A B737-500 flight crew fails to monitor their FMS while losing airspeed at FL240. Aircraft had been set up for crossing bands at 14000 ft while maintaining 300 KTS or better.

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Attributes
ACN	397400
Time
Date	199803
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : psp
State Reference	CA
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument pilot : flight engineer
Experience	flight time last 90 days : 280 flight time total : 14000 flight time type : 7000
ASRS Report	397400
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance other anomaly other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

En route iah-ont. Cross psp 24000 ft, speed 300 KTS or better. On FMC in path descent, ATC kept us at FL240 and delayed our descent to cross bands at 14000 ft. Aircraft was on autoplt and VNAV engaged. During this delay aircraft started to slow down very slowly. We were busied in cockpit with checklists and briefing approach. When we asked ATC for lower, he said, 'stand by.' he later asked our speed which had slowed trying to stay in path for bands at 14000 ft. FMC aircraft when in path descent mode will slow to maintain path but when that is exceeded due to not getting descent from ATC in time, it makes other crossing restr in SID. ATC asked us how fast or had we slowed. We said, 'yes, a little, to maintain in order to cross bands at 14000 ft.' ATC said an MD80 was behind us. It had not caused a problem but in the future please inform them of slowing which we know we should have done. We were busy and forgot to call him when we started to slow. We were going to, but he mentioned it first.

Original NASA ASRS Text

Title: A B737-500 FLC FAILS TO MONITOR THEIR FMS WHILE LOSING AIRSPD AT FL240. ACFT HAD BEEN SET UP FOR XING BANDS AT 14000 FT WHILE MAINTAINING 300 KTS OR BETTER.

Narrative: ENRTE IAH-ONT. CROSS PSP 24000 FT, SPD 300 KTS OR BETTER. ON FMC IN PATH DSCNT, ATC KEPT US AT FL240 AND DELAYED OUR DSCNT TO CROSS BANDS AT 14000 FT. ACFT WAS ON AUTOPLT AND VNAV ENGAGED. DURING THIS DELAY ACFT STARTED TO SLOW DOWN VERY SLOWLY. WE WERE BUSIED IN COCKPIT WITH CHKLISTS AND BRIEFING APCH. WHEN WE ASKED ATC FOR LOWER, HE SAID, 'STAND BY.' HE LATER ASKED OUR SPD WHICH HAD SLOWED TRYING TO STAY IN PATH FOR BANDS AT 14000 FT. FMC ACFT WHEN IN PATH DSCNT MODE WILL SLOW TO MAINTAIN PATH BUT WHEN THAT IS EXCEEDED DUE TO NOT GETTING DSCNT FROM ATC IN TIME, IT MAKES OTHER XING RESTR IN SID. ATC ASKED US HOW FAST OR HAD WE SLOWED. WE SAID, 'YES, A LITTLE, TO MAINTAIN IN ORDER TO CROSS BANDS AT 14000 FT.' ATC SAID AN MD80 WAS BEHIND US. IT HAD NOT CAUSED A PROB BUT IN THE FUTURE PLEASE INFORM THEM OF SLOWING WHICH WE KNOW WE SHOULD HAVE DONE. WE WERE BUSY AND FORGOT TO CALL HIM WHEN WE STARTED TO SLOW. WE WERE GOING TO, BUT HE MENTIONED IT FIRST.

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.