Air University Review, November-December 1968

Khe Sanh:  Keeping an Outpost Alive

Major General Burl W. McLaughlin

On many occasions, resupply by air has saved a beleaguered outpost. . . . Often the difference between success and failure in an operation is the aircraft available to move supplies in, move the wounded out and redeploy the troops.

The Honorable Harold Brown,
Secretary of the Air Force

 

That the defense of the Marine base at Khe Sanh would prove one of the most important campaigns of the Vietnam war, militarily and politically, was a foregone conclusion from the start. Even before the siege was lifted on 8 April 1988, nearly three months after it began, Khe Sanh was being called a clear-cut victory, a dramatic reversal of earlier nonmilitary warnings of disaster and predictions of another Dien Bien Phu. The successful defense of Khe Sanh was maintained primarily by the dogged determination of a small group of U.S. Marines, supported by Army and Army of the Republic of Vietnam (ARVN) forces, and a massive and skillful application of air power, which included, as an integral component, tactical airlift. The demands for aerial resupply tested tactical airlift in its classic role and vividly illustrated that airlift is, and must be, an extension of the battle, not divorced in any way from the realities of success or failure of an engagement.

The evolution and operation of the sustained air lifeline to Khe Sanh were part of a shifting tactical situation not uncommon at the time in South Vietnam. There had been, since late 1967, indications of extensive enemy buildup below the western part of the demilitarized zone, the area around Khe Sanh, signaling the possibility of a major offensive. From the beginning of the northern monsoon season and throughout the Christmas truce, enemy activities increased in all parts of the Republic. The major threat appeared to be in the northern I Corps area, and Khe Sanh, a strategic point on a vital North Vietnamese infiltration route, appeared to be a key target. In early January, an estimated two North Vietnamese divisions, 15-20 thousand troops, were reported in the Khe Sanh area, occupying the high ground surrounding the base. To counteract the threat in the northern provinces, several U.S. and ARVN units were airlifted to that area, including the 1st Air Cavalry Division and two brigades of the 101st Airborne Division. Marines and ARVN forces at the Khe Sanh base had been reinforced to a defensive 6000.

What happened during the next three months will constitute a lasting chapter in both the history of airlift and the final chronicle of the Vietnam war. This article will trace the decisions taken during those three months, the rationale behind them, and their consequences, in the hope of providing an insight into that chapter on the air resupply of Khe Sanh. Further, it will attempt to put the operation into proper perspective by revealing its impact on the overall airlift system in Vietnam and assessing the significance which the lessons learned will have on the future development of tactical airlift.

Evolution and Operation of the Resupply

On 21 January a rocket and mortar attack destroyed the Khe Sanh ammunition storage area, scattering shrapnel over half of the runway and preventing C-130 Hercules from landing. Under a tactical emergency designation (the highest airlift priority), six C-123 Providers were diverted from their scheduled missions, loaded with 26 tons of ammunition, and flown to Khe Sanh. They landed on the potholed runway, by the light of artillery flares, under heavy automatic weapons and mortar fire. Thus began the saga of Khe Sanh, which eventually ran into 78 days of emergency aerial resupply sorties to the embattled outpost.

At the outset the Commander, Seventh Air Force, then General William W. Momyer, directed the 834th Air Division, airlift headquarters for Vietnam, to begin a thorough analysis of the problems inherent in the unique situation at Khe Sanh, giving close scrutiny to all factors affecting airlift.

The resupply operation, at that time of unknown duration, would have to (1) guarantee uninterrupted air resupply regardless of weather, hazardous terrain, and enemy fire;

(2)minimize the vulnerability of delivery air craft and aircrews; and (3) minimize load recovery problems for the Marines.

Airdrop Glossary

  ALCC        airlift control center
  ARA          airborne radar approach
  AWADS    adverse-weather aerial delivery system
  CARP        computed air release point
  CCT          combat control
  CDS          container delivery system
  CEA          circular error average
  DMZ         demilitarized zone
  DR            dead reckoning
  DZ            drop zone
  GCA         ground-controlled approach
  GPES        ground proximity extraction system
  GRADS    ground radar aerial delivery system
  ILS            instrument landing system
  IMC          instrument meteorological conditions
  LAPES      low-altitude parachute extraction system
  LIT            light intratheater transport
  MHE         materials handling equipment
  PI              point of impact
  POL          petroleum, oil, and lubrications
  RAPCON  radar approach control
  STOL       short takeoff and landing 
  TACAN   tactical air navigation
  TALAR    tactical approach and landing radar
  TALC      Tactical Airlift Center, Pope AFB, North Carolina
  VMC       visual meteorological conditions
  V/STOL   vertical/ short takeoff and landing

In addition to enemy activity, a major operational consideration was the weather. At that time of year the spring monsoon brought chronic fog and rain to northwestern Quang Tri Province. The particular geographical situation of the base compounded the problem. Even when visual meteorological conditions (VMC) prevailed in the surrounding area, frequently the runway was fog-shrouded below minimum instrument landing conditions each day through mid-morning. Khe Sanh’s field elevation is 1500 feet above sea level; surrounding mountains tower 5581 feet on the north and an average of 3000 feet in other directions. A ravine on the runway’s east end drops approximately 800 feet and acts as a trough through which prevailing winds carry the warmer, moist air to the airstrip. This is Khe Sanh’s perpetual “fog factory” during the monsoon season, accounting for relatively short periods of ground-controlled approach (GCA) minimum visibility conditions each day.

This weather condition, coupled with daily mortar and rocket attacks that closed the runway, reduced the productive resupply day to approximately 2˝ to 3 hours. Successive aircraft landings brought an increase in the intensity of the attacks, indicating the enemy’s determination to destroy the aircraft on the ground.

By early February, landings had become extremely hazardous for both the jet-equipped K-series C-123 Providers and the larger, heavier C-130 Hercules. While any aircraft attracted mortar and artillery fire at Khe Sanh, the smaller Providers, requiring shorter runway space to land, were less susceptible to the intense small-arms fire than the Hercules.  On 12 February all C-130 landings were suspended. Events culminating in the edict under-scored the Hercules’ special vulnerability on the runway in that environment: enemy fire destroyed a U.S. Marine Corps C-130 and hit one belonging to the Air Force, grounding it for two days before sufficient repairs could be made to enable its crew to fly it to Da Nang.

The suspension forced the obvious: the primary method of resupply would be by airdrop, delivering ammunition, POL, and rations. Airland operations were reduced to delivery of cargo considered not airdroppable (special ammunition and medical supplies), troop deliveries, and evacuation of casualties. The C-130 and C-123K were designated for the airdrop role; the C-123K was designated as the airland vehicle, with the C-7A Caribou as backup as needed. In view of the Caribou’s relatively limited carrying capacity and the extremely congested air traffic situation at Khe Sanh, C-7As deferred to the more efficient C-123Ks to get twice as much cargo on the ground for practically the same risk and effort.

development of the IMC technique

Our two major antagonists in this logistics drama—weather and enemy fire—were formidable obstacles throughout the entire operation. Climatology data indicated from the start that there would be days at a time when the weather would be below minimum conditions. Thus, concurrent with the initial airlift sorties, planning for possible contingencies began. With airdrop a certainty as the primary mode of resupply, procedures had to be developed to drop in instrument meteorological conditions (IMC). To that date, no techniques had been established for dropping solely by instruments. Several techniques were, at the time, being explored, but none were operational.

A survey of Khe Sanh revealed the following:

—The drop zone was 300 x 300 yards, 200 yards shorter than the standard for container delivery system (CDS) drops. It was located outside the Marines’ defense perimeter, 1000 yards from the west end of the runway and within three degrees of the runway heading.

—The runway was 3900 feet long and 60 feet wide, declining on a three percent gradient from west to east.

—The airfield had GCA capability and a TPQ- 10 radar site.

—Wind velocities in the Khe Sanh valley were extreme and unpredictable.

—The terrain was hazardous, rising steeply on three sides of the field, and enemy gun emplacements were on all sides.

—Turbulence was expected to be moderate.

An airlift planning session at the 834th Air Division resulted in several alternatives and, eventually, a formulation of the instrument procedures to be used. Dropping on the runway was ruled out because of the possibility of damaging the surface at a critical time and thus precluding any emergency airland operations. The initial inclination was to have the GCA operator vector the aircraft to the computed air release point (CARP), about 600 yards short of the point of impact (PI) for CDS drops, with the ground controller providing a countdown to initiate the drop. A quick flight test, however, revealed that the GCA, because of design limitations, was incapable of vectoring the aircraft to a point located behind the radar itself, which in this case was the location of the CARP. The GCA could vector the aircraft to a point above the leading edge (threshold) of the runway, so a method of accurately steering the aircraft from that point to the CARP had to be resolved. Dead reckoning (DR) was ruled out; flight test proved the aircraft could be as much as 500 yards off track when using DR, which was totally unacceptable because of the size and location of the drop zone. Cross track was resolved by use of the C-130’S Doppler system in the drop function. By combining the features of the GCA and the capabilities of the Doppler, the IMC technique was developed and put to immediate use.

In practice, the GCA operator vectored the aircraft over the threshold of runway 28 at 500 feet drop altitude and gave the crew a “mark.” Ground speeds and winds were determined during the approach by direct readings from the Doppler instrumentation, and the desired course to the CARP was set into the Doppler instrument, establishing the correct heading. A precomputed timing sheet based on a 130-knot indicated air speed, had been devised, accounting for wind effect, providing the navigator the lapsed time from the mark point to the CARP, depending on ground speed. For example, at 135 knots ground speed, it took 24.8 seconds to fly that distance. The “green light” was given at the precise lapsed time, and a CDS drop performed. However, instead of using the standard pullup at the CARP, which is used in a visual meteorological condition, we decided that a smooth application of power combined with the effect of a load moving aft would adequately eject the containers and be more suitable for instrument conditions.

other planning

Although this IMC/GCA technique served as the primary method of instrument delivery, we had to plan for all possible eventualities. Clearly, GCA was the key to the functioning of the entire IMC technique. But it was vulnerable to incoming enemy fire, and airlift, as Khe Sanh’s only means of supply, could not cease even for one day. A backup system had to be developed.

Fortunately, a TPQ-10 radar system, normally used to direct fighter strikes, was located on base and was operational. As in the GCA/IMC formulation process, initial flight tests investigated the TPQ-10’s ability to vector the aircraft directly to the CARP. But the aircraft passed at such close proximity to the radar antenna that the antenna azimuth drive could not vector the aircraft down a predetermined glide slope; it could only position an aircraft at a point in space. Therefore, additional navigational aids were required, to guide the aircraft down the glide slope to the proper altitude at the runway threshold. Although Khe Sanh did have a tactical air navigation station, TACAN reception on C-130 aircraft is not considered reliable enough; and an airborne radar approach (ARA), using radar reflectors previously positioned along the runway, was not acceptable by itself. ‘The combined inputs from the TPQ-10, TACAN, and ARA, with the addition of a radar beacon transponder and low-frequency beacon, however, provided an acceptable method of descent to the threshold of runway 28. Since this method was not quite as accurate as GCA, we planned for level-off and drop at a slightly higher altitude (800 feet) to provide a greater margin of safety in the rough terrain. From the threshold, the same Doppler/time lapse procedure was used.

Yet even with this backup capability, further contemplation and planning had to be carried out for the not unlikely possibility of both GCA and TPQ-10 being out of commission at the same time.

We were familiar with efforts by the developmental community to provide the armed forces with a portable instrument landing system (ILS) called TALAR (tactical approach and landing radar). This system, with its compact, 35-pound transmitter, would have been ideal at Khe Sanh to replace a nonoperational GCA or TPQ-10. However, at the time, TALAR had not been fully evaluated and tested and thus could not be used at Khe Sanh.

We also had the option of using a variation of the CDS technique called ground radar aerial delivery system (GRADS), a high-altitude drop system that was initiated in Vietnam and further developed at the Tactical Airlift Center (TALC), Pope AFB, North Carolina, for use in adverse weather, darkness, or hostile ground-fire conditions. Several test runs were made using this system, also controlled by TPQ-10 ground radar. For Khe Sanh, we decided on a TPQ-10 located nearby, which would have vectored the aircraft over the CARP at approximately 4500 feet. Wind drift effects caused by dropping from the high altitude are minimized through use of delayed-opening parachute techniques.

Because of the large drop zone required, this was a last-resort technique, but, nevertheless, it could have been used to keep the supply line open.

The new IMC/GCA technique was initiated at Khe Sanh on 13 February when C-130s dropped 30 tons of supplies, and again the following day delivering 98 tons. On 17 and 18 February C-130s dropped nearly 279 tons of supplies, with a circular error average (CEA) of only 83 yards, under instrument meteorological conditions in which no other fixed-wing aircraft flew. As predictable, an enemy round’s direct hit put the GCA out of commission on 19 February, and the IMC/TPQ-10 technique was put to immediate and successful use. The significance and value of the IMC drop procedures were borne out in the final statistics, which revealed that of the 496 C-130 CDS deliveries 38 percent were performed by the instrument technique.

extraction deliveries

At the time the IMC airdrop problems were being resolved, survival at Khe Sanh dictated that the Marines go underground for protection against rocket and mortar fire attacks. Because of a severe lack of bunkering material, the Marines requested an emergency delivery of 2 x 12 x 22-foot lumber, which was too bulky for A-22 CDS containers. The use of airland was ruled out for two reasons: the hazards of enemy fire and the lack of 463L equipment to unload the material once on the ground. Two other methods were available: heavy-equipment drop (modular platforms) and low-level extraction. Heavy drop was ruled out for the following reasons:

—The drop zone was too small for this technique, which normally requires 600 x 1000 yards as a minimum standard for one platform.

—Recovery of heavy loads outside the normal perimeter was impractical due to lack of adequate recovery equipment.

—Personnel breaking down the loads manually would be exposed to rocket and mortar fire. Additionally, recovery time would interfere with the continued delivery of CDS containers.

—The lack of adequate space inside the base to allow for heavy drop.

—The desire that the material be delivered as close to the proposed bunker sites as possible.

—Increased dangers from enemy fire, since at the higher drop altitude (1100 feet) the CARP would have been within line of sight of enemy positions in the hills, thus exposing the aircraft to more severe fire.

Low-level extraction provided the most suitable solution. The west end of the runway was selected as the extraction site, and the low-altitude parachute extraction system (LAPES) was put to use on several occasions, guided down to landing minimums by GCA. However, because of a limited number of LAPES delivery components in the airlift system, it was clear that a large-scale use of LAPES was out of the question. Consequently, we began an Air Force-wide search for other available low-level extraction systems. One, the ground proximity extraction system (GPES), was found (in storage since 1966) and shipped in two days to Vietnam. The Army consented to rig the GPES loads, aircrews were expeditiously trained, and the arresting gear was installed at Khe Sanh. As the use of GPES increased, the use of LAPES decreased until finally, toward the end of the resupply operation, LAPES was entirely replaced by GPES.

In the final analysis, GPES proved more suitable for Khe Sanh than LAPES, and the advantages of each warrant discussion. The drop platforms in LAPES are free-flying objects for a short period of time; GPES is never that, for the load is always attached to either the airplane or the ground, providing a positive, controlled extraction system ideal for the confined and populated area at the west end of Khe Sanh’s runway. With GPES, irregular delivery techniques do not result in uncontrollable loads: if the hook does not engage the cable, the load simply will not extract. Once the GPES load is extracted, the arresting cable stops it in the same location every time, permitting efficient recovery and breakdown—important factors under Khe Sanh’s heavy enemy fire.

There are other advantages to GPES: it uses a standard modular platform, not the LAPES special sled, which was in short supply; there is a constant delivery altitude with GPES, versus the possibility of a high delivery with LAPES.

At Khe Sanh, the effectual recovery of delivery components also favored GPES delivery, with its comparatively simple process of picking up the hook, belly band, and clevices and quickly throwing them aboard the next airland aircraft as it completed its offload. The components were flown to Da Nang and used on following loads. For LAPES drops, the heavier parachutes had to be dismantled, bundled up, and put on board the next air-craft, then flown to Cam Ranh Bay, turned in to the repair company to be cleaned, rerigged and repacked, and flown to Da Nang for use on following loads.

It should be strongly emphasized, however, that although these advantages of GPES were applicable under the particular conditions surrounding the Khe Sanh operation, under a different set of circumstances, when quick deliveries of greater tonnages per load are required or when it is not practical or feasible to install the ground arresting gear, LAPES would be more suitable. As it was, LAPES was used on 77 percent of the extraction deliveries before GPES was phased in.

C-123 landings

While the C-130s performed the majority of the airdrop missions, the C-123s continued to land on the battered runway, delivering supplies and replacements and evacuating casualties. Only C-l23Ks were used, for they provide more rapid climb-outs over enemy positions and provide the added safety factor of four-engine performance. Again, the particularly hazardous conditions at Khe Sanh prompted specific procedures and standards to be developed and used in C-123 landings. With absolute minimum ground times necessary for all landings, extremely rapid turn-around procedures were developed. At night, the first 1000 feet of the runway was usually controlled partially by the enemy; therefore, aircrews were advised to land long. The aircraft landed in the assault configuration and stopped, whenever possible, without reversing the props, which would have caused the jets to shut down. At touchdown, the loadmaster opened the ramp and door and, upon reaching the offload area, pushed the pallets out while the aircraft continued taxiing slowly. Passengers scampered aboard the aircraft. Three minutes from touchdown to gear up was average; several times it took only 55 seconds.

During the airland operation and also while airdropping, the C-123 used a maximum assault descent procedure that had been developed in early January. By employing this high-altitude/assault-descent approach to the Khe Sanh runway and drop zone (DZ), the C-123s were subjected to hostile fire from the surrounding enemy positions for only a few seconds. The assault descent began about five kilometers (75 seconds) from the DZ, the aircraft descending at a rapid 3000-feet-per-minute rate without flaps (with flaps when landing), leveling off at 800 feet, 12 seconds from the DZ. When properly executed, the maximum period at drop altitude was 15 seconds. This technique considerably reduced hits from ground fire, with little sacrifice in accuracy.

ground operations

The ground operations performed by aerial port and combat control personnel played an extremely vital role in the success of the Khe Sanh resupply. Operating combat control equipment on the DZ was hazardous because of incoming mortar, rocket, and sniper fire on the exposed controllers. Significantly, enemy fire was at first concentrated on the runway and main part of the camp, but toward the end of the operation it was intensified on the DZ. The combat control team (CCT) discovered that when a lengthy transmission was made from the MRC-108 radio jeep, incoming rounds were soon directed at the jeep, indicating the enemy’s probable capability to home in on the radio. Consequently, the jeep was moved after each transmission. During the Khe Sanh resupply, the Tridea low-frequency beacon was used for the first time to provide a navigational aid to the C-123s, as well as an additional aid to the C- 130s. The beacon was necessary because of poor visibility and limited navigational equipment on the Provider. Three beacons were used; all were severely damaged by enemy fire, causing us to position part of the beacon and its generator underground.

Because of recovery vehicle traffic across the DZ and the helicopter downdrafts, the combat controllers had trouble keeping marker panels in place. Therefore, smoke had to be kept on the point of impact as a target for the aircrew. Sniper fire made this hazardous, too, so a deep hole, large enough for one man, was dug near the PI; there a controller was positioned, to throw the smoke grenades.

While the Marines recovered loads on the drop zone, Air Force aerial port mobility teams were responsible for offloading the airlift aircraft. Speed in recovering the cargo pallets was obviously essential, since the most intense mortar attacks came during landing and offloading. Two of the major problems aerial port personnel encountered were equipment failure because of battle damage and a low level of equipment performance caused by constant operation of forklifts and K-loaders over uneven terrain, exposure to severe dust conditions, and flat tires. The materials handling equipment (MHE) which required extensive maintenance or which sustained battle damage could not be evacuated from Khe Sanh because of the suspension of C-130 landings.

Aircraft maintenance recovery teams were originally positioned at Khe Sanh but were eventually reduced when landings became minimal. A minimum capability—tire specialists, fires, and jacks—was always maintained because of Khe Sanh’s battered and shrapnel-strewn runway. When heavier maintenance was needed, recovery teams were flown in.

airlift totals

At the conclusion of the 78-day emergency resupply of Khe Sanh, C-130s and C-123s had delivered a total of 12,430 tons of cargo, 8120 tons by airdrop and 4310 tons by airland. C-130s made 273 landings, 52 LAPES deliveries, 15 GPES deliveries, and 496 CDS drops. C-123s made 179 landings and 105 CDS drops. CEA for the C-130 IMC drops was 133 yards, and for VMC drops 95 yards. C-123s averaged 70 yards. Sorties flown by Air Force airlift aircraft totaled 1120. During the resupply, 2676 passengers were airlanded at Khe Sanh and 1574 lifted out, including 306 aeromedical evacuees (138 litter and 168 ambulatory). Over all, CDS constituted the mainstay of the airdrop operation, boasting a 99.5 percent recovery rate. A few loads were dropped excessively long or wide of the DZ; most were recovered, although three had to be destroyed by fighters to prevent them from falling into enemy hands. Fifty-three USAF airlift aircraft were hit by ground fire; 18 were extensively damaged, and three C-123s were destroyed.

impact on airlift management system

As a result of the increased allied effort shifted to northern I Corps during early 1968, most of it in support of Khe Sanh, the entire in-country airlift system was affected. To illustrate, from January to March the average monthly tonnage delivered to the eight airfields (Camp Evans, Ca Lu, Quang Tri, Quang Tri Lavang, Hue Phu Bai, Hue Citadel, Dong Ha, and Khe Sanh) served in the northern I Corps area increased by 14,533 tons, or 310 percent of the previous six-month average. Tactical maneuver elements supporting Khe Sanh and other Tet offensive engagements shifted rapidly, requiring daily resupply to give them freedom of action. Although these units normally use a certain amount of airlift, the additional aircraft movements increased requirements on the entire system.

The total amount of airlift required in Vietnam is measured in “tonnage to be delivered” rather than “ton-miles to be flown” because it is the most practical measurement for Military Assistance Command, Vietnam (MACV) transportation planning. The measurement of tonnage is feasible because of an established standard average sortie length, historically about 45 minutes. Planning factors for airlift requirements are derived from empirical data based on the total troop strength in-country. This includes a population factor of five tons airlifted per day for each 1000 troops, plus a constant eight tons per day for each maneuver battalion to compensate for their additional unit moves. The factors are based entirely on sustained levels of past activity and do not include major moves, such as those to northern I Corps during early 1968. Further, simultaneous actions—increases in total in-country population and numbers of maneuver battalions—also added to the rising airlift requirement.

As airlift forces in Vietnam are afforded a measure of flexibility by being able to call on other C-130 aircraft from out-country Pacific bases, additional C-130s were requested and received to augment the in-country force. But an interesting phenomenon develops here, proving that the amount of airlift provided by each aircraft is inversely proportional to the number of aircraft in-country; i. e., the more aircraft needed, the less tonnage each airlifts. This phenomenon is caused partially by saturation of aerial ports, maintenance facilities, air traffic control, and base support, thus decreasing the ability of those facilities to support the increased numbers of aircraft. The number of terminals remains relatively fixed, and the option of flexibility for the command and control system does not increase proportionately; the majority of cargo still originates at the same terminals and cannot be effectively shifted with changes in tactical situations. The net result is that the requirement for additional aircraft in itself adds to the requirement.

This phenomenon held true during the Khe Sanh airlift period. While the average number of C-130s in Vietnam increased from 58 to 84.7 during the last six months of 1967 and the first three months of 1968, the tonnage per day delivered by each aircraft decreased from 36.9 to 30.6. Although this downward trend appears contrary to efficient airlift management, instead it serves to underscore the primary antecedent to the existence of tactical airlift: that reliable responsiveness to emergency requirements transcends in priority the efficient use of aircraft.

As was the case during the Khe Sanh operation, unit moves and support of tactical units at temporary forward operating locations provide very little backhaul cargo. Since nearly all the locations north of Hue fall into this category, missions during early 1968 were largely productive only one way, further decreasing cargo load efficiency. The average monthly tonnage airlifted out of the eight northern I Corps fields from January to March was 5984, or 28 percent as much as the 21,300 tons flown in. By contrast, for the same time period the nine major aerial ports in Vietnam experienced an 87 percent rate of backhaul cargo.

Another condition that caused a decrease in capability was the particular geographical relationship of Khe Sanh to the location of the C-130 aircraft beddown bases (Tan Son Nhut Cam Ranh flay, Tuy Hoa, and Nha Trang), where crew housing, maintenance facilities, and security were available. Khe Sanh and its surrounding bases just below the demilitarized zone (DMZ) were farther from the beddown bases than the average sortie length, and because of the accelerated effort for that area, many sorties were flown from the more southern bases, i.e., Cam Ranh Bay and Tan Son Nhut. Approximate flying time from Tan Son Nhut is 95 minutes; from Cam Ranh Bay, where the majority of the C-130 missions originated, 75 minutes; and from Tuy Hoa 60 minutes. Consequently, during the first three months of 1968 the average sortie length increased 22 percent over the previous six months’ average, from 45 to 55 minutes, in turn decreasing the number of sorties flown per day. The long, narrow shape of Vietnam will permit beddown bases to compensate for these shifts in tactical emphasis as long as destinations are not farther from the nearest base than the average sortie length. If these limits are exceeded, as they were at Khe Sanh, the airlift job will nevertheless still be performed with the necessary responsiveness, but it will cost more in terms of aircraft and flying hours.

The airlift effort expended into the Khe Sanh area was an extreme example of the effect of a particular operation on the entire system. However, even this demand was absorbed by the flexibility of the system, and day-to-day requirements were still accomplished throughout all four corps tactical zones.

the materiel operation

Operations such as the Khe Sanh resupply also have dramatic impact on overall materiel functions. Extensive aircraft damage from ground fire greatly increased the maintenance man-hour requirements. Landings on the damaged runway prompted not only more tire changes but also increases in aircraft and component damage. The severe stresses imposed on airlift aircraft under these conditions, even though the planes were designed to withstand assault procedures, caused fatigue and failure rates never before experienced and completely impossible to program. To illustrate: In 1967 the C-130s flew approximately 30 sorties per tire change. During the first three months of 1968, when C-130s landed 273 times at Khe Sanh, the sortie rate dropped to 18 per change. Further, from January to April C-130s averaged 866 tire changes per month, compared with the 1967 monthly average of 350. The demand on base supply and the wheel and tire buildup work center was excessive and narrowly missed being a major problem. The insidious aspect is that it could not be anticipated.

As tactical emergency situations like Khe Sanh never occur without attendant priority requirements for the entire surrounding area, the resupply of Khe Sanh produced an even larger requirement for aircraft at other bases in northern I Corps. The result on maintenance and supply was a requirement for increased in-commission rates for an extended period of time. For example, during the 78-day period, the average number of C-123 aircraft possessed was 58. A minimum of 38 were fragged each day; 3 were destroyed, and 8 sustained major battle damage, eliminating 11 available airframes. Yet the number of flying hours increased from 5939 in January to 6113 in February to 6691 in March. The impact on C-123 maintenance and supply requirements is clearly evident.

In addition, C-130 utilization rates were kept at a high percentage, as shown by the accompanying table.

Date

Assigned aircraft

Missions fragged

Missions per aircraft

10 Feb

72

73

101%

11 Feb-28 Feb

88

83

94%

29 Feb-11 Apr

96

91

95%

These in-commission rates may seem incredible to those familiar with the Air Force standard of 71%. However, both the standard and in-commission rates for C-130 airlift in Vietnam are much higher because of utilization of rotational aircraft from out-country bases in the western Pacific, where the heavy-phase maintenance is accomplished. Therefore, the 29% under the Air Force standard allowable for heavy maintenance does not apply to C-130s in Vietnam. Realistically though, unscheduled maintenance produced by the hazards associated with Khe Sanh and similar combat situations precludes sustained attainment of the high goal.

To increase materiel reliability, action was necessary in several areas. Da Nang Air Ease, the primary staging base for the operation, is principally a fighter base, with no maintenance capability for C-130s and only limited capability for C-l23s. From austerely manned home bases, a 19-man maintenance team with limited amounts of equipment and supplies was sent to Da Nang, which reduced maintenance delays considerably.

At other locations where teams could not be deployed, an around-the-clock “maintenance coordinating” system, similar to a Logistics Readiness Center, was developed to recover damaged or unflyable aircraft.

A “maintenance coordinator” stationed at the 834th Air Division’s Airlift Control Center (ALCC) at Tan Son Nhut AB responded immediately to any airlift aircraft requiring maintenance support away from its home station. Depending on the requirement, the coordinator contacted the nearest support base to obtain parts, equipment, and/or personnel, then turned to the ALCC duty officer for airlift, which was usually accomplished by diverting the nearest aircraft. If major structural repair was required, the coordinator tasked the parent wing to dispatch maintenance personnel and equipment for a one-time flight to the mission support base.

The number of aircraft requiring assistance during the month 8 February-8 March is typical of the load usually handled by the maintenance coordinator in the ALCC:

Type

Number of aircraft

Average response time (hours)

Average repair time (hours)

C-130

91

2:43

5:52

C-123

55

2:36

5:54

C-7

40

1:46

3:03

The factors determining response time were parts requirements and available airlift. Response time was measured from notification to arrival of the team at the aircraft. There were instances of 30-minute response from notification to airborne.

Lessons Learned

Numerous lessons were learned and ideas crystallized at Khe Sanh, some which reinforce current concepts in tactical airlift and others which provide impetus for further discussion to improve future performance in this field.

· The initial necessity and ultimate success of the IMC drop technique at Khe Sanh confirms an obvious and immediate requirement for systems capable of performing in this kind of environment. The almost total reliance on ground radar to airdrop loads at Khe Sanh points up a definite deficiency in this system. Though we were fortunate at Khe Sanh in having sufficient backup radar components in case of battle damage to primary systems, the next location requiring IMC drops might not prove as fortunate. Reliability of a ground system is directly related to the enemy’s ability to put it out of commission. The ultimate need for IMC airdrops is a self-contained aircraft capability requiring no ground aids. Similarly, the ultimate in air-land capability under IMC is an aircraft with self-contained precision approach capability. The adverse-weather aerial delivery system (AWADS) development program will equip tactical airlift aircraft with a self-contained avionics package and provide adequate capability with possibly one exception, terrain-avoidance radar. If, in the absence of ground radar, airland had been the only method of resupplying Khe Sanh, the terrain-avoidance capability would have been necessary to provide the pilot glide slope information to complete a safe precision approach. In addition, the need to deliver loads as low as possible is dictated by the inherent inaccuracies of a parachute drop, resulting primarily from unknown wind conditions between the aircraft and ground. Therefore, the lower the aircraft, the more accurate the drop; and to provide the aircraft the capability to descend to these low altitudes for IMC drops, terrain-avoidance radar is essential. It is recognized, however that because of expense not all tactical airlift aircraft can be equipped with AWADS, even though the need to airland and airdrop in a forward area under instrument conditions will continue to exist. Therefore, a portable instrument landing system (ILS) is required. At Khe Sanh the size of the GCA and TPQ-10 radar, with the necessary location of antenna above ground, proved extremely vulnerable to enemy fire. The current TALAR IV appears to have excellent potential; had it been fully developed and available, its use would most likely have proved extremely effective at Khe Sanh. Light and portable, this miniaturized ILS system could have been placed for airlandings at the end of the runway, completely protected except for an opening for beam coverage. Another transmitter could have been located on the ground at the CARP and used to direct drop aircraft to the release point. Several TALAR units could have been stocked at Khe Sanh as replacements in case of baffle damage or malfunctioning.

· Khe Sanh taught us a valuable lesson concerning the high risk of conventional, fixed-wing aircraft performing resupply sorties to a camp surrounded by enemy forces. The most vulnerable aspect of the fixed-wing aircraft’s operation is that its approach and departure patterns are necessarily restricted to runway headings, at least for the final portion of the approach and the initial portion of the departure. If tactical airlift had been equipped with vertical/short takeoff and landing (V/STOL) aircraft, attempts by the enemy to “zero-in” the approach and departure courses at Khe Sanh could have been easily thwarted and aircraft damage reduced. As it was, the enemy was able to employ small-arms fire effectively, using a minimum number of weapons and personnel to inflict a significant amount of damage. V/STOL aircraft could have used a variety of approaches and landing techniques, similar to those used by Marine and Army helicopters, while delivering, of course, heavier loads. A V/STOL aircraft could have used the no-stop, low fly-by, dump-truck method of delivery, allowing for deliveries at various locations on Khe Sanh closer to the different supply points. The value of V/STOL to evacuate wounded is easily envisioned; worth considering is the time required for a helicopter flight from Khe Sanh to Dong Ha and then to Da Nang versus that required by V/STOL directly from Khe Sanh to Da Nang or even to Tan Son Nhut, if patients required special attention. Also, with V/STOL, all airdrops at Khe Sanh, except those performed below GCA-minimum landing conditions, could have been replaced by airlandings.

· The currently programmed light intratheater transport (LIT) is urgently needed for use in an environment like Vietnam. This aircraft should be rugged, capable of operating into extremely short dirt strips, and simple to maintain. Experience in this war has shown that, for the ground forces, it is expensive, in terms of both real estate and defensive ability, to maintain strips longer than 800-1000 feet. The LIT must be built to withstand a Vietnam situation and should be equipped with tires that will not be affected by bullets or shrapnel fragments and fuel tanks made of an explosive-suppression material. In fact, it is vitally important that our present-day aircraft be equipped with such tires and fuel tanks. The programmed LIT is considered the ultimate near-term, light tactical airlift aircraft, scheduled to replace the aging C-123 and the overworked C-7 force. However, it must be acknowledged that there is an urgent need to provide additional STOL aircraft to satisfy the immediate Southeast Asia requirement for specialized airlift. The commitment of additional C-123 aircraft or the procurement of an off-the-shelf, state-of-the-art STOL would enhance the Air Force’s ability to sustain the present responsiveness of our tactical airlift force in Vietnam until the advent of the LIT in 1974-75.

· Since integration of new tactical airlift aircraft into the inventory is, unfortunately, still years away, the value and need of the following auxiliary modes of delivery were strongly reaffirmed at Khe Sanh: (1) low-level extraction to deliver heavy, outsized cargo; (2) medium-altitude deliveries as the mainstay of most operations; and (3) high-altitude airdrop techniques to provide the flexibility of delivering cargo under adverse conditions. The availability of these aerial delivery systems allows the airlift commander options from which to select the best aerial delivery mode to support the existing tactical situation, thereby insuring tactical airlift’s primary responsibilities of responsiveness and flexibility. The effective performance of GPES, for example, as an option in low-level extraction, proved its merit in the Khe Sanh situation. Another option available during the Khe Sanh operation was an improved LAPES system, with a heavier, 36,000-pound-per-drop capability. This system, although not used at Khe Sanh, was successfully employed in the IV Corps area during that time and was available for other tactical situations if needed. GRADS served as the option in the high-altitude category and could have been used at Khe Sanh if conditions had worsened. It has, in fact on occasion since Khe Sanh, proven itself as the only means of supplying an isolated camp when intense enemy fire was too hazardous for helicopters or for low- or medium-level airdrop. Khe Sanh demonstrated, as have numerous other operations throughout Vietnam, that emergency airdropping is often requested under the most varied and unfavorable conditions imaginable. There are other systems of delivery even more exotic than these that could have been effectively used at Khe Sanh, such as a radio-controlled parachute guided to the exact point of impact by the man on the ground. But these are at present extremely expensive, especially for sustained operations such as Khe Sanh, and expense is one of the critical limitations on development today. Therefore, airlanding is always preferred and performed if at all possible, and rightly so but in Vietnam today, the hazards of landing an airplane, in itself an implied and potential financial risk, are often too great, or even impossible because of the lack of adequate airstrips. Consequently, as long as the present family of aircraft remains the backbone of tactical airlift, we must exert efforts to improve aerial delivery modes—developing cheaper parachutes, a higher degree of accuracy, greater capability and flexibility-instead of eliminating or discounting airdrop because of expense. These methods are vital to our very ability to fulfill emergency requirements of ground units in Vietnam. Future designs of tactical airlift aircraft will, admittedly, decrease the importance of most current airdrop modes, but that day is still years away.

In addition to these broad concepts of airlift developments, other brief and more specific tenets evolved from Khe Sanh which proved significant and worthy of mention and discussion.

—Whenever we establish new or reoccupy old bases away from supply lines, initial consideration must be given to air resupply, not only by airland and helicopter but most particularly by airdrop. Space should be allotted for suitable drop zones inside the defense perimeter if possible, convenient to offload points, and usable day or night.

—Prior to the start of any large-scale air operation, air traffic control facilities should be built up immediately to handle all anticipated traffic. At the start of the Khe Sanh operation, there was only one radar approach control (RAPCON) unit, at Hue Phu Bai, to direct the increasing numbers of aircraft into Camp Evans, Quang Tri, Dong Ha, Khe Sanh, and Hue Phu Bai, and it proved inadequate. Subsequently a second unit was located at Quang Tri to handle half of the traffic, thus providing a more effective and safer air traffic control operation.

—The entire Khe Sanh operation graphically illustrated one particular trend of airlift today, the evolution of the specialist. Crews flying in support of Khe Sanh performed daily airdrops that required the versatility of adapting to new techniques or variations of current air resupply standards. Those with thorough knowledge of and practice in the different modes of delivery were naturally more adept. Yet the nature of conditions and the urgency of the situation at Khe Sanh demanded proficiency and accuracy from the start. There was no time for training. The highest possible degree of accuracy and reliability could have been pledged had we been able to press into service a group of select, specialized aircrews, those identified as airdrop experts, highly proficient in LAPES, GPES, CDS, GRADS, heavy-equipment drops, and formation flying. With specialists, we could apply a variety of resupply techniques to meet a myriad of contingency and emergency situations for which the standard just doesn’t always apply. The crews would be able to adapt immediately to each situation and not need an extensive training program. At Khe Sanh, they would have readily recognized any problems connected with IMC procedures, such as not receiving the threshold mark on time and thereby running the risk of hitting the mountains ahead. Using the radar reflectors along the runway, beacons, and TACAN, they could have determined exactly when they crossed the runway. But again, this comes from experience, from knowing what to look for.

Khe Sanh also emphasized:

—That our present Air Force management system must consider the tremendous sustained surges in requirements that are absolutely essential in and an integral part of a combat situation. Manpower should be based on documented maintenance man-hours of the current year; supply levels on demands of the current year.

—That fighter cover for airlift aircraft making drops or airlands in hostile surroundings must be employed, if at all possible, to suppress enemy ground fire.

—That the enemy’s ability to listen to the frequency being utilized by the controlling agencies and aircraft and comprehend the data greatly enhances his firepower effectiveness, proving the need for frequency changes, using discreet frequencies, code words to designate loads, and certainly a secure voice transmission system.

—That maintaining adequate recovery capability is highly important. Mobility teams at Khe Sanh used K-loaders during initial minimum ground times (engines shut down) and forklifts later for the speed offloads. Our delivery rate was based not on airdrop capability but on the ground forces’ ability to clear the DZ: after each drop the average time was 45 minutes, but several hours if bundles fell outside the DZ perimeter. There is a definite requirement for a large-capacity forklift (10K) that will perform in a combat environment for extended periods of time without unacceptable maintenance delays. Concurrent with the requirement for aircraft tires, K-loaders and forklifts should also be equipped with tires, air-cooled engines, and shielded hydraulic lines capable of withstanding hits by bullets and shrapnel. We should explore the possibility of developing a ground sweeper, perhaps magnetic, capable of clearing runways and ramp areas of shrapnel and other debris. The vulnerability of our present tires on materials handling equipment and aircraft too often jeopardizes not only the equipment but the entire operation.

In Vietnam today, tactical airlift requirements are constantly changing, fertile areas for improvement are being uncovered daily, and Khe Sanh is but one example of the demands being placed upon our airlift forces in combat. As tactical airlift in the Air Force is not restricted to Vietnam, the comments and suggestions here must necessarily be considered along with requirements from other parts of the world. But Khe Sanh must indeed be the classic example of tactical airlift to date, and what happened there portends a bright and expanding future for the entire airlift field.

Hq 834th Air Division


Contributor

Major General Burl W. McLauglin is Commander, 834th Air Division, Tan Son Nhut Air Base, Vietnam. He completed flying training in 1941 and served with the armed forces until 1946. In 1947, he returned to active duty and served with Strategic Air Command until 1957, as Deputy Director of Operations at SAC’s “X-Ray” headquarters, Tokyo, Japan; as Commander, 19th Bombardment Squadron, March AFB, California; and in staff positions at Fifteenth Air Force and SAC headquarters. Other assignments have been as student, Air War College, 1958; Chief of the Colonels Group, DCS/P, Hq USAF, to 1961; student, National War College, 1962; Commander, 516th Troop Carrier Wing, Dyess AFB, Texas, to 1965, participating in Exercise Swift Strike III; Commander, 838th Air Division, Forbes AFB, Kansas, to 1966; and Commander, 322d Air Division at Chateauroux AS, France, later at High Wycombe AS, England, until his present assignment in November 1967. While in Europe he served as Air Force commander during Exercises Southern Arrow and Pathfinder Express.

Disclaimer

The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.


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