MD-80 Series (DC-9-80) Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Deviation - Speed All Types; Inflight Event / Encounter Other / Unknown
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew FLC Overrode Automation
Aircraft; Human Factors
In IMC; FL 320; Moderate chop (borderline Moderate Turb); Captain's (CA) window (L1) started to ice up. (Repeat write up) We had all the anti-ice on and the Meter Sel positions all showed positive current. We were focused on that item.We had been cleared to descend via the RNAV arrival.First Officer (FO) advised me that the Autopilot had kicked off. I thought that it had kicked off due to the moderate chop. I took the controls and maintained wings level; climbed back up to altitude (100 feet) and maintained our (on CA's indicator) speed of about 280 knots. I tried to re-engage the autopilot and noticed that the auto throttles had kicked off too. FO called out 'You are slow' I replied something to the effect 'My speed is good; 280.' He called again and I (we) began trying to identify which airspeed indicator was lying to us; if any. We realized that the FO and Stby Air Speed indicators agreed and that we were at or below 210 knots. I began to add power. It happened very quickly and was pretty confusing. The FO called for a descent right as we got just a touch (tickle) of low speed airframe buffet. I added more power and lowered the nose (we had been cleared for the descent).We advised ATC that we were descending and that we would be un-able the RNAV. They cleared us to 11000 feet. At 11000 feet; we changed controls and the FO flew the approach.
[Report narrative contained no additional information.]
MD-80 flight crew experienced a faulty airspeed indicator.