RNAV approachStep Down Fix Issue for LNAV operation CNS/ATM Steering Group 40th meeting AOB Item
SDFs • Used on Conventional/RNAV NPA procedure without vertical guidance (Non APV procedure) • A procedure designer tool (e.g. for clearing an obstacle enable lower MDA) • Concern is related to SDF located between FAF and MAPt • No more than 2 SDFs in the Final segment
During last months there have been extensive discussions in several States about the potential safety hazards associated to step down fix being encoded in the final approach segment of a procedure. One example Case of a « named » Step Down Fix (five-letter name): ME09L
Another example 2 SDFs in the Final Approach Segment. SDF are not named
ISSUES associated to SDF • Coding of SDF between FAF and MAPt in the navigation data base for RNAV approach could be unsafe. • Risk of not presenting distance to the MAPt in the primary field of view after passing the FAF if SDF is included in the navigation data base. • Risk of missing the basic intent of a SDF for the crew which is to respect the SDF constraint (altitude/distance) independently from the RNAV system (as far as practicable) in order to improve the safety of the operation. • It is necessary that RNAV systems manage SDF identically from one system to another one which is not the case today. • This inconsistent way of implementing SDF is a main issue for operators and may lead to confusion. • Standardization in this area is necessary. • It is necessary that authorities share these here above concerns in order to find jointly a solution to solve these airborne issues.
Coding Step-Down Fixes Extract from Jeppesen position July 2007(1/2) Background • ARINC 424 -18 (present version) is stating in Attachment 5, paragraph 6.2.2 that: “all fixes associated with the lateral and vertical path of approach procedures must be coded, including step-down fixes, both before and after the Final Approach Fix (FAF).” • Since 2002, Jeppesen has been notified the FMS manufacturers that beginning with the update cycle 0211, effective 31 October, published step-down fixes between FAF and the Missed Approach Point (MAP) on non-precision approaches will begin appearing in their navigational database. • In 2002, Jeppesen began capturing step-down fixes between the FAF and MAP. Since then, 3,200 step-down fixes have been captured affecting over 2,800 terminal procedures.
Coding Step-Down FixesExtract from Jeppesen position July 2007(2/2) Short coding considerations: • All source-supplied i.e. published on State procedure chart SDFs are coded between the coded FAF and the coded MAP for all non-precision approach procedures. • Each step-down fix will have the appropriate altitude constraint attached, coded according to the government source; usually, SDFs have associated ‘at or above’ (+) altitude. • The SDF waypoint name/identifiers are normally provided by official source. If no source given name is supplied, Jeppesen uses the Naming Convention rules described in the ARINC424 specifications, Section 7.0.
INSTRUMENT FLIGHT PROCEDURE PANEL (IFPP)WORKING GROUP OF THE WHOLEREPORT OF THE FIRST MEETING(Montréal, 27 August to 7 September 2007) • “9.6 Publication of a Step down Fix in a Final Segment of an RNAV Procedure (WP/7) 9.6.1 After extensive work over the past meetings, requirements for the publication of a step-down fix in an RNAV final approach were matured and agreed on in the previous working group of the whole meeting. However, due to safety issues relating to airworthiness requirements, that recently were identified, the paper was withdrawn together with the draft proposed amendments. The meeting also agreed that the Charting WG should coordinate with other IFPP working groups and ICAO bodies and possibly to solicit input from State airworthiness regulators to develop a mature proposal for the next working group of the whole meeting.”
Conclusion • Due to the possible safety issue identified: • it is necessary to have a European position on this subject and not a UK one, a German one or a French one. • EASA should be the body to coordinate such position with NAAs, Eurocontrol and FAA.