With the mandate drawing ever closer, Ken Elliott discusses all the need-to-know aspects of ADS-B - concluding with a focus on aircraft integration…
ADS-B was developed to overcome the limitations of radar as a means of openly broadcasting and sharing key information regarding the in-flight intention of aircraft operations within the vicinity of Air Traffic Control (ATC). Not only can ATC receive useful aircraft data to better manage air traffic, but other aircraft can take advantage of the same broadcasted data, if suitably equipped with ADS-B In.
Currently most operators are being equipped with the ADS-B Out broadcast feature only, which is essential for air traffic management and is mandated to be installed by the start of 2020.
Somewhat ironically, it’s the smaller GA aircraft community (as opposed to the ‘heavy iron’ operators) that has embraced ADS-B In, taking advantage of its additional graphical weather features. ADS-B In is not yet fully defined in terms of what you will need to display.
Understanding ADS-B Out Equipage
So, what is the minimum equipage for ADS-B Out? In short, you need a certain category of Transponder and GPS along with some form of reliable fail annunciation. This all sounds simple enough, and for some it really is. But for many it becomes a significant aircraft integration project that is costly and time consuming.
Avionics OEMs (dominated by Honeywell Aerospace, Collins Aerospace and Garmin) figured out long ago that the way to succeed in aviation is to control the product evolution from beginning to end.
In other words, designing a completely integrated cockpit while at the same time limiting access to its software and communication platform by third-party vendors creates a good chance of preventing others from competing on the same aircraft platform and its derivatives.
This maintains a future-proof revenue stream in product improvements. The impact on ADS-B integration, however, can be significant for some operators.
Rather than simply add ADS-B Out to the existing cockpit avionics, the manufacturer might bundle it with a number of other features such as LPV-WAAS, Synthetic Vision, Graphic Maps, Weather and more. The upgrade is usually branded in some way and will involve software and sometimes hardware changes, impacting remote circuit cards, cockpit controllers and displays.
While there may still be some options to select within the branded upgrade, it is atypical to find an ADS-B Out solution available on its own. The industry argument for taking the OEM route for an ADS-B Out upgrade, is the possible impact to aircraft resale and conformity concerns of using third-party Supplemental Type Certificates (STCs) in countries other than where the STC was issued.
Understanding the ADS-B Out Solutions
A review of the 7,344 available ADS-B Out solutions on the FAA’s ‘Equip ADS-B’ website reveals a significant number of Approved Model List (AML) STCs in use.
AML is where an STC is completed on a ‘first of type’ aircraft, and because of similar equipage, minimal complexity and significant integration commonality, the applicant can add other types and models of aircraft to the initial STC. This makes it so much easier for completion centers and brings down solution costs dramatically.
When the solution is provided by an aircraft manufacturer and its primary avionics provider, it is commonplace to have the ADS-B Out solution incorporated into a Service Bulletin (SB). (Beware that some SBs assume that your avionics are already at a particular version of software and/or hardware.)
So, at first glance, it may seem that an ADS-B Out upgrade will be quick, easy and economical until you realize that in order to incorporate the SB – specifically created for ADS-B Out – you first need to upgrade your primary avionics for compatibility. This one, simple oversight can spell the difference between a lower-cost ‘ADS-B Out only’ upgrade and a much higher-cost avionics system upgrade.
To reiterate: The avionics system upgrade provides the minimal version of software and/or hardware, permissible for the added ADS-B Out SB to function correctly.
On the FAA’s ‘Equip ADS-B’ website is a list of equipment that pairs transponders to position sources. The position source (GPS) must in most cases meet the stringent accuracy and reliability criteria of ADS-B Out Version 2.
Solutions, including AML STCs, offer different pathways for pairing transponders and GPS position sources allowing for different solution cost, convenience and standard conformity levels of equipage.
Be sure to check that whoever is quoting your solution offers you choices. Sometimes these choices will not be cost-driven but can also be decided based on the availability of product and the downtime required for its integration.
As 2019 progresses, the timescales of product deemed ‘ready to ship’, and downtime, will become increasingly important.
For Business Aviation, most ADS-B Out solutions fall into two major categories:
- Those provided by the aircraft and avionics OEMs themselves, and
- Those provided by third parties.
The third party may be providing the STC and the kit, but not necessarily carrying out the aircraft work itself. Moreover, an OEM may provide its STC or SB to approved service centers or conduct the work in-house. Additionally, the primary avionics provider will separately upgrade existing equipment, or provide new. Equipment upgrades will take place in parallel with on-aircraft integration and can be a factor in the calculation of downtime.
Because aircraft have individual characteristics (due to custom completions) there is always a danger that the integration instructions and kits supplied by the ADS-B providers will not completely match up to the aircraft.
Understanding ADS-B Out (Version 2) Installation
Each ADS-B Out Version 2 installation requires an annunciation for ADS-B FAIL. This is a crew notification indicating a loss of critical broadcast information. The annunciator can be embedded in existing aircraft displays and enabled by a software update, or (as in the instance of many third-party solutions) it can be a stand-alone annunciator.
Third-party solutions will include the use of a ‘happy box’ – a small out-of-the-way electronic device that selects the specific ADS-B FAIL status information from each of the aircraft’s transponders, converting it to an analogue signal to turn on the fail annunciator. There are often two annunciators, one for each crewmember, to ensure the message is noticed right away.
Because the GPS position source is of a critical integrity and accuracy standard, it is common for the existing dual GPS receivers to be upgraded or exchanged. However, because of cost or availability, third-party solutions can offer a separate stand-alone and remote GPS that will meet the required specifications just for use with ADS-B Out. (Keep in mind this also requires a dedicated antenna requiring access to the upper fuselage from the inside of the cockpit or cabin.)
Ultimately, it is rare for an aircraft to need a third transponder to accommodate ADS-B Out capability. Most existing transponders are upgraded, exchanged or completely replaced.
Understanding ADS-B Out Installation Downtime
Aircraft owners tend to prefer to bundle their ADS-B Out upgrade with other maintenance or scheduled inspection work, and will often add Wi-Fi capability, now that this feature is becoming more like the home or office experience. Those operators needing to travel the oceanic or remote terrestrial tracks will also add FANS (Future Air Navigation System).
Integration can range from simple to complex. To help MROs keep the integration process straightforward, operators should provide factory custom prints, as well as prints for other third-party installations since aircraft delivery.
They should have readily available a current aircraft electrical load analysis (ELA) and a weight and balance report.
You should further provide the MRO with a current aircraft status report showing actual installed equipment model and part numbers, providing all of this well before the aircraft input to help ensure the downtime proceeds according to plan.
Given these variables, ADS-B Out downtime for a typical business aircraft can run from one week for a simple SB, to more than a month.
Operators should seriously consider using these longer downtime requirements to add paintwork and carpet replacement to the work scope. Moreover, adding wood refinish, cabin outlets and optional factory airframe bulletins can make good advantage of the aircraft being ‘opened up’. Smart MRO facilities know this and will have ‘beefed-up’ their interior and paint shops to accommodate the trend.
Understanding the ADS-B Out Post-Installation Process
After completion of an ADS-B Out installation the integration facility will test the system. This can be more complex than it first appears. In the US, the FAA offers Public Performance Reports (PPR) for operators and avionics shops. This allows for confirmation of a fully functional in-flight performance of the ADS-B Out system.
Because the FAA monitors flights in real-time, for those areas with ADS-B coverage, requests are ‘after the fact’ and can provide a useful set of data to the requestor, enabling them to diagnose possible anomalies or failures.
Known as non-performing emitters (NPEs), the FAA tracks them and notifies operators to ensure compliance. A common problem exhibited in NPEs is the Flight ID transmitted by an aircraft not conforming with the call sign registered with the flight plan.
For most business aircraft operators, the Flight ID and call sign are the same. This becomes an issue for commercial flights and special operations, however. Make sure the call sign is correct and then transmitted properly.
Following are some examples of NPEs as recorded by airworthiness authority monitoring:
- Invalid 24-bit ICAO address (Mode S)
- Flight ID mismatch
- Missing Mode 3–A Codes
- Emitter category in error
- Transmitting airborne data while on the surface.
Hardware configuration, often via strapping of transponders and other devices, is another common cause of failure.
ADS-B Out systems need to be properly tested after installations simulating aircraft as airborne and receiving valid GPS signals.
Hangar testing is not always the right way to confirm ADS-B Out operation, while requesting the PPR is an effective way of establishing in-flight serviceability with confidence. Some shops have hangar mounted GPS antennas that rebroadcast into the hangar, and others have GPS satellite simulators to test aircraft within the hangar.
The FAA prioritizes in-flight ADS-B failures, including missing or erroneous squawk codes, erratic GPS position and duplicate or improper 24-bit ICAO addresses. These are all issues that cause problems for Air Traffic Control trying to track the aircraft on their monitors.
Europe and elsewhere are implementing similar plans for monitoring and assessing ADS-B Out performance, providing feedback to operators and to be used for future infrastructure and operations improvement.
With less than eight months left in the US, operators and aircraft owners have a small window of opportunity to upgrade for mandated ADS-B operations. We conclude with a summary of ADS-B (In and Out) and why it is so important to the industry…
- ADS-B enhances safety, providing ATC with a view of all nearby air traffic and their intentions, irrespective of ATC’s existing radar coverage.
- ADS-B uses a high integrity GPS source to provide precision accuracy in it broadcast of data.
- Aircraft equipped with ADS-B In can also view other air traffic on compatible cockpit displays.
- ADS-B rebroadcasts aircraft position using different formats between users, such as 1090MHz (ES) and 978MHz (UAT).
- ADS-B can provide other useful data such as graphical weather, including TIS-B (and FIS-B for UAT equipped aircraft).
- ADS-B broadcasts its identity, position and velocity frequently (twice a second), ensuring virtual real-time operations.
- The use of satellite-based ADS-B will replace radar-based ATC operations throughout most of the planet.
By flight crews being operationally prepared (see Part 1 to this article) and by maintenance directors ensuring shops are provided with all the tools they need to do the work (such as current equipment status reports, custom prints, existing electrical load analysis, up to date weight and balance and other reports), well performing ADS-B systems can be delivered on time. But hurry!
Time is running out…