Narrative:

I was a first officer on a flight which descended 1000 ft below our assigned altitude (per ZAB) of 24000 ft. Our flight originated in mexico heading for phx. As we were approaching tus, ZAB gave us a descent to FL240 from FL350. The captain acknowledged the descent to FL240. The captain, who was flying, instructed me to contact the company as we were descending. I told him I would be off #1 (the center frequency). As I was talking to company, the captain decided to make a PA announcement. At this time, no one was monitoring center. The captain, however, had broadcast his announcement over center frequency because he had not switched the microphone selector to PA as he did several times previously that day. In doing so, he had blocked out any communication with center. Also, I saw him talking into the microphone. I believed he was communicating with center seeing the selector to VHF 1 (the center frequency). As we were descending through FL250 I motioned 1000 to go, holding 1 finger and pointing to the altitude alerter set at 24000 ft. He looked at me without expression while continuing his 3000 FPM descent and continuing to talk into the microphone. At 24300, I interrupted my call to company and asked him if we were given a lower altitude. He hesitated momentarily, said, 'oh s---' and by the time he could safely level off and start to climb, we were at 23000 ft. I then realized he had not been talking to center but in fact intending to make a non essential PA announcement to the passenger only forgetting to switch the audio panel selector to PA, while leaving it selected to VHF 1. I was weighing many factors in the few seconds we were descending through our assigned altitude. Was there immediate danger? TCASII showed no conflicting traffic. If I took the airplane, would I upset the captain and get fired? Other factors that may have contributed are as follows: my altimeter reads 150 ft higher than the captain's. This caused a late altitude call. I notified him of the discrepancy prior to flight. Company policy is not to write up airworthy discrepancies until after they are corrected. This allows them enough time to repair the discrepancy without the time constraints placed by the MEL. All airworthy discrepancies must be aggressively corrected the MEL is the maximum allowable delay. Company policies and procedures should supersede FARS. My delay in reacting to anticipated error. I was weighing several things. I thought the captain was talking to center accepting a lower altitude. I trusted the captain's judgement and flying ability. He has an impressive backgnd with much more experience than I. In hindsight. I should have taken the plane when I realized he was not going to level off. Absolutely no harm could have happened to level off prior to assigned altitude whereas the possibility of a traffic conflict exists when you descend below your assigned altitude. Company policy is the captain is always right no matter what. The airline owner is quoted as saying in ground school to the entire class, 'this is a captain's airline. Whatever he says, you do. If I hear any complaints, I'll fire you.' cockpit resource management is nonexistent. If this situation reoccurs, I will take control before we violate. If the captain is upset and complains to the company, they won't have to fire me -- I will leave the airplane where it sits and never look back. I am ashamed I violated my passenger safety and trust by allowing the airplane to descend below my assigned altitude. The captain is new in the airplane. Also, although his backgnd is extensive he had not flown in 3 yrs. The captain increased his workload by flying every leg. He was talking when he should have been flying. His personality is such that he knows everything and does everything by himself. Correcting any recurrence is a matter of adhering to procedure. Possibly improving procedure. One airline I observed has a 2000 ft call. Both crew members should verbally acknowledge to each other of any change in heading and altitude. All airlines I have knowledge of progressively preach crew resource management. We have no safety committee to address. If I address this to the chief pilot, (that is, if he would talk to me), I would probably be fired, because this would be viewed as complaining about a captain. Without doubt, our company policies and procedures need to be addressed a safety committee should be established to address such issues. I called ZAB and spoke to the supervisor on duty during this occurrence. I explained the situation in which he was unaware of. I was assured there was no violation pending. I vow to never let this happen again.

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Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOOT IN DSCNT.

Narrative: I WAS A FO ON A FLT WHICH DSNDED 1000 FT BELOW OUR ASSIGNED ALT (PER ZAB) OF 24000 FT. OUR FLT ORIGINATED IN MEXICO HDG FOR PHX. AS WE WERE APCHING TUS, ZAB GAVE US A DSCNT TO FL240 FROM FL350. THE CAPT ACKNOWLEDGED THE DSCNT TO FL240. THE CAPT, WHO WAS FLYING, INSTRUCTED ME TO CONTACT THE COMPANY AS WE WERE DSNDING. I TOLD HIM I WOULD BE OFF #1 (THE CTR FREQ). AS I WAS TALKING TO COMPANY, THE CAPT DECIDED TO MAKE A PA ANNOUNCEMENT. AT THIS TIME, NO ONE WAS MONITORING CTR. THE CAPT, HOWEVER, HAD BROADCAST HIS ANNOUNCEMENT OVER CTR FREQ BECAUSE HE HAD NOT SWITCHED THE MIKE SELECTOR TO PA AS HE DID SEVERAL TIMES PREVIOUSLY THAT DAY. IN DOING SO, HE HAD BLOCKED OUT ANY COM WITH CTR. ALSO, I SAW HIM TALKING INTO THE MIKE. I BELIEVED HE WAS COMMUNICATING WITH CTR SEEING THE SELECTOR TO VHF 1 (THE CTR FREQ). AS WE WERE DSNDING THROUGH FL250 I MOTIONED 1000 TO GO, HOLDING 1 FINGER AND POINTING TO THE ALT ALERTER SET AT 24000 FT. HE LOOKED AT ME WITHOUT EXPRESSION WHILE CONTINUING HIS 3000 FPM DSCNT AND CONTINUING TO TALK INTO THE MIKE. AT 24300, I INTERRUPTED MY CALL TO COMPANY AND ASKED HIM IF WE WERE GIVEN A LOWER ALT. HE HESITATED MOMENTARILY, SAID, 'OH S---' AND BY THE TIME HE COULD SAFELY LEVEL OFF AND START TO CLB, WE WERE AT 23000 FT. I THEN REALIZED HE HAD NOT BEEN TALKING TO CTR BUT IN FACT INTENDING TO MAKE A NON ESSENTIAL PA ANNOUNCEMENT TO THE PAX ONLY FORGETTING TO SWITCH THE AUDIO PANEL SELECTOR TO PA, WHILE LEAVING IT SELECTED TO VHF 1. I WAS WEIGHING MANY FACTORS IN THE FEW SECONDS WE WERE DSNDING THROUGH OUR ASSIGNED ALT. WAS THERE IMMEDIATE DANGER? TCASII SHOWED NO CONFLICTING TFC. IF I TOOK THE AIRPLANE, WOULD I UPSET THE CAPT AND GET FIRED? OTHER FACTORS THAT MAY HAVE CONTRIBUTED ARE AS FOLLOWS: MY ALTIMETER READS 150 FT HIGHER THAN THE CAPT'S. THIS CAUSED A LATE ALT CALL. I NOTIFIED HIM OF THE DISCREPANCY PRIOR TO FLT. COMPANY POLICY IS NOT TO WRITE UP AIRWORTHY DISCREPANCIES UNTIL AFTER THEY ARE CORRECTED. THIS ALLOWS THEM ENOUGH TIME TO REPAIR THE DISCREPANCY WITHOUT THE TIME CONSTRAINTS PLACED BY THE MEL. ALL AIRWORTHY DISCREPANCIES MUST BE AGGRESSIVELY CORRECTED THE MEL IS THE MAX ALLOWABLE DELAY. COMPANY POLICIES AND PROCEDURES SHOULD SUPERSEDE FARS. MY DELAY IN REACTING TO ANTICIPATED ERROR. I WAS WEIGHING SEVERAL THINGS. I THOUGHT THE CAPT WAS TALKING TO CTR ACCEPTING A LOWER ALT. I TRUSTED THE CAPT'S JUDGEMENT AND FLYING ABILITY. HE HAS AN IMPRESSIVE BACKGND WITH MUCH MORE EXPERIENCE THAN I. IN HINDSIGHT. I SHOULD HAVE TAKEN THE PLANE WHEN I REALIZED HE WAS NOT GOING TO LEVEL OFF. ABSOLUTELY NO HARM COULD HAVE HAPPENED TO LEVEL OFF PRIOR TO ASSIGNED ALT WHEREAS THE POSSIBILITY OF A TFC CONFLICT EXISTS WHEN YOU DSND BELOW YOUR ASSIGNED ALT. COMPANY POLICY IS THE CAPT IS ALWAYS RIGHT NO MATTER WHAT. THE AIRLINE OWNER IS QUOTED AS SAYING IN GND SCHOOL TO THE ENTIRE CLASS, 'THIS IS A CAPT'S AIRLINE. WHATEVER HE SAYS, YOU DO. IF I HEAR ANY COMPLAINTS, I'LL FIRE YOU.' COCKPIT RESOURCE MGMNT IS NONEXISTENT. IF THIS SIT REOCCURS, I WILL TAKE CTL BEFORE WE VIOLATE. IF THE CAPT IS UPSET AND COMPLAINS TO THE COMPANY, THEY WON'T HAVE TO FIRE ME -- I WILL LEAVE THE AIRPLANE WHERE IT SITS AND NEVER LOOK BACK. I AM ASHAMED I VIOLATED MY PAX SAFETY AND TRUST BY ALLOWING THE AIRPLANE TO DSND BELOW MY ASSIGNED ALT. THE CAPT IS NEW IN THE AIRPLANE. ALSO, ALTHOUGH HIS BACKGND IS EXTENSIVE HE HAD NOT FLOWN IN 3 YRS. THE CAPT INCREASED HIS WORKLOAD BY FLYING EVERY LEG. HE WAS TALKING WHEN HE SHOULD HAVE BEEN FLYING. HIS PERSONALITY IS SUCH THAT HE KNOWS EVERYTHING AND DOES EVERYTHING BY HIMSELF. CORRECTING ANY RECURRENCE IS A MATTER OF ADHERING TO PROC. POSSIBLY IMPROVING PROC. ONE AIRLINE I OBSERVED HAS A 2000 FT CALL. BOTH CREW MEMBERS SHOULD VERBALLY ACKNOWLEDGE TO EACH OTHER OF ANY CHANGE IN HDG AND ALT. ALL AIRLINES I HAVE KNOWLEDGE OF PROGRESSIVELY PREACH CREW RESOURCE MGMNT. WE HAVE NO SAFETY COMMITTEE TO ADDRESS. IF I ADDRESS THIS TO THE CHIEF PLT, (THAT IS, IF HE WOULD TALK TO ME), I WOULD PROBABLY BE FIRED, BECAUSE THIS WOULD BE VIEWED AS COMPLAINING ABOUT A CAPT. WITHOUT DOUBT, OUR COMPANY POLICIES AND PROCS NEED TO BE ADDRESSED A SAFETY COMMITTEE SHOULD BE ESTABLISHED TO ADDRESS SUCH ISSUES. I CALLED ZAB AND SPOKE TO THE SUPVR ON DUTY DURING THIS OCCURRENCE. I EXPLAINED THE SIT IN WHICH HE WAS UNAWARE OF. I WAS ASSURED THERE WAS NO VIOLATION PENDING. I VOW TO NEVER LET THIS HAPPEN AGAIN.

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.