Narrative:

This report is being filed to describe the events leading up to a compressor stall in the #2 engine of a B727-222 while in cruise at FL310. On the morning of jan/xx/98, we were in cruise at FL310, en route from dfw to sfo. We were between the navaids ama and fmn while tracking on J58. Aircraft confign was stable, ie, no power changes, fuel xfeed changes, or bleed confign was taking place. ZAB advised us of crossing traffic, right to left, 10 mi ahead, same altitude, on a heading approximately 40 degrees more southerly than our own. We verified the mentioned traffic on our TCASII, and were able to see the contrails trailing behind the mentioned traffic. We visually acquired the traffic as it passed our 12 O'clock position and the contrails stretching only a short distance behind it, still to the right of our flight path. Shortly thereafter, we passed through the remaining wake of the preceding aircraft (which we were later advised was an MD80) and encountered the expected turbulence. We experienced moderate turbulence for approximately 3-5 seconds, noticed an EPR drop on the #2 engine from 2.00 down to 1.50 and then back to 2.00, and heard the compressor stall 'bangs.' passenger and flight attendants called up shortly after with concern regarding the very unexpected turbulence and the engine noises. Engine indications returned to normal very quickly and the flight continued without further incident. Company maintenance advised us to continue, and no further action was required by the crew. Area of concern: ATC vectoring of same altitude crossing traffic with 10 mi of separation. Lack of pilot ability to see and avoid wake following turbojet aircraft, even when traffic is visually idented. Unpredictability of wake dissipation (ie, distance in trail, and rate of descent/dissipation of wake). Hazards associated with wake induced turbulence causing engine compressor stalls during high speed cruise at flight level altitudes. Callback conversation with reporter revealed the following information: reporter states that he feels the controllers need to be more aware of the possible wake turbulence hanging around behind an aircraft and not clear another aircraft at the same altitude directly behind that aircraft. A compressor stall at FL310 is not normal and not something one can plan for. It certainly startled the passenger and flight attendants as well as the flight crew.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF B727-200 EXPERIENCES WAKE TURB AND RESULTING COMPRESSOR STALL FROM AN MD80 XING THEIR FLT PATH AT FL310.

Narrative: THIS RPT IS BEING FILED TO DESCRIBE THE EVENTS LEADING UP TO A COMPRESSOR STALL IN THE #2 ENG OF A B727-222 WHILE IN CRUISE AT FL310. ON THE MORNING OF JAN/XX/98, WE WERE IN CRUISE AT FL310, ENRTE FROM DFW TO SFO. WE WERE BTWN THE NAVAIDS AMA AND FMN WHILE TRACKING ON J58. ACFT CONFIGN WAS STABLE, IE, NO PWR CHANGES, FUEL XFEED CHANGES, OR BLEED CONFIGN WAS TAKING PLACE. ZAB ADVISED US OF XING TFC, R TO L, 10 MI AHEAD, SAME ALT, ON A HDG APPROX 40 DEGS MORE SOUTHERLY THAN OUR OWN. WE VERIFIED THE MENTIONED TFC ON OUR TCASII, AND WERE ABLE TO SEE THE CONTRAILS TRAILING BEHIND THE MENTIONED TFC. WE VISUALLY ACQUIRED THE TFC AS IT PASSED OUR 12 O'CLOCK POS AND THE CONTRAILS STRETCHING ONLY A SHORT DISTANCE BEHIND IT, STILL TO THE R OF OUR FLT PATH. SHORTLY THEREAFTER, WE PASSED THROUGH THE REMAINING WAKE OF THE PRECEDING ACFT (WHICH WE WERE LATER ADVISED WAS AN MD80) AND ENCOUNTERED THE EXPECTED TURB. WE EXPERIENCED MODERATE TURB FOR APPROX 3-5 SECONDS, NOTICED AN EPR DROP ON THE #2 ENG FROM 2.00 DOWN TO 1.50 AND THEN BACK TO 2.00, AND HEARD THE COMPRESSOR STALL 'BANGS.' PAX AND FLT ATTENDANTS CALLED UP SHORTLY AFTER WITH CONCERN REGARDING THE VERY UNEXPECTED TURB AND THE ENG NOISES. ENG INDICATIONS RETURNED TO NORMAL VERY QUICKLY AND THE FLT CONTINUED WITHOUT FURTHER INCIDENT. COMPANY MAINT ADVISED US TO CONTINUE, AND NO FURTHER ACTION WAS REQUIRED BY THE CREW. AREA OF CONCERN: ATC VECTORING OF SAME ALT XING TFC WITH 10 MI OF SEPARATION. LACK OF PLT ABILITY TO SEE AND AVOID WAKE FOLLOWING TURBOJET ACFT, EVEN WHEN TFC IS VISUALLY IDENTED. UNPREDICTABILITY OF WAKE DISSIPATION (IE, DISTANCE IN TRAIL, AND RATE OF DSCNT/DISSIPATION OF WAKE). HAZARDS ASSOCIATED WITH WAKE INDUCED TURB CAUSING ENG COMPRESSOR STALLS DURING HIGH SPD CRUISE AT FLT LEVEL ALTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE FEELS THE CTLRS NEED TO BE MORE AWARE OF THE POSSIBLE WAKE TURB HANGING AROUND BEHIND AN ACFT AND NOT CLR ANOTHER ACFT AT THE SAME ALT DIRECTLY BEHIND THAT ACFT. A COMPRESSOR STALL AT FL310 IS NOT NORMAL AND NOT SOMETHING ONE CAN PLAN FOR. IT CERTAINLY STARTLED THE PAX AND FLT ATTENDANTS AS WELL AS THE FLC.

Data retrieved from NASA's ASRS site as of July 2007 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.