Altitude deviation altitude undershoot. Autoplt autocapture reverted to vertical speed mode.

Attributes
ACN	360828
Time
Date	199702
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : las
State Reference	NV
Altitude	msl bound lower : 20600 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude descent : approach descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : cfi pilot : atp pilot : commercial
Experience	flight time last 90 days : 230 flight time total : 5900 flight time type : 500
ASRS Report	360828
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 3500
ASRS Report	360620
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : undershoot non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : became reoriented
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

ATC cleared flight to 12000 ft at crowe, then subsequently limited that to 21000 ft while issuing a vector north. Aircraft had been sped up, slowed down and given normal speed prior to this, causing the automation to be a hindrance to operations and tripping to vertical speed. Aircraft did not automatic level at 21000 ft -- noted by pilots at 20600 ft. While correcting, ATC advised a step descent clearance to 20000 ft, then 16000 ft, and finally 12000 ft, 10000 ft, and visual approach. No traffic conflict noted. Factors: constant programming changes to the FMC, backside clock operations, distractions of in range calls and ATC changes to speed and altitude restrs that increased cockpit workload in the descent phase.

Original NASA ASRS Text

Title: ALTDEV ALT UNDERSHOOT. AUTOPLT AUTOCAPTURE REVERTED TO VERT SPD MODE.

Narrative: ATC CLRED FLT TO 12000 FT AT CROWE, THEN SUBSEQUENTLY LIMITED THAT TO 21000 FT WHILE ISSUING A VECTOR N. ACFT HAD BEEN SPED UP, SLOWED DOWN AND GIVEN NORMAL SPD PRIOR TO THIS, CAUSING THE AUTOMATION TO BE A HINDRANCE TO OPS AND TRIPPING TO VERT SPD. ACFT DID NOT AUTO LEVEL AT 21000 FT -- NOTED BY PLTS AT 20600 FT. WHILE CORRECTING, ATC ADVISED A STEP DSCNT CLRNC TO 20000 FT, THEN 16000 FT, AND FINALLY 12000 FT, 10000 FT, AND VISUAL APCH. NO TFC CONFLICT NOTED. FACTORS: CONSTANT PROGRAMMING CHANGES TO THE FMC, BACKSIDE CLOCK OPS, DISTRACTIONS OF IN RANGE CALLS AND ATC CHANGES TO SPD AND ALT RESTRS THAT INCREASED COCKPIT WORKLOAD IN THE DSCNT PHASE.

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.