BizAv and CPDLC: Seven Things to Know

As operational benefits increase in international and domestic airspace worldwide and mandatory equipage has become necessary in a crucial area of international airspace, many business aircraft owners are becoming convinced that installing Controller-Pilot Datalink Communications (CPDLC) capability on their avionics panels is worth the investment....

Indeed, owners who buy many of the Mid-Size Jets and Large Jets factory-new will find that their aircraft comes fully equipped already. This is because equipage is mandatory in vastly important areas of international upper airspace: from flight level 290 to 410 in all North Atlantic Mandate airspace.

Although for the time being most business jets appear to be exempted from a mandatory requirement for aircraft above a certain size to be CPDLC-equipped when flying at altitudes above FL285 in all airspace controlled by Eurocontrol, mandatory equipage could be extended in the future to include Business Aviation operations.

Most business aircraft pilots will be highly familiar with the operational procedures required by CPDLC operation, but the aircraft owners themselves should be aware of seven basic equipage and operational factors that are associated with CPDLC usage, giving them all the key information they need to decide whether to invest in CPDLC installation.

According to four avionics experts interviewed by AvBuyer, following is what owners should know about installing and using CPDLC…

1. The Equipment Required

While CPDLC is ultimately a software-driven capability which is inherent — but sometimes activated as an option, for a price — in modern integrated flightdecks such as Collins’ Proline series and the Garmin G5000, it requires three basic building blocks.

First is a dual-channel VHF Digital Data Link (VDL) Mode 2 or Mode 0 radio. VDL Mode 2 equipage is mandatory for some CPDLC uses (for instance in Eurocontrol airspace and for FAA Data Comm Enroute clearances in US domestic airspace), according to Christian Renneissen, Product Manager for Flight Deck Connectivity at Collins Aerospace.

Similarly, the DCL digital-text departure clearances transmitted by FAA controllers at an increasing number of US airports (the number is currently 62) requires VDL Mode 0 or VDL Mode 2 equipage.

These radios can receive and transmit the data bursts which contain the text messages transmitted by air traffic controllers to flight decks of aircraft using CPDLC, according to Conrad Theisen, Director of Avionics Sales at Elliott Aviation.

For CPDLC operation in international airspace (such as North Atlantic Mandate airspace) under the FANS 1/A+ standard, equipage with an Inmarsat or Iridium sitcom router-and-transceiver combination is also at least advised.

The second building block for CPDLC equipage is a data entry-and-controller device loaded with the software which provides the CPDLC capability, says Theisen. This controller device is typically the Flight Management System (FMS), with both FMSs in modern integrated flightdecks being capable of controlling the CPDLC function.

The third building block is a display by which the pilots can see and verify (or otherwise) the ATC instructions controllers are sending to the flightdeck via CPDLC. In a modern flightdeck the required display is likely to be a touchscreen display, one for each FMS, by which both pilots in a two-crew aircraft can verify, accept and activate CPDLC instructions.

2. ‘Push To Load’ Required for Some CPDLC Uses

Flight Management Systems in various modern integrated flight decks offer a ‘Push to Load’ button function, by which, after the pilots verify a CPDLC text message from a controller, they can then load it directly into the FMS as a navigational instruction which the FMS will then have the aircraft perform.

The ‘Push to Load’ capability is a requirement for any aircraft wishing to use the FAA’s Data Comm Enroute CPDLC clearance service, says Renneissen. However, it is not required for aircraft wishing to make use of the FAA’s DCL digital CPDLC departure clearance service.

3. Installation Requires Some Other Equipment Changes

One other very important modification required for any aircraft in which CPDLC capability is installed is for its Cockpit Voice Recorder (CVR), one of the two mandatory ‘black boxes’ all aircraft above a certain size are required to contain, to be upgraded so that it can record digital text messages, says Theisen.

This is required so that investigators can find out all the text instructions transmitted to the aircraft by controllers in cases when CPDLC has been used to replace ATC instructions transmitted by voice.

Some other minor flight-deck panel modifications might be required in the form of installing additional annunciator signs such as ATC/FAIL or CVR PASS/FAIL, adds Melissa Raddatz, Regional Sales Manager for Flying Colours Corp.

4. Some Flight Decks Will Require a Third FMS

Older business aircraft that don’t have integrated flight decks could require a third FMS to be installed, specifically to handle CPDLC control and data entry, according to Adrian Chene, Senior Avionics Sales Representative for Duncan Aviation.

Depending on the aircraft type involved and the radio transceiver units it contains, the aircraft’s original two FMSs might not have the capability to verify, control, input and display CPDLC messaging.

In such cases the pilots would continue to use the two primary FMSs to control and navigate the aircraft and use the newly-installed third FMS to handle all CPDLC messaging functions. 

However, while the aircraft typespecific CPDLC solution might require installation of a third FMS, using it also increases pilot workload, and it can reduce the overall safety of operating the aircraft, “because it builds the potential for error,” Chene highlights.

Three-FMS CPDLC flight deck solutions are usually also likely to be more expensive to install than adding CPDLC capability to an integrated flight deck, Chene and Theisen explain. Adding CPDLC to an integrated flight deck — which sometimes can be accomplished merely by inputting a paid-for encrypted software-activation code — can cost from $50k to about $350k depending on the aircraft’s overall avionics fit.

In general, CPDLC installation in a typical mid-size business jet might average between $250k and $350k, Theisen shares. Depending on how it was originally equipped, full installation in a large, long-range jet might cost up to $600k, in part because the CPDLC digital protocols employed by ICAO’s FANS 1/A+ standard and Eurocontrol’s ATN 1B standard are different.

Many long-range business jets have to be equipped for both, and also must have satnav capability.

5. CPDLC Pricing is Often Inelastic

Unfortunately, owners might find they don’t have much leeway in terms of a lower CPDLC installation price. That’s because the installation of CPDLC capability in a given aircraft type usually requires that a Supplemental Type Certificate (STC) be obtained for the modification, notes Chene.

STC certification is an expensive process and only one STC solution has been developed for most business aircraft CPDLC upgrades.

In many cases, CPDLC capability is contained in a package of FANS 1/A+ mods which are available either as STCs, or (for the lucky owners of some aircraft types) as slightly less certification-onerous Service Bulletins (SBs), says Raddatz. (The Bombardier Learjet 40/45 family has an STC available specifically for adding CPDLC, with the STC also offering the option to add full FANS 1/A+ capability for additional cost.)

6. The Benefits of CPDLC Will Grow Over Time

While in many cases CPDLC already offers significant operational benefits in terms of expedited departure, en route clearances, and access to the much preferred upper-airspace flight levels, some of the benefits that equipage will eventually offer are still years away.

For instance, notes Chene, thanks to the Covid-19 pandemic, to date the FAA has only rolled out its en route CPDLC service at three of its many Air Route Traffic Control Centers (ARTCCs), the air traffic control facilities which control all upper airspace over the United States.

Eventually all FAA ARTCCS will be equipped and so CPDLC-capable aircraft will be able to request and receive expedited clearances and dynamic re-routes in all US domestic upper airspace.

Additionally, the FAA is working on a long-term plan to provide a massive networked real-time weather information service, taking data inputs from the highly advanced 3-D weather radars it now operates and merging that with an enormous mass of real-time data fed to the FAA from the advanced weather radars now being installed in today’s aircraft.

To that highly detailed picture, the FAA will also eventually be able to add inputs from other weather-sensing technologies such as satellite pictures and lidar detection of Clear Air Turbulence (CAT), and the conditions inside convective weather fronts.

The result, perhaps still two decades away according to Chene, is that the FAA will be able to advise all CPDLC-equipped aircraft in US airspace of exactly where, and at what altitudes CAT and convective turbulence is occurring, and be able to route aircraft dynamically away from it. “In 15-20 years it might become rare that you ever run into turbulence,” he says.

The more operationally useful that CPDLC becomes, the more likely it will be that owners who haven’t installed the capability in their aircraft will be affected adversely when they want to sell their aircraft.

Even in today’s pre-owned aircraft market, Large Jets (such as the various Falcon 900 models) are expected to have CPDLC, according to Chene. “If you don’t, the buyer will go to the most expensive vendor and get a $400k- $500k quote” for CPDLC equipage — and as the owner of the aircraft, you will be expected to reduce your sale price accordingly.

7. Important Regulatory Considerations Exist for BizJets

Most crucially for business aircraft owners and operators, four highly important regulatory considerations exist when installing and using CPDLC, according to Renneissen. Two of these concern the FAA and two concern Eurocontrol.

Consideration 1: From the FAA regulatory standpoint, it is vital for owners and operators to know that a current FAA Notice to Airmen (NOTAM) specifically excludes business aircraft from using the FAA’s En route CPDLC service. Officially, access to the service is restricted at present to commercial aircraft.

However, this does not mean that US-registered business aircraft cannot use the FAA’s En route CPDLC service at all. Instead, owners/operators have to apply to the FAA by means of a specific application process to obtain approval to use it on a trial basis.

Each application must be for a particular individual aircraft, identified by its tail number. The FAA uses the operational En route CPDLC usage data from each business aircraft application that it grants to expand its overall knowledge of CPDLC operations. Ultimately this should help the FAA improve and expand its En route CPDLC service offering.

Consideration 2: Also vitally important for business aircraft owners and operators to know is that they will only be able to obtain FAA approval for CPDLC operations if the specific avionics units with which their aircraft are fitted are all present in a list of FAA-approved avionics units.

That list is published by L3Harris, and is publicly available via the web page https://www.l3harris.com/datacomm, by clicking on the ‘Recommended and Required Avionics Version List v1.63 20210114 (En Route)’ URL link under the heading ‘US Domestic En Route CPDLC’ on that page.

Consideration 3: Eurocontrol, meanwhile, maintains a ‘Logon List’ (formerly known as its ‘White List’) of aircraft types which have demonstrated an unacceptably high ‘Provider Abort’ (PA) rate of CPDLC communication failures.

All blacklisted aircraft types cannot be considered for addition to the Logon List, unless they replace their avionics installations with different ones. While the White List is confidential to members of the Eurocontrol Data link Performance Monitoring Group, Eurocontrol has made public a useful list of CPDLC-unacceptable avionics here: https://ext.eurocontrol.int/WikiLink/index.php/Logon_List.

Consideration 4: And finally, while the situation presumably could change, the EU provided some good news in February 2020 to owners and operators of business aircraft. Although Eurocontrol at that point had mandated CPDLC equipage to its ATN 1B standard for operations in all EU upper airspace above flight level 285, aircraft with gross weights below 100,000lbs, and/or carrying fewer than 19 passengers, were exempted.

This very wide exemption appears to exclude most of private aviation from the CPDLC-equipage requirement, allowing them to fly at altitudes above 28,500 feet in Eurocontrol airspace. However, that situation should be monitored continuously, because it could eventually change.

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