YUMA PROVING GROUND, Ariz.-- Testing virtually every piece of equipment in the ground combat arsenal is U.S. Army Yuma Proving Ground's primary mission.

Yet for more than 20 years, the Military Freefall School, part of the United States Army John F. Kennedy Special Warfare Center and School, has utilized the proving ground's vast ranges to train thousands of the military's most elite paratroopers.

"Military freefall is inherently a high-risk activity," said Maj. Alan Enke, the school's commander. "It's also more of a clandestine activity that can get you into a denied area fast with all of your equipment and manpower. It's just another way to get there, from the sky."

In the six decades of military freefall, fewer than 1000 individuals have qualified as instructors, and this select group has trained well over 20,000 freefall parachutists. To qualify for this instruction, a prospective student needs to have done a minimum of five static line jumps, though most students have many more than this. Regardless, the increased complexity of freefall parachuting usually renders such experiences irrelevant to a student's ultimate success.

"The majority of the demand, I think, comes from the mental stress of flinging yourself out of an airplane wearing a parachute and gear," said Enke. "It's not a natural thing to take a step off of that ramp and have 13,000 feet of air between you and the ground."

The intensive four-week course begins with classes that teach how to pack a parachute and maneuver in freefall. Next is a week putting the classroom lessons in practice inside a vertical wind tunnel, a 16.5 foot flight chamber able to accommodate eight jumpers simultaneously with a top speed of 175 miles per hour , followed by real jumps from altitude with an instructor an arms-length away. Though the first of the real jumps aren't graded, instructors have a good sense of whether or not a student is poised for success. The presence of the vertical wind tunnel, which opened at YPG in early 2014, is a boon to students who need additional practice.

"The problem was if a student was having any problems in that final three weeks, if they weren't worked out while they were actually jumping, they didn't have the skills necessary to graduate," said Enke. "With the wind tunnel here, if a student is having trouble in the early weeks, we can just put them in the wind tunnel and work on those issues. It's an incredibly valuable training aid for us to get our students to the level they need to be in order to do this stuff back at their unit."

Regardless of the student's skill level, the time spent inside the wind tunnel is relatively limited.

"It's not conducive to the body to be in 120 mile per hour wind for an extended period of time. We rotate the students through on one or one-and-a-half minute long rides," Enke said. "A minute in the wind tunnel is equivalent in time to a jump. If a student is in the wind tunnel for 10 minutes, it's making up for 10 jumps we don't have the capacity to do otherwise."

Further, Enke observes that the wind tunnel portion of the training is far more efficient--and less expensive--than ferrying a sortie of jumpers in an airplane.

"The wind tunnel is exponentially cheaper to run for a minute than an aircraft. Putting a number of students in the wind tunnel for hours is less costly than putting any students in an aircraft for any amount of time."

The wind tunnel is available for use by other Department of Defense entities, though the freefall school's students get priority in its use.

"We've trained various Marine and SEAL units, and some demonstration teams," said Enke. "We've done evaluation training for organizations that work on emerging equipment for military freefall capabilities."

Though the wind tunnel is an important asset for the freefall school, another factor in its dramatic growth of late is the presence of larger, higher performance aircraft to ferry students on their actual jumps. Whereas in years past the school relied on aircraft such as the Casa-212 for its mission, today it uses the C27J, formerly a niche cargo plane that uses the same engine as its larger cousin the C-130.

"We can get two to three times as many jumpers in a plane at a time, get to altitude quicker, and get back down quicker," said Sgt. 1st Class Cody Gustin, detachment sergeant. "The Casa is a capable aircraft, just not that fast."

Enke thinks that the freefall school's mission training in excess of 1,500 jumpers per year in four separate, concurrently-running courses will continue at YPG far into the future.

"YPG essentially provides everything that we need in order to run our training courses here. Virtually everything but the administrative and logistical functions of the freefall school itself are provided by Yuma Proving Ground. It's plug and play for us: we're very fortunate to have this relationship with them."