Plastic Or Paper

Hi Everyone,

I've been a visitor to the forum for sometime, and finally decided to join. What a wealth of knowledge!

I have an Avistar Elite with an OS 46 and she's setup to all of the factory settings, but when she's fueled up she is very nose heavy. I learned how to fly with this plane, but due to it being so nose heavy when fueled I've bent the nose gear a few times! It is very hard to flair when coming in for a landing. More experiences pilots have flown her, and have made some suggestions. Some of those being that I should add weight towards the tail. If I do that and she gets low on fuel, then she will be tail heavy. Everything I've read says that is bad!

I would like to move the tank back towards the CG. Will this create a fueling issue for the engine? Will she go lean when climbing, and rich when diving? The tank would have to be moved back approximately 10 inches. So, the fuel will have to be delivered over a longer distance. What is the longest distance that I could place the tank from the engine? The engine has the standard Power Box muffler.

I sure do like they way everyone helps everyone else on this forum, and I thank you in advance for any ideas or suggestions that you have.

You Guys are the best!!!

JohnBuckner

My Feedback: (1)

Hi PoP please allow me to welcome you to the forum.

OK lots of varibles going on here and I suspect misinterpretation of things you may have read. First lets start with the fuel tank That tank will need to be snugged right up aginst the backside of the firewall as close to the engine as possible with the normal muffler pressure type of two line system which is what you have. Yes there are special (read expensive and cumbersome) tanks that can work on the airplanes center of gravity. That is not what you have so lets not muddy the waters yet.

Now while still on the question of the tank I have a question for you, very simple but very important one: What size tank are you using???

When the fellows tend to want to stuff oversize tanks in, some of these problems can occur. For any .46 sized engine there should be no need for anything larger than eight ounces. Unless you are planning a cross county airplane. When the fellows first start stuffing oversize tanks in a number of problems can rear its ugly head including CG problems and engine running problems. Use the right sized tank for this trainer and there will be no problems.

OK lets move on to the CG situation. First the place to balance the airplane at is in the middle of the range the manual suggests---OR--if unknown simple measure the distance from the front of the wing to the rear of the wing and divide this by four and this is the distance back from the front of the wing to balance level at. Many suggest that this should always be where the spar is and this is OK except the spar is not always at this 25% point especially with a semi semetrical wing.

Now we come to the part where I think you screwed up and why your ship is nose heavy. Notice in the statement above that this point is where you want the airplane to balance level at, Level being the key word. Too many folks will at this point always say not level but a little nose down for mother and country. Well when one does that what they have just done is not balanced at their target point but instead some unknown amount forward (nose heavy).

I would recommend you rebalance the airplane so that it actually balances level at the point your manual suggests or failing that the simple 25% method I suggested above.

John

RBACONS

My Feedback: (3)

You balance your plane with the fuel tank empty. If you need to add tail weight, that is fine. When you fuel up, you will be slightly nose heavy which is OK. By the time you land, your plane will be closer to optimal balance, but never tail heavy.

TomCrump

Why assume that the model is nose heavy ? I'd check for proper balance, as stated above.

If it doesn't flair, isn't is possible that there isn't enough elevator control ?

Moving the tank rearward, in a trainer, is not necessary. I'd look for other reasons as to why the nose gear is getting bent.

TomCrump

double post.

Plastic Or Paper

Hi Everyone,

Sorry it took a while to get back. Family's got me hopping!

Thanks for all of the valuable information, and responses.

John, it has the stock 8 ounce tank.

I'll experiment with the balancing. It's presently balanced to the recommendations from the manual. I have played around with the elevator throws.

Thanks again to all...

jaka

Hi!
C of G recommendations is just that: Recommendations. Move the C of G rearward slightly (5mm at a time ) and see what happens.

I

049flyer

My Feedback: (18)

Confucius Say "Nose heavy plane fly poorly, Tail heavy plane fly once!"

HighPlains

My Feedback: (1)

Confucius was not much of a pilot.

jetmech05

Empty the tank and balance per the instructions. Then make your throws per the instructions as well.
Go fly make sure in flight that you're trimmed correctly. How's the flair now? A nose heavy airplane won't want to flair but it won't want to slow down on approach either.

jester_s1

There are a lot of Avistars and Avistar Elites flying all around the country currently. 99% of them have the stock tank in the stock position and fly great that way.

What I'd like to know is why you believe the plane is nose heavy? Will it not flare for landing properly? Sluggish with elevator control? Elevator trim changes with speed? Something else?

On a trainer or sport plane, I skip the 25% recommendation and go straight to 27% of the MAC. Every time I've balanced at 25%, I've wound up moving it back anyway. But 25% is definitely a safe starting place for a new pilot with a new plane.