16 minute read
Understanding BizAv Avionics: Cabin Systems
Ken Elliott concludes his series on the basics of Business Aviation avionics with a look at how today’s cabin systems work in tandem with an airplane’s other avionics…
Over several articles we have covered the ins and outs of avionics in business aircraft, where it may be relevant to an aircraft owner, operator, buyer, or broker. Here, we conclude the series delving into the core category of aircraft Cabin Systems.
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The area of Cabin Systems joins four other avionics categories discussed, including Communication, Navigation, Surveillance (CNS), and Interactive, all of which applied to the aircraft cockpit, remote equipment, and the pilots. Cabin Systems are specific to passengers and cabin crew.
In the case of ‘Interactive’, there is some connectivity between the cabin and the cockpit that will be addressed here.
In the cabin there is an overlap of trade responsibility, in that some electrical aspects (lighting, galley and environmental control) are under the purview of avionics. For the purposes of this article all cabin electrical, communication, entertainment and electronics will be assumed to be ‘Cabin Systems’. The Cabin Evolution
Providing an insight into some of the evolutions of cabin technology, Figure 1 (overleaf) demonstrates changes on several fronts. For each, the development has occurred exponentially, providing increased capability, reliability and options for the cabin experience. Overall, there is now greater connectivity, allowing passengers to function as they would in their office or home.
Another evolution is an ability to ‘wirelessly connect’ within the cabin, saving on wiring and equipment. This has further permitted the use of personal electronic devices (phones, iPads, laptops and more) to replace onboard devices and stored entertainment.
Flight departments have different approaches to the cabin experience, which is essentially driven by budget, the primary purpose of the aircraft, where the aircraft will operate, priorities within the cabin, and security concerns.
It is common for flight departments to limit the cabin experience, thereby reducing cyber exposure. Connecting the passengers to a head office intranet or corporate IT network has its risks, and especially the
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Some of these concerns, and others, have applied braking to cabin systems evolution. As with cockpit systems and anything aircraft-related, the clock moves cautiously forward, ensuring safety and reliability compliance.
One specific and current example of a cautious approach is the ongoing concern of potential interference from C-band 5G internet, to be introduced soon by AT&T and Verizon for terrestrial applications.
The radar altimeter is a crucial navigation device on the aircraft, and it operates on the same frequency as C-band 5G. If the Cband 5G signal impacts the radar altimeter signal, the measurement of aircraft height above the ground may fluctuate, which could have disastrous consequences for the aircraft.
Because of this issue, heads are now locked in discussion and the US implementation of C-band 5G is on hold.
For many years there have been interference concerns when operating Bluetooth or Wi-Fi routers within the aircraft, relating to potential interference with existing aircraft electronics. Airworthiness authorities have spent years evaluating, and steadily approving, the various applications of these technologies within the cabin. Legacy versus Current Entertainment Systems
Figures 2 and 3 (below, and opposite) shows the evolution from simplicity to complexity in cabin entertainment and features. The evolution is primarily from disparate, to integrated, equipage and the use of common elements for many functions, such as a cabin data bus, touch-screen control panels, and fewer Line Replacement Units (LRUs) scattered throughout the airframe.
Interestingly, more recently the introduction of wireless technology is allowing a reduction of complexity, especially as personal devices are permitted to control multiple cabin functions.
Figure 2 depicts a typical arrangement from the 1980s or 1990s. It looks busy but is simplistic in how it lacks integration, with limited equipment and capability.
Figure 3, meanwhile, shows a typical arrangement found in modern business jets today. Although it still appears busy, it is more integrated, with significant capability and less onboard equipment. It also needs less wiring and fewer ‘Happy Boxes’. The ‘Happy Box’, as it is known in the
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industry, is for the purpose of interfacing and converting information between incompatible systems and their functions.
Note the way that nonentertainment cabin functions are shown as one output. This can be one data bus offering multiple selections for multiple cabin systems, such as temperature control or lighting.
In the last century it was common for new aircraft to be delivered with sparse facilitation for passengers, only for necessary items to be added later by third parties (and then several more times over the life of the aircraft).
Today’s business aircraft are likely to roll off the production line with an all-inclusive suite of cabin electronics, often from the same manufacturer that provided the aircraft’s CNS avionics equipment. This suite will be fully-integrated within the cabin, and to the CNS as needed, including to the Satcom, and for cockpit internet or data access.
While one evolution of cabin avionics is from independent to integrated, another is the replication of the home office and home theater. The latter includes the onboard use of personal devices and laptops, sourcing and routing entertainment or the virtual office experience to installed cabin avionics. Methods of routing include wireless Bluetooth and wired HDMI.
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Cabin Evolution: The Role of Passenger Expectation
The cabin evolution includes the ever-changing expectations of passengers. Apart from the ‘new and novel’, there will be a different experience anticipated for privately-owned aircraft and for fractional, managed, chartered, or leased aircraft.
If the aircraft is not solely used by one owner or corporation, it is likely to be more generic, less complex, and (especially) more intuitive, enabling an easier interaction for different flyers’ experience. Non-private owners look for less that can break, be damaged, or misused.
Another decider in cabin equipage is driven by the intended operation of the aircraft. Continental (North American) operations will be less reliant on satellite connectivity, preferring the less expensive and widely available Air To Ground (ATG) method of connectivity.
For aircraft flying oceanic routes, a Satcom with voice and data will be necessary. To enable streaming video, the satellite system will need to support the broader bands and
faster speeds required.
Table A (right) presents available and future cockpit and cabin connectivity services, with large Low Earth Orbit (LEO) constellations coming online soon. There will be several ‘large LEO’ offerings from Boeing Satellite’s Vband, to Space X’s Starlink, to Amazon’s Project Kuiper.
Pre-Owned Aircraft Cabin Systems
When purchasing a pre-owned aircraft, a cabin configuration resulting from several previous overlaid upgrades can be challenging to face. Here the buyer may find switches appearing to control nothing, or an illogical match between seat positions and controlled audio-visual features, or even unresolved functionality issues.
When undertaking a pre-buy inspection, take a good look at all cabin systems. There should be no unmarked switches, and all of those that are marked should match their intended function.
For any pre-buy cabin inspection, create a checklist. The list should consider:
• Functionality • Physical • Cosmetic • Ergonomic and • Environmental aspects of the cabin.
Walk up the airstair and simulate a typical flight as though you were the owner, a passenger, and then as cabin crew. For each there will be different features, functions and priorities to consider. All systems should perform as each operator would expect. Here are some examples:
Owner: Check that the overall functionality fits the expectation. Does the cabin experience feel right? Does the cabin arrangement match how you, your family, or your business team expect to experience a flight? Can you control what you need or want from each seat? Passenger: This is where the role of the aircraft must be clear. For example, will the passengers be regular flyers, or is the aircraft to be managed, chartered, or leased? Will flights be long or short in duration? Are flights domestic or international?
The overall cabin configuration must be intuitive and adequate for each passenger, aligned with where, and how the aircraft is intended to operate.
Cabin Crew: If there is to be cabin crew, is the jump-seat and galley configured correctly? How does the cabin crew communicate with the cockpit, and to each passenger? Is the galley providing the services necessary to meet the expectations of each passenger?
For these scenarios, a prepurchase inspection should establish the serviceability of every function.
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Cabin Systems in General
When surveying an aircraft, check for potential obsolescence. A major headache for some larger legacy jets, is the lack of continued support for cabin systems. Either the system manufacturer is no longer in business, or the product line has been discontinued.
Seat and zone switch-panels are perhaps the biggest victim of obsolescence. There are solutions available, but look for those that are virtual plug and play replacements.
Do not blindly accept the promise of ‘plug and play’, however. The reality with every upgrade is the potential need for additional parts, equipment, labor, and wiring – because aircraft are different to each other.
While the model of aircraft can indicate identical equipage, differences occur between groups of serial numbers. While ‘plug and play’ may apply to one range of serial numbers, it may not apply to another, because the aircraft OEM elected to change the cabin arrangement at some point during the production run.
As with cockpit avionics, cabin systems are ‘suite-like’ for new aircraft. It is not unusual to find most of the cabin electronics integrated into one package, installed on the production line, during ‘green aircraft’ completion.
In these instances, it can be difficult to integrate your own favorite feature as an add-on to the cabin. However, integrated solutions do come with several options that are selectable from completion menus.
One newer technology that seems to work around the concern of integration limitation, is the addition of ATG Wi-Fi Internet (such as Gogo Business Aviation or SmartSky Networks). This is fortunate, as many business aircraft have delivered with complex integrated cabin systems, but without highly capable internet access.
These ATG technologies have their own external broadband antennas, and cabin Wi-Fi broadcast antennas. While they look for a GPS position and other aircraft performance information from existing onboard avionics, they mostly involve stand-alone systems. As a result, and because of their astounding performance and capability, they are a popular upgrade across many aircraft platforms.
FIGURE 4: Some Cabin Functions and Either New or Popular Available Upgrades
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For those already equipped, 5G capability is on its way. For Gogo Business Aviation that means an existing Avance L5 system, a Gogo X3 unit for 5G, and two MB13 5G ‘direct replacement’ antennas.
Size of cabin matters, with larger cabins having the flexibility of allowing independent zones. The seating arrangement drives the capability and the need for each main cabin sub-zone. Club seating will lend itself to conferencing with individualized controls. Divan seating will have common controls and limited selections.
Outside of the main cabin (seating), most medium and large business aircraft will have the following cabin zones:
• Vestibule as an entry area. Pilots and passengers transit the vestibule, and a jump seat is provided for a third crew member or cabin attendant. If installing Wi-Fi in an aircraft, with the forward location jump seat make sure the internet is available (especially useful for
Part 135 or 91K operations). • Typically, the galley and forward closets are situated before the main cabin. Some aircraft will have a forward lavatory. • Aft of the main cabin is a closet and lavatory with vanity. Many aircraft extend the cabin further with additional onboard storage for larger items. Specific Cabin Experiences
Specific cabin systems are many and potentially complex, and yet there is simplicity in the wireless, Wi-Fi, and Bluetooth capabilities that are in use today. Being able to walk aboard an aircraft with your own mobile phone, select your favorite music, and hear it over transducer driven cabin walls and ceilings (Bongiovi Acoustics Labs), is simplicity in action.
To use the same, or other, device to select a movie from the internet and connect via HDMI to a flat panel 4K monitor, is a further streamlining of activity. It also involves less wiring, switches, relays or adapters.
Figure 4 (above) depicts just five cabin experiences, highlighting some of the upgrades a prospective buyer can consider.
For many new aircraft buyers, by the time their serial number airframe is delivered, its technology may not have the latest cabin functionality. Over time, some manufacturers will offer software and hardware upgrades, or there may be options that can be added post-delivery. For many, it is certainly a challenge to remain current.
It may not be possible to upgrade your aircraft with some of the features represented in Figure 4, or you may need to request them from a third party. Aircraft manufacturers do solicit feedback from owners and operators in forums such as operator conferences. These are good opportunities to request or suggest cabin solutions you cannot have now.
In addition to those listed in Figure 4, a few specific, noteworthy upgrade paths to mention include:
1. Personal Service Units (PSUs) as novel, clean overlays (Duncan
Aviation); 2. Cadence switch panel replacements, general and customized (Alto Aviation); 3. LED lighting used for cabin data broadcast, as light fidelity – Li-Fi (Lufthansa Technik); 4. Wireless Avionics Intra
Communications (WAIC) opensource operating status of cabin electronics, including items such as galley ovens (Coming to aircraft cabins soon).
The Real Cabin Avionics System
Because modern cabin avionics are moving to wireless technology, there appears to be just a few switch panels and displays in the cabin, leading some to assume that cabin avionics must be an easy upgrade.
As there are many legacy aircraft in service and a shortage of new aircraft for eager buyers, it is worth considering a typical cabin avionics system on a not-so-new business aircraft.
In most instances, legacy cabin avionics is a mix and match of various sub-systems. Older VCRs, CD players, speakers, handsets, headsets, displays, lighting, phones, internet, and more, are removed, altered and upgraded at different service events and it is the resultant outcome hidden behind the veneer that is the reality of the overall system.
Because of engineering, design, physical limitations, power requirements, wiring and access, it is necessary to integrate new capabilities to existing technologies. Here are some examples of existing cabin technology:
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• Speaker and Phone Amplifiers • Power Supplies from Fluorescent
Lighting used for LED
Replacement • Relay Boxes and Hidden Devices that Convert Data, and Control
Existing Aircraft Systems,
Including: - Temperature - Galley Equipment - Reading Lights - Cabin Briefing - Passenger Address - Cabin Call - Water Heat - Displays - Airstair.
The passenger may only see side rail-mounted tactile switches, touchscreen control panels and displays, but behind the scenes there is significant integration. Here the translation of new technology to existing airframe, electrical, and avionics systems takes place; a translation of communication and action to equipment that is not being upgraded.
Different cabin avionics systems will have several features in common. An upgrade should consider the impact on, and between, all. For illustration, Table B (above) provides examples of the many cabin avionics systems.
In Summary…
An aircraft cabin in any business aircraft is designed to meet passenger expectations, and understandably these are high. Just as the look, feel and utility of interior furnishings is given maximum attention during design and build, so is the electronics. While much of the electronics is unseen to the passenger, it still needs work as advertised.
There is as much in the design and engineering as there is in the installation of cabin electronics. It only takes one small feature to malfunction or not operate as expected for an operator to become discouraged with the complete upgrade.
Pilot expectations revolve around safety first. Passenger expectations revolve around the experience within a safe environment.
By the time you read this article there will be innovations and novel features reaching into cabins, new and pre-owned, that were not covered here. Change comes fast to the gadget-hungry Business Aviation community, and there is no better place to find gadgets than within the cabin. Here the safety criticality and operational requirement is not as stringent. Flexibility of choice and features abound.
Certification is important, as with non-interference testing between Wi-Fi internet and existing aircraft avionics, but, overall, there is more leeway given to cabin certifications.
Like the cockpit, the cabin of today is miles ahead of yesterday’s; and tomorrow’s will be further ahead still. Expect more wireless capability, and an ability for anyone, anywhere to connect in several different ways to any passenger, and the wider world outside, at any time throughout the flight.
As speeds and bandwidth expand, and satellites fill the void, the world of IoT will extend exponentially into aircraft cabins. ❙
KEN ELLIOTT
has 52 years of aviation experience focused on avionics in General and Business Aviation. Having a broad understanding after working in several countries on many aircraft types and avionics systems, he has contributed to several work groups and committees, including for NextGen, Airport Lighting, Human Factors, Unmanned Aircraft and Low Vision Technology. In retirement, he is striving to give back the knowledge gained with an eye on aviation’s future direction.
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