CBR Rwy 35 query.

[down3gr33ns]

Been visiting a friend who lives about 10 nm south of Canberra airport and under the approach to Rwy 35.

In watching multiple aircraft using that runway for landing, there are two distinct, but very close tracks, utilised. One of them passes directly overhead his house whilst the other is displaced to the west by about 0.5 nm . The a/c that regularly go overhead are the 717's, Dash-8's, RAAF, Alliance et al. Consistently using the path slightly to the west are Qantas and Virgin 737's.

Is the difference because some aircraft use the ILS whilst those to the west are using a GPS/RNAV type approach approved for those companies? Looking at the Airservices charts for both the ILS and GPS 35 approaches, the inbound track is the same.

I cannot find the inbound track for a GPS approach that may be specific to QF and VA. Can someone possibly advise what that inbound track would be? No need for a chart to be posted, just the inbound track would be enough to explain the separated tracks.

[Beer Baron]

They would be flying the RNP-AR approach. It is a curved approach that starts from the east, crosses the centreline and rejoins from the west. No single inbound track. See the plate below: (I know you didn’t ask for it but it’s simpler to show you).

https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/1125x1003/aaebeb42_aa85_47f7_8fa9_8d196941e953_75dd4d80431ee033926ae38 da867d2e955883def.jpeg

[down3gr33ns]

Good, thanks. That would explain it.

[ad-astra]

Now, can someone explain WHY a straight approach can't be achieved.
Please God its not because we are avoiding the built up areas on approach!

[Australopithecus]

No, its to put more noise on the prison. The sound of freedom and all that.

[DirectAnywhere]

Now, can someone explain WHY a straight approach can't be achieved.
Please God its not because we are avoiding the built up areas on approach!

That’s precisely why it’s done. Makes no difference for an RNP-AR whether the approach is curved or not. Autopilot is in until late for most of us. Aircraft doesn’t care if it’s curved or not. Works beautifully.

Can be curved to avoid terrain (Queenstown/ Cairns rwy 33) or for noise abatement. They’re the ducks guts as far as PBN approaches go.

[down3gr33ns]

OK, out of interest, can someone with access to the AR chart post some height comparisons at equivalent points on the AR chart and the "normal" GPS chart for 35?

I'm reluctant to believe it's for noise as there is no difference with that minimal westerly displacement for the 73's compared to the ones (including 73's) that go directly overhead.

[Judd]

Autopilot is in until late for most of us
As the plate seems to indicate a semi-curve on to final is it possible to hand fly the same approach just to keep your hand in? Can it be done without relying on the flight director?

[DirectAnywhere]

As the plate seems to indicate a semi-curve on to final is it possible to hand fly the same approach just to keep your hand in? Can it be done without relying on the flight director?

Can be hand flown. Flight director is part of the required equipment.

The RNAV GNSS and all three RNP-AR to CBR 35 are all coded at 3 degrees so heights are the same to a 50’ TCH.

[Checkboard]

There's not much point "keeping your hand in" for curved GPS approaches. You end up flying Flight Directors only, which isn't any good for your scan - and for RNP AR operations, most operators require at least one AP must be engaged prior to the Initial Approach Fix (IAF) (According to a/c equipment, RNP AR may be approved to RNP 0.3 or RNP below 0.3 (lowest certified RNP is 0.1).)

[down3gr33ns]

Please God its not because we are avoiding the built up areas on approach!

That’s precisely why it’s done.

The RNAV GNSS and all three RNP-AR to CBR 35 are all coded at 3 degrees so heights are the same to a 50’ TCH.

Which all seems to confirm it's a bit of a wank - 500 mts (at absolute best) to the west is doing bugger all for the noise envelope.

Is there an advantage with the minima on the RNP-AR approach versus the "normal" GPS approach? If not, what is the advantage?

[morno]

Which all seems to confirm it's a bit of a wank - 500 mts (at absolute best) to the west is doing bugger all for the noise envelope.

Is there an advantage with the minima on the RNP-AR approach versus the "normal" GPS approach? If not, what is the advantage?

There’s a 240ft difference between the Zulu (RNAV) and the RNP-AR approach for runway 35. But you have to satisfy all the RNP requirements to be able to even get approval to conduct the approach, it’s a little more involved than just doing an RNAV approach.

I haven’t flown one myself, but the idea is that they should also avoid unnecessary level segments from TOD to the ground too I think. So more fuel efficient if that’s the case.