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Old Mar 10, 2013, 07:26 AM
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Joined Jan 2012
7 Posts
Help!
balsa pusher take off issues

Hey my name is jake i have built a balsa twin boom pusher and recently took it out for its maiden flight. after balancing i tested all control surfaces and then powered up to take off. it didnt take off at first so i turned it around and tried again. this time i gave it more power and pulled right back on elevator but only took off a few inches before i ran out of room so i turned off engine and it suddenly climbed a few meters then stalled and crashed. not to much damage but i was wondering if anyone could tell me if its possible that this is due to the pusher engine angle of attack holding the nose down and wen i have killed the engine it has still had enough speed to take off. any info would be much appreciated.
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Old Mar 10, 2013, 06:12 PM
Registered User
United States, KY, Taylorsville
Joined Mar 2010
1,695 Posts
your engine thrust line is off. If front of engine tips down when installed on nose then it should tip up when installed on tail end of wing. I put pics here as a shameless way to let you know I speak from experience!
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Old Mar 10, 2013, 06:26 PM
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Kimber's Avatar
USA
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Like this:

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Old Mar 11, 2013, 06:15 AM
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Joined Jan 2012
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thanks guys i will adjust it and give it another go. also what degree pitch up would anyone recommend.
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Old Mar 12, 2013, 02:47 AM
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nemoskull's Avatar
United States, AZ, Yuma
Joined Sep 2009
2,783 Posts
i say start with zero. that should give a tendency to climb at higher throttle. adjust from there .
just my .02
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Old Mar 13, 2013, 01:15 AM
plane crasher extrordinaire
microairman1's Avatar
United States, IL, Waukegan
Joined Sep 2012
509 Posts
is your prop on the right way?the numbers should always point towards the front of the plane even on a pusher.
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Old Mar 13, 2013, 10:59 AM
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Blacksburg, VA 24060 USA
Joined Feb 2000
3,217 Posts
On the other hand, you may find that the engine is properly positioned, but you have to be conservative on applying power for take-off. For a pusher you can't use the same take-off procedure that you use for a puller-engine set-up.

If you are flying from grass, try applying full power until the airplane starts to move. Keep plenty of up-elevator. Reduce power a bit. If the airplane is now rolling along well, apply full power and try reducing up-elevator, to prevent a stall.

If you are flying from pavement, apply lots of up-elevator and gently apply power. As the airplane builds up ground speed, apply more (or full) power and less up elevator, being careful not to let the nose pitch up into a stall.

If that doesn't do the trick, then change the thrust angle as others have said.

Jim R.
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Old Mar 15, 2013, 09:53 AM
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Rickochet's Avatar
Central Kentucky
Joined Oct 2006
3,559 Posts
Maybe try a hand launch and see how it flies.
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Old Mar 15, 2013, 10:31 AM
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Blacksburg, VA 24060 USA
Joined Feb 2000
3,217 Posts
Having learned from bitter experience, hand-launching a model with a pusher motor is also tricky. With the typical high thrust line of a pusher set-up, application of full power on launch will nose the airplane into the dirt. I've seen this happen with other pilot's pusher airplanes, where the motor was mounted on a pylon high above the rest of the airplane.

This is the set-up of the Dynam Skyhawk. The motor is mounted on a pylon high above the rest of the airplane. The proper hand-launch method was to apply about half-throttle (I made a guess), then launch the airplane with the nose slightly elevated. If the throttle setting was sufficient to get the airplane flying, I then carefully increased the power for a good climb. If, on launch, I pointed the nose too high, the airplane stalled and crashed; too low, before I could grab the throttle and increase power, and the airplane self-landed.

I was never comfortable with that airplane.

Jim R.
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