13th Sortie, The

Flight Journal, Jun 2002 by Gabella, W F

Dictionaries define ''sortie" as a single flight of a military aircraft on a combat mission. It was not uncommon for our 16 Chinooks in the U.S.'s 242nd Assault Support Helicopter Company ("Muleskinners") to fly 20 to 30 sorties a day for a number of "customers" on the battlefields of Vietnam.

This is the true story-weird as it may seem- of the strange events that happened to me and my crew during an unlucky 13th sortie. It was right out of the "Twilight Zone"! On that fateful day, we launched as usual; starting the rotors as soon as the sun peeped between veils of mist over the eastern horizon. As a flight of three in loose trail formation, we climbed through mist and scud clouds that topped at 3,500 feet en roulte to Cu Chi, the former home of the 25th Infantry Division ("Tropic Lightning). Famed Hollywood director Oliver Stone based his movie "Platoon" on his tour as a grunt (infantry rifleman) with the division in this neck of the woods.

The 25th had returned to its home base on Hawaii. Cu Chi had also been our home before we moved east to Phu Loi and away from the Cambodian border. Cu Chi, close to Cambodia, was now a major combat base for the Army of the Republic of Vietnam (ARVN).

Our mission on that day in 1971 was to fly combat support for the 3rd Brigade of the famed 1st Cavalry Division (Airmobile). They were kicking butt inside Cambodia against North Vietnamese regulars at the huge southern terminus of the Ho Chi Minh trail. Ranger companies on long-range reconnaissance patrols had provided eyes, ears and ambuscades since 1970 with 1st Cav. units across the border.

Flying combat support for the "First Horse" was like old-home week for me, since I had served with the division during my first tour in Vietnam in 1967 and 1968. Many of the staff had cycled back to Vietnam. My old boss, who had been chief of staff in 1968, was now the commanding general and sported two stars. A peerless combat commander, he was a "gunfighter" general who rose through the ranks from private.

Our bird, the Boilermaker Special, plus the two other Muleskinner Chinooks in the flight, were estimated to have flown 75 to 80 sorties from Cu Chi into Cambodia. All in all, we carried about 150 loads (there was always some sort of "backhaul" after we delivered inbound loads). The loads were either carried internally or externally (suspended on a sling), or a combination of both, and they averaged 5,000 pounds.

After our first or second sortie, an aircraft-- systems problem popped up unexpectedly: the Boilermaker Special's speed trim became inoperative. In large, tandem-rotor aircraft, the faster you fly, the greater the nose-down attitude, and that results in high stresses on the rotors and the rotor shafts and in greater overall drag on the aircraft-and discomfort to passengers! To overcome this drawback, the Chinook used an electromechanical device to tilt the rotor systems by "sensing" pitot-tube ram air to determine the optimal angle of attack. Then the speed-trim control unit tilted both the fore and aft swashplates, which control rotor-system tilt, forward in pitch so the airframe did not have such a radical nose-down attitude. In short: the rotor systems tilted-not the airframe. This was all "scheduled" electronically according to the airspeed-a marvelous system that usually worked well.

The Chinook could be flown with the speed trim "inop," but this limited its forward speed to less than 100mph (86.95 knots) instead of the usual 100 to 120mph cruise (depending on the load). This promised a slow day because of the long hauls into Cambodia.

We refueled several times before noon at Cu Chi. On our third refueling, after a quick tin-can lunch, we topped off with 4,000 pounds of jet fuel. Warrant Officer Robert O. Spencer, my copilot, and I maneuvered to the "hook-out" pad and landed to take on a mixed load: 11 passengers and an external load of Class A rations (food).

The hook-out pad was on the southwest side of the base and adjacent to its perimeter. The perimeter itself was one quarter mile deep-a maze of barbed wire dotted with various types of antipersonnel mines and trip flares (a zone of death for anything that went into it).

With the hookup completed, we turned into the southwest monsoon, and I poured the power to the heavily loaded bird. The old Chinook (we had the oldest CH-47s in Vietnam) shuddered as we transitioned from hovering into forward flight, increasing our airspeed slowly during our climb-out in the tropical heat.

Suddenly, Spencer-his voice an octave above normal-shouted over the intercom; "Sir! Number one [engine] is running away!" I flicked a glance at the engine's torque meter (power delivery instrument) and watched the needle "intelligently" climb toward the upper-limit red line, where it should not have been. Instinctively, I pulled up a handful of pitch on the thrust lever, thus demanding greater power from the power trains by increasing the rotor blades' "bite" in the hot, thin tropical air. The idea was to absorb this excess power from the numberone engine and bring it down to a safe range.