VOR/DME Approach Chart
Only half a speed-brake
FAF is defined with DME. Why is the DME not also used for the outbound leg in the design of this particular procedure I do not understand. And the timing interval seems just plain incorrect.
Maybe, in the dim & distant past, this was once a 'VOR or VOR/DME' approach? As time moved on, corporate memory failed, and ICAO played silly buggers with approach naming conventions (again) the 'VOR' just happened to get dropped?
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According to the source document - the actual chart produced by the regulatory authority - the procedure is ICAO (ie Pans Ops) not TERPs. Using some of the Pans Ops calculations that I've used over a period of about 26 years, I found :
1. The base turn splay angle for Category A/B, based on 180 knots at the highest MSA, 4600 feet, should be 17 degrees for 2.5 minutes outbound, not 15. The nominal outbound distance would be around 8.2 NM, which would be enough to permit the inbound turn without too much of an excursion beyond the final approach track.
2. The base turn splay angle for Category C/D, based on 250 knots at the same MSA should be nearly 40 degrees for 1.5 minutes outbound, not 30 degrees. The nominal outbound distance would be 6.87 NM or thereabouts, which would be okay for a reversal to reach the FAF, but the splay angle seems manifestly inadequate to accommodate the turn.
Personally, I've never had a problem with declaring an outbound timing for a procedure that defines the FAF by means of a navaid or fix. The procedure can still be called VOR/DME but, with a titling change to ICAO charts, the procedure should be identified as VOR RWY 17 with information in another box to identify the other aids that are required by the procedure. I'm not convinced that's the right way to go but it seems to be more related to database recording than actual chart usage.
I was going to include an image of the final approach course, runway alignment and navaid locations, but couldn't be bothered with the trouble of placing the image online first. Anyway, I used the coordinates for navaids, ARP and thresholds to try to figure out why the MAPt is located at 1.65 DME MIA (according to the source chart).
What I found was that the actual intercept point for final approach course and runway centreline occurs about 1.9 DME, or thereabouts. The location at 1.65 DME MIA appears to be the very latest point at which the runway approach splay is intercepted by the final approach course. It's legal in Pans Ops but not especially satisfactory for the pilot flying a Cat. D aeroplane that might have to use the procedure.
It was interesting to note that the chart publishes a decent gradient of 5.2% between FAF and MAPt. I'm guessing that it would've been a tad steeper if the MAPt had been at 1.9 DME.
According to the source chart, the procedure has existed since a publication date of 1 January 2011 (and perhaps longer?). Either there's been no complaints because the approach has never been used, or complaints have been made and ignored.
It seems like a good chart to use for SIM work though!
Perhaps it's time for those who use, or plan to use this approach, to refer the issue to their company experts, who can make enquiries with the national regulatory agency. I doubt that an enquiry to Jeppesen would be any more helpful because it would seem that all they've done is to reproduce the chart for their own customers.
1. The base turn splay angle for Category A/B, based on 180 knots at the highest MSA, 4600 feet, should be 17 degrees for 2.5 minutes outbound, not 15. The nominal outbound distance would be around 8.2 NM, which would be enough to permit the inbound turn without too much of an excursion beyond the final approach track.
2. The base turn splay angle for Category C/D, based on 250 knots at the same MSA should be nearly 40 degrees for 1.5 minutes outbound, not 30 degrees. The nominal outbound distance would be 6.87 NM or thereabouts, which would be okay for a reversal to reach the FAF, but the splay angle seems manifestly inadequate to accommodate the turn.
Personally, I've never had a problem with declaring an outbound timing for a procedure that defines the FAF by means of a navaid or fix. The procedure can still be called VOR/DME but, with a titling change to ICAO charts, the procedure should be identified as VOR RWY 17 with information in another box to identify the other aids that are required by the procedure. I'm not convinced that's the right way to go but it seems to be more related to database recording than actual chart usage.
I was going to include an image of the final approach course, runway alignment and navaid locations, but couldn't be bothered with the trouble of placing the image online first. Anyway, I used the coordinates for navaids, ARP and thresholds to try to figure out why the MAPt is located at 1.65 DME MIA (according to the source chart).
What I found was that the actual intercept point for final approach course and runway centreline occurs about 1.9 DME, or thereabouts. The location at 1.65 DME MIA appears to be the very latest point at which the runway approach splay is intercepted by the final approach course. It's legal in Pans Ops but not especially satisfactory for the pilot flying a Cat. D aeroplane that might have to use the procedure.
It was interesting to note that the chart publishes a decent gradient of 5.2% between FAF and MAPt. I'm guessing that it would've been a tad steeper if the MAPt had been at 1.9 DME.
According to the source chart, the procedure has existed since a publication date of 1 January 2011 (and perhaps longer?). Either there's been no complaints because the approach has never been used, or complaints have been made and ignored.
It seems like a good chart to use for SIM work though!
Perhaps it's time for those who use, or plan to use this approach, to refer the issue to their company experts, who can make enquiries with the national regulatory agency. I doubt that an enquiry to Jeppesen would be any more helpful because it would seem that all they've done is to reproduce the chart for their own customers.
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EJ - as I said in post #4,
"Back to company for a decision, errajane, I think!" - do you have any feedback? This is not a 'safety' issue since the worst that will happen is a session of missed approaches, so that avenue is closed, but your company NEEDS to take this up with the CAA to get it sorted. Nothing to do with 'splay angles' - just cock-up. I'd be interested in what one of your shiny TRE's has to say about it.
"Back to company for a decision, errajane, I think!" - do you have any feedback? This is not a 'safety' issue since the worst that will happen is a session of missed approaches, so that avenue is closed, but your company NEEDS to take this up with the CAA to get it sorted. Nothing to do with 'splay angles' - just cock-up. I'd be interested in what one of your shiny TRE's has to say about it.
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OzExpat:
I can't speak to PANS-OPS, but with TERPS when DME is mandatory for the final approach segment DME goes in the title. When DME is not mandatory for the final approach segment, but for some other part of the procedure then DME Required goes in a note.
In any case, timing makes no sense when the FAF requires DME.
As to Jeppesen "copying" the AIP chart that is all they are permitted to do.
Personally, I've never had a problem with declaring an outbound timing for a procedure that defines the FAF by means of a navaid or fix. The procedure can still be called VOR/DME but, with a titling change to ICAO charts, the procedure should be identified as VOR RWY 17 with information in another box to identify the other aids that are required by the procedure. I'm not convinced that's the right way to go but it seems to be more related to database recording than actual chart usage.
In any case, timing makes no sense when the FAF requires DME.
As to Jeppesen "copying" the AIP chart that is all they are permitted to do.
