Avionics in Aviation Maintenance Avionics is a conjunction of the words aviation and  electronics. It is used to describe the electronic equipment  found in modern aircraft. The term “avionics” was not  used until the 1970s. For many years, aircraft had electrical  devices, but true solid-state electronic devices were only  introduced in large numbers in the 1960s.  Airframe and engine maintenance is required on all aircraft  and is not likely to ever go away. Aircraft instrument  maintenance and repair also has an inevitable part in aviation  maintenance. The increased use of avionics in aircraft  over the past 50 years has increased the role of avionics  maintenance in aviation. However, modern, solid-state,  digital avionics are highly reliable. Mean times between  failures are high, and maintenance rates of avionics systems  compared to mechanical systems are likely to be lower. The first decade of avionics proliferation saw a greater  increase in the percent of cost of avionics compared to the  overall cost of an aircraft. In some military aircraft with  highly refined navigation, weapons targeting, and monitoring  systems, it hit a high estimate of 80 percent of the total cost of  the aircraft. Currently, the ratio of the cost of avionics to the  cost of the total aircraft is beginning to decline. This is due to  advances in digital electronics and numerous manufacturers  offering highly refined instrumentation, communication, and  navigation systems that can be fitted to nearly any aircraft.  New aircraft of all sizes are manufactured with digital glass  cockpits, and many owners of older aircraft are retrofitting  digital avionics to replace analog instrumentation and radio  navigation equipment. The airframe and powerplant (A&P) maintenance technician  needs to be familiar with the general workings of various  avionics. Maintenance of the actual avionics devices is often  reserved for the avionics manufacturers or certified repair  stations. However, the installation and proper operation  of these devices and systems remains the responsibility of  the field technician. This chapter discusses some internal  components used in avionics devices. It also discusses a wide  range of common communication and navigational aids found  on aircraft. The breadth of avionics is so wide that discussion  of all avionics devices is not possible.  led to increased instrumentation and set in motion the need  to conquer blind flight—flight without the ground being  visible. Radio beacon direction finding was developed for en  route navigation. Toward the end of the decade, instrument  navigation combined with rudimentary radio use to produce  the first safe blind landing of an aircraft. In the 1930s, the first all radio-controlled blind-landing was  accomplished. At the same time, radio navigation using  ground-based beacons expanded. Instrument navigation  certification for airline pilots began. Low and medium  frequency radio waves were found to be problematic at  night and in weather. By the end of the decade, use of high- frequency radio waves was explored and included the advent  of high-frequency radar.  In the 1940s, after two decades of development driven by  mail carrier and passenger airline requirements, World  War II injected urgency into the development of aircraft  radio communication and navigation. Communication  radios, despite their size, were essential on board aircraft.  [Figure 11-2]  Very high frequencies were developed for  communication and navigational purposes. Installation of the  first instrument landing systems for blind landings began mid- decade and, by the end of the decade, the very high-frequency  omni-directional range (VOR) navigational network was  instituted. It was also in the 1940s that the first transistor was  developed, paving the way for modern, solid-state electronics. Civilian air transportation increased over the ensuing  decades. Communication and navigation equipment was  refined. Solid-state radio development, especially in the  1960s, produced a wide range of small, rugged radio and  The history of avionics is the history of the use of electronics  in aviation. Both military and civil aviation requirements  contributed to the development. The First World War  brought about an urgent need for communications. Voice  communications from ground-to-air and from aircraft-to- aircraft were established.  [Figure 11-1]  The development of  aircraft reliability and use for civilian purposes in the 1920s  History of Avionics 11-2 Figure 11-1.  Early voice communication radio tests in 1917.  Courtesy of AT&T Archives and History Center. 