While en route at FL310, a B73S flight crew noticed a throttle split of about 4 knob widths when matching power settings. The engine had been replaced earlier that day. The flight was diverted for maintenance and an overweight landing was accomplished.

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Attributes
ACN	331341
Time
Date	199603
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : pit
State Reference	PA
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob tower : oma
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 12000
ASRS Report	331341
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

At FL310 a throttle split was noticed. The split was about a 4 knob width apart. The left engine had been replaced that day. The flight diverted with an overweight landing in pit. The approach and landing were very routine. Callback conversation with reporter revealed the following information: maintenance communicated to this reporter via a company radio frequency that a 2 knob width throttle split was what they considered as maximum tolerance and they encouraged the crew to divert to pit. The B73S had been en route from phl to las. The reporter states that he was more comfortable with diverting than continuing. The split was so excessive that he wondered if it would keep on growing, and he didn't want to find out while in night flight over the rockies. The overweight landing required an overweight inspection. The reporter has only heard that the split was probably a result of a rigging problem and has heard nothing more since. After the landing the crew and passenger were able to make a quick airplane swap and continued the trip.

Original NASA ASRS Text

Title: WHILE ENRTE AT FL310, A B73S FLC NOTICED A THROTTLE SPLIT OF ABOUT 4 KNOB WIDTHS WHEN MATCHING PWR SETTINGS. THE ENG HAD BEEN REPLACED EARLIER THAT DAY. THE FLT WAS DIVERTED FOR MAINT AND AN OVERWT LNDG WAS ACCOMPLISHED.

Narrative: AT FL310 A THROTTLE SPLIT WAS NOTICED. THE SPLIT WAS ABOUT A 4 KNOB WIDTH APART. THE L ENG HAD BEEN REPLACED THAT DAY. THE FLT DIVERTED WITH AN OVERWT LNDG IN PIT. THE APCH AND LNDG WERE VERY ROUTINE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: MAINT COMMUNICATED TO THIS RPTR VIA A COMPANY RADIO FREQ THAT A 2 KNOB WIDTH THROTTLE SPLIT WAS WHAT THEY CONSIDERED AS MAX TOLERANCE AND THEY ENCOURAGED THE CREW TO DIVERT TO PIT. THE B73S HAD BEEN ENRTE FROM PHL TO LAS. THE RPTR STATES THAT HE WAS MORE COMFORTABLE WITH DIVERTING THAN CONTINUING. THE SPLIT WAS SO EXCESSIVE THAT HE WONDERED IF IT WOULD KEEP ON GROWING, AND HE DIDN'T WANT TO FIND OUT WHILE IN NIGHT FLT OVER THE ROCKIES. THE OVERWT LNDG REQUIRED AN OVERWT INSPECTION. THE RPTR HAS ONLY HEARD THAT THE SPLIT WAS PROBABLY A RESULT OF A RIGGING PROB AND HAS HEARD NOTHING MORE SINCE. AFTER THE LNDG THE CREW AND PAX WERE ABLE TO MAKE A QUICK AIRPLANE SWAP AND CONTINUED THE TRIP.

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.