B757-200 diverts to another airport following failure of left idg shortly after takeoff.

Attributes
ACN	804430
Time
Date	200809
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 80 flight time total : 12000 flight time type : 2000
ASRS Report	804430
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : eicas other flight crewa
Resolutory Action	flight crew : diverted to another airport flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

On takeoff roll; the left generator drive EICAS message illuminated. The captain elected to continue the takeoff roll. Once we were comfortable in the climb the captain proceeded with the in-flight checklist. The checklist had us disconnect the left idg. Prior to the disconnect; the captain called dispatch and conferred with maintenance and the dispatcher to determine the best course of action. Maintenance had us continue the checklist which the captain accomplished. Prior to disconnect; I advised the captain that I had encountered this same situation in the past. We encountered a strong jolt upon disconnect. After conferring with maintenance and instructors they advised me that we more than likely had sheared the shaft of the idg. Upon disconnect; we encountered the same strong jolt throughout the aircraft and as a result we monitored the situation carefully and decided we needed to divert. In addition; dispatch advised us that we were no longer legal to enter ETOPS airspace and that we should proceed to ZZZ. The captain tried to communicate with departure but due to ATC's workload he was unable to talk to us. As a result; the captain decided to declare an emergency so we would get priority handling. We proceeded to ZZZ and landed overweight. Landed without any further problem.

Original NASA ASRS Text

Title: B757-200 DIVERTS TO ANOTHER ARPT FOLLOWING FAILURE OF LEFT IDG SHORTLY AFTER TKOF.

Narrative: ON TKOF ROLL; THE L GENERATOR DRIVE EICAS MESSAGE ILLUMINATED. THE CAPT ELECTED TO CONTINUE THE TKOF ROLL. ONCE WE WERE COMFORTABLE IN THE CLB THE CAPT PROCEEDED WITH THE INFLT CHKLIST. THE CHKLIST HAD US DISCONNECT THE L IDG. PRIOR TO THE DISCONNECT; THE CAPT CALLED DISPATCH AND CONFERRED WITH MAINT AND THE DISPATCHER TO DETERMINE THE BEST COURSE OF ACTION. MAINT HAD US CONTINUE THE CHKLIST WHICH THE CAPT ACCOMPLISHED. PRIOR TO DISCONNECT; I ADVISED THE CAPT THAT I HAD ENCOUNTERED THIS SAME SITUATION IN THE PAST. WE ENCOUNTERED A STRONG JOLT UPON DISCONNECT. AFTER CONFERRING WITH MAINT AND INSTRUCTORS THEY ADVISED ME THAT WE MORE THAN LIKELY HAD SHEARED THE SHAFT OF THE IDG. UPON DISCONNECT; WE ENCOUNTERED THE SAME STRONG JOLT THROUGHOUT THE ACFT AND AS A RESULT WE MONITORED THE SITUATION CAREFULLY AND DECIDED WE NEEDED TO DIVERT. IN ADDITION; DISPATCH ADVISED US THAT WE WERE NO LONGER LEGAL TO ENTER ETOPS AIRSPACE AND THAT WE SHOULD PROCEED TO ZZZ. THE CAPT TRIED TO COMMUNICATE WITH DEP BUT DUE TO ATC'S WORKLOAD HE WAS UNABLE TO TALK TO US. AS A RESULT; THE CAPT DECIDED TO DECLARE AN EMER SO WE WOULD GET PRIORITY HANDLING. WE PROCEEDED TO ZZZ AND LANDED OVERWT. LANDED WITHOUT ANY FURTHER PROB.

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.