The Technical Operations branch of Air Canada recently purchased three new Air Data Testers for use in checking and calibrating certain systems and components on the company's aircraft. These testers are of a new generation, operating in a manner significantly different from the ones that they replace. A computer based lesson was developed in order to provide Maintenance personnel quality and timely training on how to operate the new tester. Dick and Carey's (1985) instructional design model was used to guide the design of the lesson. Using company equipment, and Wicat Systems, Inc.'s WISE authoring system, a portion of the lesson was produced. Three types of people participated in a formative evaluation of the lesson. An instructional design expert evaluated the lesson's design and found it to be acceptable. A subject matter expert evaluated the programmed portion of the lesson for technical accuracy. A few minor changes were required. Eight members of the target population worked through the lesson's programmed portion. Oral and written comments were positive. Some technical errors were identified. There was a statistically significant improvement between the pre-test (35%) and post-test (93%) mean scores, indicating that the students learned from the program.