LSGG south-west arrival (BELUS3S) and RWY 04 ILS appr

[Spender Vondel]

This arrival/approach confuses me. I understand how to technically fly it but I'm missing the logic: why fly over the airport, do a 180 turn, and then again a 180 turn to get on final approach when you can easily fly from the last arrival waypoint (CBY) direct-to INDIS and basically fly a straight way in.

'Radar vectoring to INDIS may be expected', so I assume ATC will do just that. But if they don't, why this elaborate 2 x 180 turn? Makes no sense to me but maybe I'm missing something. Please do tell 🙂

[Andre Bohni]

I think one part is the Airspacestructur and the other Factor is also the Terrain. If you look at the RNAV Procedure you also see, that this going above the ILS and then in an Downwind, that help a little to build a Sequence. More than only to have 8.7 Miles in beetween CBY. As Geneva only own the Airspace above CBY from FL095 up. Below there is another Airport where we have to look for Traffic.

Someone else could explane more but thats the reason i see as a Geneva Controller 🙂

[Spender Vondel]

Seems like reasonable explanations yes.

CBY is only 2 miles from the LSGG airspace from 5500ft and up though, so you can descend below 9500ft pretty quickly.  I just flew CBY direct-to INDIS for RWY 04 on VATsim and it worked out perfectly (Airbus A321N). The tower didn't like it too much since RWY 22 was in effect and 3 planes had to wait for takeoff - oops 😇 -  nonetheless he cleared me for the option 😄

 

Edited August 17, 2021 at 02:29 PM by Spender Vondel

[Dustin Rider]

It's best to look at the bigger picture to understand they why, here. There are a couple of likely explanations that pop out to me. One: the surrounding terrain near LSGG makes it such that other feeder routes, such as a DME arc or routes that come off of other nearby NAVAIDs are out of the question. Two: the full procedure is designed to take into account how someone experiencing radio failure can still land at LSGG. Take a look at the chart on Skyvector.com (one of my very favorite websites for flight simming, these days) and you'll see that there are a handful of routes that go over the GVA VOR. Since this approach starts from GVA, now you've got a seamless way to transition from the enroute structure to the approach procedure.

It looks like LSGG has its own approach control service, so the likelihood of you ever having to fly this procedure seems pretty low since most approach controls will vector aircraft to the final approach course to maximise efficiency. However, if the TRACON is closed and the overlying FIR cannot provide vectors to final, they still have a way to get you on the approach. Many airports, large and small, have similar procedures that will get you to the airport if all else fails. Take a look at the ILS 1L to KMKE. You don't necessarily overfly the airport to get onto the procedure, but the concept is very similar. Start from a VOR, take the feeder route to JUTAX, fly the course reversal and then fly the ILS inbound.