Narrative:

I was PNF in right seat. Long day after a trip to california and return. We were being vectored by approach control. As we were being cleared to a new heading and instructed to intercept the localizer; the captain simultaneously was asking for flaps to be selected to 10 degrees. His interest was in the flap selection and he did not really hear the clearance correctly. Aircraft was on autoplt and he set in the new heading and armed the approach mode. (Note that we were not cleared for the approach yet.) in rapid succession; he asked for flaps to be selected to 20 degrees and then he reached over and spun the altitude preselect knob to set a lower altitude in the window and said set something lower. (Not our SOP.) I set 2200 ft MSL; but then immediately said that we were not cleared for the approach and I believed that we were still assigned 4000 ft. Captain said clarify the altitude. I called approach and they said 'maintain 4000 ft;' and the captain added power to climb from approximately 3500 ft back up to 4000 ft. With 20 degrees flaps; the aircraft had slowed so a considerable amount of power was added to maintain a safe margin over vref and to initiate a climb. We climbed back up to our assigned altitude and shortly thereafter; gave us another heading and told us to maintain 4000 ft and to contact approach on frequency. Rest of approach and landing SOP which requires PNF to set altitudes and hold finger on altitude preselect knob until PF acknowledges altitude is properly set. When he selected lower altitude himself; I was busy and distraction with his requested flap settings and didn't catch the problem as soon as I should have. What should have been another immediate red flag for me was when captain armed approach; instead of LNAV; when we were only cleared to intercept the localizer. In my tired state; I just was wondering 'maybe he knows something that I don't;' and I did not question this right away as I should have. Contributing factor was that we were both very tired. Captain is one of our senior capts. We both knew better; but our performance was not indicative of our experience levels. Pure and simple this was a case of a lack of adherence to SOP's; impatience on the part of the captain and a lack of awareness and prompt correction on my part. After the flight we discussed the breakdown in performance and the importance to adhere to our SOP's especially when we are tired; as these are in place to protect us and keep us out of trouble. When we strayed from our procedures; this is precisely what happened.

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Original NASA ASRS Text

Title: GULFSTREAM CAPT COMMENCES DESCENT WITHOUT CLEARANCE DURING VECTORS FOR APPROACH AND IS CHALLENGED BY FO. CAPT RETURNS TO CORRECT ALTITUDE.

Narrative: I WAS PNF IN R SEAT. LONG DAY AFTER A TRIP TO CALIFORNIA AND RETURN. WE WERE BEING VECTORED BY APCH CTL. AS WE WERE BEING CLRED TO A NEW HDG AND INSTRUCTED TO INTERCEPT THE LOC; THE CAPT SIMULTANEOUSLY WAS ASKING FOR FLAPS TO BE SELECTED TO 10 DEGS. HIS INTEREST WAS IN THE FLAP SELECTION AND HE DID NOT REALLY HEAR THE CLRNC CORRECTLY. ACFT WAS ON AUTOPLT AND HE SET IN THE NEW HDG AND ARMED THE APCH MODE. (NOTE THAT WE WERE NOT CLRED FOR THE APCH YET.) IN RAPID SUCCESSION; HE ASKED FOR FLAPS TO BE SELECTED TO 20 DEGS AND THEN HE REACHED OVER AND SPUN THE ALT PRESELECT KNOB TO SET A LOWER ALT IN THE WINDOW AND SAID SET SOMETHING LOWER. (NOT OUR SOP.) I SET 2200 FT MSL; BUT THEN IMMEDIATELY SAID THAT WE WERE NOT CLRED FOR THE APCH AND I BELIEVED THAT WE WERE STILL ASSIGNED 4000 FT. CAPT SAID CLARIFY THE ALT. I CALLED APCH AND THEY SAID 'MAINTAIN 4000 FT;' AND THE CAPT ADDED PWR TO CLB FROM APPROX 3500 FT BACK UP TO 4000 FT. WITH 20 DEGS FLAPS; THE ACFT HAD SLOWED SO A CONSIDERABLE AMOUNT OF PWR WAS ADDED TO MAINTAIN A SAFE MARGIN OVER VREF AND TO INITIATE A CLB. WE CLBED BACK UP TO OUR ASSIGNED ALT AND SHORTLY THEREAFTER; GAVE US ANOTHER HDG AND TOLD US TO MAINTAIN 4000 FT AND TO CONTACT APCH ON FREQ. REST OF APCH AND LNDG SOP WHICH REQUIRES PNF TO SET ALTS AND HOLD FINGER ON ALT PRESELECT KNOB UNTIL PF ACKNOWLEDGES ALT IS PROPERLY SET. WHEN HE SELECTED LOWER ALT HIMSELF; I WAS BUSY AND DISTR WITH HIS REQUESTED FLAP SETTINGS AND DIDN'T CATCH THE PROB AS SOON AS I SHOULD HAVE. WHAT SHOULD HAVE BEEN ANOTHER IMMEDIATE RED FLAG FOR ME WAS WHEN CAPT ARMED APCH; INSTEAD OF LNAV; WHEN WE WERE ONLY CLRED TO INTERCEPT THE LOC. IN MY TIRED STATE; I JUST WAS WONDERING 'MAYBE HE KNOWS SOMETHING THAT I DON'T;' AND I DID NOT QUESTION THIS RIGHT AWAY AS I SHOULD HAVE. CONTRIBUTING FACTOR WAS THAT WE WERE BOTH VERY TIRED. CAPT IS ONE OF OUR SENIOR CAPTS. WE BOTH KNEW BETTER; BUT OUR PERFORMANCE WAS NOT INDICATIVE OF OUR EXPERIENCE LEVELS. PURE AND SIMPLE THIS WAS A CASE OF A LACK OF ADHERENCE TO SOP'S; IMPATIENCE ON THE PART OF THE CAPT AND A LACK OF AWARENESS AND PROMPT CORRECTION ON MY PART. AFTER THE FLT WE DISCUSSED THE BREAKDOWN IN PERFORMANCE AND THE IMPORTANCE TO ADHERE TO OUR SOP'S ESPECIALLY WHEN WE ARE TIRED; AS THESE ARE IN PLACE TO PROTECT US AND KEEP US OUT OF TROUBLE. WHEN WE STRAYED FROM OUR PROCS; THIS IS PRECISELY WHAT HAPPENED.

Data retrieved from NASA's ASRS site as of May 2009 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.