Temperature is available from two sensors, mounted under the left wing. The fundamental sensing element in each probe is a platinum resistance element. The de-iced Rosemount sensor is the nearer probe in the image below. It is data tag 106 in the Recorded and Derived Parameter List. This probe is more stable and more accurate in dry air and in light icing conditions. It has a response time of approximately one second. The reverse-flow temperature sensor (data tag107), the probe in the background in the image below, is designed to provide a measure of temperature unaffected by wetting in clouds or icing, even in heavy icing conditions.
It has a response time of approximately four seconds. Its response is more sensitive to variations in angle-of-attack, and to changes in airflow due to icing, than is the response of the Rosemount sensor. However, relative variations in temperature from one region to another in moderate to heavy icing regions are better judged using the reverse-flow sensor (Lawson and Cooper, 1990).
Figure 1 shows an example of the recorded temperature with the two sensors.
Figure 1. Rosemount and Reverse Flow
temperature measurements during Flight 813 (