Flight Crew Air Transport Pilot (ATP)
Distraction
Aircraft Equipment Problem Critical
Air Traffic Control Issued New Clearance; Aircraft Equipment Problem Dissipated; Flight Crew Took Evasive Action; Flight Crew Diverted; Flight Crew Landed As Precaution
Human Factors; Weather; Aircraft
During cruise flight at FL330 in IMC/icing conditions; the first indication of a problem was an amber IAS cross-side mis-comparison warning on both the Captain and First Officer's PFD. This was shortly followed by an autopilot/autothrottle disconnect and various alerts that included but were not limited to A/P UNAVAILABLE; RUDDER LIM FAIL; and unusual airspeed indications for the flight conditions. After the autopilot disconnected the airplane pitched up slightly resulting in an altitude deviation and an amplified discrepancy between the Captain and First Officer's airspeed indications. We requested a block altitude from ATC and advised we were trying to assess a problem with erratic and unreliable airspeed. The block altitude was granted and RSVM capability downgraded. After stabilizing the aircraft using known pitch and power (N1) setting we believed the Captain's airspeed indications to be malfunctioning and the First Officer took over pilot flying duties. We requested a descent to FL250 to increase the range between the high and low speed footers as well as the range between the pitch and PLI. During the descent we referenced the QRH for the AIRSPEED: LOST; SUSPECT; OR ERRACTIC emergency non-alert checklist. The descent to FL250 brought us to VMC conditions and warmer temperatures at which point all abnormal indications cleared.Captain and First Officer agreed to maintain VMC conditions and divert to a VFR airport. After coordinating with dispatch and Maintenance Control we diverted to ZZZ without further incident. At the first indication of an IAS mis-comparison; the autopilot/autothrottles should have manually been disconnected and the aircraft flown using known pitch/power (N1) settings. Nor should further attempts been made to re-engage the autopilot. The uncommanded disconnect and initial attempts to re-engage created numerous aural warnings and an unnecessary distraction during a critical time to assess the abnormal condition.
B717 First Officer reports inaccurate airspeed indication during cruise at FL330 in IMC with loss of autopilot and auto thrust capability. ATC is advised and descent to VMC is initiated. Once clear of icing conditions the Captain's airspeed indication returns to normal but the crew elects to divert to a suitable alternate.