It has not been all that many years ago where many considered electrical systems in aircraft more of a convenience than a necessity. After all, information required to fly could be obtained without the use of wires and electron flow. Instruments used to display speed and altitude were powered by actual air pressure changes and gyroscopic indicators were driven by a regulated air flow. Aircraft direction was determined based on orientation to the earth’s magnetic field via a compass and even take off and landing ques could be obtained through light signal.
Back then passenger amusement was derived by looking out the window at the shrinking sights below as the aircraft climbed ever higher into the atmosphere. In fact, considering all the transcripts and articles I have perused over the years concerning the Wright Brothers, I don’t recall any reference to cabin entertainment systems, communicating with satellites, or even use of digital data.
Reverberations of newer technology are being felt throughout our industry with many of our constituency being forced into the roles of computer network engineers, developers, and technicians. Flight crews not familiar with the ins and outs of microprocessors don’t realize the dilemmas encountered when actions are attempted prior to completion of a system boot up cycle and many a maintenance technician has been lead down an erroneous path while trying to interpret digital diagnostic systems.
Our maintenance repair organizations (MRO), being on the front lines, frequently take the brunt of the frustration as they often handle older aircraft which are being retrofitted with new generation systems. Often equipment manufacturers are more in tune with having their systems installed in bulk by airframe manufacturers on new aircraft and are not all that interested in supporting the one-off installation in an older machine. Certification these days is often more involved than in years past particularly if the planned equipment has not previously found its way into a specific type or like kind aircraft.
More of a necessity
Aircraft electrical systems have evolved into a necessity and even more so today with the advent of “fly by wire” flight controls, power by wire throttles, and even electronically controlled wheel braking. In the case of transport or business aircraft that now have the ability to circumnavigate the globe with as few as three stops, keeping the passengers amused and occupied now requires more than a newspaper and in-flight movie.
Many of the trends driving home or office electronics have been working their way into aviation with part of the dilemma being the end users do not always understand limitations may be associated with certain equipment being operated at 45,000 feet while traveling 85 percent the speed of sound. In other words, surfing the net may be a different experience in an aircraft than sitting in the local internet café.
Technology is associated with advancement and implementation of electronics in aircraft which does provide significant benefits including weight savings along with equipment made up of few moving parts theoretically reducing maintenance costs and improving longevity. Incorporating new technology does, on occasion, provide challenges.
Transport category aircraft certified in the United States are intended to be designed and manufactured in compliance with Federal Air Regulation (FAR) Part 25 and with the onset of the digital age, an addition to certification criteria was needed. Subpart H was created late in 2007 and is titled “Electrical Wiring Interconnection Systems” or just EWIS. Information covers electronic equipment installation, routing of wires, termination, connectors, and even shielding.