Here's a bit advice that all you experienced pilots know but is good for the beginner to hear. I'm no longer quite a beginner but I'm darned well still learning. I maidened my Horizon Hobby Albatros biplane yesterday. Or at least I tried to. I inserted the battery and strapped it down with the provided velcro straps. I also have a S.E. 5a with the same velcro strap arrangement and I've never had a problem with the battery shifting. So I lined the Tros up with the wind, gave up elevator to prevent a tip over on the grass field, and slowly advanced the throttle. She accelerated nicely over the bumpy grass and suddenly lifted off before I expected her to. It was instantly obvious that something was badly wrong as even full down elevator wouldn't bring her to level flight. The plane had its nose high at the edge of a stall about 6' off the ground. Worse yet, it was heading toward the road where there was an oncoming car. I cut the throttle. The crash broke the bottom wing and snapped the landing gear and one of the wing struts. I found out later that the aileron servo on that side needs replacement as well. When I opened the battery compartment to disconnect the battery I discovered that the battery had slid completely out of the forward retaining strap and was about 2.5" aft of where it should have been. This of course moved the Center of Gravity aft producing a tail heavy situation and an impossible to fly aircraft.

After I got the pieces home I took a look at the battery compartment of the S.E. 5a. The rear of the battery compartment is closed so there is no way for the battery to slide aft. The back of the battery compartment on the Tros is wide open. I'm guessing that the bumpy take off run with the tail down was enough to make the battery slide aft. I have no one to blame but myself. I KNOW I should put velcro on the battery and the inside of the battery compartment. I've now added it to the Tros as I wait for parts to come in. It's cheap insurance that would have prevented the crash.

Storm

Yep, velcro hard mounted to the battery compartment holds the battery in place, while the straps hold the battery to the velcro.

That information should have been covered in your assembly instructions . Most of the electrics that I have had the pleasure of assembling and flying ,the batteries fit snugly in a pocket and cant move . I don't have a lot of experience with electric planes as I only have three so I am glad that you have posted this information . I will be careful to watch for that type of situation . In fact I think I might have one now . I just bought a Ultra Polaris and I noticed that it has a large battery compartment with just one strap . I don't have a battery installed in it yet or the balance figured out .. Good tip . Thank you I think when I have mine balanced I will fill in around the battery with foam as well as the velcro

Are they big batteries?

I'm only a beginner but I would of thought with a full tank of fuel a 2.5" shift in batteries wouldn't have such an adverse effect on the flight behaviour.

Still you live and learn I suppose.

Carl, It's an electric plane. The flight LiPo battery is 4"X1.25"X.75" and weighs almost 5 oz.. When it's in its correct location the CG is perfect. Move it 2.5" aft and the plane is tail heavy. Enough so that full down elevator wouldn't bring it to level flight.

Storm

Apologies, I assumed nitro.