What was found
PDIS 104 34-11 7994 03JUN21 GSO IN THE DESCENT FROM FL 410 WITH SAT -61* RECEIVED A ALT DISAGREE CAUTION WITH INTERMITTENT IAS DISAGREE CAUTION. SUMMIZED THAT CAPTAINS S SIDE WAS IN ERROR. F/O SIDE MATCHED STBY INSTRUMENTS. CAPTAIN S SIDE WAS APPROX 5-6 KNOTS SLOWER AND 300 FEET LOW. CAUTIONS CLEARED BELOW 10,000 FT IN CLEAR AIR. FACT 12JUN21 18:46 MEM R/R'D LH ADIRU PER AMM 34-26-01-4. CHECKS GOOD. AIR DATA SEL SWITCH RETURNED TO LEFT POS AND SAFETIED.