Air carrier flight crew reported IAS anomalies; probably due to pitot static icing.

Attributes
ACN	1611367
Time
Date	201901
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	Widebody Transport
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	Pitot-Static System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Weather / Turbulence

Narrative:

Sometime on descent between FL290 and FL240; got numerous indications of pitot static icing; including IAS comparator alert on both pfds. Airspeed on captain's side indicated approximately 30 knots higher than first officer (first officer); and 20 knots higher than stby. Autopilot and autothrottles were inoperative. Ran QRH for airspeed unreliable. On final approach at 2000 ft; all indications returned to normal. Landed uneventfully.my impression was that the pitot static anti-icing systems seemed unable to keep up with high demand of heavy rain and low temperature; even though no icing was evident on the windscreen. Maintenance record after our write-up indicates that debris was found in the rh and auxiliary pitot systems.increase heating ability of pitot static system. I am sure pitot system inspections are normally adequate; but perhaps the interval for such inspections should be looked at.

Original NASA ASRS Text

Title: Air Carrier flight crew reported IAS anomalies; probably due to pitot static icing.

Narrative: Sometime on descent between FL290 and FL240; got numerous indications of pitot static icing; including IAS comparator alert on both PFDs. Airspeed on Captain's side indicated approximately 30 knots higher than FO (First Officer); and 20 knots higher than STBY. Autopilot and Autothrottles were inoperative. Ran QRH for AIRSPEED UNRELIABLE. On final approach at 2000 FT; all indications returned to normal. Landed uneventfully.My impression was that the pitot static anti-icing systems seemed unable to keep up with high demand of heavy rain and low temperature; even though no icing was evident on the windscreen. Maintenance record after our write-up indicates that debris was found in the RH and AUX Pitot Systems.Increase heating ability of pitot static system. I am sure pitot system inspections are normally adequate; but perhaps the interval for such inspections should be looked at.

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.