Md-10 captain reported that one of the engines had an erratic N1 indication.

Attributes
ACN	1539651
Time
Date	201805
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	RPM/N1/N2/Etc Indication
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

At 10;000 ft and 280 kts with autopilot and autothrottles engaged we saw engines 1&2 N1's cycle to idle as engine 3 N1 exceeded its limit; we saw as much as 124%. Upon seeing this I disconnected the auto throttles and moved throttle lever #3 to idle. The first officer reviewed the QRH for the indicated engine 3 exceedance. Not sure if this was real or just an indication issue we left throttle #3 at idle and operated the rest of the flight with throttles 1&2 only. Throughout the rest of the flight with the #3 throttle at idle we noticed the N1 indication for that engine continued to fluctuate even as high as 70%. We [advised] ATC and were given vectors to the ILS. We executed an autoland.

Original NASA ASRS Text

Title: MD-10 Captain reported that one of the engines had an erratic N1 indication.

Narrative: At 10;000 ft and 280 kts with autopilot and autothrottles engaged we saw engines 1&2 N1's cycle to idle as engine 3 N1 exceeded its limit; we saw as much as 124%. Upon seeing this I disconnected the auto throttles and moved throttle lever #3 to idle. The FO reviewed the QRH for the indicated ENG 3 EXCEEDANCE. Not sure if this was real or just an indication issue we left throttle #3 at idle and operated the rest of the flight with throttles 1&2 only. Throughout the rest of the flight with the #3 throttle at idle we noticed the N1 indication for that engine continued to fluctuate even as high as 70%. We [advised] ATC and were given vectors to the ILS. We executed an autoland.

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.