Neither the deluge of lead from 881S nor the suppressive fire of the jets and gunships kept the NVA completely quiet. The 120mm mortar crews in the Horseshoe were especially active during the resupply runs to 881S and always lobbed some rounds onto the hill in hopes of knocking down a helicopter. These tubes had been previously registered on the LZs and the smoke screens had little effect on their fire; as a result, the Marines frequently shifted landing zones.[43] The smoke did block the view of the North Vietnamese machine gunners and they were forced to fire blindly through the haze--if they dared fire at all. The choppers still took hits but nowhere near as many as before the Gaggle was initiated. The CH-46 pilots, poised precariously above the LZs during the few agonizing seconds it took to unload their cargo, often heard the sickening smack which meant that a bullet had torn into the fuselage of their thin-skinned helos. The members of the two-man Helicopter Support Teams (HST), 3d Shore Party Battalion who were attached to the rifle companies were also prime targets. These men had to stand up while they guided the choppers into the LZs and, every few days, they had to attach bundles of cargo nets, which accumulated from previous missions, for the return trip to Dong Ha. This was dangerous for the aircrews as well as the HST men because, during the hook-up, the pilots had to hold their aircraft in a vulnerable position a few feet above the ground with the nose cocked up and the belly exposed to fire from the front. While they attached the bundles, the ground support personnel could hear the machine gun rounds zing a few inches over their heads and slap into the soft underside of the suspended helicopter. Not all the bullets and shell fragments passed overhead; on 881S, the defenders were operating with their fourth HST when the siege ended.