A B767 crew notices a 'thump' sound during an encounter with the wake of a preceding B757 that was d...

Attributes
ACN	801313
Time
Date	200808
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 12000
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	tracon : zzz.tracon tower : bhm.tower
Operator	common carrier : air carrier
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 255 flight time total : 30000 flight time type : 6800
ASRS Report	801313
Events
Anomaly	aircraft equipment problem : less severe inflight encounter : wake turbulence
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	other
Supplementary
Problem Areas	Environmental Factor Aircraft
Primary Problem	Environmental Factor

Narrative:

The reason for this report is to alert crews that an engine surge can occur with a wake turbulence encounter. A B757 had departed in front of us and was approximately 5 miles ahead. We encountered a wake turbulence event which induced an engine surge on the right engine. We had no idea that a surge had occurred until descent into lax when maintenance sent a message stating same. All indications in the flight deck were normal. I believed the turbulence and 'thump' we heard were all related to the wake turbulence event only. Please advise all of our flight crews that an engine surge is possible when encountering wake turbulence. This could be critical depending upon when a wake turbulence event is encountered. Callback conversation with reporter revealed the following information: reporter stated that they climbed through the wake of a 'stretch' B757 that caused a roll of 10 to 15 degrees and was estimated as moderate. Maintenance determined that there had been an engine surge at that time even though it was not noted by the crew on the engine instruments. There was no damage to the engine. The engine type is subject to an airworthiness directive to prevent engine power losses due to hpc surges (2003-19-15).

Original NASA ASRS Text

Title: A B767 CREW NOTICES A 'THUMP' SOUND DURING AN ENCOUNTER WITH THE WAKE OF A PRECEDING B757 THAT WAS DETERMINED BY MAINT TO BE AN ENGINE SURGE.

Narrative: THE REASON FOR THIS RPT IS TO ALERT CREWS THAT AN ENGINE SURGE CAN OCCUR WITH A WAKE TURBULENCE ENCOUNTER. A B757 HAD DEPARTED IN FRONT OF US AND WAS APPROX 5 MILES AHEAD. WE ENCOUNTERED A WAKE TURBULENCE EVENT WHICH INDUCED AN ENGINE SURGE ON THE R ENGINE. WE HAD NO IDEA THAT A SURGE HAD OCCURRED UNTIL DSCNT INTO LAX WHEN MAINT SENT A MSG STATING SAME. ALL INDICATIONS IN THE FLT DECK WERE NORMAL. I BELIEVED THE TURBULENCE AND 'THUMP' WE HEARD WERE ALL RELATED TO THE WAKE TURBULENCE EVENT ONLY. PLEASE ADVISE ALL OF OUR FLT CREWS THAT AN ENGINE SURGE IS POSSIBLE WHEN ENCOUNTERING WAKE TURBULENCE. THIS COULD BE CRITICAL DEPENDING UPON WHEN A WAKE TURBULENCE EVENT IS ENCOUNTERED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THEY CLBED THROUGH THE WAKE OF A 'STRETCH' B757 THAT CAUSED A ROLL OF 10 TO 15 DEGS AND WAS ESTIMATED AS MODERATE. MAINT DETERMINED THAT THERE HAD BEEN AN ENGINE SURGE AT THAT TIME EVEN THOUGH IT WAS NOT NOTED BY THE CREW ON THE ENGINE INSTRUMENTS. THERE WAS NO DAMAGE TO THE ENGINE. THE ENGINE TYPE IS SUBJECT TO AN AIRWORTHINESS DIRECTIVE TO PREVENT ENGINE POWER LOSSES DUE TO HPC SURGES (2003-19-15).

Data retrieved from NASA's ASRS site as of May 2009 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.

A B767 crew notices a 'thump' sound during an encounter with the wake of a preceding B757 that was determined by maintenance to be an engine surge.