Science and Technology News

Wednesday, August 19, 2015

How GPS changed airdrops

by Airman 1st Class Autumn Velez
7th Bomb Wing Public Affairs

8/19/2015 - DYESS AIR FORCE BASE, Texas  -- When thinking of the Global Position System or GPS, satellites orbiting the earth may come to mind; but at Dyess, the 317th Airlift Group is using GPS to enhance the accuracy of airdrops.

"The term JPADS basically encompasses precision airdrops," said Capt. James Morris, 40th Airlift Squadron C-130J Super Hercules weapons officer said.  "It's a more precise way of employing airdrop capabilities by using GPS."

There are two types of Joint Precision Airdrop Systems; guided JPADS and Improvised Container Delivery System. Both applications begin with the deployment of a sonde.

A sonde is a GPS receiver that is dropped by a loadmaster and makes its way down an air column using its own parachute over the planned drop zone during the aircraft's first pass. The release point is calculated by a computer through climatology and meteorological information. The sonde then collects coordinates for its position as it moves through the air column. These points are transmitted back to the aircraft system.

"As the sonde falls to the ground, it takes snap shots, so here I am, here I am, all the way down," Morris said. "With that data, we can determine what the actual, no kidding winds are."

While traditional methods have a predetermined drop point, the sonde allows aircrews to take the information collected and calculate a better release point. This results in equipment landing closer to its targeted location.

The difference between a guided JPADS and I-CDS airdrop comes in once the sonde is dropped.

A guided JPADS, also referred to as a guided-bundle, is a bundle that has an Autonomous Guidance Unit attached to the top of it. The AGU contains a battery power pack, a GPS receiver, and guidance, navigation and control software package. Together, the AGU works to relay the bundle's position to the servomechanism, a device that communicates to the parachute to make the appropriate adjustments to reach the drop zone.

"Think of a paratrooper under a parachute," Morris said. "The box makes calculations to steer the bundle to a target on the ground just as human would."

Sondes are used in addition to the AGU to provide an accurate release pass, which ensures the airdrop is as accurate as possible.

On the other hand, there is I-CDS. I-CDS is a type of bundle that derives from the container delivery system bundle. Traditionally, I-CDS bundles drop at a predetermined point with the intention to meet the point of impact on the drop zone.  Even though this method is more accurate than traditional CDS airdrop, especially from higher altitudes, they aren't necessarily as accurate as JPADS.

With the addition of the sonde, aircrews are able to get a better idea of the effects of the air column.

"We have been using container delivery systems for years," Morris said.  "When JPADS rolled around, we thought, 'Hey we are going to take these methods and improve traditional CDS.'"

With the help of GPS, the 317th can accurately accomplish the mission.

"Being able to use JPADS greatly enhances my job by allowing me to accurately and effectively deliver much needed equipment and supplies to our ground forces throughout our area of operation," said Senior Airman Jaime Richards-Granger, 39th Airlift Squadron loadmaster.

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