The flight crew while on vectors for an approach descend below MSA for the area.

Attributes
ACN	558879
Time
Date	200208
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sjc.airport
State Reference	CA
Altitude	msl single value : 3000
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : o90.tracon tower : sjc.tower
Operator	common carrier : charter
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 135
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : o90.tracon tower : sjc.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	company : charter
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 90 flight time total : 22000 flight time type : 115
ASRS Report	558879
Person 2
Affiliation	company : charter
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 80 flight time total : 10000 flight time type : 400
ASRS Report	558312
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other other spatial deviation
Independent Detector	atc equipment : msaw other controllera other controllerb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Weather Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

An intermittently inoperative VHF transmitter may have contributed to confusion that resulted in descent below MSA while being radar vectored to final for the VOR DME runway 30R approach at sjc. I was the PF in VMC on top of scattered to broken clouds. Both of us noted the proximity to terrain, but being well clear above it, we did not immediately question our clearance. We had just noticed that somehow the active communication had been switched prematurely to tower. Whether that was a result of setting over the active frequency or accepting another aircraft's frequency, I'm not sure, but bay approach figured what happened and soon sjc tower asked us to climb to 5000 ft. Next we were given several vectors, one of which we responded to was for an aircraft with a similar call sign. This fact coupled with an inoperative transmitter may have prevented approach control from hearing our response, thus eliminating the fail safe feature of precise readbacks. The approach continued normally until we were given a low altitude alert by tower. I had prematurely transitioned to visual guidance and failed to maintain the recommended altitude after acquiring the runway. Equipment failure aside, I believe complacency played a role in this poorly executed flight. Recognition of this, plus improved CRM and adherence to non precision approach procedures, should help prevent a recurrence of these mistakes.

Original NASA ASRS Text

Title: THE FLC WHILE ON VECTORS FOR AN APCH DSND BELOW MSA FOR THE AREA.

Narrative: AN INTERMITTENTLY INOP VHF XMITTER MAY HAVE CONTRIBUTED TO CONFUSION THAT RESULTED IN DSCNT BELOW MSA WHILE BEING RADAR VECTORED TO FINAL FOR THE VOR DME RWY 30R APCH AT SJC. I WAS THE PF IN VMC ON TOP OF SCATTERED TO BROKEN CLOUDS. BOTH OF US NOTED THE PROX TO TERRAIN, BUT BEING WELL CLR ABOVE IT, WE DID NOT IMMEDIATELY QUESTION OUR CLRNC. WE HAD JUST NOTICED THAT SOMEHOW THE ACTIVE COM HAD BEEN SWITCHED PREMATURELY TO TWR. WHETHER THAT WAS A RESULT OF SETTING OVER THE ACTIVE FREQ OR ACCEPTING ANOTHER ACFT'S FREQ, I'M NOT SURE, BUT BAY APCH FIGURED WHAT HAPPENED AND SOON SJC TWR ASKED US TO CLB TO 5000 FT. NEXT WE WERE GIVEN SEVERAL VECTORS, ONE OF WHICH WE RESPONDED TO WAS FOR AN ACFT WITH A SIMILAR CALL SIGN. THIS FACT COUPLED WITH AN INOP XMITTER MAY HAVE PREVENTED APCH CTL FROM HEARING OUR RESPONSE, THUS ELIMINATING THE FAIL SAFE FEATURE OF PRECISE READBACKS. THE APCH CONTINUED NORMALLY UNTIL WE WERE GIVEN A LOW ALT ALERT BY TWR. I HAD PREMATURELY TRANSITIONED TO VISUAL GUIDANCE AND FAILED TO MAINTAIN THE RECOMMENDED ALT AFTER ACQUIRING THE RWY. EQUIP FAILURE ASIDE, I BELIEVE COMPLACENCY PLAYED A ROLE IN THIS POORLY EXECUTED FLT. RECOGNITION OF THIS, PLUS IMPROVED CRM AND ADHERENCE TO NON PRECISION APCH PROCS, SHOULD HELP PREVENT A RECURRENCE OF THESE MISTAKES.

Data retrieved from NASA's ASRS site as of July 2007 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.