A B737-300 crew reported that some component in the autoflight system autonomously transitioned into...

Attributes
ACN	917469
Time
Date	201011
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Climb
Component
Aircraft Component	Flight Dynamics Navigation and Safety
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 86
Person 2
Function	Pilot Not Flying First Officer
Experience	Flight Crew Last 90 Days 108
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Overshoot

Narrative:

During a climb from 7;000 ft to 10;000 ft with autopilot 'a' engaged; the MCP altitude window went to 50;000 ft; resulting in an altitude overshoot of 300 ft. Additionally; the first officer's airspeed indicator bug was stuck at 140 KTS. No LNAV was available; the V/south and level change functions would not work; and neither flight director indicator would come into view. Both autopilots were attempted unsuccessfully. The autopilot MCP went to 50;000 ft at least five times during the thirty-three minute flight. The aircraft was hand-flown. The center controller never mentioned the altitude deviation. Increased technology equals need for increased vigilance.

Original NASA ASRS Text

Title: A B737-300 Crew reported that some component in the autoflight system autonomously transitioned into a BITE TEST mode and caused the MCP Altitude set to go to 50;000 FT; the loss of VNAV; V/S; both autopilots; and the First Officer's airspeed to stick at 140 KTS.

Narrative: During a climb from 7;000 FT to 10;000 FT with autopilot 'A' engaged; the MCP Altitude window went to 50;000 FT; resulting in an altitude overshoot of 300 FT. Additionally; the First Officer's airspeed indicator bug was stuck at 140 KTS. No LNAV was available; the V/S and Level Change functions would not work; and neither flight director indicator would come into view. Both autopilots were attempted unsuccessfully. The autopilot MCP went to 50;000 FT at least five times during the thirty-three minute flight. The aircraft was hand-flown. The Center Controller never mentioned the altitude deviation. Increased technology equals need for increased vigilance.

Data retrieved from NASA's ASRS site as of April 2012 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.

A B737-300 crew reported that some component in the autoflight system autonomously transitioned into a bite test mode and caused the MCP altitude set to go to 50;000 ft; the loss of VNAV; V/south; both autopilots; and the first officer's airspeed to stick at 140 KTS.