Altitude loss in spins

Discussion in 'Aerobatics' started by Diana, Sep 25, 2005.

  1. Diana

    Diana Final Approach

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    I’m having a discussion with someone on altitude loss in spins. How much altitude do you all lose per turn in the different airplanes that you fly in a standard, run of the mill, upright spin?
     
  2. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    From the '77 Mooney M20J POH:

    WARNING

    Up to 2000 feet of altitude may be lost in a one-turn spin and recovery; therefore stalls at low altitude are extremely critical.


    "Run of the mill, upright spin?" Doubtful. :rofl:
     
  3. bbchien

    bbchien Touchdown! Greaser!

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    With two up and my Mooney checkout guy in the right seat, lost about 1000 per turn. Mooneys stay upright if you are vefy definite about letting elevator out PRIOR to opposite rudder- otherwise "over you go...." as in inverted. These are not logged for obvious reasons.

    To be respected.
     
  4. Diana

    Diana Final Approach

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    Wow. Why is that?
     
  5. bbchien

    bbchien Touchdown! Greaser!

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    It is because Al Mooney was a little crazy. Really. ~1 M square wetted profile, Laminar flow wings that break all at the same time (he had to washout the AOA out to the tips with wing twist until 1968 when they discovered stall fences) for most efficient production of lift, very tapered wing approximating the Ellipitcal planform, All flying tail.

    Yes, the Mooney Short field is perfectly doable. It's just MUSH though compared to a Cessna at 70 and you have to get the ONE BIG yoke movement just right or you'll smoke tires.

    Few compromises.
     
  6. gismo

    gismo Touchdown! Greaser!

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    I think that WRT a one turn spin, a lot depends on the entry. Few if any planes become stable after only one turn. By the time you get to three or more things should be pretty consistent. I've had some spins in the Porterfield that lost well over 1000 ft in the first turn and some that dropped less than 500-600. I also suspect that the altitude loss depends a lot on wing loading and CG location. With the flatter attitude and higher rotation rate of an aft CG I'd expect the altitude loss to be reduced.
     
  7. Diana

    Diana Final Approach

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    Thanks for the explanation Bruce. So, what are the advantages of the Mooney wing then? Faster? Better climb?
     
  8. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    Aerodynamic efficiency (faster, better climb, and falls like a rock). Mooney aircraft are pretty much the fastest production aircraft on a kts/hp basis. As an example, a four seat, '77 Mooney M20J produces ~160 kts on 200 hp while a four seat, Beechcraft V35B of the same era produces the same speed on 285 hp.
     
  9. gibbons

    gibbons En-Route

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    Ditto the Pitts and the Extra.
     
  10. Diana

    Diana Final Approach

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    Gosh, I didn't realize that. No wonder you Mooney guys love your Mooneys!
     
  11. Diana

    Diana Final Approach

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    Chip, how much do you lose in your Citabria?
     
  12. gibbons

    gibbons En-Route

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    I couldn't really say. I've only spun it a few times (less than a dozen) and never more than a three turn spin. I would guess it would be close to 800' - 1,000' per turn. It spins well and wraps up tighter after a couple of turns than I expected.
     
  13. gismo

    gismo Touchdown! Greaser!

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    Ed's stretching it a little. Some of the 285 Hp Bo's can do about 175 KTAS and the 225 Hp older BE35 would come within a couple knots of 160 KTAS over a narrow range of altitudes. I think he's right about some Mooney's being the winners of the efficiency race for production airplanes though.
     
  14. Diana

    Diana Final Approach

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    Is there any way we can put these wings on top of an airplane, make it a high wing airplane and therefore make it the perfect airplane?
     
  15. Rudy

    Rudy Line Up and Wait

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    Haha, but then you would have to climb a ladder to check you fuel.
    It is an extra risk and me being accident prone i prefer not to take it. hahaha
     
  16. gismo

    gismo Touchdown! Greaser!

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    Not to mention the risk of walking into the flaps from behind. Then again, you wouldn't have to wreck the knees in your pants while sumping the tanks with the wings on top.
     
  17. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    Unfortunately, Lance is the one stretching it a bit.

    From the '77 V35B POH: 75% power table, standard conditions, best number on the table is 172 kts TAS at your choice of 6000' or 7000'.

    From the '77 M20J POH: 75% power, 6000', standard conditions, the book shows 171 kts TAS.

    1 kt? You call 1 kt "stretching it a bit"? You engineers are a tough crowd.:rofl:

    BTW, book fuel flows are 13.3 gph versus 10.8 gph at those speeds and altitude.
     
  18. Ken Ibold

    Ken Ibold Final Approach

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    I think the book is stretching it a bit. My 78 M20J sure wouldn't do that.
     
  19. Michael

    Michael Pattern Altitude

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    Sheesh Ken, My "C" model can do that.....descending with a tailwind counts doesnt it?.
     
  20. Dave Krall CFII

    Dave Krall CFII Final Approach

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    P210 Cessna Centurion ?
     
  21. Michael

    Michael Pattern Altitude

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    Sorry Diana, looks like your thread got taken over, But it just goes to show you that any topic can be converted to a mooney topic rather easily. :goofy:
     
  22. Diana

    Diana Final Approach

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    LOL! I noticed that about you Mooney guys. At least I know how much altitude a Mooney loses in a spin. I'm still not quite sure how fast they go, however. :D

    Now, if Ken would just tell me how much altitude he loses in his Citabria in a spin............... ;)
     
  23. AirBaker

    AirBaker Pattern Altitude

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    We're not comparing similar weighted aircraft either here... :)

    Wait, wasn't this a spin thread? :D
     
    Last edited: Sep 26, 2005
  24. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    That's okay, the V35B book is stretching it a bit, too.;)
     
  25. Diana

    Diana Final Approach

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    Oh gosh, this is getting to be fun. I don't remember a Mooney vs Bo thread before. :D

    Hey, how much altitude does the Bonanza lose in a spin? ;)
     
  26. Ken Ibold

    Ken Ibold Final Approach

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    Honestly, I have no accurate feedback to supply right now. I'll go check tomorrow.
     
  27. AirBaker

    AirBaker Pattern Altitude

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    Spins are prohibited. :) I'd have to find an instructor who's done them in one before if I'm to test out that limitation!
     
  28. Skyport

    Skyport Pre-Flight

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    Diana-

    My GCAA looses 300-500' in each turn, I budget 500' per turn and usually have change on the recovery that can be converted into extra energy for the next manuver.

    The eye-popping Mooney number of 2000' was, no doubt, written by an attorney concerned about liability.

    The actual altitude loss per turn in most GA aircraft is similar in my experience, rising to the 500-700' range with higher perf, and slower rotating, aircraft. One huge difference with spinning in high perf, and cleaner, aircraft is the altitude loss during the recovery.
    Tom-
     
  29. Diana

    Diana Final Approach

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    OK. :)

    A gentleman from Australia asked me about it on another aerobatic forum. He was surprised that I lost about 500' a turn. He posted his video of his 20 turn spin in a Robin. He did 20 turns and recovered within 4000' and that included his dive to restart the engine. His spin looked pretty flat in his video, but he said it was normal for a Robin.

    It made me wonder if I was doing something wrong.
     
  30. Ken Ibold

    Ken Ibold Final Approach

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    How many turns are you counting? The first two will lose more altitude than the next 5 or 6 because the rotation rate increases once you're past the incipient phase.
     
  31. Diana

    Diana Final Approach

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    From 2 to 5 turns. I'll have to go back up and count again. That one strange spin I only lost 1500' with over 6 turns and I had someone counting the turns from down on the ground and called out altitudes beginning and ending. It was the one that wrapped up very fast and tight.
     
  32. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    I rode the first 1/2-3/4 rotation, twice, before concluding unequivocally that a cross-control stall demonstration is a bad idea in a Mooney. The first time I was right seat, flying, and afterwards the left seat CFI could only say, "Did you SEE the altimeter?!"

    The POH warning may have been written by an attorney but is definitely not a conservative estimate. BTW, the aircraft is inverted for the first 1/4-1/3 rotation if the aileron hits the stops before the stall break.
     
  33. Diana

    Diana Final Approach

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    Tom what things will make a difference between 300 and 500' in your spins? Is that averaging the different phases?


    Thanks Tom.
     
  34. Skyport

    Skyport Pre-Flight

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    Diana-

    While you are correct that I'm averaging the turns the CG, and type of entry will have an effect on the altitude loss per turn. The varibles make the most difference in the altitude loss during the first turn.

    Ed-

    While I must admit that I've never spun a Mooney, nor is it the type of aircraft I would choose to do a cross-control stall demo in, I have spun other aircraft that went inverted in the incipient phase and I find it difficult to see how 2000' could be lost in one turn. To do so would require that the aircraft be deeply into the stall and almost in free fall with only a modicum of lift on one wing providing a rotational force.

    Tom-
     
    Last edited: Sep 27, 2005
  35. Ed Guthrie

    Ed Guthrie Cleared for Takeoff

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    For the record, the plan was to terminate the cross-control stall demo at the first sign of either stall or loss of aileron control (i.e. stall warning horn, stall buffer, or aileron controls hit the stops). The two demonstrations that went further than I would have preferred proved that the aileron stops, stall buffet, stall horn, and stall break can be hit simultaneously without any extraordinary effort. Both times that happened we had an e-ticket ride. The first time it happened I thought I'd been a bit rough on the controls, but the second time confirmed to me that the cross-control stall demonstration simply wasn't a good idea even if the plan was to not actually stall the aircraft.



    Pretty much you just described the first 1/2-3/4 turn in a Mooney. All I can tell you is that the Mooney spin entry is not what you might expect after spinning a C152, C172, or even a Citabria (been there in all of those). The Mooney aircraft rather abruptly rolls inverted as one wing literally falls out from under you--that wing is indeed rather sharply stalled. FWIW, the CFI I mentioned previously told me that he had decided to watch the altimeter to note how much altitude I lost during a stall recovery if one occurred. He told me the altimeter was an absolute, complete blur. I have watched a C172 altimeter during spins and it was never all that exciting.

    Both times I was on the opposite rudder instantly at wing drop, so the 1/2-3/4 turn rotations I have witnessed were what it took to end rides I didn't want to take. I have no idea how the next 1/4-1/2 turn would go for a complete rotation. I'm also not crazy enough to repeat the experiment just to more accurately note the altimeter change.
     
    Last edited: Sep 27, 2005
  36. bbchien

    bbchien Touchdown! Greaser!

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    When I'm a spinnin I'm not a watching the instruments. I'll look after the pullout...I did have one inverted spin (first one, from 10,000 feet) in which when I got it stopped (2 1/2 turns because I got disoriented) the altimeter read 6,100. Very sobering. M20J.
     
  37. Toby

    Toby Cleared for Takeoff

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    Diana,

    I usually lost 800 feet in a one-turn spin in the Decathlon. Sometimes 1,000 if I wasn't quick enough.
     
  38. Skyport

    Skyport Pre-Flight

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    FYI-

    One VERY important thing missing from this discussion of Mooney spins is that SPINS ARE PROHIBITED in all models........................anyone spinning a Mooney has became an Experimental Test Pilot.

    Tom-
     
  39. bbchien

    bbchien Touchdown! Greaser!

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    Yup. But the really in the know old Mooney guys know to teach it to those capable of learning from it. My guy was (when he was wearing his other hat) a DPE. He advised me of this, I agreed to this, and we did not log it. He had done this in the four digit numbers of times, as he was one of the original Factory Test Pilots. Jeepers!

    Book from 1992 is in the Bank Vault. I'll try to remember to look up his name; he was pretty old 13 years ago.
     
    Last edited: Sep 27, 2005
  40. Diana

    Diana Final Approach

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    If a Mooney accidentally got into a spin, would the recovery be fairly standard (since the recovery technique wouldn't be mentioned in the POH)? Like PARE, or Muller-Beggs type recovery?