As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
JUST AFTER TAKEOFF DURING CLIMB THE CREW DETECTED THE SMELL OF BURNING RUBBER IN THE CABIN & HEARD A SQUEALING SOUND. SECURED THE AIR CONDITIONING SYS & OPENED THE CABIN VENT. THE ACFT WAS RETURNED TO THE HELIPAD & SHUT DOWN NORMALLY. UPON POST FLIGHT THE DRIVE BELT TO THE AIR CONDITIONING COMPRESSOR WAS FOUND TO BE BURNED THROUGH & BROKEN. THIS ACFT REMAINS OUT OF SERVICE AT THE TIME OF THIS SUBMISSION FOR THE REPAIR OF THIS SYS.