As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON APPROACH INTO PHL, THE LANDING GEAR DID NOT EXTEND WHEN SELECTED DOWN. CREW PERFORMED GO AROUND AND THEN GEAR EXTENDED NORMALLY. MAINTENANCE TROUBLESHOT SYSTEM, COULD NOT DUPLICATE PROBLEM. REMOVED AND REPLACED PSEU AS A PRECAUTION. A/C RETURNED TO SERVICE. (M)