Aircraft equipment operating procedures not followed for descent procedure.

Attributes
ACN	305910
Time
Date	199505
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lgc
State Reference	GA
Altitude	msl bound lower : 28500 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
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 : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 7500 flight time type : 1800
ASRS Report	305910
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were proceeding on a course direct to lgc with clearance to cross 70 NM west of lgc at or below FL290 with pilot's discretion to FL270. Using the FMS the descent profile was going to achieve the altitude restr when the captain elected to set the cruise FL270 which eliminated the descent profile. The descent rate slowed and the captain then had to manually set up a descent rate to achieve the crossing restr. FL270 had been set in the altitude window so the aircraft continued its descent through FL290 headed toward FL270. The captain decided late to stop the descent at FL290, but by then we had descended to FL285. We then climbed back up to FL290 and advised ATC that we would stay at FL290 with clearance of pilot's discretion to FL270. We rely so much on the FMS that at times we neglect to xchk the raw data or ensure appropriate altitudes or airspds are set as backups. This especially comes into play when the FMS reacts differently than we expect it to.

Original NASA ASRS Text

Title: ACFT EQUIP OPERATING PROCS NOT FOLLOWED FOR DSCNT PROC.

Narrative: WE WERE PROCEEDING ON A COURSE DIRECT TO LGC WITH CLRNC TO CROSS 70 NM W OF LGC AT OR BELOW FL290 WITH PLT'S DISCRETION TO FL270. USING THE FMS THE DSCNT PROFILE WAS GOING TO ACHIEVE THE ALT RESTR WHEN THE CAPT ELECTED TO SET THE CRUISE FL270 WHICH ELIMINATED THE DSCNT PROFILE. THE DSCNT RATE SLOWED AND THE CAPT THEN HAD TO MANUALLY SET UP A DSCNT RATE TO ACHIEVE THE XING RESTR. FL270 HAD BEEN SET IN THE ALT WINDOW SO THE ACFT CONTINUED ITS DSCNT THROUGH FL290 HEADED TOWARD FL270. THE CAPT DECIDED LATE TO STOP THE DSCNT AT FL290, BUT BY THEN WE HAD DSNDED TO FL285. WE THEN CLBED BACK UP TO FL290 AND ADVISED ATC THAT WE WOULD STAY AT FL290 WITH CLRNC OF PLT'S DISCRETION TO FL270. WE RELY SO MUCH ON THE FMS THAT AT TIMES WE NEGLECT TO XCHK THE RAW DATA OR ENSURE APPROPRIATE ALTS OR AIRSPDS ARE SET AS BACKUPS. THIS ESPECIALLY COMES INTO PLAY WHEN THE FMS REACTS DIFFERENTLY THAN WE EXPECT IT TO.

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.