Even though most TPQs were conducted from around 14,000 feet, the accuracy of ASRT-B was phenomenal. When new personnel arrived at Khe Sanh, they were given several check drops on a nearby hill to test their proficiency before the newcomers were allowed to conduct strikes near friendly troops. The first drop was always within 40 meters of the target and, after they adjusted there was virtually no error. Calibration drops were also conducted twice weekly to ensure the accuracy of the equipment. One member of the FSCC stated that, if he were in a foxhole and under attack, he would have no qualms about calling an ASRT-B controlled TPQ within 35 meters of his position. The rule of thumb which the FSCC generally applied when determining a safe distance for normal operations, however, was one meter from the friendlies for every pound of conventional ordnance being delivered. Thus, for TPQs, a 250-pound bomb would not normally be dropped within 250 meters of Allied troops, a 500-pounder within 500 meters, and so on. This criteria was not established because the men on the ground lacked confidence in the system but because of the large fragmentation pattern produced by the bombs. Besides, anything inside the prescribed radius could be handled just as effectively by artillery, mortars, and direct fire weapons. In an emergency, the regimental commander would have undoubtedly lifted the restriction. Concerning the quality of support he received from ASRT-B, Colonel Lownds said, "Anything but the highest praise would not be enough."(149) [Illustration: A-6 Intruder, under TPQ control, provides precision bombing around Khe Sanh despite poor weather. (USMC Photo A422000)] [Illustration: B-52 Stratofortresses flew strikes daily in support of the 26th Marines. (Photo courtesy USAF)] In addition to its accuracy, the TPQ system was extremely flexible. A strike could be programmed and executed within 10 or 12 minutes utilizing any available aircraft. Most of the missions were at night when it was inefficient and dangerous to conduct dive-bombing strikes. As a matter of routine, two Marine and three Air Force flights were scheduled every hour unless an emergency developed. On 18 February, ASRT-B set a new squadron record for a single 24-hour period by controlling aircraft which delivered 486 tons of ordnance on 105 separate targets. After that, the record was approached frequently but never broken. During the siege, ASRT-B controlled 4,989 TPQs in support of the 26th Marines.(150)