Air carrier X on ILS approach unauthorized descent from assigned altitude started descent 2 mi early...

Attributes
ACN	215180
Time
Date	199207
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : tpe
State Reference	FO
Altitude	msl bound lower : 3600 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : tpe tower : shv
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 7500 flight time type : 60
ASRS Report	215180
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure
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:

This event occurred while descending into taipei for approach. The so monitored the ATIS and advised us that runway 5L was in use. Subsequent radar vector and altitude clearance brought us to 4000 ft and clearance to intercept the localizer from our present heading. A subsequent clearance cleared us for an ILS approach to runway 5L. Continuing the approach we continued to have GS flaps and questioned approach control about the GS. They then informed us that the GS was out and we were cleared for a localizer approach. I made a quick check of the approach plate and determined a descent from 4000 to 3000 was in order. Descending to 3600 ft I realized I had started 2 mi early and climbed back to 4000 ft. In retrospect I believe that because of the multiple time zone changes, haphazard sleep patterns due to the way we were scheduled for our duty periods left the crew fatigued and not as perceptive as we would be normally. I also believe that taipei approach was not 'on the ball' and that they cleared us for an ILS approach when it was in fact OTS.

Original NASA ASRS Text

Title: ACR X ON ILS APCH UNAUTHORIZED DSCNT FROM ASSIGNED ALT STARTED DSCNT 2 MI EARLY. PLTDEV.

Narrative: THIS EVENT OCCURRED WHILE DSNDING INTO TAIPEI FOR APCH. THE SO MONITORED THE ATIS AND ADVISED US THAT RWY 5L WAS IN USE. SUBSEQUENT RADAR VECTOR AND ALT CLRNC BROUGHT US TO 4000 FT AND CLRNC TO INTERCEPT THE LOC FROM OUR PRESENT HDG. A SUBSEQUENT CLRNC CLRED US FOR AN ILS APCH TO RWY 5L. CONTINUING THE APCH WE CONTINUED TO HAVE GS FLAPS AND QUESTIONED APCH CTL ABOUT THE GS. THEY THEN INFORMED US THAT THE GS WAS OUT AND WE WERE CLRED FOR A LOC APCH. I MADE A QUICK CHK OF THE APCH PLATE AND DETERMINED A DSCNT FROM 4000 TO 3000 WAS IN ORDER. DSNDING TO 3600 FT I REALIZED I HAD STARTED 2 MI EARLY AND CLBED BACK TO 4000 FT. IN RETROSPECT I BELIEVE THAT BECAUSE OF THE MULTIPLE TIME ZONE CHANGES, HAPHAZARD SLEEP PATTERNS DUE TO THE WAY WE WERE SCHEDULED FOR OUR DUTY PERIODS LEFT THE CREW FATIGUED AND NOT AS PERCEPTIVE AS WE WOULD BE NORMALLY. I ALSO BELIEVE THAT TAIPEI APCH WAS NOT 'ON THE BALL' AND THAT THEY CLRED US FOR AN ILS APCH WHEN IT WAS IN FACT OTS.

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.

Air carrier X on ILS approach unauthorized descent from assigned altitude started descent 2 mi early. Pilot deviation.