Aircraft Instrument Systems Which of the following instrument discrepancies could be corrected by an aviation mechanic? 1. Red line missing. 2. Case leaking. 3. Glass cracked. 4. Mounting screws loose. 5. Case paint chipped. 6. Leaking at line B nut. 7. Will not adjust. 8. Fogged. a. 1, 4, 6. b. 3, 4, 5, 6. c. 1, 4, 5, 6.