Elliott Aviation technicians Jon Young and Cuc Tan perform system checks on an Airshow 410 cabin management system in a Hawker 800XP.
Photo credit: Photo provided by Elliott Aviation.
Once, it was considered supernatural to contemplate shedding the confines of the earth’s gravity. Sorcerers, wizards, and mythical beasts had the power to achieve feats of controlled flight. In days of old, enchanted airborne journeys were full of peril with humans, willing or not, experiencing new sensations with no time during the journey for boredom.
When we reduced the peril associated with flight, the probability of passenger boredom increased. With mega-airliners carrying 500+ passengers 18-20 nonstop hours, artificial stimulants are required. The primary mission for those engaged in business aviation is to provide an airborne environment conducive to getting the job done while en route to remote corporate locations. Modern corporate aircraft can truly be considered a state-of-the-art boardroom in the sky.
The need to stay connected
Recent advancements in consumer electronics coupled with the need for many to always be “connected” has provoked the aviation industry into creating an environment where something other than a cold beverage and a bag of peanuts is required to keep passengers happy.
The concept of being connected while flying close to the speed of sound at 40,000 feet again conjures up visions of wizards and sorcerers. Keeping many of these technological wonders functioning does involve incantations (at least that is one way to describe the string of four letter words uttered when the equipment is reported to be out of order).
Expectations are driving the future of cabin management systems (CMS). Today, passengers can enter an aircraft cabin, log in to the aircraft network and start sending or receiving email while interacting with the cabin using an app on a personal electronic device (PED) to start a movie or switch on/off a reading light.
Many CMS being installed accomplish their magic through the use of software and communication systems connecting all the devices. Transferring digital data efficiently makes software and data storage possible in many of the remote devices. This philosophy lessens the number and size of control components but can make system maintenance challenging. As an example: if the cabin speaker audio control software is stored in a video monitor and the monitor has to be removed, then the speakers will not function.
Technician knowledge of system architecture is essential to sustain proper system functionality. System startup will require a time frame that can typically not be rushed. In many cases boot up sequences require a disturbance-free duration. Interaction during the system startup phase most frequently either delays initialization or causes the system to lock requiring yet another restart.
Digital data has been used in aviation for about 40 years and Federal Aviation Regulations (FAR) have been recently created to take into account installation and inspection techniques critical to digital data transmission. Electrical wiring interface system or EWIS has been included in FAR Part 25 governing transport category aircraft. This should be required reading for anyone planning for an EWIS compliant aircraft or even an upgrade to an existing cabin entertainment system. The FAA has published numerous training guides to assist in understanding the critical importance of aircraft wiring and treating it more like other systems when it comes to ensuring longevity. Several means are employed to transfer data between system components and Ethernet is one of the most common. Bend radius for a CAT 5 Ethernet cable is not referenced in Advisory Circular 43.13 but is mentioned in EWIS discussions. Unfortunately folding over digital buses and tying the excess back in the bundle is still a frequent practice. Another common mistake is overtightening wire clamps or cable ties surrounding coax cables and digital buses. Compressing multi-conductor cables can impact impedance resulting in data transfer issues. Specific cable tie pullers are recommended and even have calibration requirements to ensure compression does not occur with the cables being captured. In addition EWIS targets routing like cables together and discourages situations where power cables are collocated with data buses.
Wireless data networks are widely used in aircraft. Wi-Fi is a trademarked wireless data transfer standard developed by IEEE (Institute for Electrical and Electronic Engineers) and utilizes a relatively low power radio signal within the inhabited area of the fuselage that can be transmitted on several frequencies from 2.4 GHz up to 5 GHz with further band divisions within each frequency. Several factors can influence the quality of a Wi-Fi network. Antenna placement is key for reliable service. Should it be located behind certain metalized panels such as a honeycomb bulkhead, the radiated signal can be greatly diminished. External factors such as a microwave oven can cause interference on a Wi-Fi network. Bluetooth wireless devices have been found to corrupt Wi-Fi networks in aircraft causing slowdown in data throughput on 802.11 systems.
Wireless routers are more commonly being utilized in multiple roles. In addition to providing users access to the Internet through the aircraft high-speed data connection, they are also now being used to connect portable devices to the cabin control system. Many new and refurbished business aircraft provide a cabin control app to key passengers enabling them to interact with audio, video, and cabin environmental systems with a personal smart phone or iPad.
This convenience can create challenges as some tech savvy passengers may override selections made by more senior company officials unless protocols are put in place. In addition care has to be taken against hackers. In some cases cabin management systems can be linked to the high-speed data network to receive updates or for diagnostic purposes, and it becomes possible for a person on the ground and not even in the same hemisphere to change movie selections or otherwise mess with the passengers. The FAA has explored the possibility of hackers logging into aircraft networks and corrupting flight plans or interfering with aircraft systems.
The high-def reality
New generation CMS are doing their best to keep up with the rapid-changing consumer electronics market. Unfortunately with certification and regulatory concerns, once a new piece of equipment is approved for aviation, it may have lost much of its appeal to the technology savvy passenger.
Providing entertainment to passengers is high priority and streaming a new release movie at $10 per Mbit from the Internet while cruising at 40,000 feet may cost more than buying a theater ticket so the ability to preload and renew media for extended trips within the aircraft is a value to many. Concerns with copyright violations and media ownership are often a limiting factor for determining the type of movies able to be stored within onboard media devices. In many cases, passengers can bring their own via personal electronic devices (PED). Downloading several favorites from iTunes or even loading a business presentation prior to a trip onto an iPad and then connecting into the cabin system will allow passengers to share information making travel time both productive and relaxing.
Maintaining this equipment is a concern. Where does someone go to obtain “the knowledge” to support these systems? Primary training schools for aviation technicians typically address the curriculum required by airworthiness authorities. Ethernet and Wi-Fi are not included.
Looking at the big, probably high-def picture, as long as the CMS is working, passengers will be entertained. When the system malfunctions, it will be the All Purpose (A&P) aircraft technician who must fix it. I’m willing to bet that many of us are up to the task of keeping the magic alive.
Jim Sparks has been in aviation for 30 years and is a licensed A&P. His career began in general aviation as a mechanic, electrician, and avionics technician. 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. You can reach him at firstname.lastname@example.org.