What was found
RETURNED TO DEPARTURE. BLEED 1 FAILED CLIMBING THROUGH 21,500'. AIRCRAFT LOST PRESSURIZATION, CABIN CLIMBED TO 6900'. FOUND NR 1 NAPRSOV AT FAULT, LEAKING. R & R NR 1 NAPRSOV IAW AMM 36-11-02, OPS LEAK CK GOOD. ACCOMPLISHED CABIN PRESS TEST IAW AMM 21-31-00-720-802-A. OPS CHECK GOOD.