Altitude deviation altitude excursion during a correction to an aircraft equipment problem.

Attributes
ACN	306540
Time
Date	199506
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : lrp airport : phl
State Reference	PA
Altitude	msl bound lower : 7500 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : phl
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 11500 flight time type : 6000
ASRS Report	306540
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 14000 flight time type : 4800
ASRS Report	306538
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far other anomaly other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Level flight at 8000 ft, autothrottles on, performance management system commanded airspeed increase above 250 KTS. First officer was flying on autoplt and when he reached to correct the airspeed command on the performance management system the aircraft started to descend. I called out the altitude and immediately increased power to return to assigned altitude. The autoplt was disconnected and aircraft returned to level flight. Supplemental information from acn 306538: instead of trying to adjust the autoplt below 10000 ft in order to correct a deviation, I recommended that the PF verbalizes his intentions that the autoplt is being turned off and the autothrottles are being turned off. Hand flying the airplane in this situation would have been a better option. On the ground the copilot altimeter was erratic. The altimeter was written up for its mechanical disfunction.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION DURING A CORRECTION TO AN ACFT EQUIP PROB.

Narrative: LEVEL FLT AT 8000 FT, AUTOTHROTTLES ON, PERFORMANCE MGMNT SYS COMMANDED AIRSPD INCREASE ABOVE 250 KTS. FO WAS FLYING ON AUTOPLT AND WHEN HE REACHED TO CORRECT THE AIRSPD COMMAND ON THE PERFORMANCE MGMNT SYS THE ACFT STARTED TO DSND. I CALLED OUT THE ALT AND IMMEDIATELY INCREASED PWR TO RETURN TO ASSIGNED ALT. THE AUTOPLT WAS DISCONNECTED AND ACFT RETURNED TO LEVEL FLT. SUPPLEMENTAL INFO FROM ACN 306538: INSTEAD OF TRYING TO ADJUST THE AUTOPLT BELOW 10000 FT IN ORDER TO CORRECT A DEV, I RECOMMENDED THAT THE PF VERBALIZES HIS INTENTIONS THAT THE AUTOPLT IS BEING TURNED OFF AND THE AUTOTHROTTLES ARE BEING TURNED OFF. HAND FLYING THE AIRPLANE IN THIS SIT WOULD HAVE BEEN A BETTER OPTION. ON THE GND THE COPLT ALTIMETER WAS ERRATIC. THE ALTIMETER WAS WRITTEN UP FOR ITS MECHANICAL DISFUNCTION.

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.