Joint Precision Airdrop System
The Joint Precision Airdrop System (JPADS) is an American military airdrop system which uses the GPS, steerable parachutes, and an onboard computer to steer loads to a designated point of impact (PI) on a drop zone (DZ). It integrates the US Army's Precision and Extended Glide Airdrop System (PEGASYS) and the Air Force's Precision Airdrop System (PADS) program. PEGASYS consists of several precision airdrop systems, ranging from extra light to heavy payloads, while PADS resides on a laptop which computes the release points for non-steerable parachute systems by means of software capable of mission-planning, weather forecasting, and current measurements of wind velocity, altitude, air pressure, and temperature. It can also receive weather updates and en route mission changes through satellite links.
US Army Research, Development and Engineering Command (RDECOM) was the primary developer for JPADS, which meets several requirements: increased ground accuracy, standoff delivery, increased air carrier survivability, and improved effectiveness/assessment feedback regarding airdrop mission operations.
The steerable parachute or parafoil is called a "decelerator," and gives the JPADS system directional control throughout its descent by means of decelerator steering lines attached to the Airborne Guidance Unit (AGU). They create drag on either side of the decelerator, which turns the parachute, thus achieving directional control.
The Airborne Guidance Unit (AGU) contains a GPS, a battery pack, and the guidance, navigation and control (GN&C) software package. It also houses the hardware required to operate the steering lines. The AGU obtains its position prior to exiting the aircraft, and continues to calculate its position via the GPS throughout descent.
The Mission Planner software gives the aircrew the ability to plan the mission, in flight if necessary, as well as steer the aircraft to its Computed Air Release Point (CARP), where the load is released.
JPADS involves four increments, categorized by the weight of the cargo to be dropped:
Increment I: JPADS-2K / applies to loads up to 2,200 lbs / classified as the “extra light” category / commensurate with Container Delivery System (CDS) bundles.
Increment II: JPADS-10K / applies to loads up to 10,000 lbs.
Increment III: JPADS-30K / applies to loads up to 30,000 lbs.
Increment IV: JPADS-60K / applies to loads up to 60,000 lbs.
While the accuracy of the JPADS is classified, it's good enough to drastically reduce drop zone size requirements, which significantly increases the number of locations which can be used as a drop zone. Furthermore, sequential loads which may require a conventional drop zone as long as half a mile can be dropped using JPADS into a much smaller area.
JPADS offers several main benefits, including an increase in the number of available drop zones and an increase in the cargo's precision, which benefits the user. JPADS also increases the survivability of the delivery aircraft and its crew.
Current drop zones are quite large; 600 yards or more. Airdropping sequential loads (multiple loads aboard a single aircraft) requires very long drop zones on the order of half a mile or more, or else the aircraft must make multiple passes over the same area, a tactically unsound thing to do. Furthermore, achieving a high degree of accuracy (less than 100 yards) requires the aircraft to fly at the lowest altitude possible, which can range from 400 feet above ground level to as high as 1,500 feet, depending on the altitude of the drop zone, the weight of the load, and the number and type of parachutes required.
JPADs can achieve the same or better accuracy from greater heights, allowing the aircraft to drop the load at a much higher, and usually safer, altitude.
Because JPADS allows the aircraft to drop at high altitude, the aircraft can actually drop the load a good distance away from the drop zone, which affords the aircrew to remain free of enemy threats which may be near the area where the load is being dropped.
Airdrops are usually performed at slow speeds for an aircraft, usually 130 kts for paratroopers and 140 kts for cargo. When combined with the low altitude required for precision, the aircraft are vulnerable to enemy ground fire. With JPADS, the aircraft is much more likely to survive, as it can drop at a much higher altitude, above most enemy ground fire.
Because the system can transmit its current position back to the airdrop aircraft, it provides its exact landing location which the aircrew can then transmit to ground forces which may not have arrived at the drop zone.