Altitude deviation. Overshoot on descent. Altitude crossing restriction not met.

Attributes
ACN	147858
Time
Date	199006
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : fim
State Reference	CA
Altitude	msl bound lower : 14600 msl bound upper : 15000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival : profile descent arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 45 flight time total : 9000 flight time type : 45
ASRS Report	147858
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 19000 flight time type : 2000
ASRS Report	147995
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : published procedure non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was flying the runway 24/25 profile descent to lax which calls for crossing the fim VOR between 19000 and 15000'. There is also a symon crossing 15000-12000' and bayst at 10000'. I checked the FMC to make sure the restrictions were in the computer and they were so I put 10000' in the altitude window and monitored the descent. I thought I had the aircraft in vertical navigation mode, but must have been in vertical speed. At about 15200' 12 1/2 mi from fim VOR, I could see that the aircraft wasn't going to level off on its own. At 15000' I hit the altitude hold button, but descended 300 more ft to 14700'. 1-1 1/2 mi from fim I started to climb back to 15000'. About that time the controller said he showed us 400' low and we had traffic at 13000' and climbing. With that I disconnected the autoplt and increased the route of climb to 15000'. I'm sure my low time in this aircraft (50 hours) had a lot to do with my not catching the fact that the aircraft must have been in a vertical speed mode. But even so, if when I first saw the potential problem I would have disconnected the autoplt and leveled off myself we wouldn't have gone below 15000'. This was the first time I had used the lt hold button and didn't think it would take 300' to level off. Once again I can attribute this to my low time in this aircraft. Better monitoring by the PNF could have also caught the problem, but I'm not trying to pass the buck.

Original NASA ASRS Text

Title: ALT DEVIATION. OVERSHOOT ON DESCENT. ALT CROSSING RESTRICTION NOT MET.

Narrative: I WAS FLYING THE RWY 24/25 PROFILE DSNT TO LAX WHICH CALLS FOR XING THE FIM VOR BTWN 19000 AND 15000'. THERE IS ALSO A SYMON XING 15000-12000' AND BAYST AT 10000'. I CHKED THE FMC TO MAKE SURE THE RESTRICTIONS WERE IN THE COMPUTER AND THEY WERE SO I PUT 10000' IN THE ALT WINDOW AND MONITORED THE DSNT. I THOUGHT I HAD THE ACFT IN VERT NAV MODE, BUT MUST HAVE BEEN IN VERT SPD. AT ABOUT 15200' 12 1/2 MI FROM FIM VOR, I COULD SEE THAT THE ACFT WASN'T GOING TO LEVEL OFF ON ITS OWN. AT 15000' I HIT THE ALT HOLD BUTTON, BUT DSNDED 300 MORE FT TO 14700'. 1-1 1/2 MI FROM FIM I STARTED TO CLB BACK TO 15000'. ABOUT THAT TIME THE CTLR SAID HE SHOWED US 400' LOW AND WE HAD TFC AT 13000' AND CLBING. WITH THAT I DISCONNECTED THE AUTOPLT AND INCREASED THE RTE OF CLB TO 15000'. I'M SURE MY LOW TIME IN THIS ACFT (50 HRS) HAD A LOT TO DO WITH MY NOT CATCHING THE FACT THAT THE ACFT MUST HAVE BEEN IN A VERT SPD MODE. BUT EVEN SO, IF WHEN I FIRST SAW THE POTENTIAL PROB I WOULD HAVE DISCONNECTED THE AUTOPLT AND LEVELED OFF MYSELF WE WOULDN'T HAVE GONE BELOW 15000'. THIS WAS THE FIRST TIME I HAD USED THE LT HOLD BUTTON AND DIDN'T THINK IT WOULD TAKE 300' TO LEVEL OFF. ONCE AGAIN I CAN ATTRIBUTE THIS TO MY LOW TIME IN THIS ACFT. BETTER MONITORING BY THE PNF COULD HAVE ALSO CAUGHT THE PROB, BUT I'M NOT TRYING TO PASS THE BUCK.

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.