MD80 first officer reports tri failure during takeoff causing autothrottles to disconnect and EPR ba...

Narrative:

Unknown initial failure/lockout of FMS system gave faulty indication to engine EPR limit during takeoff roll. During the takeoff roll the EPR limit showed the granite bars at 1.80. As I aligned the eprs after the auto throttle had disconnected twice it became apparent that a lower power setting was being indicated by the tri than was necessary. Later in the flight; the FMS started acting strangely and then finally quit altogether and we reverted to manual navigation procedure per the checklist. After review during climb out; I believe the tri; being linked to the FMS; failed during the takeoff roll and the orange EPR bars 'froze' at the point of failure; causing the lower than necessary power setting to cause a longer than ideal takeoff distance. If this was the case; such failure is very confusing and subtle; as there was no warning that the to button on the tri had failed.

Original NASA ASRS Text

Title: MD80 First Officer reports TRI failure during takeoff causing autothrottles to disconnect and EPR bars to indicate less than required thrust. Low thrust produced a long takeoff roll. The FMS failed later in flight and may have caused the TRI computer failure.

Narrative: Unknown initial failure/lockout of FMS system gave faulty indication to engine EPR limit during takeoff roll. During the takeoff roll the EPR limit showed the granite bars at 1.80. As I aligned the EPRs after the auto throttle had disconnected twice it became apparent that a lower power setting was being indicated by the TRI than was necessary. Later in the flight; the FMS started acting strangely and then finally quit altogether and we reverted to manual navigation procedure per the checklist. After review during climb out; I believe the TRI; being linked to the FMS; failed during the takeoff roll and the orange EPR bars 'froze' at the point of failure; causing the lower than necessary power setting to cause a longer than ideal takeoff distance. If this was the case; such failure is very confusing and subtle; as there was no warning that the TO button on the TRI had failed.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	841340
Time
Date	200906
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	PMC Performance/Thrust Management Computer
Person 1
Function	First Officer Pilot Flying
Events
Anomaly	Aircraft Equipment Problem Critical

MD80 first officer reports tri failure during takeoff causing autothrottles to disconnect and EPR bars to indicate less than required thrust. Low thrust produced a long takeoff roll. The FMS failed later in flight and may have caused the tri computer failure.