Fixed Wing Air
Introduction
Air transport by fixed-wing aircraft is the most important transportation mode in terms of rapid strategic mobility. The need for equipment to be transported by C-130, C-141, C-5 and C-17 cannot be overemphasized. Air transport has definite cargo size and weight limitations that must be met in the design and acquisition of military equipment. In addition, effective payload is often limited to provide global reach.
The maximum aircraft payloads are not the anticipated payloads that would be used during strategic deployment. Deployment payloads depend upon the mission range and flight conditions encountered. A range of 3,200 nautical miles (nm) is required to support efficient worldwide deployment. Flight conditions that reduce aircraft payload include runway lengths and winds encountered. To ensure deployment analyses reflect real-world deployment conditions is most operational scenarios, the payloads that should be used the C-141, C-5, and C-17 are 60,000 pounds, 178,000 pounds and 130,000 pounds, respectively. While reduced range will allow increased payload, other factors (ground time for intermediate stops and the potential for mission abort at intermediate airfields, and less direct routing) result in reduced air fleet throughput.
Potential USAF air transport loads can be found at the following
link.The U.S. Air Force's C-130, C-5, C-17 and the Civil Reserve Air Fleet are expected to serve until well into the next century. Although the guidance presented here is general in nature, specific design information can be found in
"MIL-STD-1791 Designing for internal Aerial Delivery in Fixed Wing Aircraft. The US Air Force Aeronautical Systems Center (USAF ASC) certifies loads for internal air transport. The aircraft loadmaster is the final authority on accepting cargo for loading.For additional information on air transport, follow this
link to the Air Transportability Test Loading Agency (ATTILA) website.Heavy Tracked Vehicle Air Transport.
The USAF C-5 Galaxy and the C-17 Globemaster are the current US strategic heavy lift aircraft. Both have the size and lift capacity to airlift heavy armored tracked vehicles.C-17
. The operational weight limit for loading tracked vehicles across the C-17'sramp is 130,000 lbs. A waiver was granted to allow loading of an M1 Abrams tank weighing up to 135,000 lbs. This waiver was based on a structural analysis by the C-17 System Program Office (SPO) and McDonnell Douglas (now Boeing) that showed the load distribution of M1 did not detrimentally affect the ramp.C-5A/B
. The operational weight limit for loading tracked vehicles across the C-5's ramps is 129,000 lbs. The ramps have an operational waiver that allows loading of an M1 Abrams tank weighing up to 134,000 lbs. This waiver was based on structural analysis of the M1 load distribution on the ramp and was granted by the C-5 Program Office at Warner-Robins AFB, Georgia.C-130 Hercules
The C-130 is a four-engine turboprop, high-wing aircraft used mainly as a tactical intraheater transport. The aircraft is loaded through an aft cargo door.
The dimensional design limits for equipment designed to be transported via C-130 are:
|
Height |
102" |
|
Length |
480" |
|
Width |
105" |
Note: The C-130 has a permanently installed rail system that limits floor width to 105" up to a height of 5.5 inches. The practical maximum floor widths for roll on/roll-off operations of wheeled and tracked vehicles are 102 and 100 inches, respectively.
These designs limits allow for 6 inches of safety clearance between the equipment being loaded and the aircraft structure.
The weight design limits for equipment designed to be transported via C-130 are:
|
Effective allowable cabin load (ACL) 1/ |
15,000 lbs @ 3,200 nm |
|
Maximum ACL 1/ |
42,000 lbs @ 1,250 nm |
|
Maximum deck load |
50 psi |
|
Maximum axle load on treadways |
13,000 lbs |
|
Maximum axle load between treadways |
5,000 lbs |
|
Maximum tire pressure |
100 psi |
|
Maximum track load per linear foot |
6,000 lbs |
1/ Maximum ACL is based on still air, one-way, and flying at best altitude/cruise speed. Since it is rare that the aircraft will fly under these conditions, designers should use the effective ACL limit
Axle loads between 6,000 and 13,000 lbs and track loads between 2,000 and 6,000 lbs per linear foot are limited to a 28.75 ft. portion of the aircraft centered on the wingbox.
Equipment designers should remember all vehicles that require C-130 transport must be capable of roll-on/roll-off loading and unloading in an operational configuration.
C-130 Deployment to a Forward Landing Strip (FLS)
While the C-130 landing weight for improved runways during peacetime is 155,000 pounds; the peacetime landing weight on a FLS is 130,000 pounds. This becomes critical for the transport of C-130 capable equipment for both training and during deployment. The last time the 130,000 pounds FLS limitation was waived (allowing 155,000 pounds at a FLS) was during DESERT STORM. All deployments since then have been accomplished using peacetime limits.
The 130,000 pound limitation results in a payload weight of about 32,000 pounds being delivered to an FLS when refueling is not available at the FLS, considering the aircraft must fly approximately 1 hour to an airbase for refueling. This can eliminate consideration of C-130 transport of vehicles weighing significantly in excess of 32,000-pounds for missions such as deployment to Bosnia and Kosovo. It also limits the ability to train during peacetime.
The airfield requirement for the 155,000-pound capability of the C-130 is use of a paved landing strip of at least 3,000-foot length and 60 foot width for tactical assault operations. Non-tactical assault operations require a 5,000-foot length and 80 foot width runway.
The FLS limitation has not been a significant C-130 restriction in the past as there have been few combat systems with a weight greater than 32,000 pounds that were C-130 capable. The current emphasis on light combat vehicles that are C-130 capable makes the 130,000-pound landing limitation a significant operating and training restriction.
Original URL: http://www.tea.army.mil/dpe/Aircraft.htm