In the final area of the second part of the mission, you can rescue the injured pilots as a bonus objective. However, instead of waiting for the lamp to flicker on and off to get past the tank safely, there is an easier way. Make sure you have a frag greanade (obtained elsewhere in the level). Go to the very top of the scaffolding and take out the frag grenade. Aim the grenade to go in the hatch of the tank. If done correctly, the grenade will explode in the tank, which will destroy it.