Basel-based AMAC is renowned for its completions and MRO work across a wide range of business aircraft, but perhaps best known for its spectacular large-jet work, focussing on airframe sizes from ACJ/BBJ, right up to the 747‑8. No different to other major players in the industry, while it welcomes its customers’ aircraft for maintenance checks, AMAC typically also performs other tasks, often depending on the depth of maintenance required and frequently involving cabin refit and a connectivity upgrade.
The company’s expertise extends to supplemental type certificate (STC) work and the list of its most recent STCs makes for interesting reading; of 12 awarded since the beginning of 2017, half involve antenna installations. Of these, four relate to Honeywell’s JetWave antenna, serving Inmarsat’s Jet ConneX, and the remainder cover the Rockwell Collins Tailwind unit for receiving satellite TV services.
The design, engineering, installation and test effort required for each of these STCs represents a serious effort, yet Gunnar Jancke, Director Quality Assurance & Design Organisation & CVE, AMAC Aerospace Switzerland, reckons it constitutes perhaps just 5% of the company’s MRO programme. “Most of the 100 people in our engineering department are working on two A320neo projects, one of which is arriving later this year and the other in March 2019. We also have a 747-8 programme running, in which we’re performing work similar to that which we did on a Dash 8 we delivered in 2015. So, all in all, we have three major ongoing programmes and the antenna business is effectively a ‘side-effect’ of our other work.
“It’s about supplying connectivity to the cabin, primarily through Inmarsat’s Ka-band Jet ConneX. I recall L-band satellite communications first becoming popular on aircraft around 2000, when we began fitting the large flat antennas – we called them ‘surfboards’ – then required for L-band service. Their principle of operation is similar to that employed today.”
As far as the antenna is concerned, the source satellite is little more than a distant ‘pinhead’, but given data about the aircraft’s flight attitude, the antenna control system steers the unit onto the satellite, either mechanically or electronically, maintaining the communications service as the aircraft manoeuvres.
The JetWave antenna shape is quite different to that of the earlier surfboards, being far closer in appearance to the dish antennas familiar from domestic satellite TV services. “They have quite a volume, with a typical installation being around 350mm high, 1,000 wide and 2,500mm long. Today, almost every large VIP aircraft actually has two satcom connectivity systems, served by a surfboard radome and a bubble radome for Ku or Ka-band.”
Tuning In
The work involved in such a large modification is extensive, but Jancke plays it down. “I think the OEM has a far larger task,” he jokes. “From that perspective ours is just a small, local modification, but the structural integrity and where we place the antenna have to be carefully engineered and calculated. The aerodynamic load is typically modelled on a computer and we also have to consider icing and birdstrike.
“Testing for the latter varies, depending on whether the antenna is in a forward or aft location. We consider what would happen if the forward portion of the radome was destroyed. Would the aft section remain in place? What would happen to the antenna itself? Might it be ripped away and hit the aircraft’s tail? For birdstrike tests we use a fuselage section, typically cut from a scrapped aircraft and equipped with a radome – they’re part of the certification requirement. We’re just now seeing EASA and the FAA accepting computer simulation as an alternative to physical birdstrike testing.” It’s an effort typical of aviation safety requirements and certification, proofing an installation against an unlikely yet potentially catastrophic event. Has Jancke ever heard of such an incident? “No. There’s been no birdstrike on a large radome that I know of.”
The STC process begins with a customer requirement, but there’s a degree of carry-over from one aircraft type installation to another. AMAC’s first JetWave STC was for the 737-900 and its next equipped a 777-200, before it moved on to the A340. Jancke says there’s a particular design philosophy for Boeing and Airbus types, but the real commonality between installations is in the ARINC 791 specification.
“It was developed to enable interchangeability between large antennas, and the Ku and Ka systems vendors all employ the standard to some degree. The ARINC 791 concept defines seven fittings, including a baseplate for the antenna and steering assembly, and a radome attached to the baseplate. The gap between the two is closed by a skirt. It provides us with a good starting point for every STC.
“When the STC regulations were defined, EASA and the FAA acknowledged that there was a business case for an organisation like AMAC to market STCs to other companies. We therefore distinguish between single and multiple STCs; it makes sense for us adopt the multiple STC concept for our antenna installations and we build that requirement into the data package for each. It means we can sell the data package, the installation package, to any Part 145 organisation, for application away from AMAC. We’ve also specified a tool for the sheet metal work and it sits ready in a transport container ready for other MROs to use.”
The STC system also works well between aircraft subtypes. Since that first 737-900 JetWave aircraft, AMAC has worked on installations for 737-700 and -800 airframes, in each case applying for an STC amendment, rather than a completely new set of paperwork. The amendment covers differences between installations, including location, since antenna position needs careful consideration with varying fuselage length, so as not to cause centre of gravity issues. It has important consequences for the Boeing 737s, as it does for the A319/320/321 and even the 777-200/300.
Functional ground and flight testing are integral to every STC, including those covering satellite communication equipment. That AMAC has the capability to perform this work in-house says much about it, especially given Jancke’s assertion that antenna installation represents such a small proportion of the overall business. So what else is involved?
“For a first STC we reckon on six weeks downtime for the aircraft, but only three weeks for an existing STC. We put scaffolding alongside the fuselage and we’ve built our own working platform, which goes across the top. It enables two or three engineers to work in parallel, taking the tools and materials they need up with them.
“We also clear the cabin area below the antenna site and introduce a platform from which people can reach the fuselage crown. It means our sheet metal workers can operate inside and out simultaneously. We complete the job as efficiently as possible, easily fitting it within the timescale of a C-check, but with multiple STCs it’s down to how clever the MRO is in packaging the tasks. Ultimately, we ensure the work is completed within the downtime agreed with the customer.”
Antennas aside, the generation of STCs on-spec, as additional offerings to customers and other Part 145s, seems a potential money spinner for a company of AMAC’s capability. Jancke does not entirely dismiss the concept but admits the volume of work currently occupying his department means he has no resource available for such developments. Conversely, he points towards another STC of which he’s particularly proud, covering the first installation of a SmartSky antenna.
“SmartSky is brand new and we had the opportunity to develop the first independent STC for it. SmartSky is now rolling out its air-to-ground network, achieving connectivity through a new Wi-Fi like technology. The company achieved an STC for its own test aircraft, but we had the opportunity to fit the system on a BBJ1 used by Boeing executives and as a demonstrator. We completed the work last year but haven’t yet been able to test the equipment. We anticipate sending a team to the US in June or July to activate it – for us it represented an exciting opportunity to be involved with a new technology at the outset.” In fact, it’s a development that seems entirely in keeping with AMAC’s STC and business philosophy in general.