Sydney DEP/ARR procedures

[Hardy Heinlin]

KAMBA FOUR - RWY 07 - SID

Either there's a knot in my brain or an anomaly in these government data:

http://www.airservicesaustralia.com/aip/current/dap/SSYDP02-129.pdf

It's not for jets, but anyway. It's about geometry.

When you are at the place-bearing SY R-040° / 5 DME it's impossible to intercept the SY R-013° radial before SHORE on a 360° track. And if you are not yet at 2000 feet at that point, you will start the 360° track even further east.

On the ND below, you can see that the 360° track, starting at 2000, would pass east of SHORE. It can't intercept any radial west of SHORE. On the screenshot there's a big gap in the magenta route because of this paradoxon. (In my database there's no intermediate intercept after 600 ft to intercept that SY R-040°; but this is neglible, these mini-curves wouldn't make a difference, at 600 you actually are already on that radial.)



Has anyone flown this SID?


Cheers,

|-|ardy

[Pierre Theillere]

Hi Hardy!

I haven't flown this SID... but I powered-up my mind and checked the charts and here are the positions of the important waypoints:
- SY040/5: S33° 53.6' E151° 15.6'
- SHORE: S33° 42.2' E151° 18.6'
So... SHORE is more eastbound than SY040/5. With the minimum required climb gradients (4.7% till 1000ft, then 3.3%), you'll reach 5 DME quite close to 2000ft (as seen on your "donuts") .
During the slight curve to turn to HDG 360° (after both 2000ft and SY040/5), you shoudn't fly the 3 minutes (18.6' - 15.6') longitude difference between SHORE and SY040/5.
The only thing that comes to my mind is (maybe) a problem with MAG VAR at YSSY?

[John H Watson]

RW07 is 063deg, I thought.

What does the superscript "040deg TRACK" signify above SY/05? The angle to intercept the radial? Or the angle to get from (0600) to SY/05 (2000')?  

Where is the left turn at 600'?

[Hardy Heinlin]

Hi Pierre,

thanks for the cross-check!

SY040/5: S33° 53.6' E151° 15.6'

Strange. Are you sure you didn't type 004° instead of 040°?

I just rechecked the 180° bearing from SHORE, it looks like the designers intended to have the 180° bearing directly cross the 040°/5 point:




Cheers,

|-|ardy

[Hardy Heinlin]

RW07 is 063deg, I thought.

What does the superscript "040deg TRACK" signify above SY/05? The angle to intercept the radial? Or the angle to get from (0600) to SY/05 (2000')?  

Where is the left turn at 600'?

Whatever you fly, you shouldn't get north of R-040° before exiting the 5 DME circle. And even you are already at 2000 at that point, you have to overfly that point, this overflight leads you further east of SHORE.

I think they should just remove SHORE from the chart and leave the text as is, i.e. intercept R-013° and track to KAMBA.

[John H Watson]

If the non-jet has no FMC, would DME slant angle distance be enough to allow an earlier  turn?

[Hardy Heinlin]

Good question :-)

To achieve a ground distance of, say, 4 nm while the eye distance is 5 nm:

5 * 5 - 4 * 4 = 9

Square root of 9 = 3 nm

3 nm is approx 18000 feet.


|-|

(At 2000 feet the ground distance is approx 4.99 nm.)

[Markus Vitzethum]

Hi Hardy,

I agree on everything regarding the geometry of the flight path. However, than there is always the question on how this data is coded into an airborne navigation database. This coding does not always correspond strictly to the chart.

Obviously, in a non-FMS equipped aircraft with steam gauges, I doubt that any problem will arise flying this departure (altough meeting the SY R-013 by 15 DME requirement will be hard).

In a FMS equipped aircraft, things look different. In the Jeppesen database, the route is coded as follows:

010   CA  062° +0600
020   CF  D040E  +2000 (D040E = SY040/5, 2000 or above)
030   CA  040 ° +2000
040   DF  SHORE  (direct)
060   TF  KAMABA (track 140°)

Read:
062° to 600',
then via 040° inbound to D040E = SY040/5 at or above 2000',
then via 062° to 2000' (reinforces the "after 5 DME and 2000' requirement)
then DIRECT to SHORE
then via track 140° to KAMBA:

Note the DIRECT to SHORE leg after reaching 2000'... the FMS equipped aircraft would just not consider flying 360° to intercept. Regarding the earlier discussion on geometry, this seems to make sense and is probably within the limits of the route design.

I just wonder ... is your FMC data from a (different) database or manually coded?

Regards,
  Markus

[Hardy Heinlin]

Hi Markus!

meanwhile I have programmed my model so that the leg -- in such offside problems -- goes directly to that offside waypoint, so that the gap is closed.

As you can see on the FIX INFO picture above, any aircraft, with or without FMS, can't fly to SHORE on a 360° track after passing SY R-040°/5. The overflight curve would have to have a zero radius. For non-FMS aircraft, SHORE is defined by a DME.

I guess pilots just ignore these details and fly "more or less" the tracks described :-) Maybe Pierre is right and it was just a mag var confusion in the designer bureau, perhaps they meant to describe the 360° as a true track. The mag track of this is ca. 347°. (As we know, these drawings are usually not to scale.)

My data is from Navtech, I don't code manually anymore. It goes like this:

010 CA 062° +0600
020 FD 040° to 5 DME SY
030 CA 040° +2000
040 CI 360°
050 CF 013° SHORE (10 DME SY)
060 TF KAMBA

Indeed, Jeppesen seems to have the problem fixed by using a DF leg and by deleting the CI/CF at sequence number #40/#50 (your sequence goes directly from #40 to #60). This is what my model now does automatically, it just replaces the paradox CF by a simple DF during SID selection.


Cheers,

|-|ardy

[Aidan]

Hi Hardy,

I don't have much to add to what Markus said but do you have to program each of these SIDS/STARS manually?    You might well miss a few AIRAC cycles in the process, there has been a lot of changes around these parts lately.

[Hardy Heinlin]

Hi Aidan,

my data is from Navtech, I don't code manually anymore.

The above issue refers to cycle 1303.

[IefCooreman]

Late add-on: there are more departures around where you are confronted with disco's. the first thing to check is always speed. The fmc here indicates 250kts after 5 miles. Speed restictions will help you out in 99% of the cases. 2nd would be to check navdata notams. We have two 'types' of intams, one being the official from the authorities, the others are 'internal'. We use LIDO charts, but they are not always 100% correct. These errors are described in the intams (it gets more confusing because LIDO doesn't handle the FMC database). Anyway, if it still doesn't resolve anything, and the disco stays, use track select and in the turn ask the PM to set a direct to the waypoint with the required track. take a shallow intercept heading and let LNAV to the rest.

And most importantl: write down the correct clearance on the flightplan, and after the flight, file an ASR that ATC required you to fly a non-jet departure. I helps your company against fines, and keeps you out of problems :-).