P80 controller described a MVA infraction when issuing an altitude assignment below the MVA minimums...

Narrative:

A dash 8-400 was south/southeast bound on a vector to final at 5;000 ft in a 5;000 ft MVA. I descended the dash 8 to 4;000 ft thinking he was in a 4;000 ft MVA. Approximately 30 seconds later I realized I had made a mistake; so I turned him 15 degrees right to expedite his departure out of the higher MVA. Had I climbed him to 5;000 ft instead of turning him he would've been out of the higher MVA before he leveled and needed to start back down again. I was the final approach controller and had the MVA numbers turned off as they tend to cover other information. The MVA changes rapidly in this sector as it's located on the west slope of mount hood (11;239 ft MSL) which necessitates many different MVA's in a short span. I'm very familiar with the MVA's; so I had them turned off. I know the MVA's like the back of my hand but I just made a mistake. Recommendation; during the busy arrival periods I will alternate turning the MVA's on and off every minute or so just to keep my brain fresh and alert and to reinforce I'm in compliance with the charted minimum vector altitudes.

Original NASA ASRS Text

Title: P80 Controller described a MVA infraction when issuing an altitude assignment below the MVA minimums. The reporter noted the MVA map was turned off; but that he was very familiar with the MVA's and just made an error.

Narrative: A Dash 8-400 was south/southeast bound on a vector to final at 5;000 FT in a 5;000 FT MVA. I descended the Dash 8 to 4;000 FT thinking he was in a 4;000 FT MVA. Approximately 30 seconds later I realized I had made a mistake; so I turned him 15 degrees right to expedite his departure out of the higher MVA. Had I climbed him to 5;000 FT instead of turning him he would've been out of the higher MVA before he leveled and needed to start back down again. I was the Final Approach Controller and had the MVA numbers turned off as they tend to cover other information. The MVA changes rapidly in this sector as it's located on the west slope of Mount Hood (11;239 FT MSL) which necessitates many different MVA's in a short span. I'm very familiar with the MVA's; so I had them turned off. I know the MVA's like the back of my hand but I just made a mistake. Recommendation; during the busy arrival periods I will alternate turning the MVA's on and off every minute or so just to keep my brain fresh and alert and to reinforce I'm in compliance with the charted minimum vector altitudes.

Data retrieved from NASA's ASRS site as of April 2012 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	952755
Time
Date	201106
Local Time Of Day	1201-1800
Place
Locale Reference	P80.TRACON
State Reference	OR
Environment
Light	Daylight
Aircraft 1
Make Model Name	Dash 8-400
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Inflight Event / Encounter CFTT / CFIT

P80 controller described a MVA infraction when issuing an altitude assignment below the MVA minimums. The reporter noted the MVA map was turned off; but that he was very familiar with the MVA's and just made an error.