Narrative:

At cruise FL340; we encountered fumes that smelled like electrical wiring burning; or a motor burning up. Having experienced this on a 767; I recognized the smell; but it was worse; and in that previous incident it was a cargo exhaust fan that failed and disconnected itself. Actions -we first donned our oxygen masks; confirmed oxygen on 100% and my first officer (first officer) immediately got the smoke/ fumes QRH out and started to accomplish the checklist items. We were in moderate turbulence; and IMC at this time; autopilot/autoflight systems on. Turbulence was causing altitude deviations of +/- 100 feet. Previous to this; since we were in IMC; we checked the OAT which was -36C so we turned on engine and wing anti-ice. We did not fly over or near any radar returns of yellow or red. Several calls from the flight attendants (flight attendant) indicated the presence of substantial electrical odor in the cabin; and it was significant. Passenger flight attendant call buttons were going off in large quantity. We immediately were thinking about a return to the departure airport. Substantial thunderstorm activity was along our route and we were immediately thinking how to break track if this didn't improve immediately. Moments later; we lost our mach airspeed indicators; which spun down; our speed tapes dropped to minimum speed; and the auto throttles advanced along with an immediate stick shaker. We also received several yellow EICAS warnings however I was immediately task focused on flying the airplane. [Past aircraft accidents] came to mind. I disconnected the auto throttles; autopilot and hand flew the jet; referencing the standby airspeed indicator which then wound down almost instantly. We had no reliable airspeed indications and a stick shaker; in moderate turbulence in IMC. I added thrust; as I was fighting moderate turbulence; and flying wings level and a relative known pitch; and with virtually no airspeed references; I resorted to an approximate known fuel flow of about 4000Lbs/engine and pitch slightly above the horizon. (Knowing cruise would also be about 1.55 EPR and pitch 2.5-3.5).we [advised our situation] on 121.5. Got a response from several aircraft; one was helpful and relayed our position and [situation] to oceanic on HF radio. I turned right to break off of the track; and was having to navigate between thunderstorms the best I could while in IMC. Knowing that ideal would be to get to 15NM parallel track; however with all the weather; I believed other aircraft may be deviating this distance left and right of track; and 15NM right/south of track was not possible with the weather. 25-30 miles or halfway between tracks probably would be safer in such an emergency; and with no airspeed references. My first officer was accomplishing the QRH smoke fumes checklist and checked with me prior to turning the left recirc fan off; which changes many things to vent any smoke/fumes; and since we were already diverting; I nodded and said yes; do it. We flew approximately 20-30 miles off to the right/south and set up a direct to the departure airport which the altn page showed as the nearest airport. We set up FL240 in the MCP altitude window. I started a gentle descent; as aircraft controllability was of significant concern without reliable airspeed indications. Turbulence was still brutal. Airspeed indications came back and were lost 3 different times; and I adjusted power based on what we had. Additionally I was having substantial right engine vibration of 5.0; and while I had no airspeed indications. Still in solid IMC; I was trying to differentiate between unrelenting turbulence; the stick shaker; engine vibration possibly due to ice crystal icing; and possibly airframe vibration/buffet possibly due to higher mach speed (by feel) to which I reduced thrust gently to combat. I resorted to an approximate fuel flow and pitch as often as I could. We closed the right engine (#2) bleed; and opened the isolation valve in the event that the fumescould have been partially coming from the right engine; since its N1 vibration was at 5.0; which was amber in color. This did not have an effect on the fumes on the airplane. My knowledge of the ice crystal icing procedures above FL250 was to have engine anti ice on (already was on) and avoid suspected conditions (we already were trying to get out of it). We were task saturated. Mindset - when we initially got the electrical smoke/fumes/smell during the high level of turbulence followed by the loss of all airspeed indications; since we weren't flying over any yellow or red radar echoes; had no moisture indications on the windshield; no sulfur smell; my thought immediately went to a chaffed electrical harness supplying heating to pitot/static and possible other systems; which may have been the source of airspeed indication failures; rather than ice crystal icing causing airspeed/mach indication losses; and the electrical fumes were very strong. My first officer had completed the smoke/fumes checklist. The electrical burning odor was still prevalent throughout the aircraft but stable and appeared to be dissipating; so we did not choose to accomplish the smoke removal checklist. My thoughts were to get off track far enough to avoid deviating aircraft; reverse course and descend to lower altitude both to safely get below the tracks; below the headwinds; other aircraft; and possibly out of the IMC so as to resolve any icing issue if we had a partially heated system; out of the turbulence to stop any electrical wiring chaffing and into VMC to help fly the airplane with more references; and less task saturation. After established heading back at FL240; an approximate speed of 280 knots indicated; airspeed indications which had returned had stabilized and I was able to engage an autopilot and autoflight systems. The engine vibration indications (N1) were normal and not indicated in amber. At this point we were able to talk with ATC and complete a phone patch with our company dispatch and maintenance folks. I explained the fumes; the loss of airspeed indications; the right engine vibration; etc. And was headed back. We contacted approach with our position and were given FL240. They provided us a squawk and cleared us direct. We reassessed the cabin situation; and I gave the passengers a PA explaining what we had; as far as the electrical smell/smoke concern and our decision to return. I did not explain the flight instrument failures or vibration issues; as this was not of concern to the passengers and would have been of no benefit to them. We eventually were provided landing data; which showed us possibly landing a couple of thousand pounds over structural landing weight but well under performance limits. My thoughts were to reassess the condition of the smoke/fumes as we got closer to the airport and determine if two slight further airports may be a better option. As we got closer; an assessment of the conditions indicated that all things were stable; no increasing smoke/fumes were being generated and while time was important; things weren't dire. The flight attendants indicated that the level of fumes would come and go but weren't increasing at this time. The weather at our destination was rapidly deteriorating; winds down the runway at close to 40Kts; as were in one of our optional airport; but the visibility at our destination was at 1 mile; mostly due to rain; which was below the cat C landing minimums and reported to be deteriorating in rain. That was no longer suitable. The other two airports were the same in time; and with the fact that winds were high and one airport had one runway; I didn't want to get in the possible situation of some aircraft getting disabled on the runway there and us having to go to the third airport anyway; so the decision was made to go to the largest of our alternative. An uneventful landing was made and we taxied to the gate; followed by emergency vehicles as they were examining our aircraft continually. At the gate the fireman looked for my thumbs up and he returned the same and we completed our parking checklist.

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Original NASA ASRS Text

Title: A B757 developed electrical fumes at cruise followed by the loss of all airspeed indications in IMC with turbulence. The crew turned toward a divert airport and completed the QRH. Airspeed indications returned prior to a safe landing.

Narrative: At cruise FL340; we encountered fumes that smelled like electrical wiring burning; or a motor burning up. Having experienced this on a 767; I recognized the smell; but it was worse; and in that previous incident it was a cargo exhaust fan that failed and disconnected itself. Actions -We first donned our oxygen masks; confirmed Oxygen on 100% and my First Officer (FO) immediately got the smoke/ fumes QRH out and started to accomplish the checklist items. We were in Moderate turbulence; and IMC at this time; autopilot/autoflight systems on. Turbulence was causing altitude deviations of +/- 100 feet. Previous to this; since we were in IMC; we checked the OAT which was -36C so we turned on engine and wing anti-ice. We did not fly over or near any radar returns of yellow or red. Several calls from the flight attendants (FA) indicated the presence of substantial electrical odor in the cabin; and it was significant. Passenger Flight attendant call buttons were going off in large quantity. We immediately were thinking about a return to the departure airport. Substantial thunderstorm activity was along our route and we were immediately thinking how to break track if this didn't improve immediately. Moments later; we lost our Mach Airspeed indicators; which spun down; our speed tapes dropped to minimum speed; and the auto throttles advanced along with an immediate stick shaker. We also received several yellow EICAS warnings however I was immediately task focused on flying the airplane. [Past aircraft accidents] came to mind. I disconnected the auto throttles; autopilot and hand flew the jet; referencing the standby airspeed indicator which then wound down almost instantly. We had no reliable airspeed indications and a stick shaker; in Moderate turbulence in IMC. I added thrust; as I was fighting Moderate turbulence; and flying wings level and a relative known pitch; and with virtually no airspeed references; I resorted to an approximate known fuel flow of about 4000Lbs/engine and pitch slightly above the Horizon. (Knowing cruise would also be about 1.55 EPR and pitch 2.5-3.5).We [advised our situation] on 121.5. Got a response from several aircraft; one was helpful and relayed our position and [situation] to Oceanic on HF Radio. I turned right to break off of the track; and was having to navigate between thunderstorms the best I could while in IMC. Knowing that ideal would be to get to 15NM parallel track; however with all the weather; I believed other aircraft may be deviating this distance left and right of track; and 15NM Right/South of track was not possible with the weather. 25-30 miles or halfway between tracks probably would be safer in such an emergency; and with no airspeed references. My FO was accomplishing the QRH Smoke Fumes checklist and checked with me prior to turning the left Recirc fan off; which changes many things to vent any smoke/fumes; and since we were already diverting; I nodded and said yes; do it. We flew approximately 20-30 miles off to the Right/South and set up a direct to the departure airport which the ALTN page showed as the nearest airport. We set up FL240 in the MCP Altitude window. I started a gentle descent; as aircraft controllability was of significant concern without reliable airspeed indications. Turbulence was still BRUTAL. Airspeed indications came back and were lost 3 different times; and I adjusted power based on what we had. Additionally I was having substantial right engine vibration of 5.0; and while I had no airspeed indications. Still in solid IMC; I was trying to differentiate between unrelenting turbulence; the stick shaker; engine vibration possibly due to ice crystal icing; and possibly airframe vibration/buffet possibly due to higher Mach speed (by feel) to which I reduced thrust gently to combat. I resorted to an approximate fuel flow and pitch as often as I could. We closed the right engine (#2) bleed; and opened the isolation valve in the event that the fumescould have been partially coming from the Right engine; since its N1 Vibration was at 5.0; which was Amber in color. This did not have an effect on the fumes on the airplane. My knowledge of the Ice Crystal Icing procedures above FL250 was to have Engine Anti Ice ON (already was on) and avoid suspected conditions (we already were trying to get out of it). We were task saturated. Mindset - When we initially got the electrical smoke/fumes/smell during the high level of turbulence followed by the loss of all airspeed indications; since we weren't flying over any yellow or red radar echoes; had no moisture indications on the windshield; no sulfur smell; my thought immediately went to a chaffed electrical harness supplying heating to Pitot/Static and possible other systems; which may have been the source of airspeed indication failures; rather than Ice Crystal Icing causing Airspeed/Mach Indication losses; and the electrical fumes were very strong. My FO had completed the Smoke/Fumes checklist. The Electrical burning odor was still prevalent throughout the aircraft but stable and appeared to be dissipating; so we did not choose to accomplish the Smoke removal checklist. My thoughts were to get off track far enough to avoid deviating aircraft; reverse course and descend to lower altitude both to safely get below the tracks; below the headwinds; other aircraft; and possibly out of the IMC so as to resolve any icing issue if we had a partially heated system; out of the turbulence to stop any electrical wiring chaffing and into VMC to help fly the airplane with more references; and less task saturation. After established heading back at FL240; an approximate speed of 280 knots indicated; Airspeed indications which had returned had stabilized and I was able to engage an autopilot and autoflight systems. The Engine Vibration indications (N1) were normal and not indicated in Amber. At this point we were able to talk with ATC and complete a phone patch with our company Dispatch and Maintenance folks. I explained the Fumes; the loss of Airspeed indications; the Right Engine vibration; etc. and was headed back. We contacted Approach with our position and were given FL240. They provided us a SQUAWK and cleared us direct. We reassessed the cabin situation; and I gave the passengers a PA explaining what we had; as far as the electrical smell/smoke concern and our decision to return. I did not explain the flight instrument failures or vibration issues; as this was not of concern to the passengers and would have been of no benefit to them. We eventually were provided landing data; which showed us possibly landing a couple of thousand pounds over structural landing weight but well under performance limits. My thoughts were to reassess the condition of the smoke/fumes as we got closer to the airport and determine if two slight further airports may be a better option. As we got closer; an assessment of the conditions indicated that all things were stable; no increasing smoke/fumes were being generated and while time was important; things weren't dire. The flight attendants indicated that the level of fumes would come and go but weren't increasing at this time. The weather at our destination was rapidly deteriorating; winds down the runway at close to 40Kts; as were in one of our optional airport; but the visibility at our destination was at 1 mile; mostly due to rain; which was below the Cat C landing minimums and reported to be deteriorating in rain. That was no longer suitable. The other two airports were the same in time; and with the fact that winds were high and one airport had one runway; I didn't want to get in the possible situation of some aircraft getting disabled on the runway there and us having to go to the third airport anyway; so the decision was made to go to the largest of our alternative. An uneventful landing was made and we taxied to the gate; followed by emergency vehicles as they were examining our aircraft continually. At the gate the fireman looked for my thumbs up and he returned the same and we completed our parking checklist.

Data retrieved from NASA's ASRS site 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.