B737-400
Flight Crew Air Transport Pilot (ATP)
Workload; Time Pressure; Confusion; Distraction
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Aircraft Equipment Problem Dissipated; Flight Crew Took Evasive Action; Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation; General Maintenance Action
Weather; Human Factors; Aircraft
On approach to the runway; we were cleared for a practice autoland. We were at 4;000 FT in IFR conditions which included moderate rime icing. We were given a heading to intercept the localizer. Flaps 5 were extended and we were at 170 KTS right before the localizer became alive; the Captain's airspeed indicator was decreasing in speed and was approaching Vref and the redline for stall. The Captain disengaged the autothrottle and autopilot and added full power but speed was still decreasing. The Captain then started a descent to gain speed. At this time; the First Officer called out to watch our speed because his airspeed indicator was approaching maximum red line. When the Captain looked over at the First Officer's airspeed indicator with full throttles in the descent; he gave the airplane to the First Officer who had reliable instrumentation. Meanwhile; the aircraft had flown through the localizer and descended to approximately 3;400 FT. We advised Approach Control that we had an instrument failure and required a new vector to the localizer. After the localizer and glideslope were captured; the Captain's airspeed indicator matched the First Officer's and the flight landed uneventfully.I can't say for sure what caused this event but a probable suspect is a frozen pitot tube on Captain's side.
[Reporter narrative contained no additional information].
A B737-400 Captain flying a practice autoland in IMC saw his airspeed decrease toward stall and added max thrust to recover while the First Officer alerted him to an overspeed condition. The Captain transferred flying to the First Officer when recognized his instrument error.