Final answer:
The AEL detector pad uses a chemically sensitive optical fiber developed by IOS that changes color in response to specific stimuli, though the exact dye type is not specified. These sensors have broader applications, including detection of chemical warfare agents.
Step-by-step explanation:
The type of dye used for the Aeronautical Engine Laboratory (AEL) detector pad is not explicitly mentioned. However, it is known that NASA contracted with Intelligent Optical Systems (IOS) to develop moisture- and pH-sensitive sensors. These sensors function through a specially manufactured optical fiber that is chemically sensitive and changes color upon contact with its target. The dyes used for these types of sensors are typically those that can react to changes in chemical composition, such as pH-sensitive dyes or moisture-indicating dyes.
After its initial development, IOS expanded the use of these sensors for the detection of chemical warfare agents and potential threats like toxic industrial compounds and nerve agents. The optical fiber cables developed by IOS have since found applications in the automotive and aerospace industries and serve as an economical alarm system for the detection of chemical release in large facilities.