I have a gas Frigidaire range with convection. Burner is on the bottom of the oven (shielded, you can't see the burner). 30 inches wide. Came with two racks, some versions came with three racks. If using racks at positions 1 + 3 or 2 + 4, no problems with burning with fan on. If using 3 + 5, the lower rack is awfully close to the bottom of the oven (with gas burner on the other side of the bottom plate) and probably even the fan can't compensate for the short distance. I avoid 3 + 5 and use either 1+3 or 2+4. Even then, if I bake cookies on both racks at 2+4, the lower rack seems to be done 1.5 minutes before the upper rack. Nothing burns, but you have to watch closely through the window and be aware that cooking times may still differ, based on rack placement, even with a convection fan. What the fan seems to be great at doing is preventing hot spots along the sides/front back, so that cooking is even on a large tray of cookies, regardless of each cookie's position on the tray.
I have baked four pies at once, using 1+3 or 2+4, with excellent results. Again, the lower pies on 3 or 4 will finish a few minutes ahead of 1 or 2, but it's easy once you "learn" the oven's idiosyncracies. With my old non-convection range, nothing cooked evenly unless I baked only one pie at a time.
