[5] The electric altimeter receives altitude data from the air data computer. The altimeter is a round, panel-mounted instrument. The face of the instrument contains a numerical and an analog display of altitude, a numerical display of the manually set barometric pressure reference, an altitude reference cursor, a barometric set knob, and an altitude reference cursor set knob to position the barometric set indicator and the altitude reference cursor. The numerical altitude display indicates between-1000 feet and 50,000 feet. When the altitude is below sea level, a NEG flag covers the two most significant digits. An OFF flag covers the same two digits when the ADC or the altimeter malfunctions, or when power is removed from the ADC system.
Fig. 31-3 electric altimeter
[6] The altitude pointer makes one complete revolution for each 1000 feet change in altitude. The pointer's 1000 feet circular scale has markings at 20 feet increments. The barometric (BARO) set indicator displays pressure in inches of mercury (IN HG) and millibars (MB),when the baro set knob is set to standard sea level pressure, the altitude indication is pressure altitude; when set to the ambient pressure, the altitude indication is BARO-corrected altitude. The altitude reference cursor set knob is used to mechanically position the altitude reference cursor.
[7] Another important instrument is the electric mach airspeed indicator. It displays airspeed, airspeed limit, mach number and target airspeed. The mach airspeed indicator receives airspeed and altitued data from the air data computer (ADC) and target airspeed from the flight control conputer ( FCC) . Displayed airspeed is from 60 to 450 knots computed airspeed (CAS). Displayed mach is from 0.400 to 0.999 mach.
READING MATERIAL
QUESTIONS TO LESSON 31 READING MATERIAL
1. What does the mach airspeed indicator display?
2. What do the displays include?
3. What is a speed reference knob used to ?
4. What is the range of displayed computed airspeed ?
What is the range of display ed mach number ?
5. Is the malfunction indications provided by the failure flags? How
many kind of malfunction indication are there?
6. What can be manually positioned around the outside diameter of the
airspeed scale?
7. What does the mach airspeed indicator receive from the ADC ?
8. What does the mach airspeed indicator receive from FCC ?
9. What is used by a servo ?
10. Why is the airspeed signal from the ADC used by a servo ?
11. How is the target airspeed cursor controlled ?
12. How is the manual control shown?
13. When is the mach/airspeed warning enabled ?
14. What value is the airplane airspeed limited to ?
15. Above 25968 feet, what is limited to 0.82 ?
EXERCISE
A. Find out the explanations of the following words in your “Englis-chinese technical dictionary"
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：第31课 大气数据系统 LESSON 31 AIR DATA SYSTEM(3)
