A B737-400 captain flying a practice autoland in IMC saw his airspeed decrease toward stall and adde...

Attributes
ACN	1152498
Time
Date	201402
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Pitot/Static Ice System
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site 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 B737-400 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.