Newbie Helipad Question

I'm new to this game but I've laboured all afternoon without posting any stupid questions, so I guess it was too long to last! :)I've made a helipad in Airport v.3.00 and everything works fine apart from one thing - when I look at the helipad, the texture of the helipad keeps kind of 'flashing'. Would someone mind having a look at the attachment and telling what stupid mistake I'm making?I don't understand how the layers can be interfering with each other, because they're at different heights (about a foot each).Any ideas much appreciated!Tomhttp://forums.avsim.net/user_files/52098.jpg