Narrative:

It was my first trip to quito. I was a bit anxious since many of my lost military friends died hitting mountains. We had an early morning wake-up XA30 after days off and were a bit tired to begin with; but by top of descent into quito prepared as usual for air carrier flying. We did the approach check at FL250; minus the altimeter setting; and I set for raw data to monitor the approach. From that point on; I crosschecked instrument readings with what I could make out through broken layers of clouds to ensure terrain clearance. We were briefly cleared to 17000 ft and then cleared for the approach. I had some difficulty making out what the approach controller said; but we confirmed each call. We stayed very near on lateral path throughout the approach; only correcting a bit with heading select outbound on the procedure turn. The approach went normally through the procedure turn and to GS capture. There I began to xchk altitude with distance and thought my math was a bit off. Before I could rechk with the OM altitude; we got a 'terrain' call. The OM is on a ridge line and I could just make the top out through the broken clouds. Before I could announce terrain in sight; we got a 'pull up' call and the captain executed the maneuver. I called terrain in sight by the first 100 ft of climb and again calling clear of terrain by 300 ft. This is about when the egpws stopped and we leveled about 400 ft high. From there we had a broken view of both the airport and ground; so we re-established the GS and continued the approach. On GS; I set for my call at 1000 ft and tried to xchk with distance. It appeared wrong and I then noticed that we had not set the altimeters from 29.92 to 30.36. We corrected the settings and were good by the 500 ft call. Several points caught out attention and we discussed these after landing. We had obviously missed the altimeter change at FL180. Second; this was the first time the captain had gotten an egpws call at quito and the first time he had the wrong altimeter setting. He was aware that others had gotten egpws calls at quito's OM and wondered at the cause for these. Was there a correlation between egpws calls and barometric altimeter error? We were on the GS and should have been altitude protected at the OM. It also visually appeared that we had adequate terrain clearance at the OM. The egpws ended about 100 ft less than our altitude error due to not setting it. We had gone from 29.92 to 30.36 pressure so we were actually higher than we registered by about 400 ft. Terrain clearance was not an actual issue based upon these factors. Was the egpws map vertical clearance based upon altimeter settings and the radio altimeter input then produced a false assumption as it registered the ridge line? Would the egpws not give adequate clearance if we had gone from higher to lower pressure readings and not set the barometric altimeter? If you are 100 ft low at the OM; do you get the egpws call? Our altimeter error and the end of the egpws would indicate that it thought we were 400 ft low and needed to climb 300 ft. Several factors came to my attention. The use of an incomplete approach checklist leaving out the altimeter changeover for a later point that is inconsistent between airports is begging for an error. I know that we need to give the pressurization system time to adjust for high airports and we need to start raw data back-up this high. Still; the use of something like a descent checklist at FL250 and an approach checklist at transition altitude would be much better. This doesn't leave such an important item as an altimeter setting to be caught at in inconsistent time later and out of the normal checklist flow. Second; as usual; air carrier rotating schedules do not fit body clocks. We are always tired and fatigue is an ever present factor. There is no consistent 'shift' that our bodies can adapt to. Third; my apprehension coupled with my first time to quito coupled with WX; a busy approach and language difficulties give plenty of distrs from a leftover approach checklist item. We should have a checklist that applies to the transition altitude and not one that is partial now and finished some time later. Our current method leaves no consistent event as a xchk before the approach begins. Fourth; how does the egpws determine altitude prior to radio altitude input and can it be fooled into giving false warnings? We had normal to greater terrain clearance on this approach due to our error; but we got an egpws call. Why? Could it work the other way and not give adequate warning when going from high to lower pressure?

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Original NASA ASRS Text

Title: A B757 CREW DSNDING INTO SEQU FAILED TO SET THE ALTIMETER AND RECEIVED AN EGPWS WARNING.

Narrative: IT WAS MY FIRST TRIP TO QUITO. I WAS A BIT ANXIOUS SINCE MANY OF MY LOST MIL FRIENDS DIED HITTING MOUNTAINS. WE HAD AN EARLY MORNING WAKE-UP XA30 AFTER DAYS OFF AND WERE A BIT TIRED TO BEGIN WITH; BUT BY TOP OF DSCNT INTO QUITO PREPARED AS USUAL FOR ACR FLYING. WE DID THE APCH CHK AT FL250; MINUS THE ALTIMETER SETTING; AND I SET FOR RAW DATA TO MONITOR THE APCH. FROM THAT POINT ON; I XCHKED INST READINGS WITH WHAT I COULD MAKE OUT THROUGH BROKEN LAYERS OF CLOUDS TO ENSURE TERRAIN CLRNC. WE WERE BRIEFLY CLRED TO 17000 FT AND THEN CLRED FOR THE APCH. I HAD SOME DIFFICULTY MAKING OUT WHAT THE APCH CTLR SAID; BUT WE CONFIRMED EACH CALL. WE STAYED VERY NEAR ON LATERAL PATH THROUGHOUT THE APCH; ONLY CORRECTING A BIT WITH HDG SELECT OUTBOUND ON THE PROC TURN. THE APCH WENT NORMALLY THROUGH THE PROC TURN AND TO GS CAPTURE. THERE I BEGAN TO XCHK ALT WITH DISTANCE AND THOUGHT MY MATH WAS A BIT OFF. BEFORE I COULD RECHK WITH THE OM ALT; WE GOT A 'TERRAIN' CALL. THE OM IS ON A RIDGE LINE AND I COULD JUST MAKE THE TOP OUT THROUGH THE BROKEN CLOUDS. BEFORE I COULD ANNOUNCE TERRAIN IN SIGHT; WE GOT A 'PULL UP' CALL AND THE CAPT EXECUTED THE MANEUVER. I CALLED TERRAIN IN SIGHT BY THE FIRST 100 FT OF CLB AND AGAIN CALLING CLR OF TERRAIN BY 300 FT. THIS IS ABOUT WHEN THE EGPWS STOPPED AND WE LEVELED ABOUT 400 FT HIGH. FROM THERE WE HAD A BROKEN VIEW OF BOTH THE ARPT AND GND; SO WE RE-ESTABLISHED THE GS AND CONTINUED THE APCH. ON GS; I SET FOR MY CALL AT 1000 FT AND TRIED TO XCHK WITH DISTANCE. IT APPEARED WRONG AND I THEN NOTICED THAT WE HAD NOT SET THE ALTIMETERS FROM 29.92 TO 30.36. WE CORRECTED THE SETTINGS AND WERE GOOD BY THE 500 FT CALL. SEVERAL POINTS CAUGHT OUT ATTN AND WE DISCUSSED THESE AFTER LNDG. WE HAD OBVIOUSLY MISSED THE ALTIMETER CHANGE AT FL180. SECOND; THIS WAS THE FIRST TIME THE CAPT HAD GOTTEN AN EGPWS CALL AT QUITO AND THE FIRST TIME HE HAD THE WRONG ALTIMETER SETTING. HE WAS AWARE THAT OTHERS HAD GOTTEN EGPWS CALLS AT QUITO'S OM AND WONDERED AT THE CAUSE FOR THESE. WAS THERE A CORRELATION BTWN EGPWS CALLS AND BAROMETRIC ALTIMETER ERROR? WE WERE ON THE GS AND SHOULD HAVE BEEN ALT PROTECTED AT THE OM. IT ALSO VISUALLY APPEARED THAT WE HAD ADEQUATE TERRAIN CLRNC AT THE OM. THE EGPWS ENDED ABOUT 100 FT LESS THAN OUR ALT ERROR DUE TO NOT SETTING IT. WE HAD GONE FROM 29.92 TO 30.36 PRESSURE SO WE WERE ACTUALLY HIGHER THAN WE REGISTERED BY ABOUT 400 FT. TERRAIN CLRNC WAS NOT AN ACTUAL ISSUE BASED UPON THESE FACTORS. WAS THE EGPWS MAP VERT CLRNC BASED UPON ALTIMETER SETTINGS AND THE RADIO ALTIMETER INPUT THEN PRODUCED A FALSE ASSUMPTION AS IT REGISTERED THE RIDGE LINE? WOULD THE EGPWS NOT GIVE ADEQUATE CLRNC IF WE HAD GONE FROM HIGHER TO LOWER PRESSURE READINGS AND NOT SET THE BAROMETRIC ALTIMETER? IF YOU ARE 100 FT LOW AT THE OM; DO YOU GET THE EGPWS CALL? OUR ALTIMETER ERROR AND THE END OF THE EGPWS WOULD INDICATE THAT IT THOUGHT WE WERE 400 FT LOW AND NEEDED TO CLB 300 FT. SEVERAL FACTORS CAME TO MY ATTN. THE USE OF AN INCOMPLETE APCH CHKLIST LEAVING OUT THE ALTIMETER CHANGEOVER FOR A LATER POINT THAT IS INCONSISTENT BTWN ARPTS IS BEGGING FOR AN ERROR. I KNOW THAT WE NEED TO GIVE THE PRESSURIZATION SYS TIME TO ADJUST FOR HIGH ARPTS AND WE NEED TO START RAW DATA BACK-UP THIS HIGH. STILL; THE USE OF SOMETHING LIKE A DSCNT CHKLIST AT FL250 AND AN APCH CHKLIST AT TRANSITION ALT WOULD BE MUCH BETTER. THIS DOESN'T LEAVE SUCH AN IMPORTANT ITEM AS AN ALTIMETER SETTING TO BE CAUGHT AT IN INCONSISTENT TIME LATER AND OUT OF THE NORMAL CHKLIST FLOW. SECOND; AS USUAL; ACR ROTATING SCHEDULES DO NOT FIT BODY CLOCKS. WE ARE ALWAYS TIRED AND FATIGUE IS AN EVER PRESENT FACTOR. THERE IS NO CONSISTENT 'SHIFT' THAT OUR BODIES CAN ADAPT TO. THIRD; MY APPREHENSION COUPLED WITH MY FIRST TIME TO QUITO COUPLED WITH WX; A BUSY APCH AND LANGUAGE DIFFICULTIES GIVE PLENTY OF DISTRS FROM A LEFTOVER APCH CHKLIST ITEM. WE SHOULD HAVE A CHKLIST THAT APPLIES TO THE TRANSITION ALT AND NOT ONE THAT IS PARTIAL NOW AND FINISHED SOME TIME LATER. OUR CURRENT METHOD LEAVES NO CONSISTENT EVENT AS A XCHK BEFORE THE APCH BEGINS. FOURTH; HOW DOES THE EGPWS DETERMINE ALT PRIOR TO RADIO ALT INPUT AND CAN IT BE FOOLED INTO GIVING FALSE WARNINGS? WE HAD NORMAL TO GREATER TERRAIN CLRNC ON THIS APCH DUE TO OUR ERROR; BUT WE GOT AN EGPWS CALL. WHY? COULD IT WORK THE OTHER WAY AND NOT GIVE ADEQUATE WARNING WHEN GOING FROM HIGH TO LOWER PRESSURE?

Data retrieved from NASA's ASRS site as of January 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.