I have a Hobbico Sturdy Birdy II and the tail hangs low like it is tail heavy, but is actually a bit nose heavy. Any thoughts on what may cause this? It just flies along kinda dragging its tail, but seems to fly ok otherwise.

What engine are you flying? Are you telling us the plane maintains its altitude with a nose up attitude? That generally means you're flying slow, and approaching a stalled condition on the wing. Alternatively, your wing incidence may be off.

Brad

The engine is an OS .25 LA. Yes it was maintaining altitude, and come to think of it I was just putting along on the slow side. This was just before I landed it in a tree too. It didn't hurt the plane or the tree so I don't know if it qualifies as a crash. My first thought was that I was just flying too slow.

Thanks for the response.

The attitude of the machine in level flight is determined by the Angle-of-Attack of the wing's airfoil and the square of the airspeed, not the weight distribution.

Tail low level flight signifies too slow, either intentionally or inappropriate use of the throttle, or perhaps an improper incidence arrangement. Improper CG only effects stability.

Good point, Hoss. I recall when flying my WildStick 40 that I was coming in for an approach, and on turning from base to final, well, the tail was pretty high as compared to normal flight and the plane was wallowing along at the brink of control. My instructor was in the background (I had already solo'ed) and yelled to me to add some throttle. I added just a couple of clicks of throttle and it immediately responded by going back to a more normal AOA and the approach was much more crisp and the landing was perfect. But, at that turn, I was very close to dumping it in. It took me a little while to learn how to land properly and to be aware of what was going on during slow turns on approach, but I've never crashed one because someone took the time to remind me of what I was doing and helped me correct that bad habit.

DS.

I suspect the 25 LA is underpowered for this plane. Its essentially a commercial SPAD (Simple Plastic Airplane Design), and these planes tend to be a bit on the heavy side. According to the specs its a 4 lb plane (hopefully that number includes the engine). What prop are you using? How many RPMs are you getting. How much experience do you have with planes, and is there someone nearby (club or otherwise) that can help you out?

Brad

Set one or two degrees positive incedence in the horizontal stabilizers or shim the lower engine mount to give some positive thrust. No offense, but I never did like the Sturdy Birdy method of rubberbanding the engine to the frame. Too much "play" allowed.

The planes weighs about 4 1/2 lbs. all up. I am using a 9x6 prop, not sure of the rpms. I am a beginner and belong to a club, but not many people are out flying this time of year. This isn't my primary trainer though, I am flying a Goldberg Eagle II for the most part and it flys like a dream.

I don't use rubber bands for the engine mount, I screwed the firewall to the fuse. I also thought about adding some incidence to the horizontal stab. Today I will fly it a little faster to see what happens. I think I will probably just get a more traditional trainer fuse to put the motor and everything in though.

I know I'm way late here. Try centering or adjusting your ailerons. I have analysis flown tail heavy, being tail heavy won't effect level flight.

Hi stormtoad and welcome to RCU. Please do not be offended but I must differ with that statement. If what you mean by "being tail heavy" is having the center of gravity to far aft then that definitely will affect level flight. The airplane will become unstable in pitch and what will happen every time is something the engineering types call a 'pilot induced phugoid oscillation'. This oscillation is directly proportional to how severely aft the CG is and it can range from just unpleasant to completely uncontrollable.

John

Hi!
Agree with John!
30-35 years ago I test flew a new Little Tony Quarter Midget pylon racer (powered by a K&B 3,5cc engine) and had the C of G to far to the rear. It's flight described a vertical Sinus curve in the air that was nearly unstoppable.

I think most of what people have written here is correct, but if your plane is nose heavy you should correct that. A nose heavy plane requires a higher angle of attack to maintain level flight, so moving the CG back will reduce the angle at which your plane flies. That will reduce drag, because the bottom of the fuselage will not be creating as much drag, and the wing will have less drag. You might find the elevator a little more sensitive, but as long as you stick with the recommended CG it should be fine. You might want some expo, or slightly reduced throws, or you might just like it.

Also, I agree that an OS 25 LA is a little marginal for a 4 1/2 lb airplane, especially with a 9x6 prop. I would try a 10x4, or maybe a 10x3 if you can find one. Perhaps the best would be a 10x4 cut down to 9 1/2 and re-balanced. None of this affects the angle of flight, but it should give you more low speed thrust, which can help you out in a pinch, and reduce your take-off distance.

Jim

One more thing about props. Even just switching to a 9x4 would probably be better than the 9x6. A 10x4 is probably a little too much prop to be ideal for that engine. That's why I suggested cutting it down to 9 1/2.

Jim

Just wondering if he still fly's that thing, 10.5 years later....