What was found
ON CLIMB OUT FROM FAT THE PILOT HEARD A "POP" AND THEN FELT A VIBRATION IN THE AIRFRAME. HE NOTIFIED ATC OF HIS NEED TO RETURN ASAP AND LANDED WITH OUT INCIDENT. UPON INSPECTION MAINTENANCE FOUND APPROXIMATELY 4" OF THE NR 3 BLADE DEICE BOOT MISSING. ALL THREE BOOTS WERE RECENTLY REPLACED DURING ROUTINE MAINTENANCE AND WAS THE SECOND FLIGHT SINCE INSTALLATION. MAINTENANCE REMOVED ALL THREE BOOTS AND REPLACED FOR A SECOND TIME. THE AIRCRAFT WAS RETURNED TO SERVICE AND REPOSITIONED TO PDX. UPON ARRIVAL IN PDX 2 OF THE THREE BOOTS HAD SIGNS OF DISTRESS AND APPEARED TO BE "SLIPPING". CONTACT HAS BEEN MADE WITH THE MANUFACTURER.