Note that the problem only occurs with the original UA engine executables. OpenUA (UA:Source) does not have this problem.
1 Overview
1.1 Signs & Symptoms
AI Helicopters do not obey orders, have problems with moving and turning, and do not track or follow targets properly. They are often unable to shift directions other than upward or downward, and when ordered to move they may uncontrollably gain altitude at the spot. It does not affect the control interface under the direct first-person mode by the players.
1.2 Technical Causes
The problem is caused by a threshold check in the engine code that processes AI helicopter rotation as found out by user Zidane on the forums. When an update time period gets short enough, which frequently happens on modern computers and hardware, the threshold condition is never fulfilled and therefore AI helicopter rotation is not processed correctly.
1.3 Workarounds
Various workarounds exist to mitigate the problem; but only one method is recommended nowadays for rectifying the glitch. See below.
2 Solution
2.1 Using the Helicopter-patched game executables
A new Helicopter Patch file with updated game executables was created by user Zidane. This patch is flawless and has no drawback unlike the other legacy methods. It should provide a definitive solution to the problem once and for all.
Direct download link for Helicopter Patch:
2.2 Important Note
If you are still using any helicopter patch made before 2016, specifically any fileset that replaces *.scr (script) files in the game's data folder, then please remove it from your machine as soon as possible. These outdated patches will not only work on modern hardware, but they will also detrimentally alter the helicopter data and properties, which will greatly impair the physics and performances of the helicopters. Moreover, since they are technically modified data, the game will detect those files as cheating on multiplayer matches. Therefore please delete any outdated heli-patch files beforehand!
If you are uncertain whether your game files contain any modified helicopter data or not, the new Helicopter Patch file also contains the fully original and default game data script files, which you can apply into the game's data folder.
3 Historical Methods
There were several legacy methods used to circumvent the helicopter bug in a primitive manner. However, since the new method offers a complete solution without any drawbacks, they have been removed to avoid confusions for now.
