The cornerstone enabler for 4D trajectory flight was judged to be technically unusable in 2014 due to disastrous system overloads and potentially dangerous radio interference.
The European Aviation Safety Agency (EASA) which carried out an investigation into datalink on behalf of the European Commission then warned that despite some tweaks to the technology, messaging between controller and cockpit using the Aeronautical Telecommunication Network was liable to randomly disconnect at ten times the acceptable level.
That meant that the datalink technology was so far from meeting its availability targets despite only a limited number of aircraft using it, that its rollout was delayed for five years until a more robust multi frequency approach was developed.
Now a study by the SESAR Joint Undertaking (SESAR JU) into the VDL Mode 2 technology at issue has identified what needs to be done to deliver high-quality data communications capabilities which are viewed as essential enablers to achieve the efficiency and capacity improvements required by the Single European Sky.
The VDL Mode 2 capacity and performance analysis study tried to identify when VDL Mode 2 datalink technology using up to four frequencies would reach its operational limits in Europe. It found that:
- VDL2 over one single frequency has already reached its capacity limits. Therefore, multi-frequency deployment in Europe is a “must” as of today;
- A four frequency implementation is a minimum requirement to support VDL2 deployment until 2025 in high density areas;
- Further optimisation options under investigation may extend the viability of VDL2 over four frequencies beyond 2025 in high density area;
- The evolution of the European datalink infrastructure in the ATM Master Plan and the development of the next generation datalink technology within SESAR must be anticipated.
The SESAR JU also launched a VDL Mode 2 measurement, analysis, testing and simulation campaign – also referred to as the ELSA Consortium study – to address the six EASA recommendations relating to what was at the root cause of the problem and potential fixes.
It will focus on end-to-end VDL Mode 2 issues today, defining potential technical solutions for multi-frequency deployment and possible VDL Mode 2 improvements. Commissioned by the SJU and conducted by a consortium of ATM stakeholders, the project is due to deliver its final report mid-2016.
“In summary, the results of the capacity and performance analysis therefore confirm the need to introduce the next generation datalink system in the coming ten to fifteen years given the current configuration, which is consistent with the 2015 edition European ATM Master Plan and the SESAR 2020 work programme,” stated the SESAR report. “The VDL Mode 2 measurement, analysis, testing and simulation campaign will try to address current problems and maximise the operational period of VDLM2.”
The study was commissioned by the SJU and was conducted by a partner consortium including Aena, Airbus, Air France, DFS, DSNA, easyJet, ENAV (lead), LFV, Lufthansa, NATS, SITA, University of Salzburg between June 2014 and July 2015.