PDQ2

Discussion in 'General Experimental Aviation Questions' started by lisa, Apr 23, 2018.

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  1. Apr 23, 2018 #1

    lisa

    lisa

    lisa

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    Hi Guys,
    About 12 months ago i purchased plans for the PDQ2 ultralight .The plans are very simple and straightforward,
    I have been obsessed with this aircraft ever since i saw this photo. Ultralight Second View.jpg
    My flying experience is limited to C172/150 and piper cherokee etc.The hight thrust line on this aircraft does not bother me as every aircraft has its quirks.My main concern is something that i have read about called pendulum effect i.e when in a tight bank/roll the aircraft wants to flip onto its back.
    Is this true?does anybody here have any experience with pylon mounted engines like amphibious planes etc to confirm this.Should i proceed with the build?did i make a mistake?
    I would appreciate any advice.
    oh forgot to add that my actually name is Matt,My acct name is because of my wife.
     
  2. Apr 23, 2018 #2

    Victor Bravo

    Victor Bravo

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    Welcome to HBA Matt.

    I have no experience flying the PDQ, however I have never heard of any serious handlung/safety issues with the design. The one issue that causes concern to many people (myself included) is that the weight of the engine, and the spinning propeller, are both right behind your head in the event of a hard landing. So it seems to me that when flying a PDQ it would be very wise to operate it off of relatively smooth surface runways without the possibility of large ruts or grooves that could bring the airplane to a sudden stop. The PDQ may actually be a better option today than it was in the past because there are many more engine choices that are lighter weight and better power now, thanks to the deveopment of paramotoring. There are numerous engines i the 20-30HP range that are lighter, more reliable, and more fuel efficient than whatever the original PDQ was forced to use.

    Definitely proceed and build the aircraft ! It is not an expensive aircraft to construct, and if for any reason you are not happy with how it flies you can "re-purpose" the engine and other components on another aircraft that may suit you more. One of the first questions I woiuld explore if I were you is whether the wings of the PDQ are identical or very similar to the wings of Wayne Ison'e later designs, MiniMax, AirBike, etc. If you would be able to re-use the main wings from a PDQ to construct a MiniMax or HiMax, then your "risk" building the PDQ is very low.

    I still think that building the PDQ is very worthwhile, if only because you will have made one of your dreams/obsessions into reality. That kind of personal achievement is what homebuilt aircraft are all about.
     
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  3. Apr 23, 2018 #3

    lisa

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    Thanks for the reply Victor Bravo
    From what i can see the c and d models of the PDQ2 are different from Wayne Isons later designs i.e no built up wing ribs etc, the fuselage if thats what it can be called, are simply welded aluminium tubing,simialr to an autogyro. My only concern with the structure is the landing gear is simply a flat bar of aluminium's therefore there is very little ground clearance and not much to absorb a heavy landing, my choice for engines being that I'm 100kg is going to be the half VW from Hummel aviation or the Hirth f23.The structure seems sound its more the handling of the aircraft in flight that worries me.
     
  4. Apr 23, 2018 #4

    Dana

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    Like VB, I've never heard of any particularly bad handling qualities of the PDQ-2 and like you, I've always thought it was a neat design. But... it was an ultralight before there were such things as ultralights. The prototype had to be N-numbered because there was no ultralight category back then. But... the technology comprising what makes a safe and useful ultralight has come a long way since the PDQ was designed back in the 1970s.
     
  5. Apr 23, 2018 #5

    BBerson

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    Pendulum effect slightly helps high wing stability. No effect on low wing. Not a concern.
     
  6. Apr 23, 2018 #6

    lisa

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    Thanks Dana,you are right many things have improved, but the overall look of this aircraft sort of has me hooked,if others with more experience than me can see or know that there will be no nasty surprises in flight,I will start building this month and post the pictures on this site.
     
  7. Apr 23, 2018 #7

    radfordc

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    I would be very concerned about hanging a 95 pound engine up on that mast behind your head. Find an engine that weighs 50 pounds and make it work.
     
  8. Apr 24, 2018 #8

    Cy V

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    That and the fact that there's a rotating prop just inches from the back of your head. What happens if you have a forced landing and that mast breaks? Does the prop turn your head into hamburger? I'm a huge fan of the Mini-Max line of aircraft, but this is one of Ison's designs that I would probably take a pass on.
     
  9. Apr 24, 2018 #9

    Riggerrob

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  10. Apr 24, 2018 #10

    Aerowerx

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    Then build an Aerosport Rail. Twin engines in a pusher configuration.
    Aerosport Rail.jpg Aeorsport Rail 3 view.jpg

    And why is the PDQ any more dangerous than the myriads of other pusher ultralights?

    What is the maximum G-force that a human can survive? Then design the engine mast to fail at twice that, then it wouldn't matter would it?;)
     
    Last edited: Apr 24, 2018
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  11. Apr 24, 2018 #11

    TFF

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    Most rear engines would have to travel through some structure instead of a simple pivot if the craft got smacked by the ground. That and ending up on your lid. Personally ditch the prop and put two small jets on the wing.
     
  12. Apr 24, 2018 #12

    Beragoobruce

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    The pendulum effect requires greater mass below the vertical centre of lift than above it. With a light engine, I'm guessing there will be slightly more mass below the wing on the PDQ than above, so this shouldn't be a concern.

    But I would be looking to fit as light an engine as possible - defo not the VW. Maybe the Pollini Thor?

    I bet the PDQ is a really fun plane to fly. Who needs a horizon reference anyway?:)
     
  13. Apr 24, 2018 #13

    lisa

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    Thanks guys for all your advice, id reply individually but we would be here all day,I have looked at the aero sport rail and even the mitchell wing p38 which i also love but unfortunately there are no plans i can find otherwise i would build the p38 instead, everyone is correct about the danger of having the engine sitting behind the pilots head but being 100kg i don't think the polini engine will get me off the ground, the half vw and hirth f23 are quite close in weight once muffler psru etc are fitted.

    Again,thanks for your replies and advice, its really appreciated.If i can't get plans for the rail or the p38 i will go ahead with the pdq2.
     
  14. Apr 24, 2018 #14

    Victor Bravo

    Victor Bravo

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    Have a trained engineer calculate the actual real-world failure load for the engine mounting mast, with three different engine weights.... half VW, Polini Thor 250, and F23 Hirth. With that information, then have that engineer determine whether there is a useful purpose in strengthewning the mast, adding more wire bracing, or adding tension/compression struts to the engine mount. The real, actual, calculated numbers MAY tell you that Ison already did that math and you will be dead before the engine hits your head. Or those numbers may tell you that the only way to save your scalp in a hard landing is if you added some amount of steel tube struts to the mast, making it an engine pylon instead of a mast.

    If the numbers and the engineering realities work in your favor, you might learn that the lighter weight of the Polini, and another three pounds of steel tube, will give you a reasonable safety margin.

    The Polini comes with a gearbox or reduction drive built into the engine,a nd it may very well provide enough thrust. Remember, you have a small maximum propeller diameter on the PDQ, and you may not have enough room for a propeller that is correct for the half-VW.
     
  15. Apr 24, 2018 #15

    Dana

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    The original engine for the PDQ-2, IIRC, was a Rockwell JLO, which evolved into the Cuyuna 430 and later the Cuyuna ULII-02. Cuyunas are still readily available used and parts are plentiful and cheap. I really like half VW engines, had one on my Fisher, but they vibrate a lot which might not be so great up on top of that pylon.
     
  16. Apr 24, 2018 #16

    Aerowerx

    Aerowerx

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    What about the Belite Skydock?
    7-19-15-960-Belite-SkyDock-PR.jpg
    Engine in the front.

    What is the status of this? The last update on their website was 2 years ago.
     
  17. Apr 24, 2018 #17

    Dana

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    Last I heard, the prototype and design rights were for sale.
     
  18. Apr 28, 2018 #18

    fmartin_gila

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    Another one you might check on from the same era is the "Monofly". Generally the same type as PDQ, slightly different construction.

    Fred
     

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