Cabin Electronics: What’s The Best Way to Upgrade? (Part 2)

Ken Elliott reviews cabin electronics upgrades, with a focus on retrofit. Having previously discussed the planning phase, this month we consider the integration of new cabin systems into an aircraft…

Ken Elliott  |  19th August 2020
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    Ken Elliott
    Ken Elliott

    Ken Elliott is a veteran with 52 years of aviation experience, focussed on avionics in General and Business...

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    Lufthansa Tecknik Nice CMS installed in Bombardier Challenger 350 jet

    Integration of cabin systems is a complex affair and it may be best not to assume anything when dealing with it...

    There is a popular mantra used in aircraft certification that fits well with cabin integration – this is the double step of verification and validation.

    Verify and Validate…

    Regarding cabin systems, determine what it is you are aiming to achieve, provide and install it, and then test it against all of your targets. This is the verification. What you were aiming for will be validated when you know all of your targets were completed as you had intended.

    While this may sound straightforward enough, you would be surprised how many times there’s a disconnect along the way either because something was misunderstood or it was overlooked.

    For cockpit systems, it is common to have tried and tested integration data, but even for complex Cabin Management Systems (CMS), there will be a lot of untried customization involved. Be sure to include every custom item in your validation check.

    OEM vs Non-OEM MRO

    Assuming the work is neither an aircraft Original Equipment Manufacturer (OEM) upgrade nor a simple install, there are likely to be specific technicalities that are aircraft type and serial number-specific for an avionics shop to understand, when working within the cabin.

    An OEM designs and develops a cabin interior over months or even years, working back and forth with vendors. Their designs are intended to be offered as several options on all aircraft of a single type. To refurbish and improve the cabin later is an easier process for those who hold the design data.

    Non-OEM Maintenance Repair Organizations (MROs) can struggle to acquire data and existing records for an interior completion. That is a disadvantage but (on the other hand) their nimbleness, flexibility and capability to provide unique custom upgrades is well understood in the marketplace.

    Customer Engagement

    For customers struggling to understand the complications of upgrading their cabin electronics and systems, there is a gap between what is sold as the product and its integration. This gap is exacerbated within the MRO when sales, engineering and installation teams have different perspectives on the finer points of a project.

    That is why it is so important for the customer to be represented and embedded within the MRO before, during and upon delivery of a cabin upgrade. Even the best of facilities reveal gaps where brochure promotional features do not quite match up to reality.

    Just as customers need to be involved in planning, they also need to engage during all steps before the aircraft moves into the hangar at the MRO.

    Even a site visit may be wise to work through the project with an onsite team before a deposit is paid (especially when multiple MRO disciplines are to be involved).

    By monitoring the installation of a project both beforehand and while it is in process, the progress is regularly verified and validated to the intended design. Just a simple matter of an incorrect switch location, or an outlet at the wrong place in a dado panel, can emerge as an in-flight headache for the owner. Sometimes installers are unable to fully grasp ergonomic considerations because they are not flying in the cabin themselves.

    For a typical cabin electronics upgrade the customer should be continuously engaged. Figure A (depicting the Customer Engagement Cube) shows at least six touch-points before, during and after a project. Allowing for delay and schedule change.

    What are the disciplines of the MRO that will be involved in your aircraft upgrade?

    • First, it is likely the potential lengthy downtime will entice you to include other work. (This may extend to engine, accessories, airframe and paint work, so imagine the coordination required to make that happen.
    • Then consider the juggling required, if just one of those disciplines incurs a delay, a problem, or an unanticipated change in work scope.

    Third Party Involvement: A significant consideration for downtime (and other aspects), will be third party work. A great example during a cabin upgrade is plating. If you change or modify a switch panel, it will invariably involve some type of plating to match the existing trim. Plating is usually an external service and requires scheduling.

    Another example of third party involvement is certification. Most shops have onsite certification capability, but some require outside expertise. Larger MROs need to serve satellite facilities (where your aircraft may just happen to be). Certification personnel will need to schedule their visits and travel to the site.

    If a project is delayed for any reason, there may be a scheduling conflict to deal with.

    Mitigation of Surprises: Experienced customer representatives know to allow more time for a cabin upgrade than that suggested by the MRO. They also know to be flexible when things just do not work out as planned. They know that it is wise to have a backup aircraft or an alternate plan ready for several days after the intended delivery date, just in case.

    An installation may be finished on time, but it could then exhibit delivery issues during verification testing. While owners and their representatives do not like surprises, especially when they involve bad news, monitoring progress on-site mitigates that possibility.

    The Integration Team

    An average corporate aircraft cabin upgrade requires the skill-sets of several experts in an integration team and not one of them is any more important than another. Following is an example of an integration team you can expect to be involved with your aircraft.

    Avionics Sales Manager: This person, having sold the product, will ‘own’ the project. Customers may have questions suitable for the aircraft integrator, but they will ask the sales manager because that person is their contact, relationship, comfort and trust point in the deal.

    Avionics Installers: The installers assemble wire harnesses, run and terminate them in the aircraft, mount the hardware, and then verify their work to engineered prints.

    Sheet Metal Mechanics: Cutting and shaping metal and other material to accommodate changes, the sheet metal mechanics will work from detailed structural drawings.

    Interior Specialists: Designing and making changes to – or adding new – interior materials and hardware, interior specialists may add switches, panels and lighting (for example) to Personal Service Units (PSUs), woodwork, bulkheads and other surfaces, and alter carpets as well as sidewall/baggage lining.

    These specialists and other team members will also participate in the Removal and Reinstallation (R&R) of existing/new interior. They will work to a schedule, so that nothing is reinstalled until it needs to be, preventing potential damage.

    Avionics Repair: Because they are skilled and qualified, it is common to involve avionics repair shop personnel in checking out the final installation. Typically that includes testing existing systems, updating databases and undertaking inspections if added to the cabin tasks.

    Engineers: There are two design engineering disciplines involved in the cabin upgrade. These are electrical and structural. Both will work closely together and will be tied into the integrators on the team. The engineers create prints and drawings from which the integrators craft their work. 

    Engineers are versed in what you can and cannot do, based on regulation, standard practice, and sometimes experience. Because the engineer designed it, you will often find an engineer in the cabin during final testing.

    Certification: Those who certify often originate from an engineering role, as (for example) does the Designated Engineering Representative (DER). They have the final say on approvals and without their early buy-in to the project, the process can unravel very fast.

    Major installations include periodic certification reviews for this very reason. During a Supplemental Type Certificate (STC) project reviews are used as milestones, both for the MRO engineering and the certification authority from the aircraft’s country of registration.

    Customer Service Representative: The liaison person between the integration team working on the project and end customer representation, this person may not be an avionics or systems expert, but they play a crucial role in communicating the progress of all tasks being undertaken, any issues that arise and delivery arrangements.

    The integration team needs to work together, collaborating on a daily basis, supported by regular progress meetings. Other disciplines will tie into the Integration Team as needed, such as paint specialists for touch-up and external paint refinish after an antenna installation.

    How Does a Cabin System Installation Typically Progress?

    Preparation: After the initial contract for a cabin upgrade has been finalized, with dates established, it is strategic to focus on ordering equipment or parts with a long lead time. This is also the time to line up the certification team and schedule third party requirements of any kind.

    It may take some time for engineering to complete their work, because of priorities and workload, but it will be helpful to conduct a few early meetings to ensure time sensitive work and materials are prioritized.

    Installers look for pre-build harness and structural instructions. These come out of engineering, so there is always a certain amount of pressure on designers to perform well ahead of aircraft input. Today, it is common for MROs to use harnesses that are custom manufactured to satisfy most of their pre-build needs. This frees up hard-to-find installers, allowing them to concentrate on in-house projects.

    For the customer it is helpful to understand the overall preparation process. This ensures you will be listened to, respected for your knowledge, and understood later on.

    Input: Upon the arrival of an aircraft it would be a smart move for the MRO to do a thorough incoming inspection before any work commences. The facility needs to know the actual condition of the interior and functionality of cabin systems, especially those that will remain.

    Make sure there are photographs of everything before opening up an interior or removing existing systems. Include pictures of all equipment, switches and controls, wire runs, circuit breakers, relay and junction panels. The facility should immediately relay all findings relating to the incoming inspection to the owner. This is the time to discuss additional work and cost, not half way through the project.

    Pay Special Attention to: One area that deserves particular attention is the location of antennas and anything related to bulkhead feed-throughs. The former can turn into a major structural engineering issue very quickly. The latter, involving wire runs, can impact both structural engineering needs as well as harness pre-build.

    • Antennas: These need to be free of electromagnetic interference from other antennas and devices. To relocate an antenna requires several engineering and structural considerations, all of which can impact downtime and cost.
    • Structural Bulkheads: Regarding the bulkhead work, one cannot punch a hole for routing anywhere they wish. Fuselage bulkheads are considered primary structure and receive special attention when their structural integrity could be compromised. The location of wiring and other feed-throughs must be carefully evaluated.

    In Progress

    Any project, however small or large, should include milestones. These provide the aircraft owner with clues as to potential delays. Remember there are several ongoing parallel activities besides the project integration itself. These include:

    • In house interior modification or paintwork
    • Third-party modifications, service and upgrades
    • Equipment and parts delivery
    • In-progress engineering (included changes)
    • Other aircraft inspections, service and repair work
    • Certification

    Customer representatives cannot always be on site, so it may be difficult to closely monitor progress. Continuous noticeable activity should be apparent on the aircraft or a good reason provided, as to why not. Facilities will move technicians and installers between various hangar activities for all sorts of reasons but, understandably, for each customer their own aircraft will be the highest priority.

    Most major MROs have rooms available for daily use by customer representatives while an aircraft is undergoing work. Representatives who find a way to conduct their business using these offices will have an advantage within the MRO.

    Completion and Delivery

    Upon completion of the integration tasks, there are three groups of interrelated activity to accomplish, including:

    • Certification
    • Checkout
    • Reinstallation of Interior & Delivery Preparation

    Certification: There are two sub-phases to certification; system validation and aircraft release (Return to Service). System validation typically employs engineering DERs, including third party personnel, while aircraft release involves the inspection department who are focused on the aircraft as a whole. Their release is final and is subject to a satisfactory sign off from the DERs.

    Checkout: The function testing or verification of systems installed or modified is termed ‘checkout’. Everything needs to be programed, function tested to the manufacturer’s specifications and recorded as meeting all airworthiness requirements.

    Checkout may include both ground and flight test phases, even for a cabin modification. Good examples of why flight testing a cabin upgrade is a good idea include:

    • Antenna installations or relocations for flight performance and no interference.
    • Bulkhead feed-through integrity (re. possible loss of pressurization).
    • Cabin systems performance in flight compared to on the ground.
    • A check for potentially loose interior items by exercising cabins during flight.
    • Exercising satellite and air-to-ground technology.
    • Ergonomics are best evaluated in flight.

    Reinstallation of Interior

    Reassembling the cabin, followed by delivery preparation, should include customer participation as much as possible. Often aircraft are delivered with either something missing (not safety- or aircraft release-related), or assembled not as existing. Having the client’s eyes on delivery progress can be very beneficial as a collaborative effort.

    For the delivery itself (and if flight testing) pilots will also need to be on hand. This is the golden opportunity to familiarize the flight crew with all cabin changes since they are the ones who are questioned on system functionality, limitations and any idiosyncrasies during trips following delivery.


    The actual ‘ins and outs ‘of certification are complex and can be challenging for an operator to comprehend – so trust and patience will be an asset. There are many documents to complete, and many approvals to seek. Table A offers a sampling of these, but is by no means comprehensive.

    Further, if an STC is required the certification becomes a whole different matter. An STC will drive both downtime and delivery. It involves multiple steps and milestones which are closely monitored by the airworthiness authority or their designated representatives.


    Finally, because of future features and customer requirements aircraft may be delivered as ‘provisioned’. This implies a partial state of completion where an aircraft is provisioned with the intent that an MRO will not need to open it all up again to complete in the future.

    This generates a specific approval and, in essence, nothing provisioned is allowed to impact anything existing, requiring unterminated wire runs, with no new equipment or components installed. Alternatively, if an aircraft arrives provisioned, be sure to check it is as represented. Missing any discrepancy here could be an expensive oversight.

    In Summary

    For cabin electronics and system upgrades, there is a lot to consider. The best advice is to stay engaged and never assume. For the purpose of this article, a moderate cabin upgrade, conducted away from the OEM, is highlighted. OEMs may use tried and tested SBs and other standard processes to upgrade cabin electronics. They will have greater familiarity, with both the airframe and the existing cabin, as designed.

    Staying one step ahead of any installation mitigates surprises for both owner and operator. 

    Equally, an owner with knowledge is more likely to understand where problems can arise, allowing for them by building in additional downtime and cost ahead of time.

    Many legacy aircraft have been transformed by thoughtful cabin refurbishments that include an upgrade of their electronics and features. These improvements are truly worthy of consideration, injecting new life into pre-flown aircraft. They can be a rewarding experience if the simple protocols of planning and installation oversight are followed.

    Do you have a specific aircraft maintenance, upgrade or repair need?

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