What was found
AFTER TAKEOFF, CASS MESSAGE AS/ALT DISAGREE, YD FAIL, RED X RIGHT ATT/AS/ALT FOR DURATION OF FLIGHT. MFD RED X ATT ONLY. REMOVED AND REPLACED RT PFD WITH REPAIRED UNIT IAW EA5OO AMM 31-10-16. PERFORMED DISPLAY AND CONTROL PANEL-ADJ/TEST IAW EA500 AMM 31-10-00 AND TRANSPONDER SYSTEM ADJ/TEST IAW EA500 AMM 34-50-60. ALL CHECKS GOOD. VERIFIED TRANSPONDER NR 1 AND NR 2 COMPLY WITH FAR 91 .413, AND FAR PART 43 APP F. PERFORMED ALTITUDE REPORTING CORRELATION TEST PER PARA OF FAR PART 43 APP E, NO DATA CORRESPONDENCE ERRORS FOUND FOR TRANSPONDER NR 1 OR NR 2.