Date: 201409
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Recirculation Fan
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew; Person Passenger
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Diverted; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Just after reaching our cruise altitude of FL350 we noticed a faint; unidentifiable burning smell. We double checked all circuit breaker panels and found them all to be normal. We then called the flight attendant; who was in the rear of the aircraft. We asked her if she had notice an odor. She in fact had noticed an odor while retrieving something from the galley and was now; along with the passengers in the rear of the aircraft; noticing the odor in the rear of the cabin. It was apparent the odor was getting strong. Unable to identify the odor; we completed the Cabin Smoke/Fire [Emergency Checklist]; and began a descent. We sent a message to Dispatch via ACARS saying we were getting a strong burning odor in the cockpit and would be diverting and where would dispatch would like. Our dispatcher responded immediately with a request for us to go to ZZZ. We notified our flight attendant to prepare for landing. We then proceeded to perform the QRH portion of the emergency procedure. However; due to our close proximity to ZZZ and the lack of severe smoke or fire; we decided that preparation for landing was more important. We completed a visual descent and overweight; smooth landing and normal taxi in to the gate. We were met at the gate by the emergency response crew; the station manager and a mechanic. We immediately shut down the aircraft and deplaned normally. The emergency responders and station manager attended to the passengers ensuring there were no injuries or issues from the odor. One passenger in particular we were concerned about was traveling with his personal oxygen system that was not approved for use on our flights. We were; as was he; made aware of this prior to departure from and upon arrival we wanted to make sure the odor hadn't caused any issues for him; as it had not. The mechanic and ourselves; in coordination with Maintenance Control; then proceeded to troubleshoot the issue. After completing an engine runup; we all agreed that the issue presented itself anytime Pack #1 was selected. Pack #1 was then MEL'd and an overweight landing inspection was completed.  We then decided it would be safe to continue on to destination. We re boarded the flight and departed. During our climb through 17000 feet we noticed that the odor was present again. We stopped our climb at FL190. We confirmed with our flight attendant that it was again noticeable in the cabin. Unable to determine the cause of the odor and not sure the nature or severity the issue could cause; in communication with dispatch; we determined that the safest course of action would be to declare an emergency and return until the nature and cause of the burning smell could be properly diagnosed and fixed. Upon our arrival our passengers were grateful that we erred on the side of caution. They were informed by the station manager that a new aircraft would be enroute shortly. We were then sent to the hotel. Communication and decision making during any emergency is essential. The First Officer was exceptional in performing; communicating and executing his duties during the emergency. Workloads under these situations can get overwhelming. We both managed our duties as best as possible under the conditions and time constraints.




Synopsis: EMB145 flight crew detects smoke in the cockpit and the Flight Attendant detects it in the cabin. The flight diverts to the nearest suitable airport where maintenance determines that the left pack is likely the culprit and is MEL'd. The passengers are reboarded and the flight departs. The odor is again detected causing another diversion.