Outside Air Temperature (OAT) Gauge  Chapter Summary  The outside air temperature (OAT) gauge is a simple and  effective device mounted so that the sensing element is  exposed to the outside air. The sensing element consists  of a bimetallic-type thermometer in which two dissimilar  materials are welded together in a single strip and twisted  into a helix. One end is anchored into protective tube and the  other end is affixed to the pointer, which reads against the  calibration on a circular face. OAT gauges are calibrated in  degrees °C, °F, or both. An accurate air temperature provides  the pilot with useful information about temperature lapse rate  with altitude change.  [Figure 8-39]  Flight instruments enable an aircraft to be operated with  maximum performance and enhanced safety, especially when  flying long distances. Manufacturers provide the necessary  flight instruments, but to use them effectively, pilots need  to understand how they operate. As a pilot, it is important to  become very familiar with the operational aspects of the pitot ­ static system and associated instruments, the vacuum system  and associated instruments, the gyroscopic instruments, and  the magnetic compass.  Figure 8-39.  Outside air temperature (OAT) gauge.  8-28  20  0  -20  -40  -60  40  60  100  140  120  80  F  20  0  -20  -40  40  60  C