<< >> NASA ASRS Report 358890, January 1997

Altitude deviation altitude overshot in descent when first officer inadvertently disarms altitude automatic capture by selecting 'vertical speed' on autoplt mode selector.

Attributes
ACN	358890
Time
Date	199701
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : jfk
State Reference	NY
Altitude	msl bound lower : 22600 msl bound upper : 23000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny tower : cun
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 210 flight time total : 10630 flight time type : 2744
ASRS Report	358890
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence : published procedure other anomaly other anomaly other
Independent Detector	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:

Flight to bos, ZNY issued clearance for descent, to slow to 300 KTS, to cross a fix north of jfk at FL240. We had a tailwind of 80-90 KTS. First officer programmed FMS for crossing restr. Descent was begun. Aircraft was on vertical navigation path to crossing restr. Tailwind was making it difficult for aircraft to maintain both VNAV path and airspeed. Aircraft maintained path and speed increased to 313 KTS. As aircraft approached FL240, center issued clearance to FL230. First officer set new altitude in autoplt altitude select window. First officer noticed speed had increased above 300 KTS, and selected vertical speed mode of autoplt to reduce speed. Apparently selecting vertical speed disarmed altitude capture for FL230. At 200 ft above FL230 I noticed aircraft was descending at 3300 FPM and would not level off at FL230. I announced this to first officer who began to level off aircraft. Aircraft descended about 400 ft below FL230 before returning to FL230. Preoccupation with FMS programming and aircraft not able to maintain both airspeed and descent path with tailwind led to selection of autoplt vertical speed mode and loss of altitude arm and capture during autoplt descent.

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Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT IN DSCNT WHEN FO INADVERTENTLY DISARMS ALT AUTO CAPTURE BY SELECTING 'VERT SPD' ON AUTOPLT MODE SELECTOR.

Narrative: FLT TO BOS, ZNY ISSUED CLRNC FOR DSCNT, TO SLOW TO 300 KTS, TO CROSS A FIX N OF JFK AT FL240. WE HAD A TAILWIND OF 80-90 KTS. FO PROGRAMMED FMS FOR XING RESTR. DSCNT WAS BEGUN. ACFT WAS ON VERT NAV PATH TO XING RESTR. TAILWIND WAS MAKING IT DIFFICULT FOR ACFT TO MAINTAIN BOTH VNAV PATH AND AIRSPD. ACFT MAINTAINED PATH AND SPD INCREASED TO 313 KTS. AS ACFT APCHED FL240, CTR ISSUED CLRNC TO FL230. FO SET NEW ALT IN AUTOPLT ALT SELECT WINDOW. FO NOTICED SPD HAD INCREASED ABOVE 300 KTS, AND SELECTED VERT SPD MODE OF AUTOPLT TO REDUCE SPD. APPARENTLY SELECTING VERT SPD DISARMED ALT CAPTURE FOR FL230. AT 200 FT ABOVE FL230 I NOTICED ACFT WAS DSNDING AT 3300 FPM AND WOULD NOT LEVEL OFF AT FL230. I ANNOUNCED THIS TO FO WHO BEGAN TO LEVEL OFF ACFT. ACFT DSNDED ABOUT 400 FT BELOW FL230 BEFORE RETURNING TO FL230. PREOCCUPATION WITH FMS PROGRAMMING AND ACFT NOT ABLE TO MAINTAIN BOTH AIRSPD AND DSCNT PATH WITH TAILWIND LED TO SELECTION OF AUTOPLT VERT SPD MODE AND LOSS OF ALT ARM AND CAPTURE DURING AUTOPLT DSCNT.

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.