My Drone is brand new but I had a bad prang and now my propellers are hitting the body after take off. The cross that holds all four motors is loose. Can I assume I have broken the cross frame? How can I confirm that this is what the problem is without pulling the whole drone apart?
Carefully peal the bottom cover off the AR Drone (2.0 I assume) and look to see if the frame is broken. It will be under the circuit boards, but if broken you will know. Order a new frame if broken, go to a tool store and buy a set of micro sized Torx drivers and Phillips head screw divers (Harbor Freight has these cheap). Do Not try to remove the Torx screws without the drivers, you will strip the heads if you use anything else. While at the store get some double sided tape too, you may need this to put it back together. On of the Torx screws will probably be glued, use a soldering iron to heat the screw head just a little, and that screw will come out easier. This is the screw at the back near the edge of the main PCB that has glue over some wire ends that were soldered to the board. The flex ribbon cables are easy to remove, carefully slide the black plastic locks out (not all the way out) and the ribbon cable will pull out. The down facing camera has a connector that will just lift off the PCB, do not crease that cable. Under the main PCB are two wire connectors, they pull out but do not tug on the wires to do this, pull only on the connector. The USB connector and battery connector will pull though the battery tray, but you will have to cut the tray sticker to make the hole bigger to get them though. Exacto knife will easily do this. On the sides of the Drone are four plastic covers around the carbon rod arms, peal these off and the frame will slide out of the body. Be careful with all the wires, take your time, take pictures so you know where it all goes back. Insert the ribbon cables fully then push in the locks. Before you put the bottom cover back on fire it up and make sure everything works, a quick indoor hover would be a good idea to make sure it fly's still. Then put the cover back on. DO NOT REMOVE THE FOAM FILTER ON THE MAIN PCB, that is the Baro sensor and it needs that to get proper altitude readings without freaking out from air flowing over it.
If it is an ARDrone, there are a few repair videos on the manufacturer's website (I think they're under the "Support" tab near the top of most webpages), and several done by owners on youtube. The owners' videos seemed more detailed, but I found the official video on how to swap out the PC boards good enough (I've been tinkering with electronics for many years, though). Ran
If not done already, definitely add some soft landing gear (zip tie mod, etc.) to it. It's pretty hard to break the central cross if you have springy landing gear.
