When a sensor on the engine becomes blocked by ice, it can lead to incorrect readings or failure to provide essential data to the engine control system. As a result, the pilot may receive error indications, which could include alerts about abnormal engine performance or potential limitations on power output.

Source: ICAO Doc 9640

The Air Florida Flight 90 crash serves as a poignant example of human error leading to tragedy. Despite evident snowfall, the pilots overlooked icing conditions. They also failed to adequately remove ice buildup before takeoff, resulting in diminished lift and increased drag. Furthermore, despite sub-freezing temperatures and snowfall, the crew neglected to activate the engine anti-ice system. This system, utilizing engine heat, prevents sensor freezing, ensuring accurate readings.

During the pre-takeoff checklist, a crucial conversation unfolded between the captain (CAM-1) and the first officer (CAM-2):

CAM-2: Pitot heat?
CAM-1: On.
CAM-2: Engine anti-ice?
CAM-1: Off.

Despite the freezing conditions, the crew omitted to activate the engine anti-ice systems, leading to erroneous readings on the engine pressure ratio (EPR) thrust indicators. The correct power setting for the prevailing conditions at Washington National Airport was 2.04 EPR. However, analysis of cockpit voice recorder data revealed that the actual power output corresponded to a mere 1.70 EPR.