Air carrier crew reported the FMS would not allow the aircraft to descend to a hard altitude on the ...

Narrative:

Captain was pilot flying; and descending on the kratr 2 STAR of 28L at pdx.the aircraft missed a programmed FMS altitude constraint on the arrival at liqwd. As per SOP we reviewed and verified all crossing altitudes and speeds prior to descent on the STAR. Nearing hyker intersection (7;000-9;000 foot altitude restriction) we both noticed the airplane was not descending as planned. The captain stated we could not make the next crossing altitude restriction for liqwd intersection at 6;000 feet. I called out our airspeed at 224 knots to when I noticed us speeding up passed our assigned 210 knots.we both spoke about this the next day after the captain had consulted other check airmen and their conclusion regarded the glide path to be high because the FMS would not permit the aircraft to descend below the published IAF at shafr (6;700 feet).this should be emphasized as a critical 'gotcha' in initial FMS training.continually test all pilots on this. I did not know this and will always be cognizant of this altitude differences when programming a transition from a STAR to an IAF that is higher than the last designated altitude on a STAR.

Original NASA ASRS Text

Title: Air carrier crew reported the FMS would not allow the aircraft to descend to a hard altitude on the KRATR 2 arrival to PDX because it was below the IAF altitude for the ILS 28L.

Narrative: Captain was pilot flying; and descending on the KRATR 2 STAR of 28L at PDX.The aircraft missed a programmed FMS altitude constraint on the arrival at LIQWD. As per SOP we reviewed and verified all crossing altitudes and speeds prior to descent on the STAR. Nearing HYKER intersection (7;000-9;000 foot altitude restriction) we both noticed the airplane was not descending as planned. The Captain stated we could not make the next crossing altitude restriction for LIQWD intersection at 6;000 feet. I called out our airspeed at 224 knots to when I noticed us speeding up passed our assigned 210 knots.We both spoke about this the next day after the Captain had consulted other check airmen and their conclusion regarded the glide path to be high because the FMS would not permit the aircraft to descend below the published IAF at SHAFR (6;700 feet).This should be emphasized as a critical 'gotcha' in initial FMS training.Continually test all pilots on this. I did not know this and will always be cognizant of this altitude differences when programming a transition from a STAR to an IAF that is higher than the last designated altitude on a STAR.

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.

Attributes
ACN	1461212
Time
Date	201706
Local Time Of Day	0601-1200
Place
Locale Reference	PDX.Airport
State Reference	OR
Aircraft 1
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR KRATR TWO
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Speed All Types

Air carrier crew reported the FMS would not allow the aircraft to descend to a hard altitude on the kratr 2 arrival to pdx because it was below the IAF altitude for the ILS 28L.