Aviation: Systems Engineer Interview
The embedded design choices keeping In-Flight Connectivity fast and dependable.
Editor’s Note: What’s embedded can go unnoticed. So can video streaming, live television and Internet shopping, as long as users’ attention isn’t drawn to annoying delays caused by slower connection speeds. The problem of keeping connection speeds at a minimum of 5 Mbps for airline crew and passengers is one Thales Group has taken on. In mid 2017 the company will launch the in-flight connectivity service FlytLIVE. Kemi Lewis, systems engineer at Thales InFlyt Experience™ in Melbourne, spoke with EECatalog shortly after the FlytLIVE announcement. He shared with us the challenges specific to gaining and then maintaining the means to keep connection speeds fast, lengthen MTBF/MTBUR and come out on the right side of SWaP calculations.
EECatalog: What should embedded designers know about some of the specific challenges involved when building a connectivity solution aimed at commercial aviation?
Kemi Lewis, Thales: One factor to be aware of is the need for FAA certification of any hardware, depending on where that hardware is being deployed in the plane. When a plane is taken out of service to be retrofitted with new hardware, the FAA requires all the testing information before giving its approval to operate the equipment on the aircraft. Product management tools like Jama Software can help meeting this compliance process by ensuring everyone from the Product Team down to Testers are aware of what requirements must be met.
Lewis notes: “Our goal is to give you the same experience you have at home: fast Internet, TV, the ability to order items and find them waiting for you when you arrive at your destination.”
The other route is LineFit, where Boeing, Airbus or another aircraft manufacturer approves the product design portfolio of equipment from Thales or another OEM approved IFE&C supplier a year to 18 months ahead. The aircraft OEM, e.g., Airbus, Boeing, Comac, would then get the approval to use this equipment as a selection feature in any of its aircraft that an airline would choose to buy. Typically, those design requirements are much more rigorous. The design must be more ruggedized and have greater redundancy because OEM manufacturers have more critical requirements for what hardware and software is approved for use on their aircraft. This is another instance where using the Reuse feature of Jama Software shortens your product time to market.
EECatalog: Is there any degree of cross pollination or synergy between the military aviation and the commercial aviation sectors, particularly with regards to SWaP?
Lewis, Thales: Much of the time fully ruggedized military-grade hardware is past the price point for the low cost In Flight Connectivity market. And it might even be too expensive for the high end of the market. Hardware that is halfway between commercial and industrial/military occupies a kind of hybrid sweet spot—that is where we look to find COTS designs that we could either use straight off the bat or have the vendor do minimal customization.
Single Board Computers that are scalable and modular work best in the evolutionary life of a design, making it easier to upgrade a design that is already in service with minimal FAA requalification.
And when the new technologies come out in the consumer market, for example, USB Type-C, there is typically a two-to-three-year lag before that technology makes its appearance on an aircraft. It has to be certified for use on an aircraft. In addition, there is a Cost Of Scale, the more a particular technology is commonly adopted across the market that majority adoption drives down the price; it makes it more feasible to use the technology in question because there is more support for it. In a situation in which there are two competing technologies and there is no majority, the concern would be that the technology could go obsolete. Also, airlines tend to be skittish when it comes to new technologies coming out for which there is no proven pedigree—given it’s going to be in an enclosed metal box flying at 10,000 feet.
EECatalog: Could you speak a bit about the architecture that underpins your solutions?
Lewis, Thales: Starting from the top you have dedicated, fast, individual bandwidth pipes to each aircraft, so there’s no sharing. That allows us to guarantee 5Mbps or more to each passenger on the aircraft and even higher if they are accessing Amazon or Netflix.
We’re always looking for less power, faster processing speed, and smaller form factors. Anything we can do to reduce the overall design footprint (SWaP) of what goes on the airplane lessens weight and results in a fuel and cost savings for the airline.
To find a sweet spot, typically we lean more to the low power. Our hardware typically stays on the aircraft for five to ten years, so we are not looking for something that needs a massive amount of cooling or additional cooling outside the standard cargo bay environment.
EECatalog: Does that need for low power mean the processors would tend to be ARM processors?
Lewis, Thales: It all depends. We have used Intel in the past, we have used Freescale; it’s really dependent on specific applications. If it’s a server, it might be an Intel based processor; if it’s a box or smart display we might go with Freescale. It all depends on the environmental conditions of the location in the aircraft.
If it’s server that’s in the cargo bay you have a little more leeway, you can go with a processor that consumes more power and might need more cooling [as opposed to] something in the passenger seat where airflow is limited. Ideally you don’t want to use a processor that is thermal-hungry and putting out a lot of heat, causing the unit to fail at some point.
Especially if it is a wide body aircraft it might need a couple of servers to split up the workload so that the longevity of each box is extended because you have divided up the workload.
EECatalog: Cooling continues to be a challenge.
Lewis, Thales: I am hoping that given the roadmaps for different COM and SBC designs that cooling will be less of a limitation constraint for avionic designs.
But we are facing limitations. For instance in the cargo bay of the aircraft there is a maximum amount of airflow focused in that particular area of the aircraft—and depending on how many boxes the aircraft needs—and that is only accounting for the normal operation of the aircraft—now you have to factor in in-flight entertainment and Internet connectivity boxes into that area. So you are constrained there from the get go. That dictates the space allotment that you have, so you have 4 MCU limited to 100W of thermal dissipation. This thermal limitation combined with box size limitation demands that the processor have a fan or a fan and heatsink. Depending on what it must do for the application it can run hot. Given all those limitations it can curtail the life of your design, and the understanding is, “okay, this box in a typical real-world application might only last three years.”