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Old Apr 21, 2012, 08:19 AM
Sgt367 is offline
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Help!

First flight (and crash!)


Hi all,

I'm a Newbie, and yesterday my friends and I flew our plane we've been building for the first time. It seemed really keen to pitch up, even doing an impromptu loop, and after a few brief flights we had a particularly heavy landing, suffering minor damage.

We have repaired the plane, and are waiting for good weather to fly it again. But we're also trying to figure out why it didn't fly level? We taped more ballast to the nose after each flight, but it didn't seem to make a difference. The aerofoil has a reflex camber, should we modify that? It has a lot of thrust for its size, and I know in manned aircraft increasing the thrust tends to cause a pitch up moment, so maybe not taking off with full power?

I dunno, there are lots of factors affecting it. And I appreciate that every individual aircraft is different. I also appreciate that investigating problems, finding solutions, and implementing them is part of the intrigue and excitement of it all!

But if anyone had any tips on how to reduce this nose-up tendency, they'd be much appreciated. Thanks a lot,

Sgt367
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Old Apr 21, 2012, 02:23 PM
Keenan smith is offline
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was geht , müssen unten kommen
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What type of plane is it?? need more info...

Keenan
Old Apr 22, 2012, 09:10 AM
Sgt367 is offline
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Its a flying wing design, no tailplane (I know, daft eh?), pusher prop configuration. Any general tips? Thanks,

S
Old Apr 22, 2012, 09:21 AM
Keenan smith is offline
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was geht , müssen unten kommen
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sounds like your cg is to far back
Old May 06, 2012, 04:42 AM
Jimmari is offline
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Hi There..Just joined my interest is in tricopters..but I have built and flown all sorts of aircraft for more years than I care to remember.. Currently I am using a flying wing so here goes. As a previous member indicated the most likely cause is incorrect centre of gravity. If it is looping on launch try moving your cg forward from where it is. Check also that your motor is in line with thrust line as it may also be pushing the nose up. Let me know results..Regards Jim
Old May 06, 2012, 07:26 AM
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Hi there again..My appologies re cg I gave you duff info..If wing is looping you need to move cg further BACK from where it is...thats defo..sorry for confusion...My Tricopter is driving me crazy Cheers Jim
Old Jun 14, 2012, 08:07 AM
jdogjennings is offline
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Aero Engineer & RC enthusiast
Jim was right the first time, you need to move your CG forward towards the nose. I think those tricopters might have taken their toll.

The effect of the 'flick up' at the rear of a reflex airfoil is to provide a little negative (downward) lift much like the horizontal tail on conventional aircraft, this negative lift provides a positive pitching moment (nose up), which must be countered by having the CG a sufficient distance forward of the wing's neutral point (aerodynamic centre).

I'm afraid this is more than likely going to be a trial and error affair. That is unless you fancy getting stuck into some calculation. If you do, there are 2 books that I recommend; Flight Stability and Automatic Control (R. Nelson) and the more simple Principles of Flight for Pilots (P. Swatton)

Also, if you think it has too much thrust, I would put a lower pitch prop on, temporarily. (walk before you run)

I hope this helps and if you need anything else just ask.

Good Luck and Happy Flying


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