What was found
PHL - FLT 738 - ON CLIMB-OUT FROM PHL, CREW REPORTED LOSS OF VNAV AND NOTED INCREASING DISCREPANCIES BETWEEN CAPTAINS AND F/O'S AIRSPEED AND ALTIMETERS. FLIGHT RETURNED TO FIELD AT PHL AND LANDED WITHOUT FURTHER INCIDENT. AIRSPEED AND ALTIMETER SPLITS WERE NOTED AS FOLLOWS AT 25,000 FEET 30 KNOTS/1,500 FOOT DIFFERENCE, AT 5,000 FEET 10 KNOT/150 FOOT DIFFERENCE AND AT 1,000 FEET 5 KNOT/50 FOOR DIFFERENCE. MAINTENANCE REMOVED AND REPLACED CAPTAINS UPPER LEFT PITOT STATIC PROBE AND STATIC PORT LINE (P/N 41075-0065). OPERATIONAL CHECK AND LEAK CHECK GOOD PER MM 34-11. AIRSPEED AND ALTIMETERS WITHIN LIMITS PER MM 34-12. (M)