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Thread: Does an Engineer need a Helicopter Air Speed IND.

  1. #1
    On Patrol's Avatar
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    Does an Engineer need a Helicopter Air Speed IND.

    Hi All,
    My new cub pilot and Father in Law George is having a hell of a time feeling the Super Cub versus his engineers mind telling him I need to give him speeds on a very accurate Air Speed Indicator.
    Now I am not a good judge at all and considering myself to be a rookie still on the learning curve.
    I watched him last season with Steve during his tail wheel transition and he has the feeling his is extremely high and refuses to round out the aircraft into a decent flare. I watch as he neutralizes the stick and flies on and on and on in slow flight over the strip at 3 feet. One old timer screamed at myself and Steve saying give up three points and let the man do all wheel landings where he can see. What is not helping is 39Y is reading 10 MPH high on the air speed. I was thinking of getting a helicopter ASI if it is approved and will solve the problem. Any suggestions? or approvals and part numbers.
    John

  2. #2
    Ruidoso Ron's Avatar
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    John,
    I have a helicopter airspeed in my Cub that reads down to 20 MPH. All I can say is that it is a waste if you have to pay good money for it. I didn't. At the time I installed mine, I happened to be in the helicopter instrument business, and I simply went in, and pulled one off of the shelf. I had my shop bench check it again for me, and it was calibrated down to the gnats rear end. But the big problem with trying to get accurate airspeed readings is pitot error, especially in an airplane like the SC that can fly at such an exagerated angle of attack. When I am down to the nub on a slow approach, with full flaps and carrying power, I am reading zero airspeed. So what good does it do me that the airspeed will read down to 20? Nada! Teach your father-in-law to fly attitude.

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    On Patrol's Avatar
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    Hi Ron,
    I have the same issue with Miss Daisy once you get real slow the ASI goes to hell and is useless particularly with a combination reading of KTS. and MPH. I have been trying to teach him to feel the airplane it is just he has been used to driving the Comanche on at 80 mph that he feels he is 20 foot high and afraid of falling out of the air.
    John
    PS you still coming out with your grandson? I notice NH is a pass this year for you...J

  4. #4
    jgerard's Avatar
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    Cover up the airspeed and vsi and make him fly it around a while practicing stalls and slow flight. Then make lots of low passes down the runway in a landing attitude without actually landing and flyin down the length of the runway in ground affect.

    Jason

  5. #5
    SteveE's Avatar
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    From the back seat of my J-3 and with a passenger in the front, you cant see any instruments anyway. Have him fly from the back for a while.

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    While getting my tail wheel endorsement, the only time my CFI raised his voice at me was when I looked at the airspeed indicator on or close to the ground. During one take off he told me that if you look at that thing again I'll cover it up. Ground loops happen on or close to the ground and we should keep the eyes looking outside.

    I don't need the indicator on take off and once I start to flair on landing I don't look at it any more. I guess that is why we practice slow flight, to learn to feel the plane, not read instruments.

    Had to add my two cents, guess that is what it's worth.

    Bill
    Flat Country Pilot
    Farm Field PVT
    54 C170B

  7. #7
    Ruidoso Ron's Avatar
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    Quote Originally Posted by Flying Miss Daisy
    PS you still coming out with your grandson? I notice NH is a pass this year for you...J
    Yes, I need to be in Highgate, VT by Sat. the 29th. Not sure how I am going to get there, as the nearest AA served airports seem to be BOS or HFD. Would like to try to swing by NH on the way. Haven't given up hope!

  8. #8
    mvivion's Avatar
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    If you are staring at the airspeed indicator close to the ground, float isn't the greatest problem you'll have.

    I'll second, or third, the comments to encourage him to fly the airplane without the A/S for a while, particularly at altitude, till he gets a better feel for it, and when it "feels" slow.

    As Ron said, the problem with the Cub's airspeed system isn't the indicator, but rather the pitot tube.

    Actually, I can make a Super Cub stall at 0 or at 60 by just tweaking the pitot tube a bit. They are pretty flexible, after all. But that notwithstanding, as Ron points out, the range of deck angles that the airplane is capable of within it's normal operating range virtually precludes accurate A/S indications at very high AOA.

    There are ways to do it, I suppose, but frankly not worth the effort or cost. And, to reiterate, if he's staring at ANY instrument while landing, he's going to have problems.

    MTV

  9. #9
    cubflier's Avatar
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    I think there is more to this phenomena of ASI's falling off at high AOA's than just the pitot tube itself. I have never had this problem in my cub and I have had the stock cub ASI and now have the helicopter version. Both read very accurate at all relevant airspeeds (anything above stall).

    I have flown other cubs that drop off dramatically at the low end and I really think this is a defect within the pitot system that should be fixable. I suppose there is a chance that my cub pitot system is configured to match some sweet spot that exists on the fringe of probability but I know of other cubs that are just like mine.

    The big advantage of having an accurate system is you can use the ASI and Ground Speeds in the GPS to judge wind direction even at very low indicated Air Speeds. This is not always necessary but in some situations can come in handy.

    Jerry

  10. #10
    Speedo's Avatar
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    The problem isn't with the airspeed indicator, it's with your father in law. He's not comfortable with the sensations involved with landing. That's understandable: when one is new to flying (especially taildraggers) there are lots of new sensations.

    He's going to need to train himself to fly a stabilized approach at 1.1Vso over the numbers, then to ignore the ASI and look for the correct sight picture. If he is looking at the instruments just before or during the flair he's not going to get the right sight picture. So he has to discipline himself to get the speed right on final (before crossing the fence), then transitioning his scan to 100% outside. If he's got the right sight picture over the numbers and the power is at idle, it will be impossible to fly down the runway (unless it's a steep, downhill runway!).
    Speedo

  11. #11
    Ruidoso Ron's Avatar
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    I have often wondered if I could jury rig an articulating pitot tube with a fin to keep it vertically oriented to the relative air. This is done on jets during the certification phase with great success. It must be an expensive device. The pressure is transmitted from the probe to the staff through the two bearings on each side of the pitot tube, which allow it to rotate about the horizontal axis. Pretty good trick to keep it from leaking, I suppose. Have the experimenters come up with something with a flexible enough pitot line that it can accommodate the rotation?

    Of course, the Lift Reserve Indicator is probably a simpler solution. See http://www.liftreserve.com/

  12. #12
    T.J.'s Avatar
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    delete

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    Crash's Avatar
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    Quote Originally Posted by T.J.
    Johnson Airspeed Indicator.
    Looks like something that would come out of Nikiski.

    Seriously, he needs to take the plane up to altitude and get the "feel" of when the "bottom" falls out of it. When the plane starts this fast sink, a little power will arrest it. A Cub if it's rigged properly will not do a sudden "break" type stall. Slowing one down too much on approch will just get you a fast sink that tells you that you are "behind" the plane. Feed in a little power to correct it. Take care. Crash

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    On Patrol's Avatar
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    Thanks Everyone,
    I believe I will address the problem by putting my butt in the front seat and let him fly from the back through a few landings to feel the plane. This should help with my Rookie tendencies and nervousness about being caught behind the curve. It appears that some slow flight at altitude would be next showing him the power response. I also have a good friend up to Millinocket that has thousands of hours in a tailwheel that I will stick in the front seat while I fly from the rear to allow me to gain the proper sight cues from the back. I will keep you posted on my progress.
    John

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    mvivion's Avatar
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    John,

    Just a suggestion, and perhaps this is what you intended, but I'd do the slow flight, and lots of "practice landings" at altitude FIRST, before I got it close to the ground. Take it up and see how slow you can fly it before it starts to complain (burble), then hold it right there, in the buffet, but maintaining altitude. Now let it accelerate out of the buffet, but hold it just above the buffet, such that any little bump will cause it to buffet.

    Now initiate a turn, right or left. You'll note that if you really are on the bubble, and you don't add power, the airplane will stall, even with a mild turn. Now you're on it.

    Drive it around with rudder alone (hold the ailerons absolutely still), through some mild banks, adding power to prevent the stall, but just barely. Now try some steeper turns, rudder ONLY, to get the feel for what the rudder will do for you. Nothing wrong with using ailerons in real life, but this exercise shows you just how powerful the Cub rudder is, particularly in slow flight.

    I call it flying the bubble. You can call it whatever you want. It will give you a good feel for what the airplane feels like and sounds like and handles like at the very slow end of the speed range. That's what you want to develop: the feel, the sound, the handling..... BEFORE you get close to the ground.

    Do all of this at first while sorta noting the airspeed guage, but after a bit, you'll find that you really don't need it, cause the airplane is telling you everything you need to know. The critical instrument in this evolution is the altimeter, actually, cause you want to hold altitude. Now, then, cover up the airspeed, and do this again.

    If at any point in this regime you are a little slow on the controls, and the plane really stalls, relax the back pressure (as in DON'T slam dunk the stick) power to idle, and stop the rotation if there is any with rudder. Recover to level flight, and go back at it.

    High AOA flight is where you need to work to make landings work out, particularly if you want to work short.

    I think way too many people spend WAAAAAYYY too little time in airwork getting the feel of a plane before they start trying to land it, and as a consequence they never quite get it. Landing is a poor place to try to learn the handling characteristics of the plane.


    MTV

  16. #16
    moneyburner's Avatar
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    Quote Originally Posted by mvivion
    John,

    Just a suggestion, and perhaps this is what you intended, but I'd do the slow flight, and lots of "practice landings" at altitude FIRST, before I got it close to the ground. Take it up and see how slow you can fly it before it starts to complain (burble), then hold it right there, in the buffet, but maintaining altitude. Now let it accelerate out of the buffet, but hold it just above the buffet, such that any little bump will cause it to buffet.

    Now initiate a turn, right or left. You'll note that if you really are on the bubble, and you don't add power, the airplane will stall, even with a mild turn. Now you're on it.

    Drive it around with rudder alone (hold the ailerons absolutely still), through some mild banks, adding power to prevent the stall, but just barely. Now try some steeper turns, rudder ONLY, to get the feel for what the rudder will do for you. Nothing wrong with using ailerons in real life, but this exercise shows you just how powerful the Cub rudder is, particularly in slow flight.

    I call it flying the bubble. You can call it whatever you want. It will give you a good feel for what the airplane feels like and sounds like and handles like at the very slow end of the speed range. That's what you want to develop: the feel, the sound, the handling..... BEFORE you get close to the ground.

    Do all of this at first while sorta noting the airspeed guage, but after a bit, you'll find that you really don't need it, cause the airplane is telling you everything you need to know. The critical instrument in this evolution is the altimeter, actually, cause you want to hold altitude. Now, then, cover up the airspeed, and do this again.

    If at any point in this regime you are a little slow on the controls, and the plane really stalls, relax the back pressure (as in DON'T slam dunk the stick) power to idle, and stop the rotation if there is any with rudder. Recover to level flight, and go back at it.

    High AOA flight is where you need to work to make landings work out, particularly if you want to work short.

    I think way too many people spend WAAAAAYYY too little time in airwork getting the feel of a plane before they start trying to land it, and as a consequence they never quite get it. Landing is a poor place to try to learn the handling characteristics of the plane.


    MTV
    Bravo! Bravo! Well said!!!
    Quidquid Latine dictum sit, altum videtur

  17. #17
    On Patrol's Avatar
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    MTV,
    Thanks for the great post. I whole heartedly agree with you in that my own tail wheel transition had little if any slow flight. The Landing was what it was all about. I will go fly the BUBBLE myself and then take George up.
    Once again thanks for the post.
    John

  18. #18

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    My helicopter airspeed indicator works every bit as good from forty down to twenty as my old conventional one worked from 60 down to 40. I did not anticipate it working so well. It is a predictable piece of equipment. It is very reliable on departure from 0 up.

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