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Rene

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  • Reg #
    N2RH
  • Model
    M20J

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  1. OK I tried the glide with my 3 blade prop control pulled all the way back, and it did make a huge difference. My glide with the prop control all the way forward was -1000 ft/min, and with the control all the way back it was -600 ft/min. So this means that at 90 knots, I would get 2.5 nm for each 1000 feet AGL, rather than only 1.5 nm. The Mooney "book" value is 1.9 nm per 1000 ft AGL. The only caveat with using the more optimistic number is that in the case of a real engine emergency you may not have oil pressure to increase the prop pitch, so the prop control may be inop. For practice with simulated engine outs, it's probably best to do it with the prop at high RPM because that is more like the worst case glide.
  2. OK Skip, that study about prop drag is really good news because it implies that a windmilling prop with engine idling is "almost" the worst case, so it's good for creating personal estimates for gliding distances. I didn't read the NACA report, but I am assuming they studied a constant pitch prop? Has there been a study on the difference in drag between the prop control all the way in and all the way out? By the way, John B, I plan to do the experiment with prop in and prop out and will let you know the results. Rene
  3. I think we are all agreeing that a Mooney gliding with an idling engine will go farther than a Mooney with a windmilling engine (no power). The idling prop has less net drag because of the "thrust" component of the idling engine. Overall, the windmilling configuration has more drag.
  4. Hi Shadrach, I agree that the idling engine makes thrust when airspeed is 0 knots. But when gliding at 90 knots, I suspect that the idling engine/prop is creating drag. Less drag than a windmilling prop on a dead engine, but some drag nonetheless.
  5. Wow. I have to admit that I had no idea I would get so many responses to my post. I'm really impressed by how active and knowledgeable this forum is, and I have certainly learned a lot. So thanks everyone for pitching in their thoughts and experiences.
  6. As I understand it, altitude should not matter when doing these experiments to determine glide ratio. So for example if we are at 10,000 feet, gliding at 90Kt IAS, of course our true airspeed is say 20% higher, but then our true rate of descent is also 20% higher than indicated on our VSI. These two factors cancel each other out, so our glide distance is the same whether we are 5000 feet over sea level terrain, or at 10,000 ft MSL over terrain that is at 5000 MSL. Do I have that right? The other interesting thing is that glide distance does not depend on weight, as shown on the glide distance chart. Heavier weights require higher glide speeds, but end up at the same distance. I always thought that this was a fascinating and very counter intuitive fact. Next chance I get, I am going to try the glide with the prop control all the way out, to see how much better I can do with my 3 blade prop.
  7. I tried to search for "performance measurements" and "glide performance" with no luck. Can you give me an idea of what to search for?
  8. I have been wondering what others experience when doing a "simulated engine out" exercise in their Mooney M20Js. My information manual has a glide distance chart which I have attached. At midweight of 2740 lbs. max glide is 90 knots with the prop windmilling. Using the chart, hypothetically my glide distance from 10,000 feet would be 19 nautical miles. When I do the math, this computes to a vertical speed of -787 ft/min at max glide. However, when I try this exercise in my aircraft my actual vertical speed at 90 knots is just about 1000 ft/min. Now the only thing that is different about my Mooney is that I have a 3 blade McCauley prop instead of the standard 2 blade. Would the extra blade on my prop be responsible for the difference in vertical speed? Does the extra prop blade mean that my best glide speed should be different from what is stated in the information manual?
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