USS MULLINNIX DD-944

Vietnam 1969 - Page 5
16 Jan - 3 Sept

A Typical 'Call For Fire' to the USS Mullinnix

Along the length of South Vietnam’s 1,200-mile coastline, from the DMZ, down around the southern tip of Vietnam and up to the Cambodian border on the Gulf of Thailand. Under Commander Task Unit (CTU) 70.8.9, U.S. and Australian ships provided on-call fir support to U.S. Marine, U.S. Army, ARVN, Korean and Australian ground forces throughout the Vietnam War.

Naval gunfire missions were generally of two types:

1. Undirected fire on areas thought to contain enemy troops, supplies or camps
2. Fire support requested on specific targets in support of ground operations, directed by aerial or embedded or support personnel.

A typical profile of a call-for-fire mission to a destroyer (ship's call name) patrolling off the coast of South Vietnam:



From Tin Can Sailors
Would have been nice to spell "MULLINNIX" correctly, just saying...

As an on-call fire support ship cruises about 1-2,000 yards from the beach just south of the DMZ, the ship’s combat information center (CIC) is at Condition III. The quartermasters replot the ship’s position every 10 minutes, as do the radarmen in the CIC. This is necessary so that when a fire mission is received, the position of the ship will be current. With each new navigational fix, the dead reckoning trace (DRT) in the CIC is updated as to the exact position on the chart overlay. The DRT receives the ship’s speed and course inputs directly form the pit log (essentially the ship’s “speedometer”) and gyro compass, respectively, providing a reasonably accurate track of the ship’s movements. The fire control room’s main battery computer (Main Battery Plot) also receives those course and speed inputs, and bases its firing solution upon them. For a target line the CIC will provide a true direction and distance to the requested coordinates.

The call for fire comes into the CIC over the gunfire support net: “(Call name – e.g. Disapprove), this is Delta-Zebra-One-Two. Fire mission.”

Immediately the CIC supervisor replies: “Delta-Zebra-One-Two, this is Disapprove. Authenticate alpha, golf, tango, uniform,”

The gunfire spotter replies, “Disapprove, I authenticate zulu, golf, bravo, mike.”

CIC responds: “One-Two, authentication correct. I have 3 barrels 5-in/54. Mission accepted.”

(Spotter then transmits the mission and target location)

“Disapprove, this is One-Two. Mission follows. Troops in the open. Target Line 020 Magnetic, Coordinates Target Mike-One-Three, Uniform-Six-Five. Fire three rounds Victor Tango Foxtrot (variable time fuze, fragmentation – which produce air bursts directly over the target – and is best against troops in the open). One barrel for spot.”

The CIC team gives the gunnery liaison officer (GLO) a thumbs-up signal as soon as it has plotted the target coordinates and confirmed the ship’s target line (gyrocompass bearing from the ship to the target). The GLO, via the sound-powered internal gunnery circuit, transmits to the fire control center: “On the mark, target will bear – 265 true, 11,400 yards. Standby.”

On the signal from the radarman on the navigation plot, he then says, “Mark.”

This procedure is repeated quickly twice more to confirm that the gunfire control system’s computed gun line to the target matches the true gun line to the target. Meanwhile, the mount captain in the forward mount, MT51, orders the shell handlers and powder men in the handling rooms below to send three rounds of fragmentation with a VT fuze up to the gun mount. The mount captain then reports “loaded” to the gunfire control system (GFCS) operator. As soon as a firing solution is reached – within seconds, the first round is fired automatically. The subsequent two rounds are fired as quickly as the gun can be loaded.

When the first round is fired, the ship’s CIC transmits, “Disapprove, shot.” This alerts the spotter and the troops that a round is on the way. Then, five seconds before the first round’s impact, the CIC transmits, “Splash, out.” That alerts the spotter to look for the fall of shot and tells those supporting to get their heads down. Upon completion of firing the third and last round, the CIC transmits: “One-Two, Disapprove. Rounds complete.”

The spotter replies; “Disapprove, this is One-Two. Up three zero, left five. Fire one zero rounds. VT-F, all barrels for effect.”

Since the spotter’s corrections are based on his line of sight to the target, and his line of sight rarely matches the ship’s target line (e.g. the target bears 020 from him, 265 from the ship), the CIC team has to translate his corrections to what they reflect for a gun firing down the ship’s target line. The GLO and a member of the CIC plotting team do this by means of a circular plotting device called a Comanche Board. By marking both the ship’s and spotter’s target line properly, the Comanche Board provides a near-instantaneous translation of the spotter’s report. The GLO communicates the “ship’s correction” down to the GFCS operator. By this time the rear mounts, MT52 and MT53 are fully manned. Both mount captains order up their rounds from the handling rooms. 5-inch/54 can sustain a firing rate of approximately 45 rounds per minute – almost twice the maximum rate of a twin-barreled 5-inch/38.

Once the rounds are in the air, the CIC transmits the “Shot” and “Rounds complete” messages (CIC does not transmit “Splash, out” when firing for effect). As soon as firing is finished, the GLO updates the target position to the GFCS operator every five minutes to ensure that the gun’s target line remains accurate.

As soon as the rounds for effect are fired, the destroyer receives: “Disapprove, this is One-Two. Fire mission on target, target eliminated. Break. Disapprove, this is One-Two. Second mission requested. From Target Alpha. Up on five, left three zero. Target is emplaced mortar. Fire one round Able-Able Common (high-explosive round) for spot.”

The GLO passes the correction to the FGCS operator, And MT51 quickly fires the round. Back from the spotter comes: “Disapprove, this is One-Two. Up 5, no correction. Request five rounds, one barrel or effect.”

Within a minute of firing the spotter transmits: “Disapprove, One-Two. Target destroyed. Good shooting. Thanks! No missions at this time.”

The destroyer responds: “One-Two, this is Disapprove. You are welcome.”

The ship then transmits over the gunfire support net: “All Delta-Zulus, this is Disapprove. Disapprove is now available for missions.”

The work on the destroyer is not finished, of course. Empty powder canisters must be collected and stored, and the remaining available ammunition must be redistributed and the inventory reported to the gunnery officer. The gunner’s mates check the guns for any damage, and clean the firing debris from the muzzles.

With the normal Condition III steaming watches set, the destroyer settles down to await its next fire mission. As the crew waits for that call, meals are prepared and served, paperwork is processed, and repairs and maintenance are performed all over the ship – all the mundane jobs of a destroyer at sea.

Normal operations also included refueling every third day by a TF-73 fleet oiler, the seemingly random replenishment of supplies and food by stores ships and the constant rearming from the ammunition ships. These underway replenishment operations had to be carried out around the gunfire support missions, with the service force ships standing by until the destroyers finished those missions.

The enclosed gun mounts were not air-conditioned. As expected in the tropics, these spaces were anywhere from hot at night to practically unbearable during the day. An even worse heat problem afflicted the snipes in the boiler and machinery spaces. But none of the tin-can sailors had any desire to trade places with the ground forces ashore.

Whump – an orange explosion iginited at the point of impact, sending a cloud of black smoke swirling into the sky. The small form lay still and smoking between the two soldiers. Standing, a ghost walked toward them. A child, wisps of smoke curling from her clothes. The thick woman’s coat she wore had taken the brunt of the flames.

God, we pray for a war-free world. Amen





1969 Mullinnix Deck Logs

January 1969 (PDF)
February 1969 (PDF)
March 1969 (PDF)
April 1969 (PDF)
May 1969 (PDF)
June 1969 (PDF)
July 1969 (PDF)
August 1969 (PDF)
September 1969 (PDF)
October 1969 (PDF)
November 1969 (PDF)
December 1969 (PDF)



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