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GCAS Operational Requirements and Certification

European Union
Complete with results
Project Acronym
STRIA Roadmaps
Vehicle design and manufacturing (VDM)
Transport mode
Airborne icon
Transport policies
Societal/Economic issues,


Background & Policy context

The most important category of aircraft in-flight crashes is related to properly operating aircraft performing a so-called Controlled Flight Into Terrain (CFIT). Reasons for aircraft crashing into the ground may be diverse, and the best way to improve safety will be new automatic alert systems to notify cockpit crews about dangerous proximity to the ground.

A new generation of Ground Collision Avoidance Systems (GCAS), which is currently under final development, will provide a predictive alert to pilots of looming contact with the ground. However, the introduction of a complex, all-new avionics system requires regulatory and certification standards to be set, prior to full operational use.


GORAC aimed to consider and develop the requirements for GCAS in terms of certification (airworthiness) and operational issues. The main objectives of GORAC have been to:

  • derive operational standards suitable for GCAS from, e.g. the existing Ground Proximity Warning System (GPWS) or similar approaches;
  • assess the use of a terrain database, predictive algorithms and a new Human Machine Interface (HMI) within GCAS;
  • assess the suitability of simulation facilities that are understood to play an important role in the verification and validation of collision avoidance systems;
  • establish certification requirements on GCAS for the European Joint Aviation Authorities (JAA) and national certification authorities;
  • provide preliminary guidance on demonstrating system compliance to defined certification requirements.


Parent Programmes
Institution Type
Public institution
Institution Name
European Commission; Directorate-General for Energy and Transport (DG TREN; formerly DG VII)
Type of funding
Public (EU)


GORAC has produced:

  • specifications for possible GCAS simulation facilities and identification of five suitable simulators in France, Germany and the Netherlands that apply both to validation requirements and the necessary implementation verification;
  • a survey of applicable existing specifications and regulations, in particular following European Joint Airworthiness Requirements (JAR), and the determination of regulatory gaps linked to GCAS features;
  • proposals for validation methods, seeking compliance with certification requirements, for the three main areas of database integrity, dynamic algorithms and HMIs, which address the interaction between cockpit crews and GCAS visual and aural outputs;
  • guidelines for GCAS database certification, specified for Terrain Elevation Databases, Obstacle Databases and Airport Runway Databases;
  • a preliminary regulation document for the Preparation of the Certification Requirements, which describes the certification methodology for GCAS and proposes corresponding Means of Compliance.

Policy implications

The project has set the framework for establishing regulatory and certification requirements to be included in JAA's airworthiness requirements, to ensure large-scale implementation of GCAS in commercial aircraft. This effort can be seen in the context of several new developments addressing in-flight safety, e.g. the Traffic Alert and Avoidance System (TCAS).

In co-operation with aviation authorities, the European Commission's RTD initiatives will contribute to increased flight safety, while coping with rapidly growing overall air traffic.


Lead Organisation
EU Contribution
Partner Organisations
EU Contribution


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