Have you already heard of GBAS and Point Merge ? If not, have a look at the latest issue of the Eurocontrol Experimental (EEC) Newsletter.

GBAS stands for Ground Based Augmentation System. GPS is not precise enough to fly an approach to minimums, particularly in the vertical plane, mostly because of atmospheric perturbations. The “Augmentation” consists in sending a correction signal from a ground station, assuming the atmospheric perturbation is the same in a relatively wide area around the airport.

This particularly means that once and airport is equipped, GBAS approaches become possible to any runway, at the cost of a single transmitter. No more need for one ILS per runway, nor for the associated maintenance costs.

A GBAS installation makes possible to fly precision approaches to any runway in range. Precision and low cost. Wow. So why is not GBAS used everywhere ? Because publishing new procedures and fitting receivers in aircrafts costs a lot of money.

Validation of a new system’s safety is also hard task, especially when it relates to guidance in the final phases of approach, where any problem can result in a controlled flight into terrain (a.k.a. CFIT – a.k.a. crash).

The paper from the EEC focuses on interoperability assessment, to see how GBAS approaches can fit in the real world, and it seems quite promising.

The links in this newsletter include a video taken from a plane approaching runway 27 in Egelsbach, with a duplication of the “instruments” displayed for the pilot. The NAV and GS flags appear a couple of time, probably because of lost signal.

This probably seems bad to any IFR pilot, but one must keep an important detail in mind. Egelsbach is not GBAS equipped ! This test flight was based on a GBAS transmitter located 10 kilometers away, in Frankurft am Main Airport… Not so bad for an experiment.