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Thread: p factor in 912 Blade

  1. #11

    p factor in 912 Blade

    It's pretty standard with all trikes with high torque motors like the 912 and more so with the S.
    Blade was first trike to be fitted with a 912 so misses a few tricks to calm this down. The connectionbetween trike and wing is not stiff in the yaw axis, so both elements fly
    Rather independently of each other leading to relative yaw which adds to
    The effect on the ensemble.

    But it's not really a problem - you get used to it and quickly forget it. But moving from a two striker exacerbates the strangeness at first as the torque is reversed in direction. First few flights are difficult to stopgently
    Turning - you have to calibrate to the slight wing down required and the offset of trike to base bar centre.

    Having said that check that nothing is bent - we had a gt450 in last week for work and the owner complained that it flew unusually skewed, and
    It turned out to have a twisted pylon.

    Paul

  2. #12
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    p factor in 912 Blade

    Pauls comment. "But it's not really a problem - you get used to it and quickly forget it. " probably applies to 90% of the current 912 fleet.

    I cant understand why for over 10 years everyone accepts that Blades are subject to big torque effects when high revs are used. Every year they get a check flight many of them having an alarming tendency to try to screw you into the ground on take off without any inspector mentioning it to the owner with a suggestion they fix the problem. This can be fixed with a little effort and it makes them so much nicer to fly.

    As has been pointed out the 912 engine on the Blade has to torsional adjusting engine mounts which can be used to "trim" out the effects of Prop torque.

    But first things first before you dive in without understanding what involved.

    First job is to check the seat frame has not moved of center if it has fix it.

    Next is a test flight to see how much torque your generating and in which direction. Measure off the center of the base bar and mark it with a piece of tape. Full power climbout and its probably moved 3 or 4 inches to one side probably the left but your probably holding on to the bar too tight to stop the plane turning to get a good view.
    Go to level flight and check where the bar mark is. Power off glide and the bar is probably somewhere close to the middle. While in the glide go to full power and the bar probably moves 3-4 inches to the left and stays there as you transition into climb.

    My bar moved left if I remember but its a long time ago now so make your own observations.

    Understand the Bar APPEARS to move left under power but actually the TRIKE is swinging to the RIGHT... and as we fly a weightshift guess what happens.

    So .. we have to move the thrustline of the Prop to push the trike to the left under power. In effect this means moving the rear of the engine (propeller) to the right.

    Lengthen the left bar and shorten the right bar looking from the rear (Prop) I suggest in 1/4 inch stages for each adjustment then go test fly and check the result.

    IMPORTANT make sure theres plenty of thread left on the bar you lengthen on the adjuster - having it come apart in flight would spoil your day and invalidate your results.

    My bar now moves about half an inch to the left when applying full power suddenly. I haven't cured the slight tendency for the bar not to be truly square to the trike but probably a new hangbracket and spacer would tighten things up a lot.

    The advantages of setting this up properly are numerous. Hands off climbout on full chat! Suddenly chopping power on roundout doesn't introduce the dreaded blade Ying Yang effect. Powered steep left hand turns are now easy while right hand ones dont end up as a spiral dive - what more can you ask for ... OK speed and maneuvering like a Quik but that aint going to happen .... its a Blade.

    PS forgot to mention that now your probably going to have to trim out the turn you have introduced with your fully adjustable tips if your lucky enough to have them or bending battens if you havent.

  3. #13
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    p factor in 912 Blade

    This actually affects the Blade 582 as well to a lesser degree. You do learn to live with it and ignore it eventually.

  4. #14
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    p factor in 912 Blade

    Not sure if you can adjust the 582 but if it can be fixed do it. The Blade is a totally different animal if you get rid of the prop torque.

  5. #15

    p factor in 912 Blade

    I sold mine because of the prop torque issue
    It flew fine two up but solo it was a nightmare so just sold it to a bigger heavier pilot than myself who as far as I know still has it and loves it

  6. #16
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    p factor in 912 Blade

    Quote.. I sold mine because of the prop torque issue
    It flew fine two up but solo it was a nightmare so just sold it to a bigger heavier pilot than myself who as far as I know still has it and loves it.

    Says it all really... Fixing the problem will probably take a couple of hours a few check flights and really is quite simple.

  7. #17

    p factor in 912 Blade

    I have greatly improved the flight characteristics of my 912 Blade by offsetting the engine 2.25 degrees counter clockwise (as viewed from top - down)
    I made two engine mount plates of 3/8" aluminum that rest upon the existing engine mount frame. I created a template that included the 6 engine mount bolt holes and the location of the exact center of the propeller. This was the most critical point as it functioned at the fulcrum for rotation of the 6 bolt holes. This was used to identify where on the two aluminum mount plates I needed to drill the 6 new holes. A bit of redrilling, fiddling and filing was necessary to make this work. When finished, the marriage between the cart and the wing is much happier. They actually want to fly along similiar paths now with less right cart leaning. Here's a picture to give you an idea.

    Karey Love

    Attached files

  8. #18
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    p factor in 912 Blade

    No need to make new engine mounts the blade 912 can be adjusted without modification.

  9. #19

    p factor in 912 Blade

    I first adjusted the upper motor mounts to counter the precession and P-factor without success, even after fully using all of the lengthening/shortening capacity. My new motor mounts did largely correct the aberrant flight characteristic.

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