What was found
IN CRUISE, BOTH CAPT AND FO STANDBY AIRSPEED INDICATORS WERE INACCURATE. STANDBY INDICATORS SEEMED TO INDICATE APPROXIMATELY HALF OF ACTUAL IAS AT ALL ALTITUDES. AT FL340, .787M, 280 IAS, CAPTAIN STANDBY AIRSPEED SHOWED 129 AND FOS SHOWED 130. AT 25K AND 280 IAS, CAPTAIN SIDE SHOWED 137 KTS AND FO SIDE 140 KTS. AT 15K AND 312 IAS, CAPTAIN STANDBY AIRSPEED SHOWED 155 AND FO SIDE I58. FOUND STANDBY PITOT PROBE CLOGGED. REMOVED AND REPLACED STANDBY PITOT PROBER PER M.M. 34-11-15-04. LEAK CHECK GOOD. A/C OK FOR SERVICE