Global Express (BD700)
Air Traffic Control Developmental
Situational Awareness; Distraction
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance
Human Factors; Procedure
I took over R 4/5 position from previous controller; Aircraft X was on an IFR flight plan and at the time DCT..ONOHI.VECKI8.KOA. Aircraft X had been cleared for the ILS approach by the previous controller. Aircraft X crossed ONOHI above 090 but descended below 088 prior to WANSI. An MSAW alert was triggered on the radar scope and the aircraft was observed as low as 068 about 3 miles north of WANSI. I advised to pilot that the Minimum IFR Altitude (MIA) on his route of flight was 088 and that after WANSI it became 040 but did not issue proper phraseology for a low altitude alert. The pilot halted his descent and then continued down after WANSI. Pilots seem confused by the VECKI8 arrival. This is not the first time I've seen a pilot descend below the MIA when cleared for the ILS in conjunction with this arrival. Also; pilots will often ask the controller to confirm altitude assignments along the arrival. I know that this is the pilot's responsibility to understand and comply with the STAR; but enough of them seem to have trouble with this arrival to suggest that maybe we should take a look at how the STAR is worded or depicted to pilots. It's becoming a systemic problem rather than associated with individual pilots.
HCF Controller reported of a problem that happens often with aircraft on the VECKI8 STAR to KOA. Pilots descend below the Minimum IFR Altitude when cleared for the ILS in conjunction with this arrival.