CE750 flight crew reports missing the bayyr crossing restriction on the hhood 2 arrival to pdx due t...

Attributes
ACN	1125371
Time
Date	201310
Local Time Of Day	1201-1800
Place
Locale Reference	P80.TRACON
State Reference	OR
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Citation X (C750)
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	STAR HHOOD2
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Undershoot

Narrative:

On the hhood 2 RNAV arrival to pdx; the FMS was correctly set up and had already captured the VNAV on the descent from cruise; making several crossing restrictions on target. However; it calculated the 'at or below FL240' restriction at bayyr as an 'at FL240'; which made it impossible to meet the 'between 15;000 [and] 10;000' restriction at hhood. After passing bayyr; the v-bars abruptly went from a normal pitch attitude to a steep dive with increasing airspeed and excessive rate of descent. I intervened and disengaged the autopilot. Shortly after; ATC vectored us off the STAR with a heading for the localizer and a lower altitude. On the avionics side of the problem -- fix the FMS VNAV issues! On the navigation publication side of the problem; descent profiles on stars are becoming more and more complicated with far too many 'cross between' altitude restrictions. It seems that there are so many parameters that the FMS is unable to calculate them correctly or in a way that makes for a smooth descent on a 'descend via' clearance.

Original NASA ASRS Text

Title: CE750 flight crew reports missing the BAYYR crossing restriction on the HHOOD 2 arrival to PDX due to an FMC malfunction. FMC 2 was MEL'd and FMC 1 created a hard altitude of FL240 at HHOOD making the BAYYR crossing restriction impossible.

Narrative: On the HHOOD 2 RNAV Arrival to PDX; the FMS was correctly set up and had already captured the VNAV on the descent from cruise; making several crossing restrictions on target. However; it calculated the 'at or below FL240' restriction at BAYYR as an 'at FL240'; which made it impossible to meet the 'Between 15;000 [and] 10;000' restriction at HHOOD. After passing BAYYR; the V-Bars abruptly went from a normal pitch attitude to a steep dive with increasing airspeed and excessive rate of descent. I intervened and disengaged the autopilot. Shortly after; ATC vectored us off the STAR with a heading for the localizer and a lower altitude. On the avionics side of the problem -- fix the FMS VNAV issues! On the navigation publication side of the problem; descent profiles on STARS are becoming more and more complicated with far too many 'cross between' altitude restrictions. It seems that there are so many parameters that the FMS is unable to calculate them correctly or in a way that makes for a smooth descent on a 'descend via' clearance.

Data retrieved from NASA's ASRS site as of July 2013 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.

CE750 flight crew reports missing the bayyr crossing restriction on the hhood 2 arrival to pdx due to an FMC malfunction. FMC 2 was MEL'd and FMC 1 created a hard altitude of FL240 at hhood making the bayyr crossing restriction impossible.