The Chainsaw is a long-range anti-air missile battery.
|Long-Range Anti-Air Missile Battery
|Vision Radius (elmo)
The Chainsaw is a long range anti-air turret, dealing out massive damage, able to knock bombers out of the sky very quickly. It can't take very much damage in return, though, and does poorly when attacked directly.
Tactics and Strategy
As far as AA defenses go, the Chainsaw is rather costly, but the cost is well worth it if your enemy is making heavy use of aerial units, as a single well-placed Chainsaw will efficiently provide protection over a very large area.
So large, in fact, that you may even be able to disrupt enemy aerial support operations with a well-placed Chainsaw. You can zone their aerial builders out of wreckfields, or out of their own forward positions.
The Chainsaw lacks burst power however, so you shouldn't count on it alone to protect high-value units: a large and willing group of enemy bombers or gunships can still penetrate the Chainsaw's range, take out the valuables, and escape with some casualties.
The Chainsaw is rather frail for its cost, and it itself can become the target of a large enemy air raid, so if such a thing seems likely you may want to protect your Chainsaw with a more durable AA turret, such as Razor or Thresher.
The Chainsaw requires line of sight to fire. Combine that with its immense range, and one quickly realizes that putting it in a high place is ideal, so that its range isn't limited by the terrain around it. Building it atop its own terraform pillar is worth the extra cost if it means it will be able to shoot over a critical hill.