Narrative:

Descent below assigned altitude in IMC during an ILS approach to santa maria, ca, airport. The writer was conducting an instrument competency evaluation for a student. We received an instrument clearance from ZOA before takeoff from paso robles airport. The WX was IMC at paso robles. Our first destination was the santa maria airport. Our en route clearance was via V113 to morro bay VOR direct santa maria. Before arriving at morro bay VOR we were assigned an altitude of 6000 ft by ZLA. A few mins later we received a further clearance which as I remember was, cleared to winch intersection via the mqo outbound 140 degree radial. The mqo VOR is an established IAF. Upon arrival at the mqo VOR we then intercepted the 140 degree radial headed for winch. After we intercepted the radial, I heard, but didn't understand, another clearance. Within several seconds my student started a descent. I assumed that he had heard the approach clearance: a poor assumption. About a min later I realized my mistake and asked him if he had received the approach clearance. He stated that he had not, so I told him to immediately return to 6000 ft, which he did. Within several more seconds the los angeles controller told us that we were assigned 6000 ft, and we acknowledged by reporting that we were on the way back up to 6000 ft. At winch we were cleared for the approach, so continued and landed. At the time the ceiling was variable from approximately 300-400 ft, and the visibility was at least a mi, as I could see the entire runway. During the improper descent I was locating the ILS approach chart for my reference (I should have had it prior to this time). Prior to this event, my student had been performing all instrument functions and procedures in an excellent manner, including some 'no-gyroscope' partial panel hood work when we were in VMC for a few mins above the overcast, and I became over-confident to the point of not questioning him immediately when he started the descent. I don't think that I have ever failed to clarify an approach clearance previously. 1) after the approach, with my student, I reviewed thoroughly the FARS and procedures related to the readback of clrncs and the dangers of descending from assigned altitudes prior to the receipt of clrncs to do so. 2) the following day, dec/xx/96, I worked with my student on relevant ground instruction and flight in mostly IMC with ZOA and fresno approach. He made an excellent ILS at visalia followed by an excellent DME arc during a VOR-DME approach to paso robles. I then signed off his instrument competency check. 3) I have learned from this experience, after 41 yrs as a CFI and 29 yrs as a cfiai, that it is possible to become over-confident and complacent. This was an event as an instrument instructor when I felt that never again would I make such a serious mistake. Never in the past have I, or any of my students, been asked to contact ATC after a training session. Supplemental information from acn 357080: I feel there is no sense in writing 2 letters, so I am attaching a copy of my CFI's letter to you. I would only add that after intercepting the 140 degree radial, I understood to descend at that point. The CFI told me to come back up, which I did. At that point center came in and gave me a number to call. The rest is explained in the CFI's letter.

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Original NASA ASRS Text

Title: AN IFR SMA WITH INST STUDENT AND INSTRUCTOR DSND FROM ASSIGNED ALT OF 6000 FT WITHOUT ATC AUTH. THE STUDENT PLT THOUGHT THEY HAD BEEN CLRED FOR THE APCH AND STARTED DOWN. THE INSTRUCTOR PLT REALIZED THE ERROR ABOUT 1 MIN LATER AND ASKED THE STUDENT PLT TO CLB BACK TO 6000 FT. THE CTR CTLR ASKED THAT THEY CALL THEM WHEN ON THE GND.

Narrative: DSCNT BELOW ASSIGNED ALT IN IMC DURING AN ILS APCH TO SANTA MARIA, CA, ARPT. THE WRITER WAS CONDUCTING AN INST COMPETENCY EVALUATION FOR A STUDENT. WE RECEIVED AN INST CLRNC FROM ZOA BEFORE TKOF FROM PASO ROBLES ARPT. THE WX WAS IMC AT PASO ROBLES. OUR FIRST DEST WAS THE SANTA MARIA ARPT. OUR ENRTE CLRNC WAS VIA V113 TO MORRO BAY VOR DIRECT SANTA MARIA. BEFORE ARRIVING AT MORRO BAY VOR WE WERE ASSIGNED AN ALT OF 6000 FT BY ZLA. A FEW MINS LATER WE RECEIVED A FURTHER CLRNC WHICH AS I REMEMBER WAS, CLRED TO WINCH INTXN VIA THE MQO OUTBOUND 140 DEG RADIAL. THE MQO VOR IS AN ESTABLISHED IAF. UPON ARR AT THE MQO VOR WE THEN INTERCEPTED THE 140 DEG RADIAL HEADED FOR WINCH. AFTER WE INTERCEPTED THE RADIAL, I HEARD, BUT DIDN'T UNDERSTAND, ANOTHER CLRNC. WITHIN SEVERAL SECONDS MY STUDENT STARTED A DSCNT. I ASSUMED THAT HE HAD HEARD THE APCH CLRNC: A POOR ASSUMPTION. ABOUT A MIN LATER I REALIZED MY MISTAKE AND ASKED HIM IF HE HAD RECEIVED THE APCH CLRNC. HE STATED THAT HE HAD NOT, SO I TOLD HIM TO IMMEDIATELY RETURN TO 6000 FT, WHICH HE DID. WITHIN SEVERAL MORE SECONDS THE LOS ANGELES CTLR TOLD US THAT WE WERE ASSIGNED 6000 FT, AND WE ACKNOWLEDGED BY RPTING THAT WE WERE ON THE WAY BACK UP TO 6000 FT. AT WINCH WE WERE CLRED FOR THE APCH, SO CONTINUED AND LANDED. AT THE TIME THE CEILING WAS VARIABLE FROM APPROX 300-400 FT, AND THE VISIBILITY WAS AT LEAST A MI, AS I COULD SEE THE ENTIRE RWY. DURING THE IMPROPER DSCNT I WAS LOCATING THE ILS APCH CHART FOR MY REF (I SHOULD HAVE HAD IT PRIOR TO THIS TIME). PRIOR TO THIS EVENT, MY STUDENT HAD BEEN PERFORMING ALL INST FUNCTIONS AND PROCS IN AN EXCELLENT MANNER, INCLUDING SOME 'NO-GYROSCOPE' PARTIAL PANEL HOOD WORK WHEN WE WERE IN VMC FOR A FEW MINS ABOVE THE OVCST, AND I BECAME OVER-CONFIDENT TO THE POINT OF NOT QUESTIONING HIM IMMEDIATELY WHEN HE STARTED THE DSCNT. I DON'T THINK THAT I HAVE EVER FAILED TO CLARIFY AN APCH CLRNC PREVIOUSLY. 1) AFTER THE APCH, WITH MY STUDENT, I REVIEWED THOROUGHLY THE FARS AND PROCS RELATED TO THE READBACK OF CLRNCS AND THE DANGERS OF DSNDING FROM ASSIGNED ALTS PRIOR TO THE RECEIPT OF CLRNCS TO DO SO. 2) THE FOLLOWING DAY, DEC/XX/96, I WORKED WITH MY STUDENT ON RELEVANT GND INSTRUCTION AND FLT IN MOSTLY IMC WITH ZOA AND FRESNO APCH. HE MADE AN EXCELLENT ILS AT VISALIA FOLLOWED BY AN EXCELLENT DME ARC DURING A VOR-DME APCH TO PASO ROBLES. I THEN SIGNED OFF HIS INST COMPETENCY CHK. 3) I HAVE LEARNED FROM THIS EXPERIENCE, AFTER 41 YRS AS A CFI AND 29 YRS AS A CFIAI, THAT IT IS POSSIBLE TO BECOME OVER-CONFIDENT AND COMPLACENT. THIS WAS AN EVENT AS AN INST INSTRUCTOR WHEN I FELT THAT NEVER AGAIN WOULD I MAKE SUCH A SERIOUS MISTAKE. NEVER IN THE PAST HAVE I, OR ANY OF MY STUDENTS, BEEN ASKED TO CONTACT ATC AFTER A TRAINING SESSION. SUPPLEMENTAL INFO FROM ACN 357080: I FEEL THERE IS NO SENSE IN WRITING 2 LETTERS, SO I AM ATTACHING A COPY OF MY CFI'S LETTER TO YOU. I WOULD ONLY ADD THAT AFTER INTERCEPTING THE 140 DEG RADIAL, I UNDERSTOOD TO DSND AT THAT POINT. THE CFI TOLD ME TO COME BACK UP, WHICH I DID. AT THAT POINT CTR CAME IN AND GAVE ME A NUMBER TO CALL. THE REST IS EXPLAINED IN THE CFI'S LETTER.

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.