing quite a bit of research on just about every aspect of it but one question remains: how exactly does it's laminar flow wing produce lift?

I've got a ton of time in Piper/Cessna/Beech products and you can hold the nose wheel up and let the aircraft fly off the ground.

With a Laminar flow wing, that same act can be fatal (see Farrell's Ice Cream incident back in 1972).

Does it fly purely off of aerodynamic deflection? I've noticed that the take offs on YouTube seem to be fairly flat or with quick rotation with no aft wheel movement until Vr.

I know about a laminar flow wing's positive qualities and how it's the holy grail of aviation, but no idea how it gets an airplane into the air.

There's no differential pressure...

Help!

All wings fly purely off deflection. I had a CFI who was the chief aerodynamicist for Douglas, also a rocket scientist on their nuclear rocket design. He made a point to prove this by taking a scientific grade graphing barometer and flying over it then doing the math and showing the exact weight of the plane. He was of the "Bernouli is just an observation of Newton" camp lol.

 

[MAKG1]

All wings fly purely off deflection. I had a CFI who was the chief aerodynamicist for Douglas, also a rocket scientist on their nuclear rocket design. He made a point to prove this by taking a scientific grade graphing barometer and flying over it then doing the math and showing the exact weight of the plane. He was of the "Bernouli is just an observation of Newton" camp lol.

I hope you're kidding.

Deflection cannot explain stalls.

Solving the NS equation gives you a solution where laminar flow over the top of the wing produces lower pressure than static. This is lost when the flow separates. There is also a comparable-magnitude increase in pressure over static on the bottom of the wing that isn't lost. That's why you don't just free fall.

The part of the usual BS that doesn't work is the usual grade school assertion that parcels of air split at the leading edge and meet at the trailing edge. That's made up. None of the legit models do that.

That's a factor of ~2 error you just made, much more than the difference between an aircraft that takes off and one that mows weeds.

Deflection models also do not explain why Fowler flaps work. The slot is critical, and 747s wouldn't exist without them. If it were all deflection, the slot loses some surface area and would be counterproductive.

The demonstration says that deflection exists, not that it's the only mechanism or even that it comes from the bottom of the airfoils.

You can use it as a rough mnemonic, but taking it further than that is wrong.

NS equations also explain cavitation on boat props. Deflection doesn't work their either. It requires local pressure to be below the vaporization point of water.

The NS equations ARE Newton's laws, plus incompressibility (you can solve the more general Euler equations if you want, but you'll get the same answer in subsonic flight). You've just misunderstood what Newton's laws actually say.

 

[Henning]

I don't get into the argument, I let the guys with the PhDs duke that one out.

 

[MAKG1]

I don't get into the argument, I let the guys with the PhDs duke that one out.

Don't quote "facts" without attribution that you aren't willing to back up.

That's why the annoying "fact" about air parcels meeting at the trailing edge won't die.

 

[Cpt_Kirk]

Don't quote "facts" without attribution that you aren't willing to back up.

That's why the annoying "fact" about air parcels meeting at the trailing edge won't die.

Did that post make you feel any better? Seriously.

Did the vague definition of lift in post #15 skim the truth in the least bit? You seem to know quite a bit about the subject.

 

[MAKG1]

Did that post make you feel any better? Seriously.

Did the vague definition of lift in post #15 skim the truth in the least bit? You seem to know quite a bit about the subject.

I owe you an apology for that tone.

Misinformation like that is a pet peeve, but of course that doesn't excuse it.

To answer your question about post #15, sort of. It confuses force with velocity, but I don't have a very good definition to offer either. The best I can come up with is that drag always opposes motion, but lift doesn't. Not very useful...

I do have an example, though. You'll have to judge whether it really is enlightening. I have my doubts.

A rotating cylinder in contact with a moving fluid generates lift.

 

[Cpt_Kirk]

I owe you an apology for that tone.

Misinformation like that is a pet peeve, but of course that doesn't excuse it.

To answer your question about post #15, sort of. It confuses force with velocity, but I don't have a very good definition to offer either. The best I can come up with is that drag always opposes motion, but lift doesn't. Not very useful...

I do have an example, though. You'll have to judge whether it really is enlightening. I have my doubts.

A rotating cylinder in contact with a moving fluid generates lift.

I've blown up one time or two on other threads. It happens. No hard feelings.

It helps, yes. If anything, it keeps my curiosity. Thanks for the input! I'm really just trying to put together a simple, yet correct, definition of lift in layman's terms. If one hasn't surfaced already, I have little hope of making any progress.

 

[Bill]

The Owner's Manual for my M20C says to keep it on the ground, then at 65-75 mph to "yank" it in the air then relax some of the back pressure.

I don't know about your C but the 201 starts to dance around on the gear at somewhere between 60 and 65kts. When this skittish dance starts, that's your signal to get it off the ground as it's ready to fly. It seems the transition between "ground vehicle" and "aircraft" is abrupt on the Mooneys.

 

[kgruber]

I don't know about your C but the 201 starts to dance around on the gear at somewhere between 60 and 65kts. When this skittish dance starts, that's your signal to get it off the ground as it's ready to fly. It seems the transition between "ground vehicle" and "aircraft" is abrupt on the Mooneys.

The 201 I bought years ago was involved in a ground loop on takeoff. It seems to be a rare occurrence because I've never heard of it before or after.

Granted, the pilot was inexperienced and had more money than brains, but you are very correct. There is a "stiffish" zone. Thank you, Mooney. I got one hell of a deal on an almost new 77', because the owner was afraid to fly it again.

 

[Cpt_Kirk]

I don't know about your C but the 201 starts to dance around on the gear at somewhere between 60 and 65kts. When this skittish dance starts, that's your signal to get it off the ground as it's ready to fly. It seems the transition between "ground vehicle" and "aircraft" is abrupt on the Mooneys.

Skittish like the "Comanche dance?"

The 201 I bought years ago was involved in a ground loop on takeoff. It seems to be a rare occurrence because I've never heard of it before or after.

Granted, the pilot was inexperienced and had more money than brains, but you are very correct. There is a "stiffish" zone. Thank you, Mooney. I got one hell of a deal on an almost new 77', because the owner was afraid to fly it again.

From what I've read, if you leave it on the ground long enough or have it set up for some weight/cg location, it will get up on the nosewheel and loss of directional control will follow.

 

[EdFred]

Skittish like the "Comanche dance?"

Since the Comanche wing is a Mooney wing, pretty much.

 

[Bill]

From what I've read, if you leave it on the ground long enough or have it set up for some weight/cg location, it will get up on the nosewheel and loss of directional control will follow.

It will wheelbarrow on the ground at high speed, yes. Once it starts to dance, rotate and fly.

 

[Capt. Geoffrey Thorpe]

FWIW Dept.

Airfoils use on most single engine Cessnas, Laminar airfoil used on Mooney (I think) and a symmetrical airfoil used on the Pitts S2

Profiles on a 0 - 1 scale, and wind tunnel data: the lift vs. angle of attack and drag vs. lift curves from Abbot and VonDoenhoff

 

[kevmor99]

One characteristic of "laminar" airfoils is that drag increases much more rapidly at higher angles of attack. This is noticeable if the pilot attempts to rotate too early on takeoff; drag rises sharply and, if the airplane is at all underpowered, the takeoff becomes unduly sluggish, or in extreme cases, impossible. The sharp leading edge can also lead to more abrupt stalls.

Thanks for the explanation, I flew a 1968 Cardinal last week and this was the first thing I noticed in slow flight, everything was going perfect and then as it got to a high angle of attack close to stall, the drag increased much more than I noticed in other 172's, etc.

 

[Cpt_Kirk]

FWIW Dept.

Airfoils use on most single engine Cessnas, Laminar airfoil used on Mooney (I think) and a symmetrical airfoil used on the Pitts S2

Profiles on a 0 - 1 scale, and wind tunnel data: the lift vs. angle of attack and drag vs. lift curves from Abbot and VonDoenhoff

Every bit helps. Thanks.

 

[gismo]

I hope you're kidding.

Deflection cannot explain stalls.

Solving the NS equation gives you a solution where laminar flow over the top of the wing produces lower pressure than static. This is lost when the flow separates. There is also a comparable-magnitude increase in pressure over static on the bottom of the wing that isn't lost. That's why you don't just free fall.

The part of the usual BS that doesn't work is the usual grade school assertion that parcels of air split at the leading edge and meet at the trailing edge. That's made up. None of the legit models do that.

That's a factor of ~2 error you just made, much more than the difference between an aircraft that takes off and one that mows weeds.

Deflection models also do not explain why Fowler flaps work. The slot is critical, and 747s wouldn't exist without them. If it were all deflection, the slot loses some surface area and would be counterproductive.

The demonstration says that deflection exists, not that it's the only mechanism or even that it comes from the bottom of the airfoils.

You can use it as a rough mnemonic, but taking it further than that is wrong.

NS equations also explain cavitation on boat props. Deflection doesn't work their either. It requires local pressure to be below the vaporization point of water.

The NS equations ARE Newton's laws, plus incompressibility (you can solve the more general Euler equations if you want, but you'll get the same answer in subsonic flight). You've just misunderstood what Newton's laws actually say.

If you consider that much of the "deflection" comes from airflow over the top of the wing I'd agree with Henning's statement, but if he was implying that lift is simply a function of the impact of air on the underside of the wing he's missing a big part of the equation.

 

[Capt. Geoffrey Thorpe]

Kutta condition.