B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 1688
Human-Machine Interface; Troubleshooting; Workload
Aircraft Equipment Problem Less Severe
Air Traffic Control Issued New Clearance; Flight Crew Returned To Departure Airport
Aircraft
Wing and engine anti-ice NOT on for takeoff or departure. During climb out from #1 engine COWL ANTI-ICE light illuminated. #1 Engine ANTI-ICE switch confirmed OFF. #1 COWL VALVE OPEN light NOT illuminated. TAI (Thermal anti-ice indication) NOT displayed on Upper Display Unit. QRH actions completed. COWL ANTI-ICE light remained illuminated; even with #1 throttle reduced to idle. Aircraft leveled at 16000 ft MSL. Contacted [Maintenance Control]; who were unable to provide guidance beyond that contained in QRH. Coordinated with Dispatch for return to [departure airport]. Captain assumed PF (pilot flying) duties prior to top of descent. #1 engine thrust moderated throughout incident. Uneventful overweight landing at [departure airport].QRH procedure for this straight-forward malfunction seems incomplete. Procedure does not direct crew to confirm engine ANTI-ICE switch position; confirm illumination of COWL VALVE OPEN light; or confirm presence of TAI indication on Upper Display Unit. Lacking ANY secondary indications that bleed air is actually being routed to engine cowl; can engine COWL ANTI-ICE procedure be expected to extinguish light? Is accomplishing engine COWL ANTI-ICE procedure warranted with no secondary indications? What is the probability that multiple switch/sensor failures will occur and allow bleed air to enter engine cowl without engine ANTI-ICE switch positioned to ON? If the probability is statistically non-existent; might flight be safely continued with engine COWL ANTI-ICE illuminated while avoiding known icing conditions when no secondary indications are present?Air return to [the departure airport] deemed our safest and appropriate response to an engine COWL ANTI-ICE light that could not be extinguished after compliance with QRH procedure.
B737 First Officer reported a persistent Engine Anti-Ice light on the climb out even after completing the QRH actions.