Blue on Top

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  1. 1. Others will know more, but Cessna does not completely enclose their gear … even on the M=0.93 Citation X 2. Drag delta is actually VERY small. In fact it might actually be less drag because it gives the horizontal a little camber which the stabilizer should have. 4. The towel bar may actually be lower drag IF the blade is not at the correct angle of incidence for that flight condition. Although the towel bar has drag all the time, if the blade separates on either surface, the drag will be higher than the towel bar. This would be a great, simple, easy tuft test for a dedicated Mooniac to do (and video) and post here. 5. Gaps, steps (forward and aft), indentations, protrusions, etc. are all drag. If it costs nothing but time, it's worth it. 6. BINGO! Unless one does very dedicated, meticulous testing. You won't know which change did what. Looking at the airplane performance over time is a great way to see improvements.
  2. 1-2. Yes. Each tuft (piece of yarn and tape) is a miniature VG which adds energy to the boundary layer (but is taken out of the engine/propeller in the form of added drag). The airflow will stay attached to a slightly higher AOA. There is a Citation (during development flight testing) that stalled poorly during one of the tests, so we tufted it. It stalled great. So we removed all the tufts … it stalled poorly. This is an unlikely case, but it can happen. 3. Yes. This picture is actually a screen shot from video that we took. His "J" stall pattern is very, very, VERY dominated by the stall strip. In fact there is a condition where the airflow separates (leaves the airfoil surface) and reattaches about a foot aft of the leading edge … very rare. Of course it separates again as AOA is increased. 4. Not unusual, but it would be cool to see. Light rain/mist on your car will show interesting patterns, too. The flow on your rear window might actually be going forward. -Ron Blum
  3. -a-: I'm going to regret saying this, but … wait … I'm gaining a brain … so I won't say it Thanks for your input. I whole-heartedly agree with you on mis-interpretations, mis-direction, mis-informaton. That is exactly what I am going after … to fix. The mountain is BIG! PS. I'm going back through old threads. Holy crap! Some people are nasty. Thanks again.
  4. Thanks! What is AOAi? is this simply indicated angle of attack? There are so many made up terms on this particular topic because people/companies make up terms when they are challenged by knowledgeable people. As a great example, "Critical AOA" is a common but made up term. It means nothing to an Aerodynamicist. They would call that the stall angle of attack.
  5. If MS users have aerodynamics questions, I can try to answer them. I know (and hope) others will chime in, too. I plan on giving an Oshkosh Forum this year on this topic. Now that I think about it, would anyone attend if I try one at Sun-N-Fun, too? I'll start with a very controversial topic: the Mooney laminar flow wing. Laminar flow is a very elusive condition. Any bug, dimple, step, etc. will trip the flow from laminar to turbulent. The picture above (of Scott Sellmeyer's beautiful "J") shows beautiful, turbulent flow. People misinterpret separated flow as turbulent flow. We are really talking about the small boundary layer right at the surface. With laminar or turbulent flow, flow velocity on the surface is 0. Hard to believe but true. This is why dust stays on your airplane … even after you fly. Let's have some fun!
  6. I'd like to know people's experiences with angle of attack instruments. Do they work? Do they not work? Are they easy to use? Are they helpful? Etc... I will be completely transparent. I know Part 23/25 and military certificated AOA systems inside and out and how they operate. I have designed a 6-hole probe (really 11 holes) to measure: airspeed, alpha (AOA), beta (angle of sideslip), altitude and vertical speed to autonomously control an unstable UAV … 30 years ago. I am currently designing a system for certificated airplanes. Thank you! Your comments will be priceless.
  7. Mark has rightfully asked me to make a new thread or two because I have moved these conversations off the original topics. I did a searches for AOA and angle of attach that yielded no results …. which surprised me. I plan to add two new threads. One thread will be labelled "AOA - Pros, Cons and Experiences. The other thread will be "Mooney Aerodynamics". Don't expect miracles as I am currently drinking from a fire hose on MooneySpace. Live as if you will die tomorrow. Learn as if you will live forever. -Mahatma Gandhi Ron Blum
  8. Dorsal fins are a unique animal. Helpful for smaller sideslip angles, hurtful for larger sideslip angles (vortex shed by dorsal comes off the vertical and sucks the rudder over, decreasing control force) and helpful for spins (area is area). I would take an (educated) guess that the dorsal was added for spins. Sharpness on the upper edge is important.
  9. Could be. Prop clearance has to be 7" with a deflated nose gear tire and/or the strut deflated (the strut is not a factor with donuts). Same gear.
  10. Hello MooneySpace members. My name is Ron Blum, and I am a chronic aviation geek and engineer that can't stop learning. I have created and managed Flight Test and Aerodynamics groups at many of the GA OEMs across the country. My last position was chief engineer on the Mooney M10 in Chino, CA. I have since started a company called Blue on Top LLC (referring to an aircraft attitude indicator). The goal of Blue on Top is to educate, consult and produce STCs and products that make aviation safer and less expensive. I dislike anonymity on the internet and freely give out my contact information:,, 316-295-7812. I am here to help you. PS. -a- I don't know that I know you, but I can seriously make your Ovation a little lighter and faster. I believe that you mentioned in another thread that you have a balance weight in the tail. That scares me. Center of Gravity is important, but so is inertia about the vertical axis of the airplane. As an example, if you put two 20 lbs. bags on the CG the GW will go up 40 lbs. If you put those same two bags one 5' forward of the CG and the other 5' aft of the CG, the gross weight and CG will be the same, but the spin characteristics will be significantly different. Again, here to help.
  11. First of all, dang you're good! In this case, spanwise flow direction does matter. Just because the flow changes direction (especially with rudder deflection), it doesn't change surface static pressure (the real force). BUT The vertical stabilizer is a very low aspect ratio wing. If the flow is going up the vertical (swept back vertical), the tip losses are huge. But if we force the flow down the vertical (Mooney tail), we have in essence end-plated the vertical stabilizer, making it much more efficient and effective.
  12. When aircraft materials get down to minimum thickness (especially control surfaces) aluminum gets far lighter than composites … yes, even carbon fiber, for a couple reasons. One, to get both the strength and the damage tolerance required, a composite layup minimum is 2 core 2 (2 fabric layers, a core layer and 2 fabric layers) which is heavier than 0.020 aluminum. Second, because carbon is (somewhat) conductive a metallic mesh (normally copper … aluminum and carbon don't get along well) must be on the entire outside of each part for HIRF and lightning protecting. Otherwise a lightning strike would burn a rather large hole in whatever it hits … including structure. As for the labor savings, that is arguable (don't ask Mooney about it). Yes, one doesn't need to buck rivets, but on the other hand, one doesn't need to layup, pressure cook and glue parts together either. A lot of this is dependent on whether one is building 1 part; 10 parts; 100 parts; 1,000 parts; 10,000 parts; 100,000 parts; or 1,000,000 parts per year. Another huge variable with that is the amount of tooling required and how the parts are assembled and are those tools different. You're right on with the aerodynamics. Not laminar flow, but smoother flow.
  13. (generically) Mooney uses the 63-215 airfoil (above). The mean camber line (average distance between upper and lower surfaces) is in green and the chord line is black. One can see that those 2 curves don't differ a lot ...especially at the leading edge. If the leading edge camber was very high, the tuft picture/video would show all the tufts aft of the leading edge back to the trailing edge swirling (separated flow) as the stalled section of the wing progressed outboard.
  14. This is turbulent flow. Each of the tufts is a little VG. None of the flow behind the second row is laminar (and little behind/between the first row of tufts). Really
  15. Mark: Definitely NOT the laminar flow wing. The wing has some, but little laminar flow like most airfoils (yes, MooneySpace people, when you flame me, please do it to me personally at or or PM me on Facebook or call me at (316) 295-7812). Or better yet, attend one of my Oshkosh presentations. Now that leads me to a great question. If I did an Oshkosh Forum on Mooney aerodynamics, would any one here be interested? I appreciate hecklers (challenges), too! Off my soapbox and back to stall characteristics. Bad stall characteristics are typically due to leading edge separation (with newer airfoils), early separation in front of the aileron span or mislocated stall strips. The Mooney airfoil has little leading edge camber, so leading edge separation is out. I have not seen separation ahead of the aileron span in the work I have done. And, in your case, either both the stall strips are fine or they are both located too low. The fact that your airplane falls off both left and right is a good sign. Scott did a great job flying stalls when we were tufted so I don't know how much tolerance their is for correcting roll variations with aileron. The forward swept vertical fin and rudder are very affective around stall. Try using rudder to level the wings during the approach to stall. If you really think that something bad is lurking in the aerodynamics. Let me know, and I'll write up a simple plan to make you feel more at ease. PS. The best stalling airplane I have flown is the Citation X (we tailored the characteristics well); the worst is the T-38 … but that one gives you tons of violent warning first.