HAS

The Hardened Aircraft Shelter (HAS), with respect to the United States of America and NATO, owes its origins to the first above-ground hardened shelters built by the United States Marine Corps (USMC) at Ewa Field, Oahu, beginning in September 1942. Made of reinforced concrete and covered with soil and plants, the shelters offered excellent protection from anything other than a direct bomb hit or head-on strafing run. Because of their clamshell design, the width and length shrinks as one moves up the side of the shelter, and height drops as one moves toward the rear. Thus this design would not be appropriate for larger aircraft with tricycle landing gear, but the design was fine for USMC tail-dragging aircraft, such as the Grumman F6F Hellcat, Grumman F4F Wildcat, and Vought F4U Corsair fighters. These shelters measured 18 feet high and 55 feet wide (floor level) in front and 39 feet deep. Concrete facing was roughly 3 feet high with 12 to 18 inches of concrete protection overall._3.1

The U.S. Air Force initiated a study on passive defensive protective measures as early as 1962. Between 1964 and 1965, the Air Force conducted a Theater Air Base Vulnerability Estimate and Evaluation (TABVEE) study at Bitburg, West Germany. The study reviewed the criteria for base survival and recovery after an enemy attack. It was clear that an enemy offensive potentially would target airfields to disrupt operations. The lessons learned from the June 1967 Arab-Israeli Six-Day War illustrated the vulnerability of air bases, the inadequacy of past base recovery tactics and materials, and the inability to retaliate after an air base attack. The Israeli Air Force nearly wiped out the entire Egyptian Air Force on the Ground._7.1

The Arab-Israeli War of June 1967 sparked one of the Mediterranean Division’s rare new construction programs outside Saudi Arabia. In 1968, the U.S. took the initiative when the first funds were appropriated for the Theater Air Base Vulnerability (TAB VEE) Program, which addressed the vulnerability of aircraft on the ground._5.1 Army engineers designed and constructed aircraft shelters that used reinforced concrete poured over liners made of corrugated-steel arches. In early 1969, the Mediterranean Division received authorization to design and build maintenance and parking hangers for the Air Force at Aviano in Italy and at Incirlik in Turkey. The number of structures and the criteria fluctuated as the Air Force repeatedly revised its requirements and specifications. Construction finally began very late in 1970 at Aviano; by early 1972, the division had completed sixteen aircraft shelters and two maintenance shelters at a cost of about $1 million. At Incirlik, the division supervised construction of eighteen TAB VEE aircraft shelters in 1971 worth $2 million. In 1973, the TAB VEE program at Aviano became a part of NATO‘s construction activities and responsibility for completing additional work passed to the Italian government._2.1

Over the years, the program encircling the development of a protective structure for aircraft, it has had many names; TAB VEE, SACEUR’s Airfield Physical Protection Program, NATO Airfield Survivability Measures (ASM), Aircraft Shelter Program with the most recent rendition of this program being standardized as the Improved Airfield Survivability Measures._4.1

From 1966 forward, the program name TAB VEE referenced the development of first-generation hardened shelters for American air bases and those of her allies.

The Air Force used the program name most frequently for NATO hardened aircraft shelters. Paralleling TAB VEE, the Air Force inaugurated a program refined specifically for Vietnam entitled Concrete Sky. Simultaneously, AFSC initiated Project 1597, “Protective Shelters for Tactical Aircraft,” to research, develop, evaluate, and test shelter cover materials. The 560th Civil Engineering Squadron at Eglin directed Concrete Sky, with the Air Force Weapons Laboratory at Kirtland handling Project 1597. The squadron was a TAC unit that was charged with establishing the Civil Engineering Field Activities Center at Eglin. Planning for the center began in November 1966, with instructors and supervisors rotating in from Southeast Asia to Field 2 during early 1967. The 560th Civil Engineering Squadron had previously erected support structures and revetments in Vietnam as a Red Horse (construction) squadron. At Field 2, Concrete Sky was just one of multiple missions focused on infrastructure needed for the war effort. Concrete Sky was a long and complicated project, with 10 phases between late 1966 and the middle 1970s. AFSC set up initial tests at Field 2, including three different prototype shelters in Concrete Sky I and II. Individual shelter components were simultaneously in test at both Eglin and Kirtland. The 560th Civil Engineering Squadron erected the test structures at Field 2 and trained men to erect the shelters in Vietnam. As of Concrete Sky III in January 1968, the Air Force Weapons Laboratory at Kirtland took on ordnance testing for the shelter, with physical testing at the UTTR. The next two phases, IV-V, completed experimentation for the first-generation Concrete Sky shelter. Phases VII and VIII offered further refinements through munitions tests at Holloman Air Force Base and again on the UTTR._1.1

The Air Force built first-generation Concrete Sky shelters for at least two very large programs overseas during the late 1960s into the early 1970s—the first of which was for Vietnam. The Tet Offensive, coupled with the six-day Israeli war, had greatly enhanced the Department of Defense’s awareness of the need for protective construction. First-generation Concrete Sky for Vietnam resulted in an aircraft shelter formed from a steel arch, with a poured concrete cover 18 inches thick. A freestanding rear wall added protection and included a jet exhaust opening. Typically, the Air Force erected these shelters with some low revetment along the sides, electing to fit only a small number with front armored doors. Most shelters stood open, front and rear. Red Horse completed the final first-generation Concrete Sky shelter in Southeast Asia in early 1970 at Tuy Hoa. The program had added nearly 400 of these shelters to the existing revetments at air bases. While the focus was on protective construction for Vietnam, the TAB VEE shelter program stalled. The Air Force did not begin construction for TAB VEE until 1968. The double-corrugated steel shell for the TAB VEE shelters was in accelerated production before the close of the year, with manufacturers producing 35 shelters per week in double shifts. The Air Force initially erected the shelters in Vietnam, but also procured TAB VEE shelters for Korea and planned them for Europe. Almost 400 shelter shells were also set aside in War Readiness Materiel (WRM) storage at the Air Force Logistics Command (AFLC) depot bases of McClellan in California and Tinker in Oklahoma. By late 1968, the United States Air Forces in Europe (USAFE) also made substantial distinctions between the shelter program underway in Vietnam and Asia, and that beginning in Europe._1.2

In 1966, the Air Force Weapons Laboratory, Kirtland AFB, began Project 1597, which evaluated various aircraft shelter designs. In 1967, Project 1597 was joined by Project Concrete Sky, which was initiated by the Director of Civil Engineering. It placed added emphasis on ease of production in the United States to meet the immediate need in Southeast Asia (SEA). In both projects, the troops in Tactical Air Command’s 560th Civil Engineering Squadron at Eglin AAFB provided support for testing and evaluation of various shelter designs._6.1

TAB VEE became a NATO effort, planned at 342 hardened aircraft shelters. The program also included dispersal pavement for the parked aircraft and protective construction for other types of facilities. From mid-June 1969 forward, TAB VEE became complicated. Multiple governments were involved. In addition, TAB VEE absorbed ongoing design and engineering improvements. By the close of that year 180 shelters were in place in Europe, with others planned for the Middle East. The Concrete Sky shelters totaled 1,500 in Vietnam, Korea, and Europe as of January 1970. The Air Force erected more than half of these with 15 to 18 inches of concrete cover. By the end of 1971, USAFE finished 360 shelters in Europe and the Middle East, with 18 in active construction. The comprehensive TAB VEE program cost stood at $95.5 million. Completion of the TAB VEE program lengthened, in part due to the addition of armored doors for the aircraft shelters and construction of ancillary facilities. Front closure for the European shelters was a serious concern in 1970, stimulating more design modifications. (During this same period, the shelters erected in Korea featured ballistic nylon closures.) Concrete Sky VIII of 1969 had partially tested prow-shaped doors that were recessed inside the shelter. Late in 1969, too, the Directorate of Civil Engineering initiated studies toward the next-generation shelter planned for the F-111 and the F-4._1.2

At Eglin, tests for Concrete Sky VI moved from Field 2 to Field 7 in 1968-1973. An isolated shelter erected on Range C-52E also appears related to the Concrete Sky VI program. USAFE had proposed an alternate to the first-generation, concrete-covered steel arch shelter of Concrete Sky, even as the shelter went in place for TAB VEE. The “improved” USAFE shelter featured “quarter-circle arch segments joined at the top of the shelter and arch ribs joined to adjacent ribs by circumferential joints extending around the shelter perimeter.” For Concrete Sky VI, the Air Force Weapons Laboratory at Kirtland contracted with the architectural-engineering firm Holmes & Narver of Los Angeles to design the hardened rear wall and exhaust system. The 557th Civil Engineering Squadron erected 12 improved USAFE shelters in a dispersal layout for an AFSC test program at Field 7 (today’s Range B-12) (see Plate 44). Plans of 1972 called for “four precast concrete actual shelters, eight dummy shelters, and 3500 linear feet (LF) of concrete taxiway.” The single shelter on Range C-52E is also of approximate 1972 construction, with selected differences. This shelter featured a double layer of reinforced concrete, rather than single as at Field 7 and its capstone treatment was peaked rather than flat. During the final years of the Vietnam War, the Directorate of Civil Engineering moved toward the design and engineering of a true second-generation aircraft shelter—Concrete Sky X, with the goal of hardening against nuclear effects. Preliminary test efforts focused at the Air Force Weapons Laboratory at Kirtland for Concrete Sky VIII and IX. As Concrete Sky X unfolded, Eglin retained the overall responsibility for the project. In late 1971, a six-man team from the Civil Engineering Center under AFSC at Wright-Patterson flew out to Cannon Air Force Base in New Mexico for tests of a shelter shell there. The Concrete Sky X shelter, described as a second generation shelter, was about twice as wide as the previous Concrete Sky shelter built for Vietnam and TAB VEE. Concrete Sky X accommodated a variety of aircraft, with design efforts focused at first on the F-111. At Cannon, the AFSC team used a large machine “capable of reshaping existing shelter steel to the required larger radius.” The Air Force completed preliminary designs for the second-generation shelter during early 1972. The immediate intent was to erect 24 steel shelters, without concrete cover, for the F-111 at four SAC bases. This figure climbed to six bases as SAC built out the program. As of about 1973, AFSC transferred Concrete Sky X responsibility to the Air Force Civil Engineering Center at Tyndall Air Force Base in the Florida panhandle to the east of Eglin. The Civil Engineering Center itself moved from Wright-Patterson to Tyndall at this same time. AFSC erected a test Concrete Sky X shelter at Tyndall in 1974. Eglin continued to be involved, with major responsibilities even after this date._1.3

As of 1974-1976, all efforts turned toward true hardening. A third-generation program, Distant Runner, was underway simultaneously with continued construction for Concrete Sky X and upgrading for TAB VEE first-generation shelters at bases all over the world. AFSC installations contributing to the project were Eglin, Kirtland, Hill, and Tyndall. Leo A. Daly, the architectural-engineering firm for the SAC alert mole-holes and Headquarters SAC underground command posts of the 1950s and 1980s, designed the shelter for Distant Runner. During 1977, NATO planned to double the number of its protective aircraft shelters through second and third-generation construction. The expansion of the program would take the total number of shelters to nearly 800. At the opening of 1979, 497 hardened aircraft shelters were operational in NATO countries. Of these, the TAB VEE shelters totaled 396—many augmented with upgrading. At this same time, the Engineering and Services Laboratory at Kirtland began a study for electromagnetic pulse (EMP) hardening of tactical aircraft shelters, and Tyndall conducted a second phase for an aircraft shelter upgrade. Through Distant Runner, new hardened aircraft shelter designs and variations for the third-generation program continued into 1981.

During August through September 1981, Field Command, Defense Nuclear Agency (FC/DNA) conducted a five-event, high explosive test series at White Sands Missile Test Range, New Mexico. This test series, Distant Runner, was part of the Defense Nuclear Agency’s Theater Nuclear Forces Survivability, Security, and Safety Program. Event 4 of that series exposed one HAS to an internal pressure/fragmentation loading generated by the simultaneous detonation of 12 Mk82 general purpose bombs (Net Explosive Weight (NEW) 1040Kg (2,292lbs) of tritonal) inside the closed shelter. Event 5 exposed another shelter to an internal pressure/fragmentation loading generated by the simultaneous detonation of 48 Mk82 General Purpose Bombs (NEW 4,159Kg (9,168lbs) of tritonal) inside the closed shelter._8.1

Marine Medium Tiltrotor Squadron 163 (VMM-163) participated in Operation Distant Runner

Distant Runner involved multiple classified tests on the UTTR and at several locations in New Mexico. Distant Runner included designs for shelters tailored to the TR (tactical reconnaissance) -1 spy plane and the E (electronic radar) -3A Airborne Warning and Control System (AWACS). Yet another upgrading, the Weapons Storage and Security System (WS3), integrated nuclear weapons storage compartments below the floors of earlier generation shelters. The Air Force sustained buildout for the entire program into the early 1990s, with Project Reliance closing down the program in 1992._1.3

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References

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