Stall Recovery vs Tail/Fuselage design

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by stankap, Feb 6, 2012.

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  1. Jun 27, 2012 #41

    topspeed100

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    Spin training may be no good if the plane is notorious for not recovering from a spin. What are the procedures for spin recovery....centering the stick and applying oppisite rudder..then loosening harness and move CG forward by pushing upper body forward ?
     
  2. Jun 27, 2012 #42

    4trade

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    I mean in that situation when GA pilot with little or no experience of spin, they just see rotation movement and ground....
     
  3. Jun 27, 2012 #43

    SVSUSteve

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    Ah, you say inverted spin, I think inverted flat spin. That's one of those "Hey, wait a second....Why is the sky down....oh ****" visuals.
     
  4. Jun 27, 2012 #44

    SVSUSteve

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    Obviously. That would also be why I don't fly those sorts of planes.
     
  5. Jun 27, 2012 #45
    I have done the spins by purpose hundreds of times, with RF-4 it's safe, fun and easy, but the case is different if you go to spin by accident. It hapened to me in late 70es with SHK glider in thermal, when following the planes above, luckily I was the lowest one. It is even hard to realize at first which way you are rotating, I try to keep on mind to push the slip indicator ball side rudder as a first thing to stop the rotation
     
  6. Jun 27, 2012 #46

    rdj

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    I certainly agree that stall training should be a part of the curriculum, as every airplane flying should have acceptable stall characteristics, certified or homebuilt. If it doesn't, it shouldn't be in the air (unless it's a military fighter, Space Shuttle, or some other corner case).

    However, I disagree that spin training is necessary in basic training. I totally agree that unusual attitude recovery training is a great way to get more 'comfortable' in a plane. With a properly certified instructor in a properly certified airplane, properly loaded and maintained, that is. There are folks out there who give such training--strap on a parachute, and go explore the boundaries of the plane. Sounds like fun to me, and good experience when those 'uncomfortable situations' arise.

    But, the only need I see for spin training during basic is recovering from bungled stalls at altitude. For most planes, just recognizing the incipient spin and making the appropriate control input to break the stall before it develops any further is sufficient. That was the case in the Cessnas I flew; in fact, with only myself in the plane I had a difficult time just getting a fully-developed stall going, much less a spin. By the time you've let the plane enter a fully-developed spin, you've just entered the aerobatic portion of the curriculum. I prefer to have a parachute available--just in case--at that point.

    There are only two cases where spin recovery training would pay off for most GA flyers:
    Case 1: load the plane to gross weight and full aft CG. Add full power, and put the plane in a steep climb. Hold through the departure-stall buffet while applying full rudder against the P-factor. Demonstrate spin recovery within 300'.
    Case 2: put down full flaps. Pull power back to idle. Slow the plane through the stall buffet while turning the plane sharply with rudder. Keep the wings level with aileron. Demonstrate spin recovery within 500'.

    I have yet to encounter a single one of those 'everyone should learn spins' mantra-speakers who will demonstrate a spin and spin recovery technique (at altitude of course) in their airplane in those two configurations within my required altitude limits. Most consider it too dangerous with flaps down or aft-loaded. So, what's the point?

    Spin recovery training is useful for glider pilots, since being in slow, banked turns close to stall is their natural condition. A glider without acceptable and recoverable stall/spin characteristics throughout it's load envelope is unairworthy in my opinion.

    I think far too many pilots are too cavilier with spins. Just because you enjoy them in your RV-6 doesn't mean they won't scare you s**tless in your friends RV-6, rigged slightly differently. When you jump in a new plane, do you fly near Vne and tap the stick to test flutter characteristics without a chute on? Why do you treat spins differently? Test pilots don't.
     
  7. Jun 27, 2012 #47

    bmcj

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    Was that the 172? Not all models of the 172 are spin certified.

    Very true!
     
  8. Jun 27, 2012 #48

    autoreply

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    I don't. Fact of the matter is that the big majority of the stall/spin crashes start low to very low. Those folks without any actual spin training recover from a developing problem just fine, lower the nose abit, brush the rudder and you're fine. But not from serious trouble. A sudden engine failure requires FULL fwd stick/yoke and 30 degrees below the horizon, maybe more in a draggy plane. I've had a number of powered pilots, most of them instructors who didn't correct nearly aggressively enough if they had ever seen a 15+ degree nose-down attitude at all. They are even less likely to do so close to the ground.

    A large fraction of those will kill themselves if they have an engine failure early in the TO.

    That's the folks that get killed, not those who slowly move into a developing asymmetrical stall. A simple instruction flight in an aerobatic ship and some aggressive stalls/spins is all it takes. If you have never done it, you won't do it when it can save your life either because it's against human nature. (The ground is nearing, so you're pulling or banking, not pushing over and the stall horn alerts you when it's too late..) Been there, seen it happen as described, went to the funeral.
    Most (performance ships) are aggressive and instantaneous in falling into a spin. No big deal, though it was rather uncomfortable watching a thermalling ASW20 on top of me that flipped inverted and started spinning down in our thermal. In a sense such an aggressive reaction keeps you sharp because you correct every small approach to stall directly.
     
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  9. Jun 27, 2012 #49

    Tony

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    This is why one should put the stick towards the ground and not learn to push. What ever way the ground is put the stick that way. Always put stick toward the ground. Rick Talks about this in his book.

    Rick also talks about letting go of the stick. He had to pull the chute more then once on that move. Sometimes it would never recover.
    He also talks about how the stall and the spin are linked and one must watch cross control when entering a stall or a spin is in the works.

    I fly a Experimental Avenger made by Fisher. One day I was flying along and thought. I might try one of those..I forgot what its called....Help me here guys...I put the bird on its tail and right before she stopped flying I wanted to kick the tail around and be pointed back where I just came from. Well it did not come out like that.

    I waited to long and let the speed drop to much. I kicked the rudder and she went almost upside down. She went right into a spirl almost a spin. I leveled the wings and slowly pulled back to level flight, watching not to over stress the airframe. I entered this at about 900' agl. I leveled off about 500' agl.
    It was such a thrill but also scary. I would love to try it again, but never will...lol


    Tony
     
  10. Jun 27, 2012 #50

    Tony

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    Rick talks about all the different tail designs and what they do and how they do it when going into a stall. He talks about how an elevator can block all the airflow to allow for recover in some airplanes when in a spin. Or how the Rudder blocks the elevator in others and when you enter a stall there is no elevator controll.


    Tony
     
  11. Jun 27, 2012 #51

    Rick McWilliams

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    The inverted spin is deceptive. The airplanes that I have flown usually spin inverted at almost 2G. Somehow your body does not pay attention to that detail. The Pitts and christen eagle do very slick cross over spins.

    I do one spin every acrobatic flight. Since it is now a precision maneuver, it is worth practicing. An acrobatic spin has a clean entry, finishes on heading in a vertical line. 5 degrees of error in any axis is one point off. The judges will see an "aileroned" heading correction. I fly with a box 1500ft bottom, I have never busted the box. The Zlin acrobatic one turn spin takes 900 ft to complete.

    Weight and balance can dramatically change spin character. I do not do aerobatics with fuel in the wing tip ferry tanks.
     
  12. Jun 27, 2012 #52

    TinBender

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    The 737 is stalled during check flight after slat rigging. Felt pretty mushy to me, but I was in passenger cabin. If I did not know that it was happening, I probably would not have noticed.
     
  13. Jun 27, 2012 #53

    bmcj

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    Hammerhead (or stall turn).
     
  14. Jun 27, 2012 #54

    Tony

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    Thats it. I wonder how many g's I put on my airframe doing that stunt? I will never do it again. There is a video on youtube of a Mini-Max doing Hammerheads. He just keeps doing one after another after another. Looked really cool.
     
  15. Jun 27, 2012 #55

    bmcj

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    Not many g's. The g's are from the pull-up to the entry and the pull-out after the maneuver. Both can be moderated to be low and the pull-out can be at a relatively low speed (but guarding against a stall, of course). The hammerhead itself is a very gentle maneuver, but the two traps in the hammerhead if you screw it up are falling into a spin (could be upright or inverted) or holding too long and ending in a tailslide (which risks damage to your control surfaces, possibly making your craft uncontrollable).

    Do a search on YouTube for "botched hammerhead" and you should come up with some results, including this one by Rich Stowell:

    [video=youtube;aRMygdyDJcA]http://www.youtube.com/watch?v=aRMygdyDJcA[/video]

    Bruce :)
     
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  16. Jun 28, 2012 #56

    SVSUSteve

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    Here's the problem with that: most sims can't adequately mimic anything beyond approach to stall because of the limits to their travel, etc.
     
  17. Jul 28, 2012 #57

    Turd Ferguson

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    Simulator stall fidelity is limited only by applicable simulation validation data. In the US, QPS requirements for level A-D simulators says they must accurately "mimic" a stall IAW with appendix A parameters.
     
  18. Jul 28, 2012 #58

    Tony

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    rdj: I did just what you speak of. I fly a fisher Avenger low wing. Flying along at about 800'or 900' I pulled her up into a steep climb, Just as she was going into the stall I kicked the rudder full left. She almost went upside down. Now was I trying to do this. NO. I was shooting for a hamerhead, I believe they call it that. I do this all the time with my RC planes. Pull up just as she slows kick the tail around and fly right back on the same line.
    I went almost upside down and then right into a spin. After about one spin I leveled her in flight. I was still pointing down but I had level wings, then I slowly pulled out. I was around 500' when I leveled off.
    It was a rush a thrill and holly terror all in one, and it was a blast. Will I do it again. No. But man I want to. They say my plane is rated +4 -6 on the g scale but I do not trust that. I will fly flat and do steep banks and be a happy camper.


    Tony
     
  19. Jul 28, 2012 #59

    Turd Ferguson

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    Tony, due to yaw/roll coupling, left rudder deflection also causes the aircraft to roll left. This will definitely put you upside down. You have to counter the roll with right aileron. When flying st & level at low speed, push the rudder full left and watch how much the aircraft rolls left. Then apply right aileron to keep wings level. This will give you an idea of how much right aileron is necessary to perform your hammerhead.

    Where did you get your Avenger? I helped someone build the basic structure of an Avenger about 15 yrs ago. He wanted an inexpensive plane for recreational aerobatics. He later got sick and gave the project away but I still have a copy of the plans. I often wonder if it would be worthwhile to build another one.
     
  20. Jul 28, 2012 #60

    Rick McWilliams

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    When the engine quits in climb, quick and correct action is required. Full forward stick is too much for all of the aircraft that I fly. The Zlin will do an nice outside snap with that kind of aggressive control. The seaplane will go way negative. The helicopter will cut itself in half.

    I have flown with Rich Stowell many times. He is the best aerobatic instructor that I have seen. We did a flight in the Zlin where we tried some of the alternative spin recovery techniques. The Beggs let go of the stick and apply heavy rudder did not recover from a normal spin. The neutralize controls and add opposite rudder did work but the stick forces were very high. PARE works every time. Aggravated spins in the Zlin are for test pilots, they are much faster than those in a Pitts, the recovery can be slow.
     

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