In reference to the patent: US6089502 , Boeing's patent on the Raked Wingtip
I'm struggling to understand how this patent is legal. When I went through the process of getting my patent, I was taught that only a device can be patented, and that it is not legal to patent an existing device to use on some "new" thing. In other words, I cannot patent the use of pneumatic tires on cars that are manufactured after 2020. While I could claim that this is completely new and novel, in that, so far no one has ever put a pneumatic tire on a car manufactured after 2020 (as it is presently only 2017), the device of a pneumatic tire has already been invented. I cannot patent this "new" use of the existing device.
Patent #US6089502 is a Boeing patent on the raked wingtip device. The earliest example of the raked wingtip I know of was used on the Rumpler Taube aircraft as far back as 1910 (an example of which hangs in the Boeing Museum of Flight). In the past 100 years, there have been many other implementations of raked wingtips used on aircraft. I don't understand how Boeing can patent the invention of putting a raked wingtip on a new airplane that flies at transonic speeds. It's the same invention used on the Taube, but used on a "new" airplane that flies faster. To my understanding, this is not a patentable invention. Am I missing something here?
How did Boeing get this patent granted, and how is this patent legal, or enforceable?