1. Find an empty server with the map VNTE-Quang Tri. Start as North Vietnamese RPG role.
2. Go to H5 and drop the RPG with back space key.
3. Switch to ARVN team and pick the commander role.
4. Go to where you dropped the RPG and pick it up.
5. Use your binoculars to put a mark on the pillar of the fence across the street. This guarantees that the bomber plane will fly exactly aligned to the street from North to South (refer to the video for the exact point).
6. Call in the Napalm bomber plane per radio, after you get the confirmation cancel the attack. This way you don't get hit by the Napalm and the cooldown for the next plane is reduced to 1:20 minutes.
7. Quickly go as close as possible to the pillar where you put your mark and listen to the sound of the approaching plane. Aim in a 90° angle at the sky and blindfire when the plane is almost exactly above you. There is some luck and much timing involved, so this might take some tries, but it is much easier than trying to aim at the plane with the ironsights of the RPG. I shot the plane down on my third try, so it's no rocket science, no pun intended.
8. If you are succesful you will get both the “A spad time” and “Triggernometry” achievements. Godspeed!