The following information is courtesy of Frank Rozendaal.
Source: Summary, Air Operations Southeast Asia, HQ PACAF, Vol. XLII, January 1968

Preview 1, a single EB-66, was launched for a selective jamming mission in support of an afternoon strike mission in Route Package VIA. The orbit point was approximately 50 nautical miles WNW of Than Hoa near the Laotian border.

The 7AF CC first became aware that Preview was down at 1805H as a result of beeper signals reported by Crown aircraft. Later checks revealed that no GCI sites or Ethan Allen aircraft had received distress calls. Other ECM aircraft had made calls to Preview without receiving a response. SAR activities on the day of the downing were restricted due to adverse weather and approaching darkness but voice contact was established with 4 of the 7 downed crewmen. The survivors were advised that pick-up would be attempted early on the morning of 15 January. The following day adverse weather precluded first light pick-up but a flight of A-1 Sandies re-established voice contact with the survivors. A flight of 4 F-4s provided continuous RESCAP by cycling elements between the CAP station and a tanker, Later in the afternoon, Jolly Green 20, an HH-3 searching for the survivors of Preview, was operating between cloud layers at 6 000 feet. The aircraft descended through an opening to VFR conditions with poor visibility. While descending, a power loss was experienced. Recovery could not be accomplished before ground impact; however, a flare-out was made which reduced the ground impact. The aircraft received major damage but there were no crew fatalities. Immediately, Jolly Green 15 and 72 were launched from Lima Site 36 in an attempt to pick up 1 the crew of #20, The 2 rescue helicopters encountered cloud cover near the crashisite of #20 and could not proceed further. While attempting to cross a ridge small arms fire was encountered which struck #15. Due to approaching darkness, weather, and ground fire, the rescue forces were withdrawn from the area. The entire crew of Jolly Green 20, downed 15 January at 1723H was successfully recovered by Jolly Green 71 on 17 January at 1550H hours. During egress from the area. #71 was hit by ground fire which caused the loss of the #1 engine but he was able to proceed to Lima Site 36 where the crew of #20 was transferred to another helicopter and taken to Udorn for medical attention, All but 2 of the crewmen were in good condition; a broken leg and another a broken arm. On the same date 3 crewmen of Preview were recovered by Jolly Green 69. 1 of these crewmen also had a broken leg. More beepers from the remaining crewmen of Preview were identified but search efforts were suspended due to darkness. Subsequent searches failed to locate any beepers or survivors and the search for the remaining survivors was finally suspended.