<< >> NASA ASRS Report 323271, December 1995

Captain of an large transport overshot descent altitude due to relying on the autoplt altitude hold capture feature which had been deactivated.

Attributes
ACN	323271
Time
Date	199512
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : rwf
State Reference	MN
Altitude	msl bound lower : 24500 msl bound upper : 25000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	other other : other pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 190 flight time total : 14000 flight time type : 8000
ASRS Report	323271
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared to FL250, told to hold at rwf VOR. Controller gave us the holding instructions, etc, etc, as I was descending from FL270. I turned autoplt on course, the first officer dialed in FL250, and I pushed the altitude hold capture button on pedestal. Problem was, in this model that feature had been deactivated. But being a creature of habit, and the fact that we operate same model with the feature operable, the aircraft sank 500 ft below FL250. I quickly caught it and leveled at FL250. The controller didn't say anything but I called on the ground anyway. No conflict, except complacency and the use of that feature on the other airplanes, etc, didn't help. We operate 5 different models of B727 and they're not all the same.

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Original NASA ASRS Text

Title: CAPT OF AN LGT OVERSHOT DSCNT ALT DUE TO RELYING ON THE AUTOPLT ALT HOLD CAPTURE FEATURE WHICH HAD BEEN DEACTIVATED.

Narrative: CLRED TO FL250, TOLD TO HOLD AT RWF VOR. CTLR GAVE US THE HOLDING INSTRUCTIONS, ETC, ETC, AS I WAS DSNDING FROM FL270. I TURNED AUTOPLT ON COURSE, THE FO DIALED IN FL250, AND I PUSHED THE ALT HOLD CAPTURE BUTTON ON PEDESTAL. PROB WAS, IN THIS MODEL THAT FEATURE HAD BEEN DEACTIVATED. BUT BEING A CREATURE OF HABIT, AND THE FACT THAT WE OPERATE SAME MODEL WITH THE FEATURE OPERABLE, THE ACFT SANK 500 FT BELOW FL250. I QUICKLY CAUGHT IT AND LEVELED AT FL250. THE CTLR DIDN'T SAY ANYTHING BUT I CALLED ON THE GND ANYWAY. NO CONFLICT, EXCEPT COMPLACENCY AND THE USE OF THAT FEATURE ON THE OTHER AIRPLANES, ETC, DIDN'T HELP. WE OPERATE 5 DIFFERENT MODELS OF B727 AND THEY'RE NOT ALL THE SAME.

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.