Narrative:

The inbound crew placed 2 items in the maintenance log; one of which had been a repeating item 3 times. Maintenance worked the items and we departed. After reaching FL390 the rt recir fan; EICAS message appeared. We followed the QRH procedure: condition -- a recirculation fan is inoperative. Crew awareness. End. After approximately 3 minutes the right recirculation fan reset itself and the EICAS message cleared. The fan ran for approximately 4 minutes and then tripped off again displaying the rt recir fan EICAS message; then cycled on clearing the message. This cycle occurred 5 times with each on cycle getting shorter and shorter. I suspected the right recirculation fan was tripping off due to a thermal overheat; resetting and then cycling on again after the thermal reset. With each on cycle getting shorter and shorter this indicated that the fan was getting hotter and hotter with each run cycle. With no guidance to the actual problem in the QRH (see above); using my captain's authority; I opted to shut off the right recirculation fan selector switch to prevent power from going to the fan [in] attempt to stop the thermal overheating and trip reset [and] to prevent a possible electrical fire due to an over temp of fan windings or circuitry. Within a few minutes of the first cycle the flight attendants informed us that a burning electrical smell permeated the cabin for over 20 minutes and then started to dissipate. Maintenance was phone patched and we quickly troubleshot the system and possible solutions to the cycling of the right recirculation fan and the connection to the previous log items and repeat items; including the ovbd ex val open and eqpt ovht items. The cycling stopped and the odor cleared the cabin after approximately 30 minutes and we continued with the right recirculation fan in the off position and landed safely. The item was added into the logbook and maintenance was briefed on the issues. The QRH; in this case; was useless due to its lack of guidance and may have led to a possible in flight fire or smoke in the cabin/cockpit situation. I would like to suggest that the company modify the QRH procedure to add the following step: place right recirculation fan selector switch to off. This would shut the power off to the recirculation fan; preventing it from thermal cycling before an overheat/fire situation. Although the QRH procedure for smoke; fire; or fumes would have cut the power to the fan; it would have been in a post smoke/fire situation instead of a prevention step to prevent the smoke/fire from happening in the first place. During the phone patch with maintenance it was determined that more than one power source controlled the right recirculation fan system. It was also determined that cycling was not supposed to happen and the right recirculation fan system on the B757 has been problematic for some time. I would like to suggest that the QRH procedure be modified to add the following language: eqpt ovht (step 2 prior to end): land at nearest suitable airport. Post flight logbook indicated that the right recirculation fan was replaced and temp sensors on the flight deck and cabin were cleaned and the placard for the left pack was removed. Subsequent flights show a repeated item for the left pack and temp control. This now makes 6 times; 3 in 2 days.

Related reports:

Google
 

Original NASA ASRS Text

Title: B757 Captain experienced RT RECIRC FAN EICAS message after leveling off at FL390. The fan cycles on and off multiple times before the control switch is placed in the off position. Fumes are detected in the cabin but dissipate when the fan is switched off and flight continues to destination.

Narrative: The inbound crew placed 2 items in the maintenance log; one of which had been a repeating item 3 times. Maintenance worked the items and we departed. After reaching FL390 the RT RECIR FAN; EICAS message appeared. We followed the QRH procedure: Condition -- A recirculation fan is inoperative. Crew awareness. END. After approximately 3 minutes the right recirculation fan reset itself and the EICAS message cleared. The fan ran for approximately 4 minutes and then tripped off again displaying the RT RECIR FAN EICAS message; then cycled on clearing the message. This cycle occurred 5 times with each on cycle getting shorter and shorter. I suspected the right recirculation fan was tripping off due to a thermal overheat; resetting and then cycling on again after the thermal reset. With each on cycle getting shorter and shorter this indicated that the fan was getting hotter and hotter with each run cycle. With no guidance to the actual problem in the QRH (see above); using my Captain's authority; I opted to shut off the right recirculation fan selector switch to prevent power from going to the fan [in] attempt to stop the thermal overheating and trip reset [and] to prevent a possible electrical fire due to an over temp of fan windings or circuitry. Within a few minutes of the first cycle the flight attendants informed us that a burning electrical smell permeated the cabin for over 20 minutes and then started to dissipate. Maintenance was phone patched and we quickly troubleshot the system and possible solutions to the cycling of the right recirculation fan and the connection to the previous log items and repeat items; including the OVBD EX VAL OPEN and EQPT OVHT items. The cycling stopped and the odor cleared the cabin after approximately 30 minutes and we continued with the right recirculation fan in the off position and landed safely. The item was added into the logbook and Maintenance was briefed on the issues. The QRH; in this case; was useless due to its lack of guidance and may have led to a possible in flight fire or smoke in the cabin/cockpit situation. I would like to suggest that the company modify the QRH procedure to add the following step: Place right recirculation fan selector switch to OFF. This would shut the power off to the recirculation fan; preventing it from thermal cycling before an overheat/fire situation. Although the QRH procedure for smoke; fire; or fumes would have cut the power to the fan; it would have been in a post smoke/fire situation instead of a prevention step to prevent the smoke/fire from happening in the first place. During the phone patch with Maintenance it was determined that more than one power source controlled the right recirculation fan system. It was also determined that cycling was not supposed to happen and the right recirculation fan system on the B757 has been problematic for some time. I would like to suggest that the QRH procedure be modified to add the following language: EQPT OVHT (STEP 2 PRIOR TO END): Land at nearest suitable airport. Post flight logbook indicated that the right recirculation fan was replaced and temp sensors on the flight deck and cabin were cleaned and the placard for the left pack was removed. Subsequent flights show a repeated item for the left pack and temp control. This now makes 6 times; 3 in 2 days.

Data retrieved from NASA's ASRS site as of April 2012 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.