CIA aerial combat. Helicopter vs Bi-plane warfare.

What happens when you have an isolated and clandestine CIA site mixed with an unusual move by the North Vietnamese to attack it using AN-2 Colt bi-planes, dashed with a bit of quick thinking courtesy of Air America in a Huey helicopter?

You have one of the most unusual air battles of the Vietnam War.

From the CIA Website....

On 12 January, CIA lookouts reported a four-plane formation heading in the direction of Site 85. Two aircraft split off, but the other two continued to Phou Phathi, where they bombed, strafed, and fired rockets at the ridgeline. Several local Hmong were killed. The CIA officers and the local Air Force forward air controller (FAC) fired on the slow-moving Antonov-2 Colt biplanes and called in an Air America helicopter in the area to assist. The helicopter, a Bell 212, the civilian version of the Huey, proved faster than the Colts. The Air America pilot flew alongside the Soviet-made biplanes and fired a submachinegun at them through the door. Both aircraft were shot down, and the rudder from one was taken to Longtiang, an Air America base, as a souvenir.
The Embassy believed the air attack was an attempt to eliminate the radar without resorting to a costly ground attack. It also considered, rightly, that the attack was highly unusual and was unlikely to be repeated. The North Vietnamese did not have the air assets to squander.
After the air attack, ground activity abruptly increased. On 19 January an informant at Samneua reported that a five-battalion group of NVA and PL had moved west and divided into two groups. Three battalions with a 105-mm howitzer moved into position to attack Phou Den Din, a key position in control of the Phou Phathi area. The other two battalions moved southeast of the mountain in an encircling maneuver. The American and Hmong forces at the Site 85 command post, a ramshackle structure next to the helicopter landing area, recognized another major assault in the making. They realized that, if the enemy were willing to accept heavy losses, the ridgeline could not be held.

Pretty dry fare from the Central Intelligence Agency.

If you want a more entertaining telling then I highly recommend you go to Sobchak Security Blog here and check out his version of events.