Narrative:

Our maintenance history indicated the airplane had four recent write-ups; including a diversion and 'info only' comment relating to an odor in the cockpit. The most recent maintenance action taken was a replacement of the weather radar unit. A subsequent flight was flown and an 'info only' comment was made that 'no fumes' were noticed on their flight. En-route airports had good weather and we felt comfortable that the maintenance action corrected the problem. [About an hour into flight]; we noticed an acrid odor. Knowing the airplane history with the weather radar (which we had on); we confirmed with dispatch that there was no convective weather near our position and was told none. We turned the weather radar off and the odor dissipated. Five to six minutes later; the odor re-appeared and because of the way the sun was shining in the cockpit; I happen to see what appeared as a very thin layer of haze. We began discussing a diversion and referenced the QRH when I noticed visible smoke coming from the first officer's instrument switching panel area. I announced 'we have visible smoke'; we then donned our oxygen mask and established communications. The first officer was the pilot flying; we declared an emergency and initiated our diversion to the airport. I contacted dispatch through ACARS and verbally discussed our intentions to divert to the airport. I briefed the flight attendants (using the emergency brief acronym). I followed the smoke; fire or fumes QRH while the first officer flew the airplane and was coordinating our arrival with approach. Upon reaching the step to turn the pack selectors off; the smoke and odor had completely dissipated. Because we were on a high left downwind position at this time and setting up for the final approach; we abandoned the checklist and set up for the landing. We landed approximately 8;000 pounds. Overweight. It was an uneventful landing. Arff was standing by and reported nothing unusually from their vantage point. We taxied to our gate and deplaned the passengers. I felt we received good support from dispatch; ATC; arff and most certainly the crew.

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Original NASA ASRS Text

Title: B757 flight crew experiences smoke in the cockpit one hour into flight and diverts to the nearest suitable airport. QRH procedures eliminate the smoke prior to landing.

Narrative: Our maintenance history indicated the airplane had four recent write-ups; including a diversion and 'info only' comment relating to an odor in the cockpit. The most recent maintenance action taken was a replacement of the weather radar unit. A subsequent flight was flown and an 'info only' comment was made that 'no fumes' were noticed on their flight. En-route airports had good weather and we felt comfortable that the maintenance action corrected the problem. [About an hour into flight]; we noticed an acrid odor. Knowing the airplane history with the weather radar (which we had on); we confirmed with Dispatch that there was no convective weather near our position and was told none. We turned the weather radar off and the odor dissipated. Five to six minutes later; the odor re-appeared and because of the way the sun was shining in the cockpit; I happen to see what appeared as a very thin layer of haze. We began discussing a diversion and referenced the QRH when I noticed visible smoke coming from the First Officer's instrument switching panel area. I announced 'we have visible smoke'; we then donned our Oxygen mask and established communications. The First Officer was the pilot flying; we declared an emergency and initiated our diversion to the airport. I contacted Dispatch through ACARS and verbally discussed our intentions to divert to the airport. I briefed the flight attendants (using the emergency brief acronym). I followed the Smoke; Fire or Fumes QRH while the First Officer flew the airplane and was coordinating our arrival with Approach. Upon reaching the step to turn the pack selectors OFF; the smoke and odor had completely dissipated. Because we were on a high left downwind position at this time and setting up for the final approach; we abandoned the checklist and set up for the landing. We landed approximately 8;000 LBS. overweight. It was an uneventful landing. ARFF was standing by and reported nothing unusually from their vantage point. We taxied to our gate and deplaned the passengers. I felt we received good support from Dispatch; ATC; ARFF and most certainly the crew.

Data retrieved from NASA's ASRS site as of July 2013 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.