Pct controller described a MVA infraction when issuing the wrong descent clearance altitude to an ai...

Narrative:

I was working a C340 for the visual approach to jyo. He was on a vector towards the airport at 4;000 ft. I then descended him to 3;300 to comply with the area MVA. I then instructed him to descend to 2;000; once he cleared the 3;300 MVA; this was 2 miles away from the 2;000 MVA and he descended while flying in the 3;000 MVA area. At 2;700 ft the low altitude alert (la) came on and I instructed the C340 to maintain 3;000. The C340 climbed and he then reported to airport in sight. He was cleared for the visual approach and canceled his IFR clearance with me in the air on my frequency. At the time I instructed him to descent to 2;000; I meant to say 3;000 and did not catch my error or his read back.

Original NASA ASRS Text

Title: PCT Controller described a MVA infraction when issuing the wrong descent clearance altitude to an aircraft being vectored for a Visual Approach to JYO.

Narrative: I was working a C340 for the Visual Approach to JYO. He was on a vector towards the airport at 4;000 FT. I then descended him to 3;300 to comply with the area MVA. I then instructed him to descend to 2;000; once he cleared the 3;300 MVA; this was 2 miles away from the 2;000 MVA and he descended while flying in the 3;000 MVA area. At 2;700 FT the Low Altitude Alert (LA) came on and I instructed the C340 to maintain 3;000. The C340 climbed and he then reported to airport in sight. He was cleared for the Visual Approach and canceled his IFR clearance with me in the air on my frequency. At the time I instructed him to descent to 2;000; I meant to say 3;000 and did not catch my error or his read back.

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	947271
Time
Date	201105
Local Time Of Day	1801-2400
Place
Locale Reference	JYO.Airport
State Reference	VA
Aircraft 1
Make Model Name	Cessna 340/340A
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Trainee
Qualification	Air Traffic Control Developmental
Events
Anomaly	ATC Issue All Types Inflight Event / Encounter CFTT / CFIT

Pct controller described a MVA infraction when issuing the wrong descent clearance altitude to an aircraft being vectored for a visual approach to jyo.