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HAC Communique – Aeronautical study of VHF-DF service

July 3, 2008  By Corrie

July 3, 2008 - Nav Canada is proposing changes to the VHF-DF Services they now provide.  They are requesting comments and feedback from HAC members on the impact of the proposed changes.

July 3, 2008 – Nav Canada is proposing changes to the VHF-DF Services they now provide.  They are requesting comments and feedback from HAC members on the impact of the proposed changes. 
The following document outlines the proposed changes.

Comments can be sent to:
Rob Bishop
Service Analyst
Ph (613) 563-5616
Fax (613) 563-5602
Comments should be submitted by 15th July 2008.
Alex Holliday
Co-chair HAC Safety Committee
(250) 769-4111

•NAV CANADA is conducting an Aeronautical Study to determine if the current Very High Frequency Direction Finding (VHF-DF) service meets the operational and safety requirements of pilots.
•A previous Aeronautical Study was completed which determined where VHF-DF equipment was required (i.e. at all tower and FSS where radar coverage and ATC communications were inadequate).
•VHF-DF equipment is provided at 27 FSS, two Towers and one RAAS site. The Study recommended new installations at 9 FSS sites.
•This Study focuses on the VHF-DF service itself.
•Current VHF-DF service elements are:
–Emergency Cloud-Break;
–Emergency No-compass Homing;
–Track-out Assistance; and
–Time & Distance Estimates.
•There is no evidence that any of these elements, other than homing, have been required in the last 10 years.
•ICAO recommended practice recognizes only homing with no compensation for wind drift
•Homing is the only element of the service that most pilots are aware of, receive training on, or use.
VHF-DF Cloud-break procedures are complex. Most of the required maneuvering must be conducted above or between cloud layers (VMC) followed by a descent in IMC. Even under optimum conditions, a VFR pilot could be exposed to an unacceptable level of risk.
•No-compass homing is unrealistic – assumes failure of primary, back-up (wet) compass and GPS.
•Fix, Track-out Assistance, Time & Distance Estimates not required as under normal conditions pilots are able to navigate around and between aerodromes either by map reading, using conventional NAVAIDs or GPS.
•Study recommendation is to provide only VHF-DF homing, consisting of aircraft’s bearing from the station and a heading to steer to the station with no compensation for wind drift.
•This homing service, to be called “VHF-DF Navigation Assistance”, complies with ICAO recommended practice.
•In a weather related emergency when radar assistance or an alternate aerodrome is not possible ATS will provide:
–Local weather information;
–Location of significant terrain and obstacles;
–If possible, coordinate assistance from other pilots in the area; and
–Where VHF-DF is available, navigation assistance service consisting of the aircraft’s bearing from the aerodrome/station and a heading to steer to the aerodrome/station.
•VHF-DF Navigation Assistance Service is intended to help pilots in the vicinity of an aerodrome who are lost or unsure of their location and are having difficulty in navigating to the aerodrome.
•To complete the study, NAV CANADA needs pilot input. What are your issues and concerns with this proposal?
•Please provide feedback on the VHF-DF Study to:
–Rob Bishop (613) 563-5616

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