Economic pressures are driving many commercial and governmental operators within the aviation system toward purchase of COTS products. Although these products may have a favorable cost-to-performance ratio, they may not have been subject to the verification and validation rigor required to maintain safe, dependable operation of the aviation system. Examples include microprocessors (from PC industry), operating systems (e.g., Windows and LINUX), and graphics processors (from video game industry).
The effect of a manufacturer’s changes to aviation COTS can be summarized by specific difficulties:
- Forced modifications
- Interoperability among COTS products
- Counterfeit parts that are vital to the computer industry is expected to reach record high levels
Airworthiness is the primary safety characteristic of any aircraft. A forced modification is one that is caused by the change of form, fit, interface, function, mission characteristic, or supply of the item. When supply is affected, the acquirer must support the discontinued item or find a replacement. The latter may force a modification. More common in aviation COTS is an FAA-directed change to an item called an airworthiness directive (AD) FAA, 1996). The manufacturer has two choices in implementing the AD: Discontinue the product or make the required change. The user of the item also has two choices: Get a replacement product, if available, or make the changes required by the directive. But there is no requirement for the government to change its COTS items to accommodate an AD. In such cases, the item becomes government-unique. Because the government self-certifies, it is not uncommon for non-FAA-certified government aircraft to not make AD-directed changes. Non-FAA-certified aircraft (military and other federal agency-owned aircraft) are a significant segment of aviation.