A B737-300 crew, descending into las, undershot published STAR ATC assigned altitude.

Attributes
ACN	542017
Time
Date	200203
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	intersection : misen
State Reference	CA
Altitude	msl bound lower : 24000 msl bound upper : 25000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : vacating altitude
Route In Use	arrival star : skebr1
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 188 flight time total : 9500 flight time type : 6700
ASRS Report	542017
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : multi engine pilot : instrument
Experience	flight time last 90 days : 250 flight time total : 8375 flight time type : 810
ASRS Report	541920
Events
Anomaly	altitude deviation : undershoot non adherence : far non adherence : published procedure non adherence : clearance
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert none taken : unable
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On the skebr 1 (RNAV) STAR to las, we were told to cross the misen intersection at FL240. We both acknowledged the clearance and acknowledged FL240 was loaded in the 'box' as the crossing restr altitude for misen. I failed to notice that the altitude in the FMC was depicted as FL240A, which caused our descent profile to be based on the next 'hard' altitude in the box. I realized we were above profile at 2 NM prior to misen and pushed the nose over in an attempt to make the restr. We were at FL260 when this took place, and I think we were about 1000 ft above profile by the time we crossed misen. The first officer was 'off frequency' obtaining ATIS for las during this event. Of particular importance here: on the skebr 1 arrival, the misen intersection is a hard altitude crossing at FL240. However, the software in the FMC loaded is at FL240 or above (FL240A). It is still my fault because I failed to catch the bad information that was loaded, but this situation sets us up for violations/failure and should be corrected. As we crossed misen, ZLA asked if we were descending, and I said 'yes.' he then replied to 'just descend and maintain FL240.' we complied and I queried him as to whether there was any problem with the altitude, and he said 'no.' supplemental information from acn 541920: we were on the skebr 1 (RNAV) STAR to las. ATC assigned us to cross misen at FL240. I responded and the captain agreed with this. The captain checked the FMC and saw misen at FL240A. He did not change this to a hard crossing altitude. The FMC proceeded based on the other hard altitude. It did just as we had read in the read before fly. The captain was flying and I left the frequency to get ATIS. He started down from FL290 and out of FL265 ATC questioned our crossing altitude at misen. The captain increased the rate of descent and we crossed misen at FL250. ATC advised us that we did not conflict with any traffic. This event should not have happened because we had both read the read before fly file warning us about the skebr arrival. However, it is still the crew's responsibility and I will be more vigilant in the future.

Original NASA ASRS Text

Title: A B737-300 CREW, DSNDING INTO LAS, UNDERSHOT PUBLISHED STAR ATC ASSIGNED ALT.

Narrative: ON THE SKEBR 1 (RNAV) STAR TO LAS, WE WERE TOLD TO CROSS THE MISEN INTXN AT FL240. WE BOTH ACKNOWLEDGED THE CLRNC AND ACKNOWLEDGED FL240 WAS LOADED IN THE 'BOX' AS THE XING RESTR ALT FOR MISEN. I FAILED TO NOTICE THAT THE ALT IN THE FMC WAS DEPICTED AS FL240A, WHICH CAUSED OUR DSCNT PROFILE TO BE BASED ON THE NEXT 'HARD' ALT IN THE BOX. I REALIZED WE WERE ABOVE PROFILE AT 2 NM PRIOR TO MISEN AND PUSHED THE NOSE OVER IN AN ATTEMPT TO MAKE THE RESTR. WE WERE AT FL260 WHEN THIS TOOK PLACE, AND I THINK WE WERE ABOUT 1000 FT ABOVE PROFILE BY THE TIME WE CROSSED MISEN. THE FO WAS 'OFF FREQ' OBTAINING ATIS FOR LAS DURING THIS EVENT. OF PARTICULAR IMPORTANCE HERE: ON THE SKEBR 1 ARR, THE MISEN INTXN IS A HARD ALT XING AT FL240. HOWEVER, THE SOFTWARE IN THE FMC LOADED IS AT FL240 OR ABOVE (FL240A). IT IS STILL MY FAULT BECAUSE I FAILED TO CATCH THE BAD INFO THAT WAS LOADED, BUT THIS SIT SETS US UP FOR VIOLATIONS/FAILURE AND SHOULD BE CORRECTED. AS WE CROSSED MISEN, ZLA ASKED IF WE WERE DSNDING, AND I SAID 'YES.' HE THEN REPLIED TO 'JUST DSND AND MAINTAIN FL240.' WE COMPLIED AND I QUERIED HIM AS TO WHETHER THERE WAS ANY PROB WITH THE ALT, AND HE SAID 'NO.' SUPPLEMENTAL INFO FROM ACN 541920: WE WERE ON THE SKEBR 1 (RNAV) STAR TO LAS. ATC ASSIGNED US TO CROSS MISEN AT FL240. I RESPONDED AND THE CAPT AGREED WITH THIS. THE CAPT CHKED THE FMC AND SAW MISEN AT FL240A. HE DID NOT CHANGE THIS TO A HARD XING ALT. THE FMC PROCEEDED BASED ON THE OTHER HARD ALT. IT DID JUST AS WE HAD READ IN THE READ BEFORE FLY. THE CAPT WAS FLYING AND I LEFT THE FREQ TO GET ATIS. HE STARTED DOWN FROM FL290 AND OUT OF FL265 ATC QUESTIONED OUR XING ALT AT MISEN. THE CAPT INCREASED THE RATE OF DSCNT AND WE CROSSED MISEN AT FL250. ATC ADVISED US THAT WE DID NOT CONFLICT WITH ANY TFC. THIS EVENT SHOULD NOT HAVE HAPPENED BECAUSE WE HAD BOTH READ THE READ BEFORE FLY FILE WARNING US ABOUT THE SKEBR ARR. HOWEVER, IT IS STILL THE CREW'S RESPONSIBILITY AND I WILL BE MORE VIGILANT IN THE FUTURE.

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.