Narrative:

We pushed off the gate approximately 10 minutes late due to the time it took to determine the cause of a hot mic and writing up an MEL for the observer's seat audio panel. After being cleared for takeoff I set the takeoff power to approximately 87.8 percent. As we accelerated; I transitioned to looking outside. At approximately 100 knots; the first officer pointed out that the number one engine N1 gauge had rolled back to 62.3 percent. Not knowing the immediate cause of the rollback; I rejected the takeoff. We informed ATC of the reject; and exited the runway. I taxied the aircraft to the east ramp. At that point I spoke with the F/as; and made a PA to the passengers. We ran the procedure for brake cooling requirements for a reject at 100 knots. The required cooling time was 52 minutes at the gate. I coordinated with operations; and taxied to gate X. Upon completion of the parking checklist with both engines shut down; the number one N1 gauge was still indicating 62.3 percent on the analogue and digital portions of the gauge. I contacted dispatch and spoke with maintenance control and the chief pilot on duty. A logbook entry was made. The aircraft was taken offline.with a historical perspective; I believe that the N1 rollback was a faulty gauge indication; and not an engine problem. It is difficult to say if I could have done something different. At the moment I felt I did not have the time to methodically analyze the situation; and felt the safest course of action was to stop the aircraft due to a potential engine rollback. I do regret my delay in informing the passengers of the situation. I neglected to immediately inform them to remain seated and let them know that everything was ok. Procedurally we had a moment of confusion finding the rejected takeoff checklist in the QRH.

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Original NASA ASRS Text

Title: B737 First Officer reported that on takeoff engine #1 N1 RPM had rolled back to 62.3% so the Captain rejected the takeoff. At the gate with engines shutdown; engine #1 N1 continued to indicate 62.3%.

Narrative: We pushed off the gate approximately 10 minutes late due to the time it took to determine the cause of a hot mic and writing up an MEL for the observer's seat audio panel. After being cleared for takeoff I set the takeoff power to approximately 87.8 percent. As we accelerated; I transitioned to looking outside. At approximately 100 knots; the First Officer pointed out that the number one engine N1 gauge had rolled back to 62.3 percent. Not knowing the immediate cause of the rollback; I rejected the takeoff. We informed ATC of the reject; and exited the runway. I taxied the aircraft to the East Ramp. At that point I spoke with the F/As; and made a PA to the Passengers. We ran the procedure for brake cooling requirements for a reject at 100 knots. The required cooling time was 52 minutes at the gate. I coordinated with Operations; and taxied to Gate X. Upon completion of the Parking Checklist with both engines shut down; the number one N1 gauge was still indicating 62.3 percent on the analogue and digital portions of the gauge. I contacted Dispatch and spoke with Maintenance Control and the Chief Pilot on Duty. A logbook entry was made. The aircraft was taken offline.With a historical perspective; I believe that the N1 rollback was a faulty gauge indication; and not an engine problem. It is difficult to say if I could have done something different. At the moment I felt I did not have the time to methodically analyze the situation; and felt the safest course of action was to stop the aircraft due to a potential engine rollback. I do regret my delay in informing the Passengers of the situation. I neglected to immediately inform them to remain seated and let them know that everything was ok. Procedurally we had a moment of confusion finding the RTO Checklist in the QRH.

Data retrieved from NASA's ASRS site 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.