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Performance Based Navigation

4 juillet 2016 - Transports

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What do YOU want to know about DSNA PBN strategy ?

4 juillet 2016

Why publishing PBN/SBAS guidance (LPV MINIMA) ?

  • DSNA wants to provide the best back-up solution in case of ILS failures or outages on its major airports. PBN/LPV procedures allow operating minima close to ILS CAT I.

The SBAS technology has proven to be as reliable and as performing as ILS CAT I operations and thus may complement ILS service at major airfields by providing identical operational minima and maintaining safe and optimum accessibility in case of unavailability.

The first implementation for Europe was at Paris CDG on April 28th 2016. Airlines and aircraft manufacturers have now the opportunity to clearly observe that PBN/LPV approaches support much higher airport accessibility than PBN approaches using other technologies. The operational benefits, in addition to the very high safety standards notably delivered by EGNOS, reinforce DSNA conviction that SBAS (System Based Augmentation System) is a key technology in modernizing its nav-aids infrastructure.

  • DSNA deploys PBN approaches with LPV minima for all IFR runway ends, to make EGNOS benefits available to the entire aviation community ,and thus encourage retrofit.

Lateral & vertical guidance provided by a SBAS such as EGNOS is free of charge and has no airport infrastructure costs. SBAS fully support navigation and surveillance performance requirements.

PBN/LPV approaches based on SBAS are high performance/safety approaches. They have been highly appreciated by pilots during the various test campaigns that were carried out.

Jean-Christophe Lair - Airbus test pilot
« As a test pilot, I had the opportunity to perform LPV approaches based on the EGNOS constellation on three different types of aircraft : A300ST, A350XWB and ATR72-600.The first observation, an unanimous one, is the ease of system acquisition because the pilot interface is designed like that of an ILS which is the best known and thus the most “intuitive” for use by an airline pilot. The second is that the LPV has better performance than even CAT I ILS because it is not sensitive to the “traditional” ILS disruptions, for example secondary LOC or Glide beams, or signal disruptions encountered when an aircraft overflies the localizer antenna.”
  • Today, PBN/LNAV-VNAV approaches based on delivered barometric information correspond to the most likely satellite navigation approach to be flown by airlines, but still suffer from some limitations :

QNH mis-setting events have been reported.
« RAIM unavailability » issues may occur when PBN is the unique existing approach.
As a reminder, Receiver Autonomous Integrity Monitoring (RAIM) is a technology developed to assess the integrity of the GPS signal in a GPS receiver system.

Anticipation is key to the evolution of PBN. DSNA will continue to deploy PBN/LPV minima approaches while maintaining the publication of GPS and Barometric guided procedures at runway ends of highest interest to its customers, hence taking into account the progression of the fleet equipment status.

What is DSNA’s position towards RNP 1 and radius to fix legs ?

One of the key concerns for DSNA in high density TMA is to guarantee optimal capacity at all times. With the introduction of RF (Radius to Fix) legs, capacity flaws may occur mainly due to additional radio exchanges and specific required ATC management in relation with unequipped aircraft. It is therefore difficult to introduce new functions, such as RF, without penalising the global TMA capacity, unless the equipment rate of aircraft operators approaches 100%.
One other means to derive benefits with RF would be to design specific trajectories to be flown during periods of low traffic only. This solution is under discussion with airspace users.

DSNA remains interested in future developments towards RF, but will need to monitor airlines’ equipment rates to support the future operational introduction of this function.

The transition from RNAV 1 to RNP 1 specification raises an issue that needs to be clarified : long term (say more than one day) loss of GNSS signal. With the RNAV 1 specification, a lot of flexibility for reversion is maintained, especially thanks to the large number of users equipped with DME/DME multimode receivers. However, interrogations remain regarding the acceptable conditions for using DME/DME along RNP 1 published routes when the outage lasts for a longer period. A meeting with Eurocontrol and EASA has been requested to clarify this issue and decide on the way forward.

It is DSNA intention to publish RNP 1 trajectories when it will be proven to be of operational relevance in terms of safety and performance. All projects and customers’ expectations in that regard will be looked into.

Will DSNA implement visual RNAV procedures ?

In close cooperation with Air France, DSNA designed and assessed a Visual RNAV approach at Bordeaux airport. Over 120 flights have tested it since summer 2015 with very positive feedback from both ATC and crews. The evaluation is still ongoing thus providing key inputs towards a new concept of operations to be defined at ICAO level and in the meantime gaining further practice for all first line actors.
Through a SESAR project at Nice airport, with participating partners, DSNA successfully designed and evaluated a visual RNAV approach in a very demanding terrain environment imposing a curved path until the short final.
A study has also started at Marseille airport, where obstacle-rich environment is also an issue and leads to the necessity of a steep slope to be followed by aircrews.

DSNA is ready to publish Visual RNAV approaches when the concept of operations will be agreed upon and established at ICAO level.

Looking into the future with GBAS CAT II/III ?

A Ground-Based Augmentation System (GBAS) is a system that supports augmentation of the primary GNSS constellation(s), at airport level, for all phases of approach : landing, departure and surface operations. While the main goal of GBAS is to provide integrity assurance, it also increases the accuracy of the signal. Click here to view GBAS cat III video

DSNA supports R&D for GBAS CAT II/III notably by a SESAR station deployed at Toulouse Blagnac and within the Paris CDG 2020 performance roadmap. The objective foreseen is a substantial improvement of airport performance in low visibility conditions.

What is DSNA position towards GBAS CAT I ?

DSNA will not proceed further with GBAS CAT I than the support that has been provided for Airbus Industries operations at Toulouse airport and that lead to the installation of a station. The deployment and implementation planning of GBAS CAT I is very limited in other European countries, showing the cost effective limits of this solution. No airlines have requested further deployment elsewhere since.

PBN@DSNA high level objectives

  • Improving safety & accessibility notably for secondary runways not equipped with legacy ILS.
  • Allowing conventional navigation aids rationalization, especially ILS CAT I reduction, at airports where the economic model is no longer valid.