Md-11 flight crew reported anomaly that caused multiple false overspeed warnings. They chose to decl...

Narrative:

On climb passing 17;000 ft max airspeed tape dropped from 360 KTS to 285 KTS; also got overspeed warnings. This event happened 9+ times; max time length was 15 seconds. In cruise when this happened the throttles started retarding; crew intervention was required. I decided to select airspeed 280 KTS this way speed tape would not be an issue. Ran airspeed erratic checklist. We made a satcom with sme; maintenance and flight control. After discussion we felt the best course of action was return to base. We also declared an emergency. At lower altitudes we turned the afs override to off and flew manual throttles back to [departure airport]. No other airspeed issues on final. Weather was clear and we were not in turbulence. This was a repeat write up! Did extensive debrief with tech support team. Maintenance found pseu and autothrottle issues.

Original NASA ASRS Text

Title: MD-11 flight crew reported anomaly that caused multiple false overspeed warnings. They chose to declare an emergency and returned to departure airport.

Narrative: On climb passing 17;000 FT max airspeed tape dropped from 360 KTS to 285 KTS; also got overspeed warnings. This event happened 9+ times; max time length was 15 seconds. In cruise when this happened the throttles started retarding; crew intervention was required. I decided to select airspeed 280 KTS this way speed tape would not be an issue. Ran Airspeed Erratic checklist. We made a SATCOM with SME; Maintenance and Flight Control. After discussion we felt the best course of action was return to base. We also declared an emergency. At lower altitudes we turned the AFS override to off and flew manual throttles back to [departure airport]. No other airspeed issues on final. Weather was clear and we were not in turbulence. This was a repeat write up! Did extensive debrief with tech support team. Maintenance found PSEU and autothrottle issues.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1113031
Time
Date	201308
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Route In Use	Other Controlled
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Events
Anomaly	Aircraft Equipment Problem Less Severe

Md-11 flight crew reported anomaly that caused multiple false overspeed warnings. They chose to declare an emergency and returned to departure airport.