Hello guys. Happy hollidays. I'd like to know if I'm correct in this: RNAV approaches have higher minima than a catiii (which technically has none), plus a catiii has auto flare and rollout, and an rnav does not. If the above is correct, why would ILS approaches are being slowly replaced by rnavs throught the world? Is it purelly economical?RegardsArmando Arjona

RNP approaches may be used to replace CAT1 ILS because they may have similar minima and no required ground transmitter equipment. RNP/RNAV currently can't replace a CAT3 ILS for the reason you cited.(Also, CAT3 is not necessarily autoland.)

Other reason is ILS required long, 3deg slope final, while RNP approaches could be turns or to follow a valley of example, Turn around mountains...

That would not be why it replaces ILS though.

Other reason is ILS required long, 3deg slope final, while RNP approaches could be turns or to follow a valley of example, Turn around mountains...

That would not be why it replaces ILS though.

Why not? If you are in places where an ILS is unusable due to high mountains (the ILS would hit the mountain after a few miles for example, so becoming unusable) then RNAV will be able to give you a 3 degree glidepath all the way untill final even in the turn onto short final, so I fail to see where it can't replace the ILS in certain circumstances?

Well there you go, can't replace something that is not even there in the first place...

Well there you go, can't replace something that is not even there in the first place...

I am just makinga point, there might be other possibilities with the RNAV, as it also doesn't require a somewhat expensive ILS system on smaller airports where there's quite some traffic (good example is Saint Maarten). On places like this, they don't feel the need for ILS because there's barely bad weather, but when there is low visibillity, then can utilise the RNAV as it's much safer then a VORDME approach.

That is indeed all true, but thats beside the point. Question was about replacing ils with rnp approaches.

Mostly because traditional radio equipment is becoming outdated... And it costs a lot to repair/perform maintenance.

Hello guys. Happy hollidays. I'd like to know if I'm correct in this: RNAV approaches have higher minima than a catiii (which technically has none), plus a catiii has auto flare and rollout, and an rnav does not. If the above is correct, why would ILS approaches are being slowly replaced by rnavs throught the world? Is it purelly economical?RegardsArmando Arjona

I don't think that it so much a case of existing ILS installations being replaced (I.e. eliminated completely) in favor of RNAV. Rather, many new RNAV approaches are coming out every month to (1) provide instrument approaches for airports which never had any kind of instrument procedures available in the past, and (2) to supplement existing ILS installations. In the latter case, you will find many major airports like KLAX and KJFK which have existing ILS installations on every runway. There is now a complementary RNAV approach for each of those runways as well. This serves two purposes: to permit landing aircraft to conduct an instrument approach, even if their inboard ILS receiver has become inoperative, and also to permit any or all aircraft to perform an instrument approach to a given runway, even if the ground-based ILS transmitter fails.Indeed, many RNAV procedures have minimums that are almost the same as a CAT I ILS, for aircraft with RNP-certified GPS/FMS equipment, but it will be a long time before we will see an RNAV approach with the equivalent minimums of a CAT II or CATIII ILS.Now, there are many NDB approaches that have been replaced by RNAV equivalents (often with much lower minimums than the NDB version ever had), with the corresponding NDB transmitters and antennas being decommissioned and removed. Many of the NDB transmitters which were removed were truly ancient, and the original manufacturers have long since gone out of business, which has made repairs and maintenance a real problem.But, I don't know of many examples (at least here in the U.S.), where an existing ILS has been decommissioned in favor of RNAV.

I don´t think it´s that far off. GLS approaches (which really are GPS/GBAS-based Rnav approaches) should be just around the corner. Newer NGs are rolling off the facotry floor with the equipment necessary to perform said approaches. Couple that fact with Boeing´s IAN (which requires virtually little or no training for ILS-qualified crews) and ILS´s days are pretty much numbered. That´s my take on it anyway. Yet I´ve never been known for making Nostradamus-like predictions. Just an educated guess really - if such things do exist