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bombs hit the target at the same time. Obviously the calculations
of trajectory and flight information had to be carefully dovetailed
to have the desired effect and yet avoid shooting down an aircraft.
The "Micro Arclight" was a smaller version of the Mini Arclight using
smaller targets and lighter ordnance.49

Even with the Arclights, the TPQ missions, and the Mini and Micro
Arclights, a basic ingredient of Marine air at Khe Sanh remained the
visual close air support missions.* Despite the crachin, the
breaks in the weather permitted the Marines to provide their traditional
support of the Marine ground forces. Upon arrival in the sector, the
fixed-wing aircraft would report into the Khe Sanh DASC who in turn
would assign the pilots to a Marine or Air Force airborne controller.
These controllers were from the Air Force 20th Tactical Air Support
Squadron or from Marine H&MS-36 and VMO-6. At least five pilots flying
either Cessna 01E "Birddogs" or Huey "Slicks" remained overhead during
the day in radio communication with both the ground and air. Once in
visual and radio contact with the attack aircraft, the controller would
make a "marking run" where he fired either a smoke rocket or dropped
a colored smoke grenade upon the target. Given the correct headings
by the airborne controller and possibly after a few "dummy" passes,
the jets would then strike the enemy positions. In the meantime, the
controller would be in contact with the ground and make any necessary
adjustments in his instructions to the attack pilots. Once the attack
aircraft released their ordnance, the air controller made an assessment
of the strike and radioed the results to the fixed-wing pilots. A typical
transmission would be:

BDA follows: 5 KBA [killed by air]; 2 bunkers, 1 automatic weapons,
and 50 meters of trench-line destroyed; one secondary explosion. You
have been flying support of the 26th Marines; your controller has been
SOUTHERN OSCAR. Good shooting and good afternoon, gentlemen.50

Air support involved more than dropping bombs. With Route 9 cut, Khe
Sanh depended upon air-delivered supplies for its survival. Even with
its 3,900-foot airstrip, this was not always a simple task. The first
challenge faced by an aircrew inbound to Khe Sanh was to find the combat
base. In addition to the crachin which for much of the morning made
navigation difficult, the Khe Sanh airstrip was located hard by a "fog
factory," which complicated the task even further. Just off the east
end of the runway, the ground dropped away sharply into a gorge over
l ,100 feet deep. The wind channelled warm, moist air from the coast
into the gorge, producing the right conditions for thick, heavy banks
of fog which spilled onto the plateau to obscure the combat base and
the surrounding area. Before the siege began, the structures at Khe
Sanh showed up vividly on aircraft radar, allowing pilots to "see" through
the fog. But soon, heavy shelling forced the Marines further underground
and leveled many bunkers and revetments, resulting in poor radar return.
A detachment from Marine Air Traffic Control Unit-62, MAG-36, operated
a ground control approach (GCA) radar from the airstrip to guide aircraft,
but enemy fire knocked it out on 19 February. As an expedient, the ground
air controllers pressed into service the ASRT TPQ-10 radar, normally
used to control bombing, to direct landings, with some success.51**

If the weather was clear, as occasionally happened, or if a pilot
had the skill or luck to find the airstrip despite the fog, he and his
crew next had to brave North Vietnamese antiaircraft fire. The enemy
cleverly concealed heavy machine guns and some 37mm antiaircraft guns
along the approaches to the runway and invariably engaged aircraft on
landing and take-off. Even when the supply planes approached the field
in dense fog under radar control, the NVA gunners fired away, "in the
dark," so to speak, presumably firing at the sound of the engines. For
an aircraft loaded with several tons of fuel or ammunition, a single
hit could be disastrous.52***

* While the TPQ missions in many instances could be classified close
support, Marine close air support usually refers to missions where the
pilots under the direction of an airborne or ground controller visually
obtain and attack the target.

** Lieutenant General Carey then on the wing staff commented that
ASRT at Khe Sanh "proved to be invaluable in a multitude of roles. We
utilized it in conjunction with aerial delivery on the tin foil strip,
for supplementary positioning and control of A-6 . . . strikes which
we conducted when the Arclights were not available, and we used them
for Special Close Air Support on the hill positions surrounding Khe
Sanh." Carey Comments.

*** Colonel Twining observed that "one of the problems with the Khe
Sanh defense was that the terrain overlooking the airfield was close
enough for the NVA to cover the base with direct fire but too far to
include within the Marine perimeter. The covering artillery was emplaced
in caves with narrow embrasures, making it almost invulnerable to counter-battery
or air strikes. According to a defector, the guns were aimed with an
awkward but ingenious system of mirrors, moved by lines and pulleys.
Once completed, it was possible to fire on aircraft that were in the
process of landing or taking off, as well as those stationary and unloading."
Twining Comments.

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