As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DSM - DSM - FLT 539 - AFTER TAKEOFF, LANDING GEAR SELECTOR HANDLE WAS LOCKED IN THE DOWN POSITION. RETURNED TO DSM. FOUND NOSE LANDING GEAR STRUT AIR PRESSURE LOW. SERVICED NOSE LANDING GEAR STRUT WITH NITROGEN. LANDING GEAR OPERATION THEN CHECKED NORMAL. (M)