Future Air Navigation System (FANS)

September 2011

The world’s aviation community is currently changing. One of the biggest changes is the FAA’s vision of the future of national airspace management and control called NextGen. FANS 1/A – CPDLC is one of the many components of NextGen and will play an integral part in many aspects of future systems.

What is FANS 1A/CPDLC?
CPDLC or Controller Pilot Data Link Communication is a means of communication between controller and pilot, using data link for Air Traffic Control (ATC) communication. You can think of this like texting, only in this case ATC and the flight crews are using text messages to replace many of the voice communications that are traditionally used.

Future Air Navigation System (FANS)-1/A is a format of communication for CPDLC. FANS 1 was originally developed by Boeing and later adopted by Airbus (FANS A). FANS 1/A uses an early version of protocol that has been used for 15 years by the airlines. There are two parts to FANS: ADS-C and CPDLC.

ADS-C – Automatic Dependent Surveillance Contract
Automatic Position Reports are known as ADS-C and require no pilot interaction. The Contract in ADS-C means that ATC will control the reporting system. There can be up to five separate ATC contracts at any one time. Following is a description for each of the three types of Contracts:

• Periodic Contracts - ATC can set or alter the update rate as needed (a higher update rate is usually required in high traffic areas).
• Event Contracts - Communicated if there is a change in Vertical Rate, Lateral Deviation or Altitude.
• Demand Contracts - ATC can request a one-off update as needed. This does not affect an existing contact preset rate.

There is a fourth type of contract, but unlike the previous three it is initiated and cancelled by the pilot, not the controller. This Emergency Contract is automatically triggered by the MAYDAY message.

CPDLC
CPDLC - Controller Pilot Data Link Communication refers to the messages and responses sent from ATC and the flight crew.

There are two benefits to FANS:

• Reduction in the amount of frequencies required for aircraft ATC communications
• Reduction of separation minimums between aircraft longitudinally and laterally

History of FANS

In the early 1980s, the International Civil Aviation Organization (ICAO) developed a council to investigate ways to increase safety in aviation. This council studied the technologies available and applied them to develop new concepts for future air navigation systems or FANS. FANS 1 was originally developed by Boeing, and later adopted by Airbus (FANS A). It is now commonly referred to as FANS-1/A. ICAO produced two main documents in this effort, the Global Operational Data Link Document or GOLD and the Fans Operating Manual or FOM. There are two main FAA advisory circulars to give guidance for FANS installations:

• AC 120-70B - gives guidance for operational authorization
• AC 20-140A - gives guidance for design approval

For those of us who have spent more than just a couple of days working on aircraft, we know there are wide variances in the equipment installed on aircraft. Because of this, there will be no single equipment solution to cover FANS. Currently, STCs will be required to equip aircraft for FANS for multiple reasons:

• There are multiple equipment upgrades required including FMS, GPS, Datalink, potentially Satcom and the CVR.
• The world aviation authorities see the text messages sent between the cockpit and ATC as voice communications, and as such are required to be recorded on the CVR.
• A TSO-177 compliant CVR will be required to meet this capability.
• While multiple STCs may be required to meet the equipment requirements, there also will need to be an operational STC required as well, which may specify the service provider for the aircraft. (ARINC and SITA who will host the information exchange between ATC and the aircraft with Satcom solutions.)

If this sounds familiar, you are not mistaken. If you remember back to the RVSM upgrades, there were equipment STCs required to upgrade the aircraft, then an operational STC required as well. After that, crew training was required then an operator could submit a package to the regional authority and receive an LOA from them to operate at RVSM altitudes. This process will be the same with FANS, and is expected to be the case with most NextGen solutions.

As NextGen initiatives continue to become a reality, the question most operators ask is, “If I need to upgrade my aircraft, what am I getting for the investment? Unfortunately there is no one answer, just like there is no one solution.

At Duncan Aviation, we are on the cutting-edge of all avionics technology and FANS 1A/ CPDLC. We have done ample research and talked with hundreds of customers to develop the most valuable information we can provide.

Our team of avionics experts has developed Straight Talk booklets for RVSM and ADS-B. A Straight Talk on FANS1A/CPDLC and NextGen is scheduled to be released in October. Visit www.DuncanAviation.aero/straighttalk for more information.

As always, we look to improve ourselves and our knowledge. Feel free to contact our avionics experts to answer any of your questions and talk about your challenges when the subject arises.