P80 controller described a MVA infraction event when traffic initiated a descend below assigned alti...

Narrative:

A B737 was cleared on initial contact to proceed to jepip; descend and maintain 055. Immediately; I recognized that he was landing 28R so I changed his clearance to proceed to naciy descend and maintain 055. My trainee came back from break and I briefed him and he assumed the position while I remained to monitor. I noticed that the B737 started descending below the MVA (055); so I advised my trainee to climb him. The B737 then entered a 040 MVA and continued to 037. My trainee climbed him to 040. The MSAW alert did not go off and the plane landed safely. Recommendation; I believe that the pilot descended below his assigned altitude. There have been problems with finals frequencies in the past and it is possible it is not has clear and reliable as it should be.

Original NASA ASRS Text

Title: P80 Controller described a MVA infraction event when traffic initiated a descend below assigned altitude; the reporter noting ATC frequency coverage may have been a causal factor.

Narrative: A B737 was cleared on initial contact to proceed to JEPIP; descend and maintain 055. Immediately; I recognized that he was landing 28R so I changed his clearance to proceed to NACIY descend and maintain 055. My trainee came back from break and I briefed him and he assumed the position while I remained to monitor. I noticed that the B737 started descending below the MVA (055); so I advised my trainee to climb him. The B737 then entered a 040 MVA and continued to 037. My trainee climbed him to 040. The MSAW alert did not go off and the plane landed safely. Recommendation; I believe that the pilot descended below his assigned altitude. There have been problems with Finals Frequencies in the past and it is possible it is not has clear and reliable as it should be.

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	979856
Time
Date	201111
Local Time Of Day	1801-2400
Place
Locale Reference	P80.TRACON
State Reference	OR
Aircraft 1
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

P80 controller described a MVA infraction event when traffic initiated a descend below assigned altitude; the reporter noting ATC frequency coverage may have been a causal factor.