I was checking out a newbies plane for its maiden flight. It looked ok on the outside and he had the wing on all ready. I started a range check and the ailerons would start to flutter at only 10 feet away from the plane. I told the new guy that this was bad and to shut down the radio and take the wing off because it wasn't safe to attempt a flight. I stood by just to see how the inside of the plane looked and when he lifted the wing the aileron connection to the receiver came apart!! I told him that the loose connection might be the problem. He put it back together and I checked it myself. Re-did the range check and no more jitters! Ran the engine up, adjusted it and did the took off. Now the plane climbs to about 30' and the engine suddenly dies! Managed to turn back and land safely even though it was very windy. The problem was the muffler bolts fell out!! At least the controls worked well and the range check helped make sure of that! The new guy was very happy that that I didn't break his new plane on the first flight! Me too!