Flight Instruments

Outside Air Temperature (OAT) Gauge The outside air temperature (OAT) gauge is a simple and 40 effective device mounted so that the sensing element is 20 60 0 exposed to the outside air. The sensing element consists 0 20 80 of a bimetallic-type thermometer in which two dissimilar -20 materials are welded together in a single strip and twisted -20 40 100 into a helix. One end is anchored into protective tube and the -40 other end is affixed to the pointer, which reads against the -40 60 120 calibration on a circular face. OAT gauges are calibrated in C -60 140 degrees °C, °F, or both. An accurate air temperature provides F the pilot with useful information about temperature lapse rate with altitude change. [Figure 8-39] Figure 8-39. Outside air temperature (OAT) gauge. Chapter Summary 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. 8-28