C-17 Globemaster III - Strategic Brigade Airdrop

Efficiency is critical when Air Force cargo planes are dropping equipment and supplies into a combat zone. Fewer planes mean reduced exposure to enemy ground fire. Airdrops are more feasible since a shortage of aircraft can force cancellation of some missions. By 1999 the Air Force was upgrading the C-17's capability by developing a new air drop system that increased its cargo air drop capacity by 266 percent and reduced, by as much as 30%, the total number of C-17 aircraft required for the Army's strategic brigade airdrop.

By late 2000 the Air Force Air Mobility Command's (AMC's) C-17 Globemaster transporters were able to meet the Army's goal of airdropping a brigade's worth of troops and equipment within 30 minutes. The requirement, called strategic brigade airdrop (SBA), was previously met by a mixed fleet of C-141 Starlifters and C-17's. The C-141 was retiring from service, so the C-17 must be able to meet all of the Army's SBA requirement.

An Army brigade, which contains about 3,250 soldiers and 3,450 tons of equipment, is airdropped and airlanded in two phases. During the first phase, aircraft must be able to drop roughly 2,500 troops and 1,350 tons of equipment within a limited amount of time. During the second phase of the operation, the remaining 750 personnel and 2,100 tons of equipment are delivered to a landing zone.

The SBA delivers - via airdrop (echelon A) and airland (echelon B) - a brigade-sized Army force of the 82d Airborne Division directly from CONUS (whenever possible) to any target area in the world. When performed solely by the C-17, the SBA consists of 53 airdrop (Alpha Echelon) and 46-48 airland (Bravo Echelon) sorties to deliver the XVIII Airborne Division's Ready Brigade-Medium. Items contained in the echelon B include some items that are too large to airdrop, such as tracked and other vehicles from the Immediate Ready Company (IRC). Ultimately, the force package will be tailored to a specific mission, with the Division Ready Brigade (DRB) medium the optimum force for planning.

C-17 Airdrop Enhancements

Without the initiatives, it would take a C-17 SBA formation about 25 minutes longer than the Army's requirement for the airdrop.

Several initiatives were undertaken to equip the C-17's to meet the SBA requirement: reducing spacing between aircraft in flight during personnel airdrops, installing dual-row airdrop capability aboard C-17's, and incorporating equipment that will enable the aircraft to fly in tighter formations during inclement weather.

Only 12,000 feet was required between lead aircraft airdropping personnel with the C-141. However, because of the vortices created by the C-17 a space of 40,000 feet between element lead aircraft was required currently to ensure jumper safety. The C-17 has the same length and wingspan as the C-141 but a much wider cargo compartment and is heavier overall. The heavier airplane, especially with the same length wings, causes a lot more wake turbulence. Using computer models, Air Mobility Command investigated 15,000 feet spacing between element leads and gradually increased the spacing to 40,000 feet to decrease the number of interactions between the aircraft's vortices and the jumpers.

Before progressing to using real paratroopers, AMC dropped 712 mannequins with aircraft spaced 32,000 feet apart to ensure that interval was safe. Then 60 test jumpers, followed by 302 paratroopers from the Army's 82d Airborne Division at Fort Bragg, North Carolina, were airdropped to complete the testing. All test events were completed successfully and safely. The risk hasn't increased by moving the aircraft from 40,000 feet apart to 32,000 feet apart, and it meets the Army's pass time requirements. For safe training and during contingencies, 32,000 feet is right for standard spacing.

More time is shaved off the airdrop time by installing dual logistics rails that allow two rows of equipment to be airdropped from the C-17, doubling its capacity and cutting in half the number of C-17's required to airdrop the heavy equipment portion of the SBA. The airplanes rolling off the assembly line have dual-row capability, and the Air Force had enough dual-row airplanes by July 2000 to meet the Army's SBA requirement.

The new Dual Row Airdrop System [DRAS] delivers equipment more safely and efficiently than the single row airdrop system previously used. The system is used on C-17 Globemaster III cargo planes. Instead of a single row airdrop system, the Dual Row Airdrop System uses a two-row, side-by-side rail system. Loads exit the aircraft sequentially by row. The airdrop altitude range for operations will be 1200 to 750 feet at conventional airspeeds of 130-150 knots and deliver a fully mission capable load in 17 knot surface winds utilizing a parachute release. The system can deliver the same amount of supplies as the single row using half the number of planes or twice as many supplies using the same number of planes.

The Dual Row Airdrop System reduces the number of C-17s needed to support the Strategic Brigade Airdrop (SBA) and airdrop resupply from 45 to 25, and reduces the tactical insertion time. The dual logistics rails allow two rows of equipment to be airdropped from the C-17. This more than doubles the capacity of each C-17 and cuts in half the number of C-17s required to airdrop the heavy equipment portion of the SBA. Some equipment is still required to be dropped in a single row.

The DRAS maximizes the cargo potential for airdrop of the C-17 by permitting airdrop use of the aircraft's dual logistics rail system (side by side) verses the single row airdrop system currently in use. The system reduces drop zone dispersion, results in faster delivery of troops and equipment and reduces threat exposure to both aircraft and airborne forces. The DRAS is composed of common rigging items and modified type V airdrop platforms in lengths of 16 and 18 feet which are 88 inches in width verses the standard 108 inch type V compared to the standard type V version.

The DRAS is able to gravity airdrop loads with a rigged platform weight capability of 14,500 pounds (HMMWV). The system can deliver eight platforms of Humvees and 105 mm howitzers from a single aircraft. It also can be used to deliver trailers, ammunition, food, medicine, power generators, water purifiers and other bulk supplies. On a rigged platform, airdrop items are lashed to a platform with energy-absorbing material underneath to prevent damage on impact. Also, parachutes, slings and other airdrop components are attached to the load.

Initially, station-keeping equipment (SKE) used radio wave frequencies (channels) to enable aircraft to fly in formation during inclement weather. A new version of this equipment called SKE follow-on permits C-17's to fly in poor weather while reducing the amount of space needed between aircraft. The Station Keeping Equipment are updated to allow pilots to keep track of their location relative to up to 99 other aircraft flying in formation over a 100-square-mile area.

On December 10, 2002 McDonnell Douglas Corp., Long Beach, Calif., was awarded a $10,722,968 time and materials contract modification to support Stationkeeping Equipment (SKE) Follow-on-Retrofit (ECP 02090R2C1) includes the procurement of CY01 and CY02 retrofit kits (119 total) and kit installations (86 total) to support the C-17 SKE system upgrade. The SKE upgrade was implemented to support the U.S. Army's Strategic Brigade Airdrop functional requirements. The total funds have been obligated. This work will be completed by December 2003. The solicitation began in November 2001 and negotiations were completed in October 2002. The Headquarters Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (F33657-01-C-2002, P00071). The SKE follow-on was installed in C-17's by the fourth quarter of fiscal year 2004.

McDonnell Douglas Corp., Long Beach, Calif., is being awarded a $15,457,620 firm fixed price with economic price adjustment contract modification. This is a modification to the C-17 production contract to incorporate the effort one engineering change proposal for formation flight system (28 aircraft) (Lots 17-19). The formation flight system is a replacement system and incurred a large credit to delete the station keeping equipment system being replaced. Total credit negotiated is $17,136,680 and total debit negotiated is $1,679,060. This work will be complete by July 2008. Negotiations were completed August 2005. The Headquarters Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (F33657-01-C-2001, P00039).

McDonnell Douglas Corp., Long Beach, Calif., was awarded on January 30, 2004 a $5,987,675 cost-plus-fixed-fee contract modification. In support of the C-17 Global Reach Improvement Project, this effort will acquire 33 kit installations (labor) and spares modification for 10 line replaceable units for the Terrain Awareness Warning System. Additionally, 33 kit installations will be purchased for station keeping equipment. At this time, $2,993,838 of the funds had been obligated. Further funds will be obligated as individual delivery orders are issued. This work will be complete by December 2005. Headquarters Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (F33657-01-C-2002, P00141).

McDonnell Douglas Corp., Long Beach, Calif., was awarded on September 2, 2005 a $15,457,620 firm fixed price with economic price adjustment contract modification. This is a modification to the C-17 production contract to incorporate the effort one engineering change proposal for formation flight system (28 aircraft) (Lots 17-19). The formation flight system is a replacement system and incurred a large credit to delete the station keeping equipment system being replaced. Total credit negotiated is $17,136,680 and total debit negotiated is $1,679,060. This work will be complete by July 2008. Negotiations were completed August 2005. The Headquarters Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (F33657-01-C-2001, P00039).

C-17 Airland Semi-Prepared Runway Operations

The C-17 can operate on paved or semi-prepared airfields and matting. Paved airfields consist of conventional rigid and flexible pavements and are generally used for routine operations. A "semi-prepared" airfield refers to an unpaved airfield. The amount of engineering effort required to develop a semi-prepared airfield depends on the planned operation, the service life needed to support these operations, and the existing soil and weather conditions. Semi-prepared construction/maintenance preparations may range from those sufficient for limited use to those required for continuous routine operations. Options for surface preparation may include stabilization, addition of an aggregate course, compaction of in-place soils, or matting.

Three types of operations are anticipated with the C-17 aircraft. Visual flight rules apply for contingency and training operations. Routine operations consist of normal day to day operations conducted on paved surfaces. Training operations involve training for contingency situations. They can be conducted on paved or unpaved runways (semi-prepared). Since training airfields are for long-term operations, semi-prepared surface structural and dimensional requirements are more stringent than for contingency airfields. Stabilization may be required. Contingency operations are normally short term operations connected with conflicts or emergencies. Airfields for contingency operations can be paved or unpaved. Since operations are limited, structural requirements are not as great. In addition, higher risk to aircraft and personnel may be justified, so requirements such as clearances, are not as stringent.

For a semi-prepared runway located between sea level and 6,000 feet pressure altitude, the minimum length requirement for C-17 operations is 3,500 feet with 300-foot overruns on each end. This length requirement, based upon an RCR of 20, assumes an ambient temperature equal Standard (1962) plus 31 ºF, and a landing gross weight of 447,000 pounds.

A semi-prepared pavement structure typically consists of three layers, the existing subgrade, a subbase, and a base course. A semiprepared airfield may or may not have a subbase or a base. If the existing material (the subgrade) is determined to be capable of supporting aircraft operations, no subbase or base will be required. A subbase may consist of subbase material and a select material if a select material is available and of better quality than the subgrade.

Contingency airfields typically have a short design life, and a reasonable estimate of the mission's requirements in terms of aircraft passes is required in order to produce an adequate airfield design with the minimum resource requirements. From the mission statement or an estimate of the situation, determine the minimum number of design aircraft passes that will accomplish the mission. For contingency airfields that have a parallel taxiway, one aircraft pass is defined as one takeoff and one landing. For contingency airfields that do not possess a parallel taxiway, one aircraft landing and one takeoff each count as an aircraft pass. Thus, if an airfield is to be designed for 100 aircraft operations (landings and takeoffs), the design aircraft passes would be 100 if the design includes the construction of a parallel taxiway. If a parallel taxiway is not in the overall design, then the design aircraft passes should be 200. In combat conditions, the Army must be able to deploy a brigade (up to about 3500 soldiers), and their vehicles and equipment, to a field position in combat conditions. The Air Force provides the air transport for the deployment. Until recently, C-130 aircraft landed in field positions. The Army is in the process of replacing these aircraft with the larger C-17 aircraft. Though C-17 aircraft were designed to land on small remote semi-prepared runways, the performance of different soil types under different climate conditions has not been widely tested. Tests previously conducted provided sufficient information regarding approximately 7% of the world's soil surfaces. By testing aircraft performance during landings on Silty Sand [SM] soils in an arid climate available at Fort Hunter Liggett (FHL), California, this would increase to about 24% of the world's soil surfaces. Results of the test are needed to guide construction requirements for semi-prepared runways that can support C-17 operations worldwide, and the information is critical for adequate construction of SPRs in combat zones.

The US Army Combat Support Training Center [CSTC] proposed to expand Schoonover Airfield in the southern Cantonment area and support the C-17 Semi-prepared Runway Operations [SPRO] test at FHL, California. The preferred timeline for the project was October - December 2005; however, if weather or other conditions are not favorable, the proposed action could occur in 2006.