The Campbell did more than service PCF 19, the crews were based on the Campbell (two crews, one boat). There is some question about the true fate of that boat, the Navy declared it friendly fire, but another swift boater who was on a nearby boat swears that they came under fire from North Vietnamese helos. The Navy says that the N. Vietnamese didn't have any helos. The whole thing was kept pretty quiet.
That's incorrect. In fact, helos were observed from time to time in certain places on the Ho Chi Minh trail by SOG recon teams. The description of the helo on the Swift boaters' site doesn't sound like a Soviet aircraft. At the time, the NVA was operating Mi-4, Mi-8 and perhaps a few Mi-26 helicopters. I am unaware of any gunship capability, but in the 1970s rocket pods on Mi-8s became very, very common. Rockets were a standard air-ground weapon for MiGs as well, but PAVN-AF MiG drivers didn't do much air-to-ground practice.
The NVA could be quite daring. On 19 April 72 two MiG-17s came out and attacked the destroyer Higbee and cruiser Oklahoma City with bombs. They scored a hit on Higbee's X-turret, but the gun crew were not in the turret as they had had an emergency inside... this attack is credited to Nguyen Van Bay the ace, but appears now that the NVA are opening up the archives a little to be a different guy with the same name (hardly unusual for a Vietnamese).
The US forces fired at the MiGs with Terrier missiles and F-4 Phantoms chased them -- apparently the suckers got away.
In another case, well-recorded in history, two An-2 Colt biplanes attacked a classified operational location in Laos. They were shot down by a crew chief in a slick Air America Bell 205 (civil Huey), using a handheld weapon -- ISTR it was an AK. The tail feathers of one of the Colts was last seen in the Ravens' bar in Long Tieng.
I take the 1972 attack particularly as an indicator that the PAVN-AF would take a shot at an unaccompanied patrol craft at night if they thought they could get away with it.
Criminal Number 18F