By Jim Harris 832078
#527424 I've been watching Airline2sim's excellent videos, he's done an approach into GCTS recently. He flew a VOR approach. In real life.. when would you fly that sort of thing (or an NDB etc)? I'd expect to be vectored most times. Why are they published and who would use them and when. If you see what I mean.

Jim Harris
EGBN
By Don Desfosse 1035677
#527427 Jim,

I'm sure there are plenty of other answers/opinions also, but I'll take a crack at it from my experience. I am wondering if/assuming you are referring to a full approach (vs. vectoring). Getting vectors to a final approach course if convenient and efficient. However, in many parts of the world, terrain and/or radar placement can severely limit the altitude that radar can "see" you. And in order for an instrument approach to be most effective, it needs to get you down as low as you can go and still safely complete the approach (and landing). So you may be directed to fly to an initial approach fix and get cleared for the full approach, with the radar controller not being able to see you, because your approach may be below the radar controller's minimum vectoring altitude. Another reason is workload; a busy controller may save many transmissions by simply saying "proceed direct SUMFX, cleared VOR ___ approach, report procedure turn inbound." Hope this helps.
By Andreas Fuchs 810809
#527433 IAPs (Instrument Approach Procedures) are established at all airports, that operate IFR-traffic. They are the basic way to proceed from an IAF (Initial Approach Fix) to a FAP or FAF (Final Approach Point/Fix). If radar control is available, vectors to take you more efficiently to your FAP/FAF will be more likely.

So, in addition to what Don has pointed out - terrain - the fact that radar is available plays a major role. No radar, no vectors. And if you have a radio-failure you will also fly a standard approach according to the IAP.
By Simon Kelsey 810049
#527437 Jim,

As Don mentions, there are two factors at play here: 1) radar vectoring/sequencing to final approach vs flying the full procedures and 2) flying a non-precision approach rather than an ILS.

The former (procedural approaches) are common at smaller airfields where there is no Radar, because perhaps terrain/traffic levels/investment (to give just a few examples) precludes installing radar and recruiting/training/maintaining radar controllers. Many of the Greek islands, for example, have no Radar.

With no radar, aircraft have to be procedurally separated which is not very efficient as it relies effectively on position reports from the pilots and time and altitude-based separations -- however, the approach procedure provides a convenient means for that to be accomplished whilst keeping the aircraft terrain safe and within a reasonably compact piece of airspace. Thus, an aircraft can be cleared for the procedure whilst another sits in the hold over the beacon at a higher level - once the first approach is completed the aircraft in the hold can be cleared for the approach and so on. Clearly, using radar to sequence aircraft on to a final approach track is much more efficient for busier aerodromes! A procedural approach, however, could be a non-precision approach like a VOR/NDB etc, or it could be to an ILS.

On the other hand, there are some aerodromes where it is impractical to install an ILS. This is often because of terrain concerns -- there are minimum terrain/obstacle clearance surfaces for the glideslope and the missed approach which must be met and terrain can interfere with the ILS signal to the extent that it is not usable. At these aerodromes there may be a VOR or NDB, for instance, that can be used as an approach aid to enable an aircraft to let down through cloud to a position where the pilot can see the runway sufficiently to manoeuvre the aircraft visually to land. Because such aids are less accurate than an ILS and there is no glidepath guidance the minima for such approaches are higher and the final approach track is unlikely to be directly in line with the landing runway.

However, it is quite possible to be radar vectored to the final approach track of a VOR or NDB approach just like an ILS if a radar facility exists, but obviously once established on the approach it is then over to the pilot (just like an ILS).

When would a pilot choose to fly one? In most modern airlines, generally when there is no other approach available as most specify that the most accurate available approach should be flown, which will normally be an ILS if one is installed and serviceable. Otherwise the order of preference would then, nowadays, often be RNAV if one is available and the aircraft is equipped, then VOR and finally NDB.
By Trent Hopkinson 812681
#529924 Some airport runways don't have an ILS installed, for various reasons, perhaps relating to terrain, or noise/political issues. Recently, the Australian Government approved an ILS for one of the runways at YBCG (Gold Coast airport.) There were several political protests regarding this decision as having an ILS was seen as increasing the capacity of the airport - therefore increasing the amount of flights arriving there, and people like their towns to be quiet, even if it costs the occasional aircraft running low of fuel having to divert.

https://www.abc.net.au/news/2017-03-03/ ... rt/8321304

So with an airport (or in many cases, specific runway at an airport) without an ILS, the only other options used to be to base an instrument approach on another type of navaid. IF there is no navaid at an airport, the only valid IFR approach is a GNSS derived RNAV approach, and not all aircraft are equipped for that.

Most airports will have at least a VOR or NDB located at or near the airport, and this can be used as a basis for some kind of instrument approach to at least get the aircraft positioned at a lower minimums than just VFR flight. Useful when there is cloud below several thousand feet ceilings.

Image

Now you may think airports without an ILS must be rare. But there's plenty of big International airports out there without an ILS on every runway. Gold Coast - at least till later this year - which receives not only the usual mix of domestic A320 and B738 aircraft, but also daily flights of Air Asia X Airbus A330's, Scoot Boeing 787-8's to name a few.

Melbourne's runway 34 has no ILS either, and does indeed have a VOR approach.
http://www.airservicesaustralia.com/aip ... EB2019.PDF

And an airport you may have heard off called "Princess Juliana Airport."
Image
By Brad Littlejohn 811975
#529959 Another thing to consider in addition to all of the above, and given that the field doesn't have anything relative to an ILS approach (LOC, LOC/DME, LOC/GS, etc.) is the weather.

If the field in question has a VOR approach (precision, non-precision, or otherwise), but your field is IMC, no amount of vectoring is going to get you down. You're going to need an instrument approach to get you to the field. And the good thing about a VOR approach, is that it would be applicable to nearly all modern equipment types. So if you're flying an aircraft that is /A equipped, you're golden for getting that VOR approach to that field.

BL.
By Andreas Fuchs 810809
#529971 Hi Brad,

I think you misunderstood the bit about vectoring: vectoring normally shortens the distance that is needed to intercept the final track of an instrument approach. There are only a few places where you will or can get "talked down". Actually, a proper PAR approach will have similar minimums like a CAT I ILS.
By Andreas Fuchs 810809
#529983
Magnus Meese 997444 wrote:PAR is mostly MIL, but you can get SRAs all over the UK if you ever want to be nagged down by someone! The minimums are usually a few hundred feet higher.
Oh, really, I did not know this :lol: (I regularly fly the PAR into EGWU).

With the availability of RNP approaches at almost all airfields SRA/SRE approaches will happen even less, since broken nav stations on the ground are not a limit anymore.
By Magnus Meese 997444
#530013 Yep, these days they're more often done in order for the ATCO not to lose their SRA endorsement than anything else (certain no. required over a certain period), I guess. I bet pilots love to be queried to do one for that reason when they had a nice and easy ILS set in their mind :lol:
By Andreas Fuchs 810809
#530022 Ha, I enjoy flying PARs/SRAs as well. Northolt is particularly interesting, as you know, due to the proximity to Heathrow, dictating a relatively late line-up with the axis of runway 07.