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The minimums for the Van Nuys ILS Z Rwy 16R are 1095/40. The minimums for the Van Nuys ILS Y Rwy 16R are 1461-1 1/2.

Question: Why are the minimums for the ILS Z so much lower than the minimums for the ILS Y?


Van Nuys ILS Z Rwy 16R

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Van Nuys ILS Y Rwy 16R

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The equipment requirement (in the aircraft) are different for each of these approaches. In the upper-left box of the Z approach, you can see that DME is required to make this approach. This requirement is not listed in the Y approach.

If your aircraft has the right equipment, you can reduce your minimums by selecting the appropriate approach plate.

In this particular case, the missed approach procedure from the lower minimums is more precise. The procedure includes DME distances that must be used while executing the missed approach procedure. Without DME onboard the aircraft, you would have to use the less-precise missed approach procedure requirements of intersecting VOR radials. This lack of DME, and thus a less-precise procedure, results in higher minimums.

In Section 4, para. 140 of the TERPS, the reason for multiple approaches to the same runway, using the same navigation system (ILS in this case) allows better-equipped aircraft to gain an "operational advantage".

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  • $\begingroup$ I see that, but why does having DME result (allow for) in lower minimums? $\endgroup$ – 757toga Nov 11 '18 at 17:19
  • $\begingroup$ Answer updated to reflect the answer to this comment, as well as provide just a bit more detail. $\endgroup$ – Jimmy Nov 11 '18 at 17:31
  • $\begingroup$ I can't find a "Section 140" in the TERPS manual. Can you tell me what page it is on so I can review the info? $\endgroup$ – 757toga Nov 11 '18 at 17:42
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    $\begingroup$ Sorry... Paragraph 140, under section 4. Answer updated. It's on the 82nd page of the linked PDF (not "page 82" ... it's actually page 3 following a whole bunch of change-notification pages) $\endgroup$ – Jimmy Nov 11 '18 at 18:17
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    $\begingroup$ Doing a bit more research, it seems that when there are approaches being flown into Burbank (just east of VNY) the ILS Z at VNY restriction to be at or below 1750 on the missed until 1.5 dme is to protect for that BUR traffic. I'm not sure what the operational advantage might be, but it must be based on traffic flow. The Y missed approach obviously has higher obstacles to consider in the profile, that normally is why the minimums are what they are. Note the hill at 2126 msl southwest of the airport on the missed appch profile. $\endgroup$ – 757toga Nov 11 '18 at 20:41

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