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CDFA vs step-down minima on non-precision approaches

Asked by: 2523 views , ,
Helicopter, Instrument Rating

Hey,

I have a question regarding CDFA minima. I got my first instrument training in aircraft equipped with ADF only, so I was trained performing "company-only" NDB and PAR approaches. Then I got a real-world instrument rating in Canada in 2016 on fixed-wing aircraft, good for Cat I and that time we "simply" started to descend from FAF/FAWP. We were not required (although it was encouraged) to calculate a nominal descent rate for an approximate glide path, and we flew on MDA until reaching MAP/MAWP.

Then I started to fly on new "company" aircraft (also good for Cat I including RNAV with SBAS) and my task was to work on new instrument training within company that is conformal to GAT rules. We started to use Jeppesen's approach plates and their landing minima says DA/MDA (CDFA). I started to do some research about the usage of CDFA technique and it's all clear why it is useful. However, concerning MDA/DA, I got a bit lost. I researched EU-OPS, ACJ-OPS 1.430, Jepppesen Bulletin JEP-15A and it is simply not clear whether I have to apply altitude add-on to a CDFA MDA if I want to use the technique or not - and how many? And if I have to, then why the heck they call it DA since I have to apply additional altitude to use it as DA?

From my previous training, it was always clear that I cannot bust MDA without seeing RWY environment. I  (we) started instructing our "company" pilots to do step-down descents on an NDB, LOC/DME, VOR/DME or RNAV, even with +V advisory glidepath, because it always works and clear, and on helicopters, it is not as big issue not to be on the nominal glide path as it is on a fixed-wing. My friend flies bizjets and they ("company" rules) apply a 50 feet addition to CDFA MDA, although they are Cat C, usually go to bigger aerodromes for Cat II ILS and other fancy stuff so non-precision approaches are rare.

It is also confusing to me because on the Jeppesen plate it says that a given RNAV approach has DA/MDA, and it is, say, 1010 feet. But I saw the original "company" AIP approach plate and the altitude was the same 1010 feet but they issued OCA/OCH, instead of MDA/MDH. I think this is the point where I got totally lost. But I don't want to teach bullshit to our guys.

Thanks for your help in advance.

Regards, Andy

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