B767 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 138; Flight Crew Type 138
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Weather / Turbulence
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Human Factors; Weather
We were in level flight at 320 on with Marseille Center frequency 127.54. We were in moderate turbulence and the airspace was relatively congested. We got a TCAS descent RA from the aircraft above us. The Captain who was the flying pilot disconnected the auto pilot and immediately followed the TCAS command. We descended from FL320 to 31;500 feet. As soon as we were clear of the conflict we climbed back to FL320. I reported to ATC that we had responded to a TCAS decent RA and that we had deviated from our altitude. The aircraft that descended into our altitude said he had hit severe turbulence and could not control his altitude. We never got a traffic advisory from TCAS only the resolution advisory. Our TCAS showed zero altitude separation from the aircraft.
Cruising at FL320; LNAV/VNAV PATH; Autopilot (AP) on; Seatbelt sign on. Started to experience Light Chop/Turbulence. Without warning TCAS RA; Descend popped up (NO TCAS TA; system went directly to RA) Disengaged AP and followed RA guidance. Advised ARTCC of 'TCAS Descent'. Aircraft visually acquired passing left to right at our original altitude. We descended 300 feet in response to RA. After clearing other Aircraft we climbed back to FL320 and advised ARTCC of return to altitude and details of incident. During event we heard [the other aircraft] call ARTCC and advise them of inability to maintain altitude due to severe turbulence. Do not know if other aircraft was unable to maintain altitude due to turbulence or if they chose to descend without ARTCC clearance. After event we did experience moderate chop. Flight attendants were seated. Turbulence was not forecast. Reported event to Dispatch along with turbulence report. TCAS descent response was prompt but smooth with no excessive G-loading and no issues for flight attendants.
B767 flight crew at FL320 experienced a TCAS RA with an aircraft above them that was unable to maintain altitude due to turbulence. A descent was initiated to FL315 to receive a 'clear of conflict' from the TCAS.