Would be interested to know which countries (let’s focus on Europe) mandate CDFA for private operations. Even the author of that article doesn’t seem to know.
FAA AC 120-108 is guidance for airlines and other certificated operators. AC-120 series are not intended for part 91 operators. What is appropriate for Jets is not necessarily relevant or appropriate for small piston aircraft flown by part 91 operators. A part 91 piston aircraft does not have the mass, speeds, and spool up times or other flying characteristics of a jet. We fly single pilot, to a totally different type of airport that jets would never have a need or ability to fly into. ONE SIZE DOES NOT FIT ALL!!!!
Try flying a CDFA into N23 Sidney NY, RNAV RWY 7. If you survive by not boring a hole into the side of the ridge, you won’t make that mistake a second time. The FAA commissioned a study by MITRE Corporation on the safety difference between dive and drive and CDFA. With jets, it was obvious that CDFA had a safer record by more than two to one. They repeated the same analysis for smaller GA aircraft and found there was no statistical difference in the US, in fact the D and D was slightly better safety than the CDFA. There are a substantial percentage of airports that serve GA in the US that are not suited for the CDFA method. Some countries would solve the non issue by simply outlawing these airports. Fortunately in the US, that is not the view. Don’t misconstrue what I am saying, I enjoy the LPV approaches and take advantage of the advisory glidepath in places where it is warranted. But in many locations in the US, it is not.
in fact the D and D was slightly better safety than the CDFA
Is that maybe because a lot of people bust the minima, which you “can” do on an ILS or LPV (which should give you obstacle clearance all the way to the runway) but – as in the Sydney example – can’t necessarily do on a nonprecision approach.
Try flying a CDFA into N23 Sidney NY, RNAV RWY 7. If you survive by not boring a hole into the side of the ridge, you won’t make that mistake a second time.
You mean that the nominal glidepath will intersect the ridge? I’m surprised the plate doesn’t say, but you could get a clue from the note that the procedure is unavailable at night.
Anyway, surely the MDA must be at a safe height about the ridge?
That airport has a rock below the MDA, so if you bust the minima and continue a +V “GS” past the MAP, you hit the rock.
There aren’t many of these but there are some.
But while you can see the temptation to just keep going., with a LNAV+V you still have to treat the MDA as a hard limit.
so if you bust the minima and continue … you hit the rock.
I see. That’s not obvious from that chart. It shows some close-by obstacles but to the side of the centreline. On a Jeppesen chart this would be much more clearly visible by a shaded grey area under the profile.
But obviosuly this has not been a big problem so far: Link
It isn’t shaded there, BUT it is a nonprecision approach so you have to go missed at the MDA.
BUT it is a nonprecision approach so you have to go missed at the MDA.
Now that’s the big question. Doing a dive&drive approach, you should legally be allowed to continue at MDA until reaching your missed approach point. Which in this case would be the threshold 07 that you will be crossing at an altitude of 1115 ft AGL which is pretty much useless for a subsequent landing unless you are in a helicopter. On the other hand, CDFA approaches always (?) come with a DA (as well as most RNAV approach procedures from the European Jeppesen coverage) which means that you have to go around immediately when no contact can be established.
And this is also my objection against Boscomantico’s statement from yesterday “it is entirely legitimate to fly dive and drive, even in Europe.” It may be, but then you must use a chart that has values for MDA. If you use a Jeppesen Chart with only a DA given you must treat that as what it is (at least during your annual IR checkride).
