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Old 10-23-2023, 02:06 PM
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Default VOR Rwy 32 MUMBAI, INDIA

I had a question about the VOR Rwy 32 in Mumbai that I'm not sure about, anyone care to take a stab? Let's say we can't use FMC generated RNAV waypoints as a substitute, ILS is unavailable, and we have to fly this as a non-precision approach. My question specifically is how to apply the lowest MDA of 650' using the D2.8 fix.

This is what I came up with:

This is a non-precision approach that is offering a continuous decent profile (CDFA) instead of the “dive and drive” step down profile. The chart allows a lower altitude (MDA) IF a point along the final approach point can be identified.

See Note 1: DME REQUIRED, also note that it’s a 3.29 degree vertical path, so it’s not exactly 3:1

If I was flying the approach inbound and start my decent a D7.5 I’d expect to cross D3.8 at 1330’ and could decent to 780’, arriving at 780’ as long as I STILL have DME and can ID D2.8 I can continue to 680’ the MDA. Note that on profile you’d cross D2.8 at 980’. The missed approach point is at D1.0 at 650’.

However, if you lose DME and can't identify MAP you'd have to go missed anyway. Can some explain this with any authority?
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Old 10-23-2023, 03:32 PM
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I'm not sure I understand your question: the chart is self-explanatory and you covered the bullet points. If you can identify D2.8, then you're legal down to 650'.

You indicated that the condition for your question is "FMC waypoints" not available, apparently inferring that other sensors that might be used in lieu of DME to establish a position (GPS) are unavailable, and the procedure is being flown as a direct-tune, sole-source procedure. So, VOR with DME. As you noted, DME is a requirement to fly the procedure (operators who have the capability of using other data in lieu of DME might be able to do it without DME, but that's been excluded in this question). Bottom line: DME required.

Note that the initial approach to this procedure is flown from chart 13-4; a DME arc. Clearly it's built around DME. Chart 13-4A does include two depicted procedure turns (one for Category A/B, and one for Category C/D). These also are predicated on DME fixes.

Because you have established that no other navigation capability beyond a direct-tuned sole-source VOR with DME is available, clearly DME is required. If DME is lost or becomes unavailable, the procedure is not authorized, because DME is required.

Your question asks which minimum is to be used. There are three choices, each with the requirement to identify the fix using DME.
With identification of the D2.8 fix, minimums are 650'/2500m (Category C/D)
With identification of the D3.8 fix, minimums are 780'/30000m (Category C/D)
Without identification of the D2.8 AND D3.8 fixes, the minimums are 1330'/5000m (Category C/D)

If you can't identify either fix, you're restricted to 1330'.

The briefing strip advises that the MDA is 650' and that it's conditional; a check of the minimums section shows what condition is required to authorize and achieve 650': the D2.8 fix.

This is all off the chart, and unambiguous, so I'm not sure what you're asking. Are you asking what happens if you lose DME and can't identify a fix? If so, you answered your own question. Execute a missed, if the visual references are not in sight.
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Old 10-30-2023, 12:15 AM
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Your question, if I understand it correctly (flying the approach and then losing DME so you can't identify the MAP) is the same as asking if you are flying an ILS and lose your LOC receiver. You go around, unless visual. It's required for the approach.
So at D7.5 as long as you have DME, you can descend to 1330. If you still have the DME at 3.8, keep on trucking, at 2.8 same thing. If at any point you lose it, you go around. Missed approach does not require DME for this reason.
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Old 11-26-2023, 06:30 PM
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I think his question is why even have seperate mins for difference points if DME is required. Possibly the answer is while a continous decent is offered, it is not required. If not used, such as the aircraft is not capable, it may not be practical to try and dive down after D3.8, it will exceed a 3° glide path and it will also exceed the 3.29°, since reaction won't be instantenous. I don't know for sure, but I'd wager it probably has something to do with this descent profile.

Obviously if you lose DME you lose the ability to shoot the approach, it's not a station-passage-type approach, so there is no allowance for "no DME".
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