Air Force Civil Engineer Magazine, Vol. 20, No. 1 (TPD1402058)

Because of its resemblance to Afghanistan, Melrose Air Force Range, located 20 miles west of Cannon Air Force Base, N.M., provides some of the most realistic training available to special operations forces. But the dust conditions there reduce engine flight hours to 140 to 250 as opposed to the designed 500 in normal conditions. Once the limit is reached both engines are removed from the aircraft and rebuilt — a maintenance cost of approximately $1.6 million a year.

Due to these high costs, Air Force Special Operations Command tasked the 27th Special Operations Civil Engineer Squadron to engineer a solution — a low-dust landing pad — that could extend the lifecycle of the CV-22’s engines while maintaining realistic training on MAFR.

 Design

While there are many commercial methods for dust control, none are capable of withstanding the intense heat of the CV-22 engine’s exhaust. Options considered for the problem included a full-depth concrete pad, large river rock and a liquid polymer or synthetic fluid soil treatment. The soil treatment method was ultimately selected as the most cost-effective and expedient.

Having never constructed such a project, 27 SOCES engineers consulted experts from the U.S. Marine Corps as well as the U.S. Army Dust Control Field Handbook. Marine Wing Support Squadron 374 has used the soil treatment method in constructing several helicopter landing zones and a short field runway for heavy aircraft. There was major concern about the limited amount of data on the durability of the chosen technique.

Choosing the right commercially available dust control product was crucial. There are two main types of products on the market: synthetic fluids and liquid polymers. Synthetic fluids are oil-based and control dust by binding soil particles together. However, this can cause large chunks of soil to stick to aircraft landing gear, a safety issue that immediately excluded synthetic fluids from consideration. This left liquid polymers, which are water-based and control dust by gluing particles together. Once dry, the liquid polymer doesn’t stick to aircraft tires.

Our application needed a product with polymer content greater than the 20 to 30 percent in most commercial products. The MWSS 374 recommended the Soilworks product called Soiltac, with a polymer content of 50 to 60 percent that allows for greater strength while reducing the amount of product required. Using data from the U.S. Army Dust Control Field Handbook and information provided by the MWSS 374, 27 SOCES engineers developed a mixture using Soiltac, Portland cement, recycled asphalt and water.

To meet training requirements, the landing pad is a 340- foot diameter circle with an inner 240-foot-diameter landing area and an outer 100-foot-diameter dust control zone (see figure). The landing area consists of six inches of recycled asphalt, Portland cement, Soiltac and water. The dust control zone was created by applying a Soiltac and water mix to the graded surface, in quantities determined by following the recommendations of both MWSS 374 and Soilworks engineers.

Construction

The landing pad construction area was an existing unimproved heavy landing zone. The heavy equipment shop spent three weeks excavating and hauling soil from a borrow pit, and then backfilling to bring the site up to grade. Recycled asphalt (840 cubic yards) was used to further improve the soil. With the site prepped, the final mixture of Soiltac, water, recycled asphalt and Portland cement was placed and mixed in under two days.

The manufacturer recommended an asphalt reclaimer or tractor with disk plows to mix the materials, but such unique equipment was unavailable in the local area and sourcing from a larger metropolis wasn’t cost effective. So, the 27 SOCES improvised and used a grader for mixing.

With the pad complete in less than a month it was time to test it. The initial assumption of the 20th Special Operations Squadron at Cannon was that the pad wouldn’t be able to withstand the loading of a CV-22. An Air Force CV-22 completed nine test landings, including several low hovers a few feet over the pad. The pad showed no sign of structural or heat damage.

Five months and more than 100 landings later, the pad is holding strong with no signs of damage. Leadership from AFSOC and the 27th Special Operations Wing was so impressed that the 27 SOCES was tasked to construct three additional pads before the end of the calendar year.

1Lt Buscemi was the officer-in-charge, Operations Engineering, 27 SOCES, Cannon AFB, N.M. He is now the Energy Manager, 8 CES, Kunsan AB, Republic of Korea.

Building a Better Landing Pad

Figure (1.) Grading the recycled asphalt after it was placed on the site.

 Figure (2.) Placing Portland cement before the Soiltac and water was applied.

 Figure (3.) A grader mixes the Soiltac, water, Portland cement, and recycled asphalt together. At the same time a water truck sprays the Soiltac and water onto the center of the pad.

Figure (4.) The Steel Wheel roller compacts the pad. (U.S. Air Force photos by 1st Lt. Matthew Buscemi)

(Figure) Design dimensions for landing pad.

 (Figure) A CV-22 Osprey makes a test landing on the low dust landing pad constructed by the 27th Special Operations Civil Engineer Squadron. (U.S. Air Force photo by Senior Airman Ericka Engblom)