Optimizing precision final approach through gbas

Running head: OPTIMIZING PRECISION FINAL APPROACH 1

Optimizing Precision Final Approach

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Introduction

Navigation is a very ancient science, which began with human travel. Literally,

navigation can be described as to determine the exact position, orientation and velocity of a

moving object based upon the previous position (which is also known as dead-reckoning) or

with the assistance of a map, celestial charts or any external information (termed as position-

fixing) at a specified given time. Nowadays, space technology has advanced to a stage where

humans can use a consumer satellite receiver to pinpoint his/her position at virtually any place in

the world. This is thanks to navigation satellites, and the advantages of this technology will be

extended even further as the modernization of the Global Positioning Systems (GPS) takes place

as scheduled and the full deployment of GLONASS and Galileo satellite constellations are

completed according to time and roadmap.

For civil aviation applications, more accurate and precise data are required. This is where

augmentation systems are essential. One common problem faced by navigation satellite users for

civil aviation purposes is availability. In order to increase the availability, this work proposes a

way to interoperate between several Navigation Satellites, i.e. GPS, GLONASS and GALILEO,

and possibly the Chinese COMPASS/Beidou and the Indian IRNSS (FAA 2013).

Ground-based Augmentation Systems (GBAS)

Ground-based augmentation systems (GBAS) is a localized reference system within 20

km that supports navigation satellite augmentation through the use of terrestrial radio messages

composed of an individual or a network of accurately surveyed ground stations, which take

measurements concerning the GNSS, and one or more radio frequency signals, which transmit


the information directly to the user receiver., while DGPS is a differential system specifically

designed for GPS. Current requirements on-board an aircraft as well as on-ground for precision

approach in (ATC) for GBAS (FAA 2013).

In the past, the FAA referred to GBAS as the Local Area Augmentation System (LAAS).

Current GBAS systems approved by the FAA only monitor and augment the Global Positioning

System (GPS) L1 C/A broadcast. Compared to traditional ILS the GBAS have extended

advantages. Multiple runway ends can be supported by just one GBAS thus reducing a number

of systems in a single airport. Due to reduction in Very High Frequency (VHF) requirements.

This reduces the Very High Frequency (VHF) requirements and simplifies airport infrastructure.

Just one VHF assignment for 48 individual approach procedures is required by the GBAS, and

not like ILS which needs one frequency for each system. Besides flexible sitting criteris allows

the GBAS to manage runways, unlike the ILS which cannot support.

The GBAS, which is a generic term, has more flexible siting criteria, allowing the GBAS

to serve runways which ILS is unable to support. A GBAS is sited to minimize critical areas

which place fewer restrictions on aircraft movement during ground taxi and air operations. The

GBAS approach guidance is steadier than ILS approach guidance. Also,

GBAS requires less frequent flight inspections compared to those required of ILS systems.

GBAS implementations example is the United States Local Area Augmentation System (LAAS).

Air services is implementing the Honeywell Smartpath™ SLS-4000 GBAS into the National

Airways System (FAA 2013).


GBAS working principles:

GBAS on Ground Facility consists of at least three antennas, a central processing system,

a VHF Data transmitter on ground near the airport. In the aircraft the GBAS avionics within the

multi-mode receiver system provides continuous GPS implementation, GBAS and ILS with the

help of antennas and hardware. On Ground GBAS Facility utilizes VHF radio link to provide

aircraft with GPS corrections and information about the approach path. Reference antennas of

GBAS gets signals through satellites, its receivers then measure the time of transmission between

the reference antenna and the GPS satellite subsequently determining the distance the signal has

travelled. GBAS Facility on ground compares the measured distance and the actual distance,

based on satellite position and GPS receiver position and then determines the error in the

measurement. If GBAS Ground Facility determines some potential problem with a GPS satellite,

it broadcast of corrections are stopped for that particular satellite, thus preventing the GBAS

avionics from using the satellite. The GBAS Ground Facility transmits correction messages

twice in two seconds by means of the VDB, or VHF data broadcast, and guidance to 48 approach

paths. Within a 23 nautical mile radius the GBAS provides its services, the volume of which

supports aircraft during its transition for en route airspace through the terminal airspace by

means of precision landing approach.


Illustration of GBAS System on ground and air-borne

Benefits of Capacity

GBAS supports intricate procedures and paths of terminal area and does not impacts the

safety. By reducing aircraft separation needs, it de-conflicts airspace by means of extended PTV

ranges. It also empowers the creation of approach procedures change with no infrastructure

changes, and offers the ease of implementation of multiple and variable glide slopes.

Benefits of Efficiency


GBAS helps reduce the workload of air traffic controller by means of less

communication clutter and radar vectoring. It also helps shrink the time and distance in terminal

area which ultimately leads to fuel saving, which remains the most important benefit in terms of

cost and expenses to operators. IFR availability is increased through GBAS, including rollouts,

and arrival time procedures (ERCD 2012)

Benefits to the User

The in-aircraft procedure database is not required because the GBAS terminal area path

procedures are uplinked to the aircraft. It not only supports low powered descent touch downs

but also the TAP procedures up linking provides additional time to the aircrew for touchdowns.

Locations of aircraft and time or landing at key points along the TAP are necessary in order to

improve operations in the terminal.

Nose

Airports the world over are expanding rapidly with the increase in air traffic, similarly

those living as communities near the airports also are expanding, the vacant lands in the vicinity

of the airports get filled with human habitats. Due to this the concern for aviation related noise,

the ear shattering take-off and take-down nose of huge double decker aircrafts has a great impact

to the communities. Although the new era aircrafts with noise suppressed airframes have been

introduced, but it still remains a problem for airports around the world. Restricting the aircrafts

to a pre-defined three dimensional routes designed to suppress noise, the navigation provided by

GBAS offers an opportunity to reduce noise levels. GBAS offers flexibility to construct highly


repeatable flight course for all weather, hence the costs related with noise mitigation may be

reduced to a considerable level. It was identified by Ray et al (2001) that code-range, carrier

phase and signal-to-noise ratio (SNR) measurements are impacted by multipath. These three

measurements can be parameterized and developed as state variables for the Kalman filters.

Potential areas of improvement and the necessary technical (GBAS) and operational changes.

GBAS, with all its benefits, is taken as a local and not a regional solution to providing

APV (Approach procedures with Vertical Guidance), because of its cost, more than $1.5 million

per aerodrome establishment cost. Besides GBAS avionics are neither feasible no available for

smaller aircrafts, hence practically it offers no solution for lower traffic volume or regional

airports. Heathrow is actively working with NATS and the airlines to assess the safety case

associated with LVP operations and the triggers (in particular cloud ceiling). LVP is safety

critical and so progress in this area has to be measured. We are also conducting research and

development as part of the SESAR programme, looking to certify Ground Based

Augmentation Systems (GBAS) to CATII/CATIII standards which will eventually replace the

use of ILS in low visibility and improve the landing rate so that LVPs cause less disruption to

airlines‟ schedules. For approach and landing operations down to Cat I, it is expected that

conventional non precision approaches (NPA) will be progressively replaced by standalone

RNAV approach operations. These RNAV approaches will also be implemented as a backup of

ILS Cat I. Depending on local business case and coordination with users, some ILS Cat I (small

airfields) are also expected to be replaced by SBAS or GBAS based approaches.

Many airports are working in tandem with airlines to evaluate the safety case related to

LVP operations. Heathrow has conducted R&D program as part of SESAR program in order to


certify (GBAS) to CATII/CATIII standards which will ultimately replace the use of ILS in low

visibility. The Boeing Company has a private use GBAS installed and approved at its research

and development (R&D) facility at Moses Lake Airport (MWH) in Washington State. While

Japan is also investing in GBAS at Kansai International Airport and has already adopted Baro-

VNAV enabled APV at selected airports.

Case Study

Modifying approaches with the use of Ground-Based Augmentation System and

Required Navigation Performance Newark-Liberty International Airport (the Airport) is a critical

transportation hub for the New York-New Jersey metropolitan area and the nation. The port

authority has carried out various projects and actions over the last few years, like Sutainable

Infrastructure Guidelines in all port Authority and installation of GBAS system for flight

operations (SMP, 2013). It has also implemented full airside ground management program by

modifying course using GBAS and RNP (Required Navigation Performance). It is also

supporting other activities like new procedures to support environmental goals. Newark-Liberty

International Airport also installed GBAS as one of the first commissioned systems in the United

States and it is collaborating with FAA for its full implementation. In order to enhance safety in

US airports, the FAA program will help the port authority for the implementation of the Next

Gen air traffic control technologies, this will go a long way into making air travel more

convenient and safe. Besides for getting solutions to problems the Port Authority consults

regularly with external stakeholders on all issues, these stakeholders are:

- New Jersey Department of Environmental Protection (NJDEP)

- Federal Aviation Administration Eastern Region


- Federal Aviation Administration-New York Airports District Office

- City of Newark, NJ

- City of Elizabeth, NJ

- Tenant Airlines

- Concessionaires

- Air Services Development Office

- Council for Airport Opportunity

- Rental Car Companies

- Hotel Operators

- Cargo Operators

- Flight Kitchens

The stakeholders are consulted by the Port authority on major issues pertaining to community

engagement, aircraft noise issues, greenhouse effect and leasehold. The authority is also

connected with various organizations and industrial groups in this regard, they are:

- Airports Council International

- National Alliance to Advance NextGen (co-founder)

- American Association of Airport Executives

- US Green Building Council

- Transportation Research Board

- And others

The port Authority is also engaged in various community engagement activities which are:


The authority ensures that the communities around the Airport have an open dialogue with a

representative of the region’s aviation industry on all important subjects, like aircraft noise

abatement, air traffic congestion, construction projects, besides other important quality of life

issues. The staff at the authority also prepares sustainability report card which shows all the

achievements and other EWR programs like noise abatement to keep the stakeholders and the

community apprised of the developments (SMP, 2013).

Recommendations

The FAA’s National Airspace System (NAS) Enterprise Architecture is the blueprint for

transforming the current NAS to the Next Generation Air Transportation System (NextGen). The

NAS Service Roadmaps lay out the strategic activities for service delivery to improve NAS

operations and move towards the NextGen vision. They show the evolution of major FAA

investments/programs in today's NAS services to meet the future demand. The FAA plans to

replace legacy navigation systems with satellite based navigation technology. The FAA has

determined that GBAS is the only cost effective alternative to the existing Instrument Landing

Systems (ILS) by providing terminal, non-precision, and CAT I/II/III precision approach

capabilities in the NAS. Some of these existing ILS systems will be phased out over time as

GBAS are installed. A number of ILS facilities are expected to remain operational, to continue to

provide precision approach service as a backup in the event of unavailability of GBAS services.

This plan has been also envisaged by Eurocontrol’s Single European Sky ATM Research

Programme as a critical enabler for improving air traffic capacity. Eurocontrol's GBAS activities

are managed by Eurocontrol GBAS Project.


Limitations

But GBAS has not been used to its full potential because it is necessary for airplanes to

be equipped and the ground facilities installed. Besides all aircrafts do not have the capability to

use GBAS and the ones using it are the Airbus A380 and Boeing 747-8 only. Although the

navigation capabilities today have greater sophistication, the fact is the navigation professionals

are busy primarily aound positioning and steering (horizontally, vertically and in the 4th

dimension, time). So far as the PBN and landing application are related, the focus is to navigate

via various phases of flight as well as on the requirement of an increase in levels of trust in

navigational performance.

GBAS should have a major impact on noise pollution around Frankfurt. “There is a big

debate around the airport about noise levels,” according to DFS Chairman and CEO Klaus-Dieter

Scheurle. It is expected by the FAA that ICAO will approve by 2015, the GAST-D Standards

and Recommended Practices. Regarding GBAS system capable of providing CAT-I precision

approach, the FAA has given GBAS System Design Approval.

Conclusion

As GBAS is being used by major global airports in their daily aircrafts operations, it is

vital for the aviation managers, operational supervisors and navigation service providers to know

the capabilities and the improved potential enabled by GBAS, including the cost reduction

potential for present infrastructure of air space system. A major improvement can be available by


the GBAS for the enhanced performance. A major contribution towards greater reliability as

provided by the GBAS can be vital for advanced air traffic operations.


References

EUROCONTROL (2015) . Accessed on 17th March, 2015, from

http://www.eurocontrol.int/navigation-activities

ERCD data compared the CACI population databases from 1991 and 2011 for the 201057dBA

and 2011/12 48dBA 6.5hr noise contours ii. Hounslow Council. Accessed 17th March,

2015 from

http://search.hounslow.gov.uk/highlight.aspx?aid=418946&pckid=68946230&rn=1&sp_

id=1916497123&lid=144628766&highlight=census+#firsthighligh

Precision landing softens noise impact. Airport Focus (August 6, 2013). Accessed on 17th March

2015 from http://airportfocusinternational.com/precision-landing-softens-noise- impact/

Sustainable Management Plan. The Port Authority of NY and NJ, Newark Liberty International

Airport. Accessed on 17th March, 2015, from http://www.panynj.gov/airports/newark-

liberty.html

United States Federal Aviation Administration Journal. Satellite Navigation - GBAS benefits.

Accessed on 17th March, 2015 from

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navse

rvices/gnss/laas/benefits/


Engineering

Optimizing precision final approach through gbas