!!!WALL OF TEXT ALERT!!! (but spoiler free)
I've battled the chopper and won twice now because the first time I was captured by the Special Forces (SF)
and wanted to unlock the SF Uniform at the end of the game. This solution is intended for those who want a fairly easy method and want to know
EXACTLY how to do it.
BackgroundThe location you want to use is the canopy over the picnic area in Leisure Park (on your map it's just west of "Jill's Sandwiches" (P104) in Paradise Plaza). You can jump onto the roof without the need to stand on a zombie's shoulders and you'll use this frequently in following this solution. The chopper will fly in a figure of 8 pattern, pausing to turn towards you (often out of site behind trees) and then quickly flying at you while firing it's machine guns. Every few "laps" it will stop for a longer duration to fire rockets at you. Both times I battled the chopper I was carrying 3 books (Criminal Biography, Entertainment & Skateboarding), Real Mega-Blaster (RMB), Small Chainsaw (Clownsaw), 2 Sniper rifles and 5 Orange Juices.
RecommendationI would recommend the Sniper Rifle personally and I can't snipe to save my life in any game. Stand on the canopy and watch what the chopper does. When it flew at me I dropped off the canopy and used it to block the bullets while taking out nearby zombies with the Clownsaw. When it stopped to fire rockets at me I was getting between 3 and 5 shots with the sniper, again using the canopy to save me from the rockets. I didn't check how many shots it took but I didn't need more than the 2 Sniper Rifles.
ThoughtsI have no idea whether leaving Leisure Park to stock up on ammo/food and then returning resets the health of the chopper when you return. The 2nd time I took it out I entered Leisure Park and didn't leave till it was flying away with it's tail on fire (take a picture if you like)
What I did the first timeHaving started off using the Machine Gun I quickly abandoned it as a pain in the ass. I fired about 170 shots of the RMB but the chopper was still flying around so I headed to the Hunting Shack in the North Plaza and grabbed the 2 Sniper Rifles and went back to attack it again. At this time I was still trying to shoot the chopper (from the picnic area canopy) while it was flying around or obscured by trees. I used up all my sniper ammo and was left with only the RMB so I carried on shooting. After about another 60 shots I finally took it out (and then got captured by the SF).
Map Link - in case you're interested