Cases
Most cases are fabricated from panels joined by metal or plastic extrusions, molded plastic, or metal. Fabricated cases are typically made from panels constructed of two layers. An outer layer of ABS or fiberglass laminate is adhered to a middle layer of lightweight 3⁄16-to-1⁄2-inch (4.8 to 12.7 mm) cabinet-grade plywood such as birch, poplar, or maple. These two layers are known as laminate panel, and high-grade cases are made from composite material. Inside the case, an internal shock-absorbing filler such as polyurethane or polyethylene foam has cavities that correspond to the shape of the components it is preserving. Alternate shock protection methods include mounting the case contents to racks or panels attached to the case walls with shock isolators. The corners of fabricated cases are commonly reinforced with stamped sheet steel case corners commonly finished in zinc, nickel, chrome.
The term ATA case is frequently used to describe cases that resemble those that comply with ATA Specification 300 category I or II, but have not been certified by the independent testing defined in ATA Specification 300. Category I and II cases are required to be tested both as a pre-production prototype and as a sample selected from the first production lot. Tests include stackability, drop or impact, water resistance, vibration (category I only), and penetration (category I only). Of these, the drop test, stackability, and vibration tests are probably the most severe. For cases under 50 pounds (23 kg) gross (loaded) the drop test requires 160 face drops from 30 inches (760 mm), 80 edge drops from 36 inches (910 mm), and 40 corner drops from 36 inches. The face drop distance is reduced to 21 inches (530 mm) up to 100 pounds (45 kg), 18 inches (460 mm) 150 pounds (68 kg), 16 inches (410 mm) 200 pounds (91 kg) or more. Category II cases are dropped one-tenth as many times from 22 inches (560 mm) and 27 inches (690 mm) at 50 pounds, and proportionally for heavier cases. The stackability test requires every case face over 0.37 square metres (4.0 sq ft) to support 135 kilograms (298 lb) centered on 0.09 square metres (0.97 sq ft) of the face for 24 hours. The vibration test searches for the four strongest resonances between 5 and 50 Hz, and then tests each at 0.5 standard gravities (4.9 m/s2) for 2 hours on each principal axis. The penetration test is a 6-kilogram steel bar 3.2 centimeters in diameter with a hemispherical end dropped 0.5 meters on the weakest point. For all tests no degradation or functional damage is allowed.
Caster wheels are often built into or attached to the case for ease of transit, and may be removable to prevent damage to other containers or to the airframe.
Molded cases are typically made of polyethylene or polypropylene plastic by injection molding or rotational molding and may be gasketed for splash protection. They typically have similar interior and wheel options as fabricated panel cases. The ATA specified performance temperature range −40 to 130 °F (−40 to 54 °C) tends to exclude thermoplastic cases large enough to be subject to the stackability test.
Cases may be further customized by adding a power adapter and a computer fan. Thus certain equipment may operate in transit or at destination without leaving the protection of the case.
