if a plane flys fine and level and then when you go inverted it heads down to the ground what is the problem and how do ya fix it?

what type of plane is it. some planes dont like flying upside down. it is normal for a plane to need some down (on tx) elevator to keep it level.
it may be a little nose heavy? (not sure on that)
try flipping it upside down and seeing where it balances

That's normal for any model but especially for a flat bottomed wing. A fully symmetrical wing section will minimise this but will still need a slight amount of down elevator to fly level. With a flat bottomed wing (pure lifting section) you could find you'll run out of down elevator travel and still head for the ground.

Could be CG or other issues. Could even be normal some planes. Knowing the type of plane might help.

sorry should have told that its a sky raider machII

When you are flying straight and level, your plane is generating lift to hold it up in the air. When you flip inverted, that "lift" is being generated toward the ground. So applying down elevator is perfectly normal. How much depends on the plane.

Nothing is wrong.

For a plane to fly, it must create lift. The angle of attack of the main wing and the shape of the main wing work in concert with the air speed to create lift. The angle of attack is adjusted in flight by the elevator. The elevator must counter any additional nose weight the plane may have, depending on how its balanced in order to maintain this correct angle of attack.

For a plane that is trimmed for normal flight, you create a stable situation where all the forces of lift exactly counter the forces of gravity, Depending on the plane, this is normally a level attitude.

Now invert the plane. You have completely changed the forces of lift. The angle of attack must be adjusted back to the static condition. This normally requires some down elevator to bring the nose back up. You could trim the plane in this condition if you so desired, but when you go back to normal flight with all that down elevator - guess what happens!

A symmetrical air foil will reduce this tendency, as the angle of attack adjustment is normally very small. For a flat bottom wing, the adjustment will be much bigger since the difference in lift is so much greater.

For a neutrally balanced plane, the adjustment will also be smaller as there is less elevator adjusting for the nose weight. Thats why aerobatic planes have symmetrical airfoils and are neutrally balanced.

Brad

A normal part of flying a properly trimmed aircraft, one that has the CG set right, or slightly nose heavy ( whether that's called forward or rearward), will most likely result in a little up elevator trim to keep it flying level with the plane upright. All of mine do, but I tend to keep the CG slightly nose heavy.

When going inverted, this results in a few things happening. bkdavy spelled it out for you. Gravity works and so does trim. Trying to keep the nose level in upright flight results in pushing the nose down in inverted flight because now, you are not working against gravity, but with it. So, pushing a little down (now remember.. stick wise, up is back and down is forward so pushing means push the stick forward a bit) will pull the nose back up for level flight when inverted. You don't trim for this, you hold this because, sooner or later, hopefully , you will return to upright flight.

Some planes take less up to hold inverted than others. Rarely will you find one that needs no up to hold it straight when inverted, but some report that they have. I find that a tad bit dubious.. come on.. not even a little teeny bit of up?

Some of the tougher ones to fly inverted are the high wing high dihedral trainer aircraft. The wing shape tends to fight inverted flight. It's not impossible, but it takes a bit more control to keep them inverted for any lenght of time.

CGr.

Everything said above is true.....When you set CG by the instructions that is a starting point....how much you have to "push" or give down elevator is up to you....You can slide CG aft no more than an 1/8 of an inch at a time....this will lessen the amount of "push" you will have to have......BIG CAUTION NOTE as you slide CG aft the airplane will become much more responsive especially in pitch to the point it just won't fly....Therefore if the amount of push is not excessive leave CG set where it is.
Good Luck

This is sooooo true. That CG point can be a very touchy adjustment, so if you are going to do any changes to your CG, do it in very small increments, put it on your CG machine and record what you did. Mark the wing with a marker (even a sharpy can be wiped off with alcohol prep afterwards, so use something that you can see and that won't come off easily until you want to take it off).

Fly the plane, noting the behavior changes, especially pitch control.

Always remember that a nose heavy plane will fly. A tail heavy plane will fly once.

That is to say, to heavy in the tail.

Some prefer slightly tail heavy, and this is good for certain types of flying, but beginners to intermediate flyers should really aim for something that will still slightly dip the nose at extremes of the center of gravity point. Be very careful with this. Any real mistakes, well, you will fly that plane once. Landing it is quite a handful if it is to tail heavy. Trust me on this one.

LOL I don't know why but that hopefully cracked me up now. I just can't stop laughing. Sorry

Using Elevator too keep the plane flying level during inverted flight is normal. I think some planes, as mentioned, may need more that others.

Yes be very aware when changing the CG. Just for a stupid sample - when I first started flying my Stryker with the LIPO (way ligther) it was WAAAYYY tailheavy. It was pitch sensitive like crazy. In 1 minute of flight I almost crashed it nose first about 9 times (this is not a overstatement). Everytime I saved it a few centimeters from the ground - it was horrible. I did manage too bring it in where I want too and put it down (WITH A LOT OF TROUBLE AND EFFORT) on the grass.

I know it two way different planes, but just saying the CG plays a big role when flying.

thanks for the help i have a pulse xt and it flys great inverted but the mach 2 doesnt and i thought there was a problem but obviously just because of two different type planes!

There are other factors that could help. The easiest to change is CG. You can try moving it back. Just be careful and go alittle at a time or you could end up with an unflyable plane. Even with aerobatic planes a slight amount of down is usually necessary for inverted flight.

Most guys have way more control surface deflection built into their planes than what is necessary to be fully aerobatic. This is why moving the CG back seems so scary to so many pilots. If the controls are first set [mechanically, not electronically] to allow nothing more than what it takes to be functional, then rearward CGs [up to 35% or more] are no big deal to explore. Most conventional models that aren't too heavy fly great at around 28-30% and will fly without too much heroic input inverted even with assymetric airfoils.
Once you get your CG dialed in, then expore more control throw if the plane isn't aerobatic enough for you.
Published CG locations are just a starting point.

It's nose heavy. The way I trim my Sky Raider Mach II's is to climb at a 45 deg. nose high attitude, full throttle and roll it inverted. What does it do? If it wants to head for the deck quickly then its nose heavy. If it wants to start a gentle ark the CG is set correctly, and if it wants to start climbing it's tail heavy. I have yet to have a Sky Raider Mach II that hasn't required some weight in the tail, regardless if I power it with a Super Tiger GS-40 or OS .46 AX.

You can shift the CG by moving the battery pack or adding some lead to the tail. It shouldn't take much lead to get it to balance correctly. If you add lead, add a 1/4 ounce at a time and it won't take long to find the CG where the plane is a happy camper.

Hogflyer