<< >> NASA ASRS Report 447800, August 1999

Air carrier prompted by controller to increase rate of descent to meet crossing restr after crew loses track of what their FMS is doing.

Attributes
ACN	447800
Time
Date	199908
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : okk.vor
State Reference	IN
Altitude	msl bound lower : 29300 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc tower : mem.tower
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : descent cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : multi engine pilot : commercial
Experience	flight time last 90 days : 170 flight time total : 2500 flight time type : 700
ASRS Report	447800
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to original clearance
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft ATC Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

While descending from FL330 to FL280 received further clearance to descend to FL240 (320 KIAS). PF was programming FMS for new descent clearance ('cross 20 mi south okk at FL240'). When FMS navigation function disengaged (not noticed by either pilot) a rate of approximately 200 FPM started in pitch only mode. ATC asked about our altitude. We were at FL293 (29300 ft). We then promptly descended to FL240, rest of trip routine. We suspect programming FMC close to or during altitude acquire caused VNAV to disengage.

Related reports:

• Prompted by a spacing error by his developmental; an approac...
• Enroute controller described a weather encounter that prompt...
• Tower controller in charge described a go around event promp...
• Bos local controller describes go around event prompted by a...
• Sea tower controller described go around event involving tra...

	Enter your search terms Submit search form
	Web www.37000feet.com

Original NASA ASRS Text

Title: ACR PROMPTED BY CTLR TO INCREASE RATE OF DSCNT TO MEET XING RESTR AFTER CREW LOSES TRACK OF WHAT THEIR FMS IS DOING.

Narrative: WHILE DSNDING FROM FL330 TO FL280 RECEIVED FURTHER CLRNC TO DSND TO FL240 (320 KIAS). PF WAS PROGRAMMING FMS FOR NEW DSCNT CLRNC ('CROSS 20 MI S OKK AT FL240'). WHEN FMS NAV FUNCTION DISENGAGED (NOT NOTICED BY EITHER PLT) A RATE OF APPROX 200 FPM STARTED IN PITCH ONLY MODE. ATC ASKED ABOUT OUR ALT. WE WERE AT FL293 (29300 FT). WE THEN PROMPTLY DSNDED TO FL240, REST OF TRIP ROUTINE. WE SUSPECT PROGRAMMING FMC CLOSE TO OR DURING ALT ACQUIRE CAUSED VNAV TO DISENGAGE.

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.