Avionics Technology: Evolution or Revolution in the Cabin

Cabin management systems (CMS) have come a long way in the last few years. I still have vivid recollections of long nights in the hangar troubleshooting relay logic circuits trying to figure out why certain passenger lights wouldn't work or why the boss could not hear the VCR audio on the headset. Everything was two wire technology and testing was accomplished using a Volt Ohm Meter (VOM) or test lamp.

Many systems of today use digital technology and almost anything in the virtual world may become possible to replicate.

The term "cabin management" does not necessarily blanket all the capabilities that are achievable in aircraft of today. Most CMS do include lighting controls along with audio and video selections but the ways these functions are achieved can be revolutionary.

Back in the good old days it was easy to run a wire to a switch from a power source. When the switch was selected on, electrical current would flow to a lamp and if a ground was in place and electrical current flowed, the light would glow. Back then the best quality light would come from halogen lamps and of course accompanying the light would be an abundant amount of heat. It was not uncommon for a cabin accommodating nine or 10 people to require 15 amps of current in the cabin reading light circuit. This was supported by large diameter wires, heavy-duty switches, and lamps but the concept employed two wires; one for power and the other for electrical ground.

Now cabin lighting can be engineered to complement the interior furnishings. Light emitting diodes (LED) are constructed to operate at rather precise color temperatures emitting tailored glows to enhance the surroundings. Not to mention the fact that LEDs produce significantly less heat than their halogen counterpart and enjoy notably longer life spans while requiring significantly less current consumption.

The control of these lights is often accomplished through a digital network. Reading light switches along with other passenger service items are grouped in a removable switch panel which is electrically connected through a digital bus to some type of controller that when commanded will provide the desired current flow to the appropriate lamp. Even the old fluorescent tubes can be replaced by LED strips which can provide as much light without the frequent fluctuations and high voltage associated with this technology along with being much less susceptible to breakage associated with handling (or mishandling).

Relay controllers can include built-in diagnostic capability with indicators advising the state of the various internal and external circuitries. This almost eliminates the need for a test lamp as indicators are already in place to see if the remote switch is functional along with power into and out of the control box. Another valuable feature is the ability to access this diagnostic information without having to physically put your hands on the box. Technology may allow cabin monitors to serve as diagnostic displays and either laptop interrogation or password access can allow technicians to view first hand system operational status.

Audiovisual systems
Audiovisual systems are also supported by newer digital controls. In the age of iPods and other forms of electronic media access, having a CMS that is multifaceted can significantly enhance both passenger comfort and make the most of the office in the sky. Provisioning interface ports for laptop tie in gives the cabin occupants the ability to review and edit presentations while en route. Having this feature coupled to Internet access will enable the home office to have the capacity to interact with on board conferences so those chosen to participate in the mission will be armed with the most up-to-date information when they disembark at their destination.

CMS is not always intended to be strictly a business tool. Adding components such as Direct TV or a Blue Ray player can bring an element of fun to the cabin. In addition, several makers of premier audio systems can turn an aircraft passenger chamber into a virtual concert hall complete with sub-woofers and surround sound. Individual headsets, some with noise-cancelling abilities, can be tuned into any active iPod or even XM Radio when the aircraft is operating in or around North America. XM Weather can be presented to passengers and those with an aviation background will interact with the system through a computer mouse to select en route or destination weather.

Devices such as external cameras or infrared sensors provide those in the cabin with a sense of what is going on around them even on the darkest nights.

Maps displayed on monitors have gone from grainy and vaguely defined to those with the resolution of Google maps and may even incorporate street level or pilots eye views of the terrain beneath the aircraft.

Ergonomic features
The ability to control other ergonomic features is another possibility. It is now achievable to control cabin temperature and in some cases humidity from any seat position, and based on cabin design, separate temperature zones can be established and independently regulated. Of course independent temperature controls will only function as well as the airframe air delivery and recovery circuits will allow.

Potable water systems have been brought in under the control of CMS. Water quantity can easily be displayed along with system operating pressure and on/off controls for water heaters. Safety circuits are engineered through software that will turn off the water heaters automatically when the water storage tank is empty.

Various preset modes are custom designed to select various situations. A "boarding" mode will bring up a specific slide show on the video monitors perhaps showing a "welcome aboard" message along with a map illustrating the route of flight and a company logo where applicable. This mode may also engage specific cabin lighting and appropriate audio. A "movie" mode may dim select cabin lights and can also command cabin window shades to darken the windows against ambient light. The "night" or "sleep" feature can further reduce cabin lighting and may command designated night lights to illuminate along with automatically deploying berthing divans and driving motorized seats to a position conducive to supporting the body at rest.

One of the great features is maintenance access. A design plan that includes back doors will often be a life saver if required lights are inoperative and a normally hidden circuit can be initiated that will restore lighting through secondary controls.

The great thing about digital technology is that most of the common buses work on a two wire principal, almost like the old time reading light. What could be simpler than troubleshooting a pair of twisted wires?

One of the most desirable applications I see is the ability to interact with the CMS from an iPhone no matter where in the world the aircraft is flying. This is a tremendous asset to help stage parts and support at the destination even before the aircraft arrives in the event of a problem reported in flight.

Conceptually if someone you need to get even with is on a night trip and sound asleep on one of the electrically berthing divans which might happen to be located next to a highly amplified sub-woofer, you can make their waking experience very memorable from miles away.

Jim Sparks has been in aviation for 30 years and is a licensed A&P. Currently when not writing for AMT, he is the manager of aviation maintenance for a private company with a fleet including light single engine aircraft, helicopters, and several types of business jets. He can be reached at sparks-jim@sbcglobal.net.