SPECIAL CATEGORY-I in Norway:THE SYSTEM AND ITS CERTIFICATION

Börje Forssell, Norwegian Univ. of Science & Techn., Trondheim.Gunn Marit Hernes, Civil Aviation Authority, Bodø.Linda Lavik, Park Air Systems, Oslo

Airports in Norway

• 9 International• 9 medium sized• 28 regional with 800 - 1200 m runways• with LLZ/DME or VOR/DME• + military & private

Norwegian STOL airports

• Difficult terrain surroundings,

• LLZ/DME or VOR/DME nav aids, i.e. no glidepath (too expensive or physically impossible),

• non-precision step-down procedures using baro altimeters.

One of the difficult airports

Position 69.79°N, 20.96°E. Sample angle 1°

90 180 270 360 0

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Elevation

Azimuth

S E N W N

Horizon diagram of Sørkjosen community airport in northern Norway (ENSR).The approach to runway 15 lies along a fjord from the north.

Reasons for satellite-based aids

• Two fatal accidents (in 1988 and 1993).

• Parliamentary decision to establish glidepaths.

• ILS glidepath too expensive or impossible → satellite-based system was the only possibility.

SCAT-I

Most significant parameters transferred by the data link

• Integrity information;• Satellite identity;• Pseudorange corrections (PRC);• Range-rate corrections (RRC);• Issue of data (IOD), Z-count, etc;• PRC standard deviation;• Difference between corrections derived from two

independent GPS receivers and antennas;• Approach path (final approach segment);

The integrity parameters

• Integrity risk is the probability that an error caused by the system leads to a computed position error that exceeds the alert limit without warning users within the specified time-to-alert.

• The alert limit is the maximum allowable error in the user’s position solution before an alarm must be given within the specified time-to-alert.

• Time-to-alert is the time from the occurrence of the system error that causes the computed position error to exceed the specified alarm limit, to the display of the alarm at the user’s interface.

Allocation of the total SCAT-I system integrity (10-7 per approach) among the various functions

Composition and tasks of integrity panels

• Highly qualified people who are independent of the system designers, manufacturers, etc.

• scrutinise the assumptions and calculations embodied in the system in order to verify that the results can be trusted,

• examine in detail the system and subsystem descriptions, assumptions, algorithms, formulas and calculations, to ascertain that they meet the integrity requirements.

Approval by such an independent integrity panel is requiredbefore the system may be certified and used.

The Norwegian SCAT-I project

Airborne avionics: Universal Avionics Systems Corporation, Tucson, Arizona, USA.

Airline to use the new system in its Bombardier DASH-8 (DHC) aircraft: Widerøe.

Approval of the airborne avionics: The US Federal Aviation Administration,the Los Angeles Air Certification Office.

Responsibility for approval of the ground equipment, each individual SCAT-I ground installation and its approach procedures, and validation of aircraft installation approval:The Norwegian Civil Aviation Authority, Bodø.

Responsibility for developing the regulations, policies and services for transportation inCanada (incl. installations in the DASH-8): Transport Canada, Ottawa.

Responsibility for the installation of avionics in the DASH-8: Field Aviation, Toronto.

Ground system development: Park Air Systems (previously Navia), Oslo.

Project leader: Avinor, the state-owned airport owner and operator.

Early history of the Norwegian SCAT-I

• Parliamentary decision in 1996;

• Proof of concept and beginning of development in 1997;

• Initial test flights (at Torp airport) of a prototype Park Air ground station in 2001 with very encouraging results;

• More test flights followed, giving valuable data for further system development.

First part of the integrity validation process

Regulatory aspects of the project, including integrity validation and certification, were to be administrated by the NCAA;

Agreement with the US FAA that integrity matters would be the responsibility of the existing FAA LAAS Integrity Panel (LIP), who were preparing for certification of thebroadly similar Local-Area Augmentation System (LAAS);

In 1999, the LIP issued its first report on the formal documentation concerningthe ground and airborne avionics prepared by Park Air and UASC. As is customary withinitial integrity panel reports, the LIP raised numerous comments, questions andrecommendations and required changes and improved documentation covering multipleissues;

Park Air and Universal responded to this report with revisions and additional documentation. The LIP followed up with its second report in May 2002.

Continuation of the integrity validation process

In 2002, the FAA withdrew its support of the LIP with regard to SCAT-I.

Avinor resolved to proceed with the integrity process, andin mid-2002 the NCAA appointed a new panel:the SCAT-I Integrity Panel (SIP).

The mandate of the new SIP was tocontinue the work started by the LIP.This included some 80 outstanding issues.

The mandate was not to iterate the LIP work, but to look at the Park Air and UASC responses to the LIP report and see if that was found sufficient or not.

The ground equipment

The Park Air ground station was certified in February 2005.

The NCAA took over the ground station certification in Dec. 2003, continuing and completing the work started by the FAA.This work was based on RTCA DO-217 (“Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I”) and RTCA DO-178B (“Software Considerations in Airborne Systems and Equipment Certification”).

The SIP initially concentrated its workon the ground equipment, andby January 2004 all 60+ issues had been solved.

NM 8005 SLS ground equipment

Ground Station Tasks

• Send differential corrections, integrity parameters and three-dimensional approach data to the aircraft via the VHF link

• Monitor data before and after transmission

• Handle control and status panels

• Maintenance and monitoring functions

Landing System Characteristics

Integrity Risk - ”not correct, but no alarm” 1 • 10-7

Continuity - ”signal will be OK all the way” 3.8 10-4

Accuracy - ”normally within...” 1.1 m

Availability - ”signal is OK when you need it” 95%

NM 8005 architecture

The airborne equipment

The work of the LIP and the SIP had taken 8 years and 6 cycles.

The airborne equipment integrity process restarted in 2004 after some delays and was concluded satisfactorily by the SIP in January 2006.

Activities in Parallel with the SIP Work (2004 – 05)

Flight trials in Tucson using the Park Air ground equipment in conjunction with UASC’s certified (TSO approved) avionics;

Installation (by Field Avionics) of the avionics in 18 Widerøe aircraft;

Completed certification (by the FAA LA ACO) of the airborne avionics

RTCA/EUROCAE 178B (“Software Considerations in Airborne Systems and Equipment Certification”)

approval of the ground station software (follow-up after SW audit);

Verification by system-level testing that accuracy requirements were met.

Operational Approval of the NORMARC 8005 SCAT-I Ground Station

NCAA approval in January 2007 (incl. approach procedures developed by Avinor which were based on ICAO requirements ).

Issue of an Aeronautical Information Circular (AIC) and a supplementary Aeronautical Information Publication (AIP).

Update of the System Safety Assessment Operational Performancedocument for the Brønnøysund SCAT-I installation.

In March 2007, the NCAA received Readiness Statements from the Air Traffic Services at Brønnøysund and the regional Air Traffic Control Centre in Bodø.

Avinor applied to the NCAA for operational approval of the firstSCAT‑I ground station, installed at Brønnøysund airport (March 2006).

Operational approval for the Brønnøysund ground station was given bythe NCAA on 20 April 2007.

Approval of Widerøe as an airline operator of SCAT-I given by the NCAA on 31 August 2007.

European Supplemental Type Certificate (STC)

In February 2006, the FAA issued an STC to UASC covering the installation of the airborne equipment, a single UNS-1D Flight Management System, including the VHF data link. In March 2006, UASC applied to the European Aviation Safety Agency (EASA) for validation of this STC.

In May 2006, EASA requested the NCAA to execute this validation on its behalf.

The NCAA then organised test flights at Brønnøysund between 15 and 27 June 2007. These were successful, and EASA issued the required European STC in July 2007.

An STC was issued for the Norwegian flight inspection aircraft, LN-ILS, and for all Widerøe aircraft of types DHC 8-101, -102, -103 and -106,covering the use of dual Universal GLS-1250 DGPS SCAT-I Landing System airborne equipment.

Summary of the Certification Process

Wideroe aircraft

certification

Training

SCAT-1 Operational Procedures

Flight Inspection

Airborne equipment

certification

Ground station

certification

SCAT-1 certification

Brønnøy-sund

SCAT-I InaugurationBrønnøysund 29 October 2007

Park Air Systems awarded Jane's ATC Industry Global Award, March 2008!