Destroy the heli's

The  task is a storyline mission featured in S.T.A.L.K.E.R.: Lost Alpha.

"Thanks for coming, Marked One. We've been caught off-guard by this attack. Damn these mercs; they've gotten the big stuff out! Is this retribution?! Anyways, Arnold was up on the water tower with the RPG, but he bit the dust. Please, take the choppers down while we hold them off here! I'll mark his last position on the map the RPG is all yours."

- Petrenko

Overview

 * This is a three part mission that involves finding an RPG-7u followed by the elimination of two airborne threats.
 * Returning to Petrenko afterwards will conclude the mission.

Known issues

 * As has been repeatedly noted here and at GSC forums, some players experience the "invisible heli problem."
 * There is a straightforward workaround for this that involves:
 * 1) Making a convenient interim save.
 * 2) Entering the game options screen and setting the visuals to "Static Render."
 * 3) Exiting and restarting the game from the save point.
 * 4) Complete the task and save again.
 * 5) Revert any render changes, exit and restart from the second save point.

Trivia

 * The weapon may be sold back to Petrenko for around 12500 Ru in v1.3003 (early patches had him paying around 25000 Ru)
 * (v1.4007) The RPG-7u can no longer be sold, repaired, nor upgraded in any way.
 * There are a few other OG-7vs on a parapet high up on the tower, but the five found in the Military Scrapyard in Yantar are far easier to preposition.