SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Apr 21, 2012, 08:19 AM
Registered User
Joined Oct 2011
3 Posts
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
Sgt367 is offline Find More Posts by Sgt367
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 21, 2012, 02:23 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,838 Posts
What type of plane is it?? need more info...

Keenan
Keenan smith is offline Find More Posts by Keenan smith
Reply With Quote
Old Apr 22, 2012, 09:10 AM
Registered User
Joined Oct 2011
3 Posts
Its a flying wing design, no tailplane (I know, daft eh?), pusher prop configuration. Any general tips? Thanks,

S
Sgt367 is offline Find More Posts by Sgt367
Reply With Quote
Old Apr 22, 2012, 09:21 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,838 Posts
sounds like your cg is to far back
Keenan smith is offline Find More Posts by Keenan smith
Reply With Quote
Old May 06, 2012, 04:42 AM
Registered User
Joined May 2012
5 Posts
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
Jimmari is offline Find More Posts by Jimmari
Reply With Quote
Old May 06, 2012, 07:26 AM
Registered User
Joined May 2012
5 Posts
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
Jimmari is offline Find More Posts by Jimmari
Reply With Quote
Old Jun 14, 2012, 08:07 AM
Aero Engineer & RC enthusiast
United Kingdom, England, Bristol
Joined Jun 2012
6 Posts
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
jdogjennings is offline Find More Posts by jdogjennings
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! First Flight / ESC Failure / Crash Bonzer1 Hoverfly Technologies 3 Apr 07, 2012 10:28 AM
Discussion Bixler first flight crash Lpbug Beginner Training Area (Aircraft-Electric) 18 Oct 24, 2011 04:21 PM
Discussion my first FPV flight=first FPV crash, and first lipo gone. gundamnitpete FPV Talk 24 Jul 21, 2008 01:28 PM