TCASII RA received when medium large transport overshoots altitude in descent.

Attributes
ACN	241721
Time
Date	199305
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sie
State Reference	NJ
Altitude	msl bound lower : 15800 msl bound upper : 16000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument pilot : atp
Experience	flight time last 90 days : 210 flight time total : 8100 flight time type : 1500
ASRS Report	241721
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 210 flight time total : 13870 flight time type : 930
ASRS Report	241726
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 18000 vertical : 800
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Center issued a descent to 16000 ft. Aircraft descending on autoplt with pms mode engaged. Descending through 17000 ft center called out traffic at 1 O'clock and 10 mi at 15000 ft. Traffic appeared on TCASII. Autoplt malfunctioned and aircraft descended through 16000 ft to 15900 ft (100 ft low). At this time the autoplt was disconnected and a manual climb initiated back to 16000 ft. During this maneuver the aircraft descended to 15800 ft (200 ft low). In addition to the autoplt malfunction and failure to level off, the automatic throttles could not be disengaged. The pms AC and dc circuit breakers had to be pulled in order to disconnect automatic throttles. A TCASII RA was displayed as the aircraft descended through 16000 ft and the traffic was in sight visually. No evasive action was taken. Center inquired about aircraft altitude and whether or not the traffic appeared on TCASII. Upon landing at phl an appropriate maintenance write-up was entered in the logbook.

Original NASA ASRS Text

Title: TCASII RA RECEIVED WHEN MLG OVERSHOOTS ALT IN DSCNT.

Narrative: CTR ISSUED A DSCNT TO 16000 FT. ACFT DSNDING ON AUTOPLT WITH PMS MODE ENGAGED. DSNDING THROUGH 17000 FT CTR CALLED OUT TFC AT 1 O'CLOCK AND 10 MI AT 15000 FT. TFC APPEARED ON TCASII. AUTOPLT MALFUNCTIONED AND ACFT DSNDED THROUGH 16000 FT TO 15900 FT (100 FT LOW). AT THIS TIME THE AUTOPLT WAS DISCONNECTED AND A MANUAL CLB INITIATED BACK TO 16000 FT. DURING THIS MANEUVER THE ACFT DSNDED TO 15800 FT (200 FT LOW). IN ADDITION TO THE AUTOPLT MALFUNCTION AND FAILURE TO LEVEL OFF, THE AUTO THROTTLES COULD NOT BE DISENGAGED. THE PMS AC AND DC CIRCUIT BREAKERS HAD TO BE PULLED IN ORDER TO DISCONNECT AUTO THROTTLES. A TCASII RA WAS DISPLAYED AS THE ACFT DSNDED THROUGH 16000 FT AND THE TFC WAS IN SIGHT VISUALLY. NO EVASIVE ACTION WAS TAKEN. CTR INQUIRED ABOUT ACFT ALT AND WHETHER OR NOT THE TFC APPEARED ON TCASII. UPON LNDG AT PHL AN APPROPRIATE MAINT WRITE-UP WAS ENTERED IN THE LOGBOOK.

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.