An ac-powered internal vibrator automatically energizes in the standby mode to lessen friction in the display mechanism. The standby operation is selected by placing the mode switch to STBY. The altimeter automatically switches to standby operation during an electrical power loss or when the altimeter or altitude computer fails. During standby operation, a red STBY flag appears on the dial face. The servoed mode is selected by placing the mode switch to RESET for 3 seconds. pressure from the static system that is uncorrected for position error. In this mode, it uses static Figure 2-9.-Counter-drum-pointer altimeter. In the standby mode, the altimeter operates as a standard altimeter. In the servoed mode, the altimeter displays altitude, corrected for position error, from the synchro output of the air data computer. The mode of operation is controlled by a spring-loaded, self-centering mode switch, placarded RESET and STBY. This sample altimeter has a servoed mode and a pressure mode of operation. The pointer serves as a precise readout of values less than 100 feet. The second way is to read the counter window and then add the 100-foot pointer indication. This will give a direct readout of both thousands and hundreds of feet. One way is to read the counter-drum window without referring to the 100-foot pointer. There are two methods of reading the indicated pressure altitude.
In this way it prevents the reading error when the 1,000-foot counter switches.
This drum follows the 100-foot pointer, and it is this drum that actuates the 1,000-foot counter. Counter-Drum-Pointer Altimeter. The only real difference between this altimeter and the counter-pointer altimeter is the addition of a 100-foot drum (fig. This error is possible because the 1,000-foot counter changes when the foot-pointer is between the 900- and 1,000-foot position. CAUTION It is possible to misinterpret the counter- pointer altimeter by 1,000 feet immediately before or after the 1,000-foot counter moves. 1,000-foot counter and then add the 100-foot pointer indication.