Cost Benefit Assessment
The viability to install a GBAS should be assessed in parallel with the development of the GBAS CONOPS. During the development of the Cost Benefit Assessment (CBA), the following considerations should be taken into account:
- Life-cycle costs associated with GBAS implementation, including:
- Acquisition
- Operation
- Maintenance
- Decommissioning
- Other industry costs, including:
- Upgrade aerodrome infrastructure (e.g. to achieve CAT II/III operations, airfield lightning, surface movement guidance and control)
- Integration in existing ATM environment
- Need to retain conventional navaids in one or more runways
- Staff training and update of internal documentation (for all stakeholders)
- Update aircraft equipment
- Identification of key benefits and translation into direct economic costs/benefits
- Assumptions taken in the CBA and how these impact in the Business Case
- Identification of community benefits, for example:
- Reduction in emission
- Reduction in aviation related noise
The following benefits might be identified for the implementation of a GBAS:
- A GBAS ground facility supports precision approaches for multiple runways at an airport to improve airport safety, access, and utilisation.
- GBAS can support multiple, variable approach paths to the same runway end to enhance airport capacity and environmental performance.
- A GBAS ground facility does not have critical and sensitive areas (CSA). Protection areas are linked to the service availability, but not integrity related. The absence of CSA that need to be protected during the operation can increase runway throughput compared to the equivalent category of ILS if more aircraft are GLS equipped.
- GBAS has flexible siting requirements, leading to increased airport efficiency.
- GBAS equipment does not require to be placed close to the runway, reducing the risk of aircraft and localiser damage in overrun situations or aircraft and glide path damage due to runway excursions.
- GBAS can reduce risk of controlled flight into terrain (CFIT), flight delays or diversions at airports which cannot install ILS on all runway ends because of terrain or other challenges.
- GBAS could reduce system support and maintenance cost in the long term, including simpler, less frequent flight inspections, compared to ILS.
- GBAS could provide stable and consistent approach with no vertical guidance fluctuations. The final approach path is clearly defined through a digital data set.
- The GBAS system is not affected by baro-setting errors.
- The number of radio frequencies used at the same airport could be reduced, as the same GBAS station could serve multiple runways at the same airport and even in different airports if they are within the coverage of the VDB transmitted signal and integrity range.
- GBAS category II/III operations using 3.2º glide path angle are regarded by ICAO PANS-OPS as nominal operations (whilst the maximum glide angle for nominal ILS category III operations is 3º).
- GBAS can support multiple thresholds on the same runway.
- GBAS can support several approach glide angles to the same runway and it could allow setting approaches at different glide angles to best fit different kind of aircraft landing at the airport.
- Regarding RNP to xLS procedures, the RNP to GLS has a shorter distance from the RF leg to the final approach fix (FAF) than the RNP to ILS.
- Due to the previous point, there is a benefit in fuel savings.
- GBAS can provide enhance efficiency by supporting terminal area PBN procedures when GBAS positioning service is available, allowing more aircraft to follow preferred trajectories.
The outcomes of the analysis may be documented in a Business Case that clearly articulates the costs associated with implementation and ongoing operation, along with the envisaged benefits of the technology to the ATM/ANS provider or airport operator.
