Quick question. In the 747, is the spoiler and the speed brake the same thing?
How do you arm the spoilers in the 747?
Yes they are. They are operated by pressing / and armed by pressing SHIFT + /
Spoilers are deployed right after touchdown and they create more drag. When you are in the air and you deploy your speed brakes, which is the same as spoilers, as Jon said, the aircraft will slow down.