Altitude deviation altitude excursion.

Attributes
ACN	218507
Time
Date	199208
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pvd
State Reference	RI
Altitude	msl bound lower : 13700 msl bound upper : 14000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other cruise other other
Route In Use	enroute airway : zbw
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 225 flight time total : 14000 flight time type : 155
ASRS Report	218507
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : became reoriented other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft was descending to cross pvd at 14000 ft to enter hold. Because anti-ice system was turned on in descent the automatic throttles had advanced power and aircraft was not holding assigned airspeed. Disconnected a/T's and was concerned with proper airspeed and power for anti-ice. I did not notice immediately that aircraft on autoplt had descended below 14000 by 300 ft. When I realized we were off altitude, I immediately disconnected autoplt and climbed 300 ft to proper altitude. ATC asked if we were at 14000 ft. I really don't know why the autoplt did not engage 'altitude hold.' I am now on the aircraft and was somewhat distracted by the power problem/airspeed problem. Just as I noticed our altitude excursion the altitude alerter on the aircraft sounded. Even though this aircraft has a glass cockpit and full automation, I have learned from this experience that even with all the magic you don't drop your vigilance for 1 second. We flew the aircraft 1 more leg and found the altitude capture function worked properly, so it may have been operator error on my part but at this point I just can't say for sure. I will continue to review the occurrence and my techniques and of course watch the autoflt system much more carefully in the future.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION.

Narrative: ACFT WAS DSNDING TO CROSS PVD AT 14000 FT TO ENTER HOLD. BECAUSE ANTI-ICE SYS WAS TURNED ON IN DSCNT THE AUTO THROTTLES HAD ADVANCED PWR AND ACFT WAS NOT HOLDING ASSIGNED AIRSPD. DISCONNECTED A/T'S AND WAS CONCERNED WITH PROPER AIRSPD AND PWR FOR ANTI-ICE. I DID NOT NOTICE IMMEDIATELY THAT ACFT ON AUTOPLT HAD DSNDED BELOW 14000 BY 300 FT. WHEN I REALIZED WE WERE OFF ALT, I IMMEDIATELY DISCONNECTED AUTOPLT AND CLBED 300 FT TO PROPER ALT. ATC ASKED IF WE WERE AT 14000 FT. I REALLY DON'T KNOW WHY THE AUTOPLT DID NOT ENGAGE 'ALT HOLD.' I AM NOW ON THE ACFT AND WAS SOMEWHAT DISTRACTED BY THE PWR PROBLEM/AIRSPD PROBLEM. JUST AS I NOTICED OUR ALT EXCURSION THE ALT ALERTER ON THE ACFT SOUNDED. EVEN THOUGH THIS ACFT HAS A GLASS COCKPIT AND FULL AUTOMATION, I HAVE LEARNED FROM THIS EXPERIENCE THAT EVEN WITH ALL THE MAGIC YOU DON'T DROP YOUR VIGILANCE FOR 1 SECOND. WE FLEW THE ACFT 1 MORE LEG AND FOUND THE ALT CAPTURE FUNCTION WORKED PROPERLY, SO IT MAY HAVE BEEN OPERATOR ERROR ON MY PART BUT AT THIS POINT I JUST CAN'T SAY FOR SURE. I WILL CONTINUE TO REVIEW THE OCCURRENCE AND MY TECHNIQUES AND OF COURSE WATCH THE AUTOFLT SYS MUCH MORE CAREFULLY IN THE FUTURE.

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.