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Blue on Top

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  1. Blue on Top
    The aileron push-pull control tube is a great example to look at the tradeoffs in materials, tolerances, costs, weights, certification, manufacturing, etc. and how each of these is related to each other. I probably won't think of everything but here's a conversation starter. 1) weight - aluminum, composite then steel, but I think that they would all be fairly close. 2) cost - steel, aluminum then composite. 3) manufacturing - steel/aluminum then composite 4) Stiffness - composite, steel then aluminum The problem is they all relate to each other and all have very strong positives and negatives. Here's some random thoughts. Steel produces the smallest diameter. Flexibility (buckling) is both good and bad. For metallic tubes, it allows less binding (and resulting lower control force); for composite (very stiff), alignment has to be perfect or it won't move. To back this, the 3 hinges on the aileron are rarely in perfect alignment, but when installed they move easily because the aluminum aileron flexes slightly to allow for it. A composite aileron does not (an M10 learning experience). Certification would be a large expense for composite as the material and processes would need to be qualified and tested. BUT (and this is where OEMs today are missing it) if one could find an off-the-shelf, commercially-produced tube that would work, end pieces could be designed to mate with the tube and the current attach points. Each tube assembly would need to be strength tested, but that is A LOT less work than certifying an original design. The match has been lit. Go!
  2. Blue on Top
    Ut oh, I'm getting too comfortable with MS already. I'm going to try to move this topic to a new thread (it's not really directly aero related. So, @Cargil48, @carusoam, @PT20J, and those stalking in the shadows (who I appreciate, too). Look for the new topic "Aileron Push-Pull Control Tube"
  3. Blue on Top
    1) How is the stall warning set on a FIKI-equipped Mooney? Is it assumed that there is never any ice on the airplane? 2) I have heard this before. What is the cost for heated and non-heated? Thanks, Ron
  4. Blue on Top
    @donkaye I'd like you to be my first customer with you being an influencer and all.
  5. Blue on Top
    @PT20J <-- I like this ; thanks! (I've re-written this post 20+ times) Now I'll try to answer what you asked - aileron effectiveness (or lack thereof). The Mooney wing uses a flap to aileron ratio of ~70/30. This is fairly typical. More modern designs use higher ratios (to lower stall speeds). As a result they have smaller ailerons, smaller ailerons with roll spoilers or no ailerons with all roll spoilers (MU-2, another Mooney product). You are correct in that hinge moment in = hinge moment out, but both ends of that equation can be tailored. IOW, at the pilot input end, the yoke diameter can be made larger or smaller and travel more or less. At the aileron end, the input arm can be made shorter or longer (which will change the internal system travels) and the hinge line can be moved fore and aft. The Mooney hinge line is very close to the front (higher hinge moments), and the Cirrus hinge line is near 40% (no hinge moments - the control feel is all springs). There are pros and cons to both. In addition the aileron leading edge can change hinge moments dramatically (more elliptically pointy -> higher and more bread loaf -> lower hinge moments). Also note that making internal control system travels less, makes internal control forces/load higher … and we have to account for 2 gorillas on the yokes. Another note is that there is a single, small-diameter, very long pushrod that activates the aileron. This pushrod goes from side of body out to the aileron bellcrank. Personally, I don't think that this would be allowed today … especially control system buckling prevented by clearance holes in the nose ribs. Don't get me wrong, it is simple, light and works well. This is one reason the "Predator" wasn't the best airplane. Bottom Line: 1) Al and Art did a great job with aircraft layout and planform. 2) The M20 has grown significantly since the early 50s, but control forces/effectiveness/harmony can be adjusted … some will take more certification work than others
  6. Blue on Top
    Unless complicated algorithms are used, attitude vs. flight path does not account for the air itself having vertical and gust components. Why would AOAi be aircraft dependent?
  7. Blue on Top
    100% agree with your statement and FAA reference … I deal with it daily. 1) To flip the coin, how many pilots realize that there is no requirement for accuracy on NORSEE items (AOA is a great example)? 2) One of the hardest parts of certification of these types of items is how to alleviate misleading information. How do you ethically address that issue? One of the largest flying clubs in the nation has AOA on their training airplanes. They are teaching students to not use the information because of the poor and erratic information being presented. Instructors can't use them either. The Pegasus (FAA) program at Purdue proved this, too. Part of that issue was training, though. I believe that AOA has gotten a bad rap because it's not (calibrated) AOA that is being presented. BTW, LRI is a made-up word because people finally admitted it wasn't AOA.
  8. Blue on Top
    It will definitely make a difference. Drag on each one will be challenging.
  9. Blue on Top
    And here is the problem with NORSEE (no safety effect) installations of AOA. How's this for irony? A device designed to improve the safety of the #1 fatal accident cause falls under "no safety effect". NONE of these low-end devices are certificated. They are allowed to be put on certificated airplanes in the hope of helping the accident numbers … time will tell. ASTM self-approval only states that the same device must be produced over and over. It does NOT require the data to be accurate … it's NORSEE. NONE of these devices show compliance to a regulation. If they did, they would be required to be accurate. Agree on FIKI. But, on that note, the vast majority of these fatal accidents are in Day, VFR flight.
  10. Blue on Top
    … and this is one of the reasons this thread was started … education. Vanes accurately measure LOCAL AOA, period. They can be "calibrated" to indicate when AOA is at 1.3Vstall (all weights, etc.; not all configurations, in icing, etc … unless those are inputs into an AOA computer). They can be calibrated to: produce aircraft AOA, produce correct values and margins in ALL configurations … if those parameters are input (i.e. flap positions, speed brake position (if they affect stall AOA), icing conditions, etc.) "LRIs" should be broken into at least a couple categories: differential pressure and Cp measurement. Differential pressure is NOT AOA nor is it directly related to AOA … unless Qc (airspeed) or G-load is known. It is simply an "off-angle" airspeed. And, before I get flamed , people (like Mr. Baker) that have installed one and uses it as he does, I applaud him. The device is making him a better pilot! If you want to question me, I respect your opinion. Ironically, placing them on the aft lower side of the wing is an area where AOA doesn't change (the airflow is parallel to the airfoil, which is why Piper puts pitot tubes in that location. Now, for Cp measurement devices (like Garmin). They measure differential pressure ("off angle" airspeed) and divide it by Qc (airspeed pressure or Ptotal minus Pstatic). That value is what aero people call Cp. That value is directly related to AOA. Again, and in addition, an aircraft calibration and all the other inputs need to be there to make it all calibrated AOA. Process timing is also an issue with these devices. IOW, all the pressures need to be taken at the same time, each data bus adds delay, each transfer of data adds delay .. it adds up quickly. Please remain respectful. I want to educate, but I also want to learn. There are no dumb ideas or dumb questions. There is A LOT of bad information out there … FAA included Let's discuss and learn.
  11. Blue on Top
    Personally, Cargil48, I like your comments and insights. It is thought like yours that have the potential to advance our industry.
  12. Blue on Top
    "Speed with Economy" by Kent Pacer is a great real world drag clean-up book! It is for Experimental aircraft, but as got noted above, airflow is well airflow. For those that are thinking of experimenting, I'll give a couple words of caution. Modifications that affect type design data are not legal unless the airplane has been put in an experimental category (R&D, show compliance, market survey, etc.). One is often surprised by a little change that makes a large difference. Oh, and that insurance thing, when they find out, modified airplanes are not covered by insurance. With that said, let's do some really cool stuff! PS. Once air goes into an enclosure (the inlet on an airplane), a price will be paid for any changes before it exits.
  13. Blue on Top
    CYA 1000 is a true AOA. ALL AOA systems measure local AOA. I believe what brndiar is saying is that it is not converted to aircraft AOA. I believe the CYA is calibrated at two points. Certificated AOA (typically business jets and up) is corrected and calibrated for each flap setting, icing, etc. CYA works well … if toward the front of the wing where local AOA actually changes.
  14. Blue on Top
    AOA can be derived from an LRI type unit … Garmin does it in a sneaky way. "Off angle" differential pressure divided by Qc (or pitot - static or airspeed differential pressure) is proportional to AOA. GeeBee is correct in saying it has to be derived … through an ADC (Air Data Computer). Harco (Eclipse jets) do this and so does the Goodrich (United Technologies) Smart Probes, but they are very expensive … even for business jets. The SafeFlight system is measuring force on the flipper. The stall warning works because it is a single point value. When the stagnation point (where airflow first contacts the wing) goes aft of the vane, the forward airflow pushes the flipper up into the contact points, and you hear a tone (stall warning). On the "similar" AOA unit it measures force on the flipper. (making up numbers) At an AOA of 10 degrees and 70 knots, the flipper has X oz. of force on it. If I keep AOA constant and increase airspeed to 140 knots (yes, I'm now pulling 4Gs), the flipper will have 4X oz. of force on it. The displayed AOA will be converted/calculated as significantly less (guessing near 2 degrees). In addition and in turbulence (which is a change in AOA) and knowing that the flipper is not mass balanced, it will record vertical loads as changes in AOA. Vanes are mass balanced so they don't do this.
  15. Blue on Top
    It's not either. The force on the flipper vane is airspeed dependent … and changes in rain.
  16. Blue on Top
    No, we are flying newer technology airplanes that are not Cub-like … and even those have their fair share of stalls-spins-spirals on takeoff and during moose turns (maneuvering near the ground). Today's airplanes may or may not give the pilot a natural warning before they depart. This answers the question about Wolfgang, too. And, although I love his book, AOA is not the acute angle between the chord line and the direction of flight … unless the air is perfectly calm (no thermals, no bumps, no gusts, no etc.)
  17. Blue on Top
    A ROUGH estimate on price. I know, this isn't fair because I'm not telling you all the features. Actual, calibrated AOA is the only way to go.
  18. Blue on Top
    All clean up of steps and gaps will decrease drag. As the airplane gets smaller (like Mooneys), what we call crud drag becomes a larger percentage. For example, 20-25% of the drag on a business jet is crud drag (antennas, steps, gaps, etc.). On a Mooney, that value goes up to ~30%. Smooth is good. You are also correct in that the further aft on an airplane the less it matters (the boundary layer is thicker), but it all matters. You're an inspiration!
  19. Blue on Top
    Cargil48: Flow around the airplane is more efficient than flow through the engine compartment. As Skip mentioned, you can throttle at the inlet or exit. OEMs look at failure modes (either way hurts the same here), complexity and part count. Exit openings are the easiest. In fact, the Ovations don't have those because people complained that they were too complicated, maintenance was high, cowling removal was difficult and cost too much … for 3-4 knots. I like the innovative idea!
  20. Blue on Top
    Yes, air is compressible, but below M=0.3 even engineers ignore it.
  21. Blue on Top
    Yep! … and that is before the lightning strike material is added to the composite. Typical engineering weight tolerance on aluminum is 0%; 7% for composite material. Same is true for thicknesses, too. Clarence: I would give you a "thumbs up" emoji, but I am too passionate and ran out of them for the rest of the day ... Oh wait! It must be tomorrow somewhere
  22. Blue on Top
    Engine cooling is a really, really complicated problem and one that can't be modeled very well. Bottom line is that the inlet openings and cowl exits are designed solely for cooling the engine/engine compartment/engine accessories during a maximum gross weight climb, maximum electrical draw, Vx climb on the hottest day the airplane is certificated for. That's the reg. Drag on the other hand is all the OEMs issue. One can think of the engine cowling and cooling as a converging-diverging nozzle. Air comes in the inlet(s), is slowed to near static (to gain the positive effects of dynamic air pressure, ~1psi at 200 knots), shoved down through the cylinder fins and reaccelerated to exit out the bottom of the cowling (down draft cooling … which is to keep the engine fire and smoke off the windshield in that event). So, at speeds above Vx, more than enough air is available at the inlets and the excess air needs to go around the inlets. This is why the lower drag inlets are round. The slower we can push enough air through the cylinder fins, the more heat we can transfer to the air. We want the exit air to leave the airplane at the airspeed of the airplane (lowest drag), As mentioned previously, opening the cowling flaps all the way in cruise will cool the engine better (slightly), but because the cowl flaps form a low pressure area on an aft facing surface/area, it increases drag. We all know Mooniacs and Draggiacs have been feuding like Hatfields and McCoys for decades.
  23. Blue on Top
    You, too, Mitch. I must be too passionate, as I have run out of MooneySpace emojis to respond to others' posts. I'm good with that.
  24. Blue on Top
    I agree that the changes appear on the earlier models in 69. The "F" was certified in 1965 with the larger elevator travels. I also see that the certification basis for the "F" was also made a later revision (earlier models were Amdt 54 and "F" is Amdt 59). This could be the reasoning, too. The down spring is in the system for low speed stability. Could there have been an accident in '69 or, a more simple answer, were some control system parts made differently and it was easier to make all of them the same?
  25. Blue on Top
    I love your idea! (though I don't think it will work). Trust the AOA vanes that are near the wing, they work well, but that is another topic entirely.
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