Altitude deviation altitude overshot.

Attributes
ACN	201634
Time
Date	199202
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mco
State Reference	FL
Altitude	msl bound lower : 12000 msl bound upper : 13400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mco
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 8000
ASRS Report	201634
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10000
ASRS Report	202006
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

Departed mco, handed over to departure control and assigned 12000 ft. Captain flying aircraft, first officer set 12000 ft and armed altitude alert system. Captain verified 12000 ft set and armed in DFGS. Crew attention was diverted momentarily by radio calls and required cabin announcement. Aircraft passed through 12000 and at 13000 ft captain noticed altitude in window set at 13000 and alert system not armed. Captain subsequently disengaged autoplt and recovered at 13400 ft and began descent back to 12000 ft. Shortly after, ATC called and informed crew 12000 ft assigned. Crew verified 12000 and noted altitude with him. ATC then immediately cleared us to FL230 and climb was initiated. Both myself and the first officer concur that the DFGS altitude capture mode disarmed at some point and altitude window displayed 13000 ft after our verification of 12000 set earlier. With over 1000 hours in type, this is not the first occurrence of this to happen. Occasionally the altitude set wheel will linger between detents and subsequently 'click' in to the incorrect altitude, thus disarming the alert system and displaying incorrect altitude.

Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT.

Narrative: DEPARTED MCO, HANDED OVER TO DEP CTL AND ASSIGNED 12000 FT. CAPT FLYING ACFT, FO SET 12000 FT AND ARMED ALT ALERT SYS. CAPT VERIFIED 12000 FT SET AND ARMED IN DFGS. CREW ATTN WAS DIVERTED MOMENTARILY BY RADIO CALLS AND REQUIRED CABIN ANNOUNCEMENT. ACFT PASSED THROUGH 12000 AND AT 13000 FT CAPT NOTICED ALT IN WINDOW SET AT 13000 AND ALERT SYS NOT ARMED. CAPT SUBSEQUENTLY DISENGAGED AUTOPLT AND RECOVERED AT 13400 FT AND BEGAN DSCNT BACK TO 12000 FT. SHORTLY AFTER, ATC CALLED AND INFORMED CREW 12000 FT ASSIGNED. CREW VERIFIED 12000 AND NOTED ALT WITH HIM. ATC THEN IMMEDIATELY CLRED US TO FL230 AND CLB WAS INITIATED. BOTH MYSELF AND THE FO CONCUR THAT THE DFGS ALT CAPTURE MODE DISARMED AT SOME POINT AND ALT WINDOW DISPLAYED 13000 FT AFTER OUR VERIFICATION OF 12000 SET EARLIER. WITH OVER 1000 HRS IN TYPE, THIS IS NOT THE FIRST OCCURRENCE OF THIS TO HAPPEN. OCCASIONALLY THE ALT SET WHEEL WILL LINGER BTWN DETENTS AND SUBSEQUENTLY 'CLICK' IN TO THE INCORRECT ALT, THUS DISARMING THE ALERT SYS AND DISPLAYING INCORRECT ALT.

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.