Friday, June 26, 2009

The VOR-DME Approach

In this post I'll explain the VOR-DME approach. I haven't wrote the different approaches there are in Mexico:


There are many other airport charts, but I'll explain the approach charts first.

The VOR-DME approach has some differences from the VOR approach, but the major difference is that you use the DME (Distance Measuring Equipment). Here's the example:

The VOR-DME Rwy 22 of Puerto Vallarta. As we can see, the difference from a VOR chart is that we fly on a radial and then turn to intercept the inbound course.

Very simple. Crossing the PVR VOR at 5000ft, we fly on the 044 radial 13 DME (13 nautical miles) from the station. After reaching 13 DME, we make a left turn to intercept the 211 inbound course to PVR and descend to 4100ft. When crossing 13 DME on the 211 inbound course, we start our descend to 2600ft. At 8 DME to 1400ft and when reaching 5 DME, we must descend to the MDA. What is our MDA? 720ft.
If we don't have the runway in sight, we execute the missed approach procedure: Climb via the 223 radial to the 7 DME of the PVR VOR, with a teardrop turn to the right within 10NM from the station and level off at the MHA=5000ft.

Now, we have a different type of approach if we are arriving from an airway. The final approach phase is the same (note the (IF) in 15 DME) for all VOR-DME Rwy 22 approaches. This is the VOR-DME 3 Rwy 22:

Why the number 3? Because there are 3 different approach procedures for the VOR-DME Rwy 22 aproach. The difference depends on the airways we are arriving from. Most procedures are made if the airway is near the inbound course of the approach. If we are arriving from an airway from the south or the west, we would use the VOR-DME1 approach. The airways are shown in the chart.

Suppose that we are flying on the V14N/UJ14N airway. We would start our descent so that we cross 50 DME from the PVR VOR at 14000ft. Then we descend to 11000ft at 24 DME and 8000ft to the Initial Approach Fix=IAF, which is 17 DME from the station. We must cross the IAF, unless ATC clears us to fly to the final approach phase.
Now the things become interesting. When reaching the IAF, we must descend to 6000ft and make a 15 DME Arc to intercept the final approach course. Crossing the 052 radial still making the arc, we can descend to 5000ft. When reaching the 039 radial, we descend to 4100ft and intercept the inbound course. The procedure after crossing the 039 radial is the same as the VOR-DME1 procedure.

I personally love this approach. It combines a DME-Arc and a VOR-DME approach. Oh and of course... we land at a famous tropical destination in Mexico ^^.

Next one: NDB approach.

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