Such hangars-also called expeditionary hangars or deployable hangars-are much more than just big tents. They are places where the climate and humidity can be controlled in order to create ideal conditions for maintenance and storage. They aid concealment from the enemy by blocking the escape of light and heat radiation. They shield aircraft and personnel from wind, rain, sand, insects and other elements. And with the B-2 bomber, they obviate the need to fly back to the United States to refuel and rearm, giving the planes a much quicker restrike capability.

The Air Force is upgrading its entire Base Expeditionary Airfield Resources (BEAR) infrastructure. As part of the upgrade, the existing Aircraft Hangar (ACH) for tactical aircraft will be replaced with a new generation of hangars, dubbed the Large Shelter System (LSS). The LSS program is designed to provide an air-transportable hangar to support tactical fighter aircraft at expeditionary airfields worldwide. A request for a LSS proposal is expected soon by the Air Armament Center, Combat Support Systems, System Program Office at Eglin Air Force Base, FL.

The Air Force has 55 ACHs, the last of which was purchased in 1984. There are newer hangars in the inventory, including the dome shelter and the frame-supported tensioned fabric shelter. But these newer shelters have been more commonly used for vehicle maintenance, warehousing and the like, rather than for tactical aircraft. The original dome shelter is too short for the majority of tactical aircraft, with the exception of the F-16.

The LSS calls for substantially increased wind load resistance, an upgraded electrical system and better climate control. Such improvements are to be accomplished while at the same time reducing the overall logistical burden associated with the structures.

In disassembled form, the LSS will be lighter and take up much less space than the current ACH, enabling the Air Force to fit more of them into a C-130 or other transport aircraft. Among other things, maximizing the number of disassembled hangars that can be carried on a transport plane reduces the number of sorties needed to supply the bases. The new hangars also will require less time to set up.

"The LSS program is designed to reduce the logistical footprint of getting these assets into the AOR [area of responsibility]," said Jennifer Morgan, acquisition program manager for the LSS. "That means reducing their weight and volume, and making sure they require fewer spare parts and other things that go into maintaining a shelter."

Pilot unit responsibilities for expeditionary resources reside with the Materiel Maintenance Group at Holloman Air Force Base, NM, also known as the BEAR Base. It is responsible for installing flight line kits (hangars, maintenance facilities), billeting, tenting and other infrastructure for forward-deployed, temporary air bases. As the pilot unit, it develops packing plans, maintenance and repair procedures as well as fielding the next generation of BEAR equipment.

By expediting the BEAR Base set-up process, the LSS will enable faster deployment of aircraft missions. "The current ACH requires specialized technicians to repair and is labor intensive," according to Colonel Hal Tinsley, BEAR Base commander. "Because of the aging technology, repair and replacement parts are no longer available. The LSS will provide BEAR Base maintenance personnel the ability to perform rapid field repairs on the LSS, while fielding state-of-the-art technology."

The LSS will be used for performing maintenance on various fighter aircraft including the F-22, Joint Strike Fighter     (F-35), A-10, F-15, F-16 and others. One shelter accommodates one aircraft. At a typical BEAR location, there are three hangars-two in the initial flightline kit and an additional shelter in the follow-on flightline kit. As more aircraft are needed for a particular mission, BEAR Base can keep adding shelters.

The current LSS procurement calls for fabricating hangars by using existing commercial technology, by developing a new design, or a combination of both. In the future, there will be a follow-on procurement for an environmental control system provided by the hangar manufacturer-not BEAR, as is currently the case-for heating and cooling.

Objectives of the LSS include:

• Reducing airlift sortie requirements by 25 percent.
• Improving functional, physical and operational performance characteristics.
• Being capable of operating in worldwide environmental and climatic conditions.
• Long storage life and high erection/teardown cycle usage.
• Minimal erection/strike-down time.
• Maintainable and repairable using standard or common tools.
• Able to interface with existing and programmed BEAR utility systems, concepts of operations, and logistics support framework.

The LSS is to be able to withstand 100 mph winds and 20 pounds-per-square-foot snow loads. It should take no more than 32 hours to erect with a crew of 10.

The shipping and storage containers are to be optimized for transport on C-130s and compatible with 463L pallets. The 463L cargo system is the Air Force standard for moving concentrated cargo to be air landed. It will withstand a minimum of 20 shelter erection/strike cycles and enable extended periods of outdoor storage up to 20 years anywhere in the world (desert, oceanic/tropical and arctic environments). The maximum shipping weight of the LSS will be around 27,000 pounds or less, based on a 25 percent reduction of the existing ACH system.

"We want to make sure that the warfighter can get more assets in theater with fewer sorties," said Morgan. "So we want to reduce the volume and the weight of the shelters in order to get more of them-and other equipment-on that sortie."

Not Just a Big Tent

Most shelters are made of an aluminum-extruded frame and a PVC-type of fabric that protects against UV rays, wind, rain and other elements. PVC, or polyvinyl chloride, is a type of water- and fire-resistant plastic commonly used for plumbing pipes, vinyl siding and linoleum. There are also inflatable shelters, steel-frame shelters and carbon fiber frame shelters. "We have not narrowed down the solicitations to zero-in on any specific technology," said Morgan. "This is a best value acquisition. So based on our requirement, whichever technology affords us the best value-performance and cost-will be the successful offer."

Tensioned fabric shelters made their debut during Operation Desert Storm, mainly for warehousing and maintenance. But most of the portable hangars at that time were the older ACHs. "After Desert Storm, we found that the old equipment was falling apart. They attritioned over time. We would cannibalize parts off of them," said Drew Markulin, military program manager at Universal Fabric Structures, Las Vegas, and formerly with BEAR Base while on active duty.

Universal uses a special type of fabric from Seaman Corp., Wooster, OH, which has blackout capabilities preventing light from passing through to the outside when the building is lit up on the inside.

"It's all about the mission in the end," said Markulin. "To set up bases, we want to supply our people with the best equipment. Today's structures do go up a lot quicker and have a longer lifespan. Reconstitution costs-inspection, repairing and repackaging after the hangar is used-have decreased as well, thanks to the tensioned fabric shelters."

The newer fabric and the materials lengthen the lifespan of the structures. "Whereas in the early 1990s you could expect maybe three years out of the fabric, now you can expect seven, eight or 10 years-in 120 degree ambient temperatures, 365 days a year," said Greg Naiman, president of Canvas Specialty, Los Angeles.

In addition to better fabric and frames, there are also improvements such as lightning protection systems, and fall protection systems (a new Occupational Safety and Health Administration requirement). There is tent material that has infrared masking properties, so  a hot vehicle cannot be seen through the walls or ceiling of the tent. Solar panels can be integrated into the structures, which Canvas Specialty is in the process of doing.

The fabric technology of portable hangars comes from the sail manufacturing industry. "If you think about a tent, it's a big piece of material that tries to resist being blown away," said Naiman. "It's not significantly different than what goes on with a sailboat except that a sailboat is harnessing that power."

Naiman's company has a proprietary fabric used for dehumidified storage. According to Naiman, "You can put an aircraft or a tank inside a shelter, zip it closed with rubber zippers, hook a dehumidifier system up to it and have a constant humidity inside the shelter." He said this can result in less maintenance. "If you're out in a desert environment and all the lubricants dry up, that's a huge maintenance issue. So you can create humidity inside the structure-or the opposite is true as well. It's like a ziplock bag."

Naiman said the shelter is far more than just another big tent. "You're dealing with a structure that has a fabric with a low vapor moisture transmission rate and can do some really special things with it." Among other things, he said, it can save the military a lot of money in terms of maintenance. He added, "It's amazing what you can do with these buildings when you're inside of them. A lot of times you're not really conscious you're inside a tent."

Vertigo Inc., Lake Elsinore, CA, has developed a technology for inflatable structures. Its Aviation Inflatable Maintenance Shelter (AIMS), a joint Army-Air Force-sponsored program, is 83 feet by 120 feet. For the Army, the hangar is tailored for the CH-47 Chinook helicopter. For the Air Force, it fits all tactical aircraft.

Deflated, the material is soft and pliant. But inflated, "it's very strong, very stiff and very light," said Glen Brown, Vertigo president. The technology comes from the same patented technology Vertigo uses to make inflatable wings. Manufacturing the material starts with a seamless tube made by a braiding process, and fiber reinforcements are added. It is flexible when not pressurized and very hard when pressurized.

Around the time of Desert Storm, the Air Force's model was based on air dropping the shelter components and erecting it with no heavy equipment, according to Naiman. Today the model involves unloading the components from a landed plane and erecting it with equipment. "That's helped us think about how this will go together," he said. "For example, we can create much larger systems than we could have during Desert Storm because back then, everything had to be done by hand."

The air-drop model has been discarded, at least for now, because the Air Force has placed more importance on reducing the volume and weight of the disassembled unit for more efficient transportation, observed Naiman. Moreover, typically there is equipment already on the ground to erect the structures.

Some tents can house multiple aircraft or very large aircraft. "We're making storage shelters that are 220 feet wide so that you could cover a C-130. You'd be amazed at the expanse that we can cover," said Naiman. However, shelters of this size are not part of the LSS procurement.

The Navy also uses portable shelters, such as on aircraft carriers when an enclosure is needed to protect against the elements or to allow 24-hour-a-day work schedules (typically while in port or in drydock).

Third in a Series

The LSS is the third in a series of shelter updates to the BEAR Base inventory. The first began in 1997 with the Small Shelter System, used for billeting. Then in 1998, there was the Medium Shelter System used for backshops for maintenance purposes. Eglin has no plans at this point for a fourth shelter system.

"The team here at Eglin is really excited about the LSS project," said Morgan. "It's a great opportunity to deliver an updated capability to the warfighter."