A320
Flight Crew Last 90 Days 240; Flight Crew Total 16000; Flight Crew Type 3000
Human-Machine Interface; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Became Reoriented
Aircraft; Procedure
There is a potential terrain conflict on the HHOOD 2 RNAV Arrival; to PDX. The Airbus FMGC; when executing the arrival; descends the aircraft below the published MEA. The segment in question is from HHOOD to BLRUN when landing on 28L/R. There is no charted crossing restriction at BLRUN; the next charted restriction is at SHAFR (At 240 KTS and at or above 6;700 FT). There is; however; the listed MEA of 7;200 FT(in small print) between HHOOD and BLRUN which is very easily missed. The Airbus FMCG sees the path beyond SHAFR as too steep for the aircraft to accomplish under normal circumstances; so it attempts to get the aircraft as low and slow as possible to get ready for the approach to 28L/R. When looking at the FMGC before the arrival; I saw that it ignored the 240 KTS requirement at SHAFR (common for the Airbus); descending and slowing the aircraft to be at SHAFR exactly at 6;700 FT; but at 203 KTS. To do this; it descends at 250 KTS from 10;000 to 6;700 FT; [and] then starts slowing. Unfortunately; this descends the aircraft to 6;700 FT PRIOR to BLRUN; the FMCG shows the aircraft at 6;700 FT and slowing at BLRUN; which puts it 500 below the published MEA. If a crew follows SOP and sets the lowest published restriction on the arrival when cleared to 'descend via'; they will descend below the MEA and cause a terrain conflict if they follow the VNAV path. I'm guessing that this hasn't come up before because PDX approach normally vectors you and stops you at 7;000 FT right after HHOOD; then steps you down to avoid terrain as you approach the airport. However; the safety potential is there; and needs to be addressed.
A319 Captain reports that the Airbus FMGC will ignore MEA and airspeed requirements on the HHOOD 2 to Runway's 28 at PDX if left to its own devices.