Mooney Aerodynamics

[PT20J]

4 hours ago, 0TreeLemur said:

Skip,

This paper by Selig, Maughmer, and Somers (1995) is really interesting.  It compares the root aerofoil on our Mooneys, the NACA 63₂215 against a more modern design NLF(1)-0015, showing about 25% less drag in cruise at Re~~9.0E+06.  This more modern airfoil does indeed have an extensive region of laminar flow for a narrow range of alpha around cruise that they refer to as  "laminar bucket" in the polar diagram.  Wow- it also apparently is landable without flaps.   I think it is a very interesting read.

Fred

SeligMaughmerSomers-1995-JofAC-NLF-Airfoil-Design.pdf 406.88 kB · 7 downloads

That was really interesting. It shed a lot of light on how one goes about defining a set optimum parameters then designing to them. And that was nearly 30 years ago, so I’m sure there have been advances in design tools since then. Thanks for sharing it.

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[0TreeLemur]

46 minutes ago, PT20J said:

That was really interesting. It shed a lot of light on how one goes about defining a set optimum parameters then designing to them. And that was nearly 30 years ago, so I’m sure there have been advances in design tools since then. Thanks for sharing it.

Skip

 

It would be interesting to test that airfoil.  Like you say- probably something better possible now.   The optimization problem of cruise performance vs. safety/low speed characteristics is one of the features I liked about that paper.

Best,

Fred

[Blue on Top]

Interestingly, the GA(W)-1 airfoil is considered by many to be a very poor GA airfoil (I think mainly due to its high pitching moment.  On the other hand, the GA(W)-2 has been much more successful and is on many (certificated and experimental) aircraft.  In addition, the GA(W)-2 that is on the NASA X-57 … but modified slightly for blown, high lift flap system.

As for true, laminar flow … well … I have been a part of a lot of flight testing.  It's all relative.  The Citation CJ-series has a very specifically-designed, laminar airfoil.  We didn't see a lot of difference, and the FAA made us contaminate the leading edges for FAA-approved certification.

[cliffy]

May I interject something (talking about contamination and control ability)-   Anyone know why the 737 is certified for FIKI WITHOUT  tail surface deicing capability ? The wing is hot but the tail has no protection.

BTW, very interesting paper above. Thanks    It would be very interesting to put that airfoil on a Mooney and see what happens.

[Blue on Top]

1 hour ago, cliffy said:

May I interject something (talking about contamination and control ability)-   Anyone know why the 737 is certified for FIKI WITHOUT  tail surface deicing capability ? The wing is hot but the tail has no protection.

It doesn't need it (on the tail).  Because the tail is designed to never stall (and there is margin).  The leading edge radius is large enough to handle the FAA-required ice accretion and still preform all the required maneuvers.  It's the little guys that have the problem.  Opposite of what one would think, smaller LE radii accrete ice at a much quicker rate.  Hint, hint, hint.  If you see ice on your (Mooney) wings, there is significantly more on the tail.

Bonus Note:  Some airplanes have vertical stabilizer de/anti-ice and others don't.

Bonus Note 2: Some airfoils are better with ice on them   ... drag is always higher and weight is always higher.  Some airfoils are very poor with a little ice but good with a lot.  Go figure.

[cliffy]

OK Bonus Question-   How did they prove it didn't need anti-ice devices? :-)

 

[0TreeLemur]

6 hours ago, Blue on Top said:

Bonus Note 2: Some airfoils are better with ice on them   ... drag is always higher and weight is always higher.  Some airfoils are very poor with a little ice but good with a lot.  Go figure.

Is the 63₂215 one of those airfoils that is better with a lot of ice?  Not planning on testing the theory, of course, in an aircraft with 960lb UL.   Just curious.

[Austintatious]

6 hours ago, cliffy said:

OK Bonus Question-   How did they prove it didn't need anti-ice devices? :-)

 

I believe that they put forms on the tail (basically plastic shaped like ice accumulation) and test the tail in a wind tunnel.  I Have seen video of a similar test at least.

[Blue on Top]

6 hours ago, cliffy said:

OK Bonus Question-   How did they prove it didn't need anti-ice devices? :-)

 

1. Define shapes for worst possible icing encounter.  Normally accomplished through LEWICE, a CFD icing program.

2. Validate shapes through tanker and/or natural encounters (icing tunnels can help, too).

3. Fly airplane with shapes (real or artificial) to meet all stability and control requirements that have already been shown compliant when the airplane was clean.

Easier said than done.  Often FIKI is added later on business jets.

Sandpaper (40 grit) is used for inadvertent encounters.  It simulates a 5-minutes encounter well.

[cliffy]

The story I hear from several sources is that they bolted 4X6 lumber on all three LEs and flew it. Supposedly it had no affect on the flight qualities (I'll bet they did one LE first).  This was way before big computers and computer defined programs :-)

Worst ice I ever got was in a 737 at KMDW from the OM to touch down. Went from 3,000 lbs per side FF to 4500 lbs per side FF due to the increased drag. 50% increase in FF.  Filled the flap slots so I couldn't raise them after landing for fear of damaging them. 3 inches on the nose gear at the gate. It was a popsicle.   No ice prior to the OM! No clouds prior to the OM. All undercast. 

Icing just isn't up in cruise. Ya gotta think going down also. FR and FF can be real killers. Either one usually grounds 121s

Edited December 17, 2019 by cliffy

[Blue on Top]

9 hours ago, 0TreeLemur said:

Is the 63₂215 one of those airfoils that is better with a lot of ice?  Not planning on testing the theory, of course, in an aircraft with 960lb UL.   Just curious.

@0TreeLemur I can honestly say that I don't know about the Mooney airfoil.  The biggest strange characteristic that I noted during the stall testing on Scott's "J" is that in certain conditions, flow will separate aft of the stall strip AND THEN reattach a foot later.  Very strange, but possible with a stall strip that comes in early and very  high suction pressures on the forward section of the airfoil.  Note: One of the Lear wings has a bunch to hof BLEs in the leading edge (hint).

Just for laughs, I'll let you know that: BLEs (Boundary Layer Energizers), LM GeneratorssTs (Little Metal Things), LRTs (Little Rubber Things) and VGs (Vortex Generators) are all the same thing.  They all rotate the air to add energy (yes, they all produce drag) to try to keep the flow attached (not separated) to the surface (wing, tail, etc.).

[ArtVandelay]

[mention=16506]0TreeLemur[/mention] I can honestly say that I don't know about the Mooney airfoil.  The biggest strange characteristic that I noted during the stall testing on Scott's "J" is that in certain conditions, flow will separate aft of the stall strip AND THEN reattach a foot later.  Very strange, but possible with a stall strip that comes in early and very  high suction pressures on the forward section of the airfoil.  Note: One of the Lear wings has a bunch to hof BLEs in the leading edge (hint).

Just for laughs, I'll let you know that: BLEs (Boundary Layer Energizers), LM GeneratorssTs (Little Metal Things), LRTs (Little Rubber Things) and VGs (Vortex Generators) are all the same thing.  They all rotate the air to add energy (yes, they all produce drag) to try to keep the flow attached (not separated) to the surface (wing, tail, etc.).

I thought they were used on jets to enhance control/sensitivity of flight controls?

The air would separate and leave a dead space around the control surfaces.

 

Tom

[Blue on Top]

26 minutes ago, ArtVandelay said:

I thought they were used on jets to enhance control/sensitivity of flight controls?

The air would separate and leave a dead space around the control surfaces.

Tom

Each airplane is different.  None of the Citations have them there for normal operations.  The design should have been vetted better in CFD.  There are a lot of aero "fixes".  Each has it's place where it is most efficient and effective.  Some of this is not science; it's still an art … some say black magic  

[Ibra]

18 hours ago, cliffy said:

Anyone know why the 737 is certified for FIKI WITHOUT  tail surface deicing capability ? The wing is hot but the tail has no protection.

My guess, something do with the relative geometry of their oversized tail vs the wing, the tail is mainly designed to produce enough down force to balance the wings at high speeds where icing does not matter, for icing at slow speeds the tail surface can be oversized twice for the same weight penalty as installing an ice protection, also it will not pick too much ice weight or create that much drag to bring the aircraft down, then manufacturers will only have to show controllability for certification?

This should be the case for all aircrafts with over-sized tails like B737 but probably not the case for MD80, F100 likes 

DC8 seems to be an outlier though 

Edited December 17, 2019 by Ibra

[cliffy]

And what did ol' man Lear call those things sticking up on the wing ahead of the ailerons?  :-)

[Blue on Top]

@cliffy  I'm guessing you want me to say VGs, which I have no problem doing ... and for improved roll control.  I'll also repeat that every airfoil is different.  I've never worked at Lear or Bombardier (though they are on the other side of the airport and we've traded pilots and FTEs).  I do know that every time a leading edge is removed (and either reinstalled or replaced) a stall series need to be completed by a factory test pilot.  That tells me that although the VGs might be doing something, the LE is a much, much bigger driver of the stall characteristics.  This is just aerodynamics.  Learjets are good airplanes, too.  I agree with you Cliffy.

I know several wings on certificated airplanes that separate at the LE first.  That doesn't mean stall characteristics are bad.  In fact, as I say in my presentations, 2D airfoil characteristics have little or nothing to do with whole aircraft stall characteristics. 

To bring this back to Mooney, small, GA business jets fight for every 1/2 knot of stall speed (it determines takeoff/landing performance).  Sales are won and lost over 100-200 feet of runway performance.  This is not true for small, propeller-driven, GA airplanes.  But, the Mooney wing is currently limiting other aspects of the aircraft because of its CLmax.  A real winglet would help the M20 … in many ways.  There's a big hint, Kerrville. 

[cliffy]

Lear would call them (way back in the 60s) F&^% UP Fixers   He didn't like them at all. Evidently the wing flow detaches before the aileron so to counteract that tendency they added the fence to keep it attached Better aileron control. 

I've done the stall series test in 20 series Lears after wing demate (a 12 yr cycle IIRC) We went clear through the stall break in both straight and turning conditions. Takes full aileron throw to keep it upright

We all remember that the Mooney stall strips are fixed in place only after the first flight tests at the factory, on every airplane. 

WINGLETS- Interesting this is brought up.  Several years ago I saw a short article (can't find it now) that was talking about (and has pictures) of a wing tip add on that looked like a large can on the tip pointed long ways to the slipstream that supposedly cancelled tip vortex without too much extra drag.  Wish I could find the article, it was interesting 

Not being an educated aero engineer, I do wonder what just a flat end plate  on the Mooney wing tip would do for drag reduction.Clean simple, cheap. Could it do 75% of a more complex expensive winglet system?

I, too, wonder what something done on the wing tip might accomplish for performance (considering everyone is looking for 1 or 2 mph more) and it could be retro fitted to all the flat end rib Mooneys. 

[MB65E]

6 hours ago, Ibra said:

My guess, something do with the relative geometry of their oversized tail vs the wing, the tail is mainly designed to produce enough down force to balance the wings at high speeds where icing does not matter, for icing at slow speeds the tail surface can be oversized twice for the same weight penalty as installing an ice protection, also it will not pick too much ice weight or create that much drag to bring the aircraft down, then manufacturers will only have to show controllability for certification?

This should be the case for all aircrafts with over-sized tails like B737 but probably not the case for MD80, F100 likes 

DC8 seems to be an outlier though 

Falcon series aircraft do not have any tail de-ice either.  I haven’t been told a detailed answer yet either. It’s a thin airfoil, ice build up may not be that great. I’ll try and find what airfoil it is. 
-Matt

[Blue on Top]

39 minutes ago, cliffy said:

1) We all remember that the Mooney stall strips are fixed in place only after the first flight tests at the factory, on every airplane. 

2) WINGLETS- Interesting this is brought up.  Several years ago I saw a short article (can't find it now) that was talking about (and has pictures) of a wing tip add on that looked like a large can on the tip pointed long ways to the slipstream that supposedly cancelled tip vortex without too much extra drag.  Wish I could find the article, it was interesting 

3) Not being an educated aero engineer, I do wonder what just a flat end plate  on the Mooney wing tip would do for drag reduction.Clean simple, cheap. Could it do 75% of a more complex expensive winglet system?

4) I, too, wonder what something done on the wing tip might accomplish for performance (considering everyone is looking for 1 or 2 mph more) and it could be retro fitted to all the flat end rib Mooneys. 

1) I think this is a rumor that was brought up again at MooneyMax.  I am (educated) guessing the stall strip locations are documented on a drawing with a small tolerance on location.

2) The article sounds cool, and I think I remember it now that you mention it, but it would definitely be fun to read it and learn more again.  If the idea were good, it would be on every airplane made today, though.

3) A winglet doesn't have to be expensive or complex.  I want to say more, but I'm guessing that Mooney won't give me access to a couple of their reports I'd need. .

4) I know the gains would be a lot more … (and this is heresy) … not everything is about top end speed  

Thinking out loud way too much.  -Ron

[carusoam]

If our wing got a 25% less drag design....

what would that equate to in terms of...

• KIAS more speed?
• NMPG more efficiency?

Or is it too soon to know or estimate?

Best regards,

-a-

[AH-1 Cobra Pilot]

7 hours ago, carusoam said:

If our wing got a 25% less drag design....

what would that equate to in terms of...

• KIAS more speed?
• NMPG more efficiency?

In steady state, T = D = 1/2 ρ V² S C_D.  Thus, if D is 25% less, (V₁)² / (V₂)² = 3/4, and V₂ = 1.155V₁. 

KIAS more speed?  +15.5%.

Edited December 18, 2019 by Ah-1 Cobra Pilot

[ArtVandelay]

In steady state, T = D = 1/2 ρ V² S C_D.  Thus, if D is 25% less, (V₁)² / (V₂)² = 3/4, and V₂ = 1.155V₁. 
KIAS more speed?  +15.5%.

You’re assuming the wing is the only drag, cooling and fuselage drag probably at least as much, so split the difference...7.25%?


Tom

[PT20J]

11 hours ago, cliffy said:

WINGLETS- Interesting this is brought up.  Several years ago I saw a short article (can't find it now) that was talking about (and has pictures) of a wing tip add on that looked like a large can on the tip pointed long ways to the slipstream that supposedly cancelled tip vortex without too much extra drag.  Wish I could find the article, it was interesting 

I think this is one of several devices that have been proposed to reduce induced drag by reducing wingtip vortices. Retired Boeing engineer Doug McLean discusses why these generally don’t work in his excellent book, Understanding Aerodynamics.

The gist of his argument is that these ideas are based on the fallacious assumption that wingtip vortices are the source of induced drag and that induced drag could be reduced by simply installing a localized device to reduce the vortices. But, in reality induced drag is a function of the entire 3D airflow about a finite span wing of which the vortices are one component. It is not possible to eliminate the vortices without affecting the entire lift distribution. 

Skip

[Shadrach]

20 minutes ago, PT20J said:

I think this is one of several devices that have been proposed to reduce induced drag by reducing wingtip vortices. Retired Boeing engineer Doug McLean discusses why these generally don’t work in his excellent book, Understanding Aerodynamics.

The gist of his argument is that these ideas are based on the fallacious assumption that wingtip vortices are the source of induced drag and that induced drag could be reduced by simply installing a localized device to reduce the vortices. But, in reality induced drag is a function of the entire 3D airflow about a finite span wing of which the vortices are one component. It is not possible to eliminate the vortices without affecting the entire lift distribution. 

Skip

So would it not be simplest to just say that wingtip vortices are symptom of induced drag rather than a cause?

[Cargil48]

About the effect of wingtips

https://aviation.stackexchange.com/questions/2111/what-do-winglets-do-to-increase-aircraft-performance/2113#2113