Eug TRACON controller reported an aircraft turned early on the jackson one departure.

Attributes
ACN	1595956
Time
Date	201811
Local Time Of Day	1201-1800
Place
Locale Reference	MFR.Airport
State Reference	OR
Aircraft 1
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Route In Use	STAR JACKSON ONE
Flight Plan	IFR
Person 1
Function	Departure
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 7
Events
Anomaly	Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types Inflight Event / Encounter CFTT / CFIT

Narrative:

Aircraft X departed mfr on the Jackson1 off RWY32. [I] told aircraft 'leaving 042; turn right heading 120; when able direct aclob (fix on flight plan).' aircraft repeated 'out of 042; turn right...say again heading...when able direct aclob.' I repeated 'leaving 042; turn right heading 120; when able direct aclob; resume own navigation.' pilot read back instructions correctly. I observed a slight turn of the aircraft out of 032 (MVA in area is 033); but I thought they might just be correcting heading to oed; which is part of the Jackson1. Nope; they continued to turn ene; but not in a sharp turn to 120 [heading]. I almost thought they were maybe issued the eagle departure instead; and just had started turn late. They were above MVA at this time; and no conflicting traffic. I just allowed them to continue turn to 120 [heading] and aclob.not sure if aircraft X may have an FMS issue with this departure procedure. I am not the only controller who has noticed them start a turn to the ene on the Jackson1; without instructions to do so.

Original NASA ASRS Text

Title: EUG TRACON Controller reported an aircraft turned early on the JACKSON ONE departure.

Narrative: Aircraft X departed MFR on the Jackson1 off RWY32. [I] told aircraft 'leaving 042; turn right heading 120; when able direct ACLOB (fix on flight plan).' Aircraft repeated 'Out of 042; turn right...say again heading...when able direct ACLOB.' I repeated 'Leaving 042; turn right heading 120; when able direct ACLOB; resume own navigation.' Pilot read back instructions correctly. I observed a slight turn of the aircraft out of 032 (MVA in area is 033); but I thought they might just be correcting heading to OED; which is part of the Jackson1. Nope; they continued to turn ENE; but not in a sharp turn to 120 [heading]. I almost thought they were maybe issued the Eagle departure instead; and just had started turn late. They were above MVA at this time; and no conflicting traffic. I just allowed them to continue turn to 120 [heading] and ACLOB.Not sure if Aircraft X may have an FMS issue with this departure procedure. I am not the only controller who has noticed them start a turn to the ENE on the Jackson1; without instructions to do so.

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.