chic
Joined: 12 Apr 2019
Posts: 55
Location: Riverside Calif
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 Posted: Wed Mar 31, 2021 10:25 am Post subject: Thrust line (posting for a friend) |
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Hello chic.
Would you mind posting this message for me? I seem to have lost my ability to get replies in although I receive the digest. Thanks.
What you said is absolutely true about pointing the thrust line down. Maybe most pusher owners know this but I didn't and I didn't think it was intuitively obvious that pointing the thrustline down would add up thrust.
When I purchased this pusher with an 80 horsepower 912, both the owner and the builder said that it had issues with an inability to trim at high power settings and difficulty in rotating on takeoff without easing off on power. They thought I should be going back to a lower powered engine.
I looked at it and thought the engine was pointing down too much and so raised the thrust line to compensate. That caused so much back pressure on the stick that I could barely complete the flight even with full up trim. It was then I started digging around to find out how things really worked and the best source of information aside from a couple of people who knew what was going on, was at model airplane sites which had good diagrams showing the effect of thrust line relative to the centre of gravity. This got me adding down thrust and I now have, after about a 6 degree change, an aircraft where I can go from low-power to full power with no change in trim on the stick.
Mine was the first and maybe only one with a 912. Aircraft is a Skywatch.
Peter
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