<< >> NASA ASRS Report 297800, February 1995

Altitude deviation altitude excursion - air carrier did not engage altitude hold mode of autoplt. Night operation.

Attributes
ACN	297800
Time
Date	199502
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : dsm
State Reference	IA
Altitude	msl bound lower : 37000 msl bound upper : 37400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 18000 flight time type : 10000
ASRS Report	297800
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was advised by center to verify altitude. It was noted that the aircraft was in a very slight climb - approximately 100 FPM - and that the altitude was passing through 37.4. The autoplt was disengaged and altitude reestablished at FL370. This altitude excursion probably was the result of the autoplt attitude controller wheel being inadvertently dislodged from the 'altitude hold' detent or from the wheel being slightly out of the detent after the aircraft was retrimmed and the autoplt engaged.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION - ACR DID NOT ENGAGE ALT HOLD MODE OF AUTOPLT. NIGHT OP.

Narrative: I WAS ADVISED BY CTR TO VERIFY ALT. IT WAS NOTED THAT THE ACFT WAS IN A VERY SLIGHT CLB - APPROX 100 FPM - AND THAT THE ALT WAS PASSING THROUGH 37.4. THE AUTOPLT WAS DISENGAGED AND ALT REESTABLISHED AT FL370. THIS ALT EXCURSION PROBABLY WAS THE RESULT OF THE AUTOPLT ATTITUDE CTLR WHEEL BEING INADVERTENTLY DISLODGED FROM THE 'ALT HOLD' DETENT OR FROM THE WHEEL BEING SLIGHTLY OUT OF THE DETENT AFTER THE ACFT WAS RETRIMMED AND THE AUTOPLT ENGAGED.

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.