As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PERFORMED APU BLEED ON TAKEOFF DUE TO ENGINE 2 BLEED BEING ON MEL. AFTER TAKEOFF WHEN TRANSITIONING FROM APU BLEED TO ENGINE ONE BLEED A STRONG DIRTY SOCK/SOUR SMELL WAS NOTICEABLE IN FLIGHT DECK. UNABLE TO IDENTIFY SOURCE OF SMELL. (OPEN)