Mechanic notes he may have misjudged a stall report from a flight crew and did not perform an engine...

Attributes
ACN	792145
Time
Date	200806
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	ground : maintenance ground : takeoff roll
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
Qualification	technician : powerplant technician : airframe
Experience	maintenance technician : 27
ASRS Report	792145
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper maintenance non adherence : far non adherence : published procedure
Independent Detector	other other : 1
Resolutory Action	none taken : detected after the fact
Consequence	other
Factors
Maintenance	performance deficiency : non compliance with legal requirements performance deficiency : logbook entry performance deficiency : inspection
Supplementary
Problem Areas	Maintenance Human Performance Aircraft
Primary Problem	Maintenance Human Performance

Narrative:

Aircraft returned to gate after a rejected takeoff with the following irregularity: takeoff roll after pushing toga button there was an immediate N1 differential. Left N1 went to approximately 70%; right N1 lagged around 40% N1. Takeoff roll aborted at approximately 30 KTS. Aft flight attendants said they heard a loud boom immediately before abort. My correction action: inspected #1 and #2 engines; both check good. Ran engines to takeoff power with autothrottle engaged and also manually; both check good -- N1; N2; egt match. Ran autothrottle bite test; no faults. Torque test shows #2 takes 1.5 in-oz more to move thrust lever than #1. Forward autothrottle to mco/placard per MEL 22-00-04. After the troubleshooting; I could not find a problem with the power plants and the autothrottle operation was fine. I was instructed by our maintenance control center to defer the autothrottles per MEL as precautionary. I asked the captain about the flight attendant's report of a loud boom. The captain stated verbally that he did not hear a boom. I then deduced that there was no engine stall and the report was an overreaction of the flight attendant. The maintenance control center set up to perform a stall inspection the next day. The reason for this report is that I may have misjudged the stall report and did not do a stall inspection before I returned the aircraft to service.

Original NASA ASRS Text

Title: MECHANIC NOTES HE MAY HAVE MISJUDGED A STALL REPORT FROM A FLT CREW AND DID NOT PERFORM AN ENGINE STALL INSPECTION BEFORE RETURNING ACFT TO SERVICE.

Narrative: ACFT RETURNED TO GATE AFTER A REJECTED TKOF WITH THE FOLLOWING IRREGULARITY: TKOF ROLL AFTER PUSHING TOGA BUTTON THERE WAS AN IMMEDIATE N1 DIFFERENTIAL. L N1 WENT TO APPROX 70%; R N1 LAGGED AROUND 40% N1. TKOF ROLL ABORTED AT APPROX 30 KTS. AFT FLT ATTENDANTS SAID THEY HEARD A LOUD BOOM IMMEDIATELY BEFORE ABORT. MY CORRECTION ACTION: INSPECTED #1 AND #2 ENGS; BOTH CHK GOOD. RAN ENGS TO TKOF PWR WITH AUTOTHROTTLE ENGAGED AND ALSO MANUALLY; BOTH CHK GOOD -- N1; N2; EGT MATCH. RAN AUTOTHROTTLE BITE TEST; NO FAULTS. TORQUE TEST SHOWS #2 TAKES 1.5 IN-OZ MORE TO MOVE THRUST LEVER THAN #1. FORWARD AUTOTHROTTLE TO MCO/PLACARD PER MEL 22-00-04. AFTER THE TROUBLESHOOTING; I COULD NOT FIND A PROB WITH THE PWR PLANTS AND THE AUTOTHROTTLE OP WAS FINE. I WAS INSTRUCTED BY OUR MAINT CTL CTR TO DEFER THE AUTOTHROTTLES PER MEL AS PRECAUTIONARY. I ASKED THE CAPT ABOUT THE FLT ATTENDANT'S RPT OF A LOUD BOOM. THE CAPT STATED VERBALLY THAT HE DID NOT HEAR A BOOM. I THEN DEDUCED THAT THERE WAS NO ENG STALL AND THE RPT WAS AN OVERREACTION OF THE FLT ATTENDANT. THE MAINT CTL CTR SET UP TO PERFORM A STALL INSPECTION THE NEXT DAY. THE REASON FOR THIS RPT IS THAT I MAY HAVE MISJUDGED THE STALL RPT AND DID NOT DO A STALL INSPECTION BEFORE I RETURNED THE ACFT TO SVC.

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.

Mechanic notes he may have misjudged a stall report from a flight crew and did not perform an engine stall inspection before returning aircraft to service.