Assessment of current DME performance and the potential to support a future A-PNT solution

With the broad implementation of Performance Based Navigation (PBN), GNSS (satellite navigation, e.g. Global Navigation Satellite System) is becoming an essential infrastructure. Consequently, the role of terrestrial aids is evolving from supporting conventional procedures on a primary and exclusive basis to one that has a complementary function in the context of PBN. Current work in various SESAR (Single European Sky ATM Research) projects revolves around the use of DME/DME (Distance Measuring Equipment) as the main reversionary capability to maintain safety and continuity of operation during a GNSS outage in the short and medium term. In the long term, GNSS reversion is addressed in a wider context, considering various solutions supported by advanced terrestrial systems/technologies, referred to as Alternate Positioning, Navigation and Timing (A-PNT). While there are several new technologies proposed to support a future A-PNT solution, DME/DME navigation is still a potential long term candidate to support the positioning and navigation functions due to its large equipage base on the ground and in the aircraft fleet, as well as its two-way ranging principle reducing the required number of ground facilities (a fix is possible with two stations only). However, current DME standards are at the limit of what would be operationally required to support DME/DME based PBN in the coming years. The paper is mainly dedicated to the analysis of the DME range accuracy data and the comparison with the requirements of current aviation standards. This analysis is based on data collected in extensive static (on-ground) and in-flight data recording campaigns organized with the contribution of the AVINOR (Norwegian Air Navigation Services Provider), the flight inspection unit of DSNA (Direction Generale de l'Aviation Civile of France), Rhode&Schwarz and EUROCONTROL. An overview is also be given on the potential use of DME to support some aspects of the future Alternate Positioning, Navigation and Timing concept.