FORT CHAFFEE, Ark. -- The CH-47D Chinook helicopter is the U.S. Army's primary troop and supply transport aircraft. It's been around since the Vietnam War and has stood the test of time with its twin rotor blades and 42 cubic meters of cargo space, room enough for two Humvees. But on this warm day in July along the Arkansas River, this legendary aircraft is supporting the Army Reserve's River Assault 2018 with a helocast drop for the Soldiers of the 420th Engineer Brigade.

"We have the flight crews for two CH-47s flying at 10 feet, 10 knots," said Sgt. 1st Class Jared Gay, a subject matter expert with the U.S. Army's Sapper Leader Course out of Fort Leonard Wood, Missouri. "The real-world environment that the helocast will provide will be the infill for any unit. It's an engineer task, but all units can do it."

Held July 22 outside of Fort Chaffee, Arkansas, this training mission took 170 Reserve Soldiers from the comfort of the grassland and dropped them into the Arkansas River with nothing more than a uniform and safety vest.

"It wasn't scary at all," said Pfc. Crystal Rothman, a fueler with the Forward Support Company, 489th Engineer Battalion, 420th Engineer Brigade. "Everybody thought the water was going to be cold. It was not cold, it was pretty warm, actually. There's a long swim to the shore, though."

Although any Army unit can do it, helocasting is an insertion technique developed by Airborne troops whereby Soldiers step off the aircraft's ramp at a low altitude and low speed directly into the water below. Preparation for the exercise included checks on swimming skill and clear directions from the instructors.

"For the first training," said Rothman, "they took us to a pool, it was about nine feet deep. They wanted you to do a deadman float and then swim from corner to corner all the way around the pool to make sure that you're going to be okay for this jump."

"You don't have to be Airborne qualified or go to a school," said Gay. "You spend 20-30 minutes here on the ground with a cast master or senior instructor and you can be able to exit the aircraft into any water at any time. So it's the fastest way to get Soldiers in."

Elements from the Army Reserve and regular Army came together to make this training possible, with guest instructors from the Sapper Leader Course on site and support from the Army's Deep Sea Dive Team.

"The helocast is a once in a lifetime feeling for some of these guys," said Capt. Stephen Potter, commander for the 806th Engineer Company, 489th Engineer Battalion, 420th Engineer Brigade. "Getting them out of the helicopters into the water, I think that's a really cool opportunity, great training for them to have."

This helocast drop fits into River Assault 2018 as one of two main training engagements in the Arkansas River. Later this week, the engineers will conduct a full-scale wet gap crossing, uniting four companies in a joint effort to send Army assets across a river four football fields wide.

"Wet gap and dry gap crossings in the current operations overseas is incredibly vital," said Potter. "We emplaced numerous, uncountable gap crossings in Syria and Iraq during [Operation Inherent Resolve], so this is great training for them to have. If they get this and they execute it, and if something happens and they're needed, this is training that's vital to them."