Narrative:

After takeoff during climb checks; we got a burning smell in both the cockpit and cabin. A grinding noise could be heard in the aircraft; it was the loudest in the rear. Light visible smoke was present in the rear of the aircraft. We declared an emergency and went back into ZZZ. During the return; the packs were turned off; the grinding stopped; and the burning smell dissipated. Callback conversation with reporter revealed the following information: when the packs were shut down; the grinding noise stopped and the burning smell dissipated. On the ground it was discovered an air cycle machine had failed; allowing oil into the conditioned air. No warnings were present and no pack trip occurred during this event.

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Original NASA ASRS Text

Title: AN EMB145 ON TKOF CLB DECLARED AN EMER AND RETURNED DUE TO A BURNING SMELL IN THE COCKPIT AND CABIN WITH LIGHT SMOKE IN REAR. GRINDING NOISE FROM AIR CONDITIONING PACK.

Narrative: AFTER TKOF DURING CLB CHKS; WE GOT A BURNING SMELL IN BOTH THE COCKPIT AND CABIN. A GRINDING NOISE COULD BE HEARD IN THE ACFT; IT WAS THE LOUDEST IN THE REAR. LIGHT VISIBLE SMOKE WAS PRESENT IN THE REAR OF THE ACFT. WE DECLARED AN EMER AND WENT BACK INTO ZZZ. DURING THE RETURN; THE PACKS WERE TURNED OFF; THE GRINDING STOPPED; AND THE BURNING SMELL DISSIPATED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WHEN THE PACKS WERE SHUT DOWN; THE GRINDING NOISE STOPPED AND THE BURNING SMELL DISSIPATED. ON THE GND IT WAS DISCOVERED AN AIR CYCLE MACHINE HAD FAILED; ALLOWING OIL INTO THE CONDITIONED AIR. NO WARNINGS WERE PRESENT AND NO PACK TRIP OCCURRED DURING THIS EVENT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.