Technology in Airdrop Operations
CPT Stephen R. Davis CPT Mary E.
Denniston CPT Edward F. Ehlers
Quartermaster Professional Bulletin-Autumn 1997
Operation Provide Promise was the largest humanitarian airdrop operation in the history of the United States. Relief supplies to the former Republic of Yugoslavia (Bosnia-Herzegovina) started in February 1993 and officially ended near the close of 1995. More than 30,000 bundles of humanitarian aid were airdropped in support of this operation. These bundles included food, medical supplies and winterization items (such as blankets, clothes, plastic sheeting, nails, candles and tape).
Dangerous Drop ZonesBecause of the drop zones dangerous locations, none of the airdrop equipment was recovered during Operation Provide Promise. This resulted in $30 million worth of air items depleted from US war reserves. Though humanitarian resupply was a success, emerging airdrop technology demonstrates that airdrop missions could have been conducted more efficiently and cost effectively.
At the beginning of the mission, eight aircraft (six US, one German and one French) were loaded with bundles daily. In the wintertime, because of the necessity of the relief items, the mission increased to 16 aircraft (12 US, 3 German and 1 French) nightly. To accomplish the expanded mission, the 5th Quartermaster Detachment employed more than 200 soldiers, to include 30 additional riggers from US Army-Italy, nearly 100 soldiers from other US Army Europe units, 30 Reserve Component soldiers from Georgia, and 20 allied soldiers from France and Germany.
The two main types of airdrops were high velocity for airdrop altitudes of 10,000 to 18,000 feet and free drops for situations when ground convoys could not reach towns to distribute the food and supplies. The high-velocity method consisted of the Container Delivery System (CDS), a 26-foot ring slot parachute on top of an A-22 container. There were over 200 different CDS food and medical configurations developed for this operation.
When the operation expanded, the demand for the 26-foot ring slot parachute surpassed the quantity on hand. After conducting several tests, a larger parachute, the G-12D, was used. This parachute, 64 feet in diameter, cost $2,500, roughly five times more than the 26-foot ring slot. Part of the decision to use the G-12D parachute was based on a stock of 26,000 of these parachutes in Europe that were starting to deteriorate. With the smaller 26-foot parachute, one bundle was attached. The larger G-12D parachute allowed riggers to connect one to four loads on a single parachute.
The G-12D is a standard low-velocity parachute designed to drop heavier loads from a much lower altitude than what Operation Provide Promise airdrops required. To change this low-velocity parachute to a high-velocity one, the riggers had to modify the G-12D. This procedure adds about 10 minutes to the packing process. Instead of taking 1 soldier 30 minutes to pack the 26-foot parachute, the G-12D took 3 soldiers 49 minutes. After the rigging, the G-12Ds modification gave the parachute the same capabilities as the 26-foot parachute, but the G-12D could handle twice the weight.New Inexpensive System The other airdrop method used is free drop. A newly developed system is called Tri-wall Aerial Delivery System (TRIADS). This system is very effective and inexpensive, costing only $72 per bundle, compared to the CDS costing almost $800 per bundle. Unlike the CDS, where one package would draw a large crowd to one location and not distribute the food evenly, the TRIADS would spread supplies such as Meals, Ready to Eat (MREs), blankets and clothing over a larger area. Thus, TRIADS distributes the relief supplies to more people. The supplies were packed into a 39-inch x 41-inch x 50-inch cardboard box with cardboard honeycomb padding.
When the bundle left the aircraft, the box would open up, allowing the supplies to free fall to the ground. Although some supplies were destroyed upon impact, enough survived the drop to make this method worthwhile. However, TRIADS does have drawbacks. The number of MREs delivered by using one CDS is 768, while the TRIADS only can deliver 480 meals. A TRIADS is very labor-intensive to build and generates large amounts of trash.
The humanitarian aid operation in Bosnia-Herzegovina showed several drawbacks in the techniques and equipment used by US airdrop personnel. The relief effort also demonstrated a need for improved methods, cost-saving equipment and reduced man-hours for conducting stability and support operations. These operations are no longer the exception, but the rule. As a result, the US militarys concept of airdrop operations must be adjusted to reflect this trend. The adjusted concept must focus on capacity, survivability and efficiency.
Capacity can be defined as tons of supplies per mission per aircraft. The goal of the new airdrop equipment is to increase capacity, therefore reducing cost, increasing accuracy and increasing aircraft survivability. Two methods of increasing capacity are building larger airplanes and designing CDS to handle more supplies. The procurement of the C-17 increased aircraft capacity. Now, however, the focus is on CDS innovations.
Survivability refers primarily to protection of aircraft, crews and equipment. The best protection is surprise. Two release techniques that increase survivability are high and offset, and low and fast. Low and fast delivery relies solely on surprise and does not work well with humanitarian relief operations.
High and offset delivery uses a standoff distance to decrease aircraft vulnerability, but several problems arise when the distance to the drop zone is increased. In particular, some problems are reduced accuracy, larger drop zones, and loss of supplies and equipment. Parachutes enhanced with the Global Positioning System (GPS) and manual guidance capability would greatly increase accuracy, but at a cost unacceptable for one-time-use humanitarian relief operations. The key to relief operations is achieving maximum survivability of aircraft at a lower cost. Currently, no military innovations address this specific issue.Current Cost Efficiency is driven mainly by cost, labor and transportability. The primary factor affecting the cost of humanitarian relief operations is the one-time use of current airdrop items that were intended for multiple use. Labor involves the packaging of supplies into CDS, packing parachutes and attaching parachutes to loads. The primary concern is reducing the number of times supplies are handled. If supplies were prepacked suitable for airdrop and manufactured in dual-purpose containers and parachutes, the workload of riggers would decrease dramatically.
Operation Provide Promise identified the need for more accurate, less labor-intensive and less costly aerial delivery equipment. The need for better delivery equipment has opened the door for new technologies, taking into account todays three main concepts: the Low Cost Aerial Delivery System (LCADS), the Enhanced Container Delivery System (ECDS), and the Humanitarian Airdrop Container System (HACS).One-Time Use Parachute The LCADS features a prepackaged, one-time-use parachute. This low-cost parachute can be used at all altitudes. The greatest advantage of LCADS is its impact on efficiency. First, the production cost is about one half of the current 26-foot ring slot parachute used in Operation Provide Promise. Second, having the parachute prepackaged at the manufacturer greatly decreases the time required to rig supplies and the strain on the riggers workload. Riggers can focus on the load itself and not worry about packing or repairing the parachutes. There is no apparent effect on capacity and survivability.
The ECDS improves the existing CDS. It uses a 463L-based platform that is easier to transport and rig. The ECDS can be moved by forklift and transported by various means. Capacity increases from the current 2,200 pounds to 10,000 pounds. Increasing the capacity reduces the number of bundles. This has a positive impact on accuracy at multiple altitudes. The disadvantage for ECDS is cost. One systems cost is estimated at $10,000, and the ECDS is not reusable based on the current design of 463L pallets.
The HACS, intended for one-time use, consists of cardboard and durable plastic for the top and bottom. This system was developed out of necessity to reduce the cost of humanitarian relief operations. The HACS cost is about one-third of the current CDS. During relief food distribution, the use of airdrop containers proved labor-intensive and time-consuming. Trailers arrived with different types of food to be packed by riggers. The food then had to be moved from the trailers and dispersed into the different containers. Because of this time-consuming function, alternatives have been developed to reduce labor, as well as cost. Containers are received directly from the depot, prepackaged and ready to airdrop. Riggers attach a skid board and disposable prepacked parachute. The container is then ready for airdrop. Although HACS reduces labor and costs, its disadvantage still outweigh its advantages at this time. Capacity is yet to be determined but has the potential to reach the equivalent capacity of the current container systems. Survivability of supplies delivered using HACS, in the testing phase, has not been successful.
During Operation Provide Promise, the US forces dropped an average of 100 containers per day and recovered none. This resulted in the virtual depletion of war reserve stocks of aerial delivery systems at a substantial cost of over $30 million. The TRIADS and modifications to the G-12D parachute developed through human ingenuity greatly reduced the cost to the US government. The need to explore all commercial capabilities and options in the arena of airdrop equipment is crucial for continuing humanitarian operations. Implementation of newly designed single-use equipment, such as parachutes and containers prepackaged at the depot level, gives the airdrop community the ability to provide humanitarian support without depleting war reserves at a substantially lower cost.
Computer Simulation Equals Better Parachutes Parachutes have long played an important role in the deployment of soldiers and supplies. Airdrop technology will take on an even greater role in the future, as humanitarian operations increase in frequency and demand for the rapid deployment of food, medicine and relief shelters rises. The US Army Soldier System Commands Natick Research, Development and Engineering Center (NRDEC), Natick, MA, is constantly looking at ways to advance airdrop capabilities. NRDECs Mobility Directorate is paving the way for more efficient parachute design and safer parachute deployment. Parachute Physics Understanding the physical forces that govern the deployment, inflation, terminal descent and impact of airdrop systems is important to designing parachutes. The physics of these events are very complex, however, because they involve not only the motion of the airdrop system itself but also the turbulent airflow around and through the parachute. Analytical or numerical models describing and predicting parachute deployment and inflation have therefore been difficult to construct, and parachute designers have traditionally relied on trial and error tests in the field.
The Mobility Directorates Computational Analysis Team (CAT) is now developing analytical models that predict the physics of parachutes by coupling equations that govern the air with equations that govern the motion of the parachute. Soon, designers will be able to use computer software based on these models to create new parachute systems, rather than relying on full-scale testing.
CAT aerospace engineers say that using computer simulations to develop parachutes and airdrop systems will reduce the time and save the expense associated with large-scale testing. It will also assist in the optimization of new capabilities and provide an "airdrop virtual proving ground environment."
The goal is to develop a relatively user-friendly design tool that can predict realistic parachute performances so that engineers can design new parachutes to meet a variety of performance goals. During humanitarian airdrop missions in Bosnia, for example, when the G12 parachute was found to be too large for the load, the technology was used to come up with ways to make the chute act like a smaller model.
Working with researchers from the Army High Performance Computing Research Center, the University of Connecticut, the Army Research Laboratory and elsewhere, with support from the Army Research Office, CAT researchers are trying to numerically couple software that predicts fluid dynamics with software predicting structural dynamics.