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bert.laverman

Need help/advice for landing at Sion (LSGS)

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I'm flying with a small group every week, mostly VFR short hops, and our planned route for next weekend will be by 737 and visiting Sion (LSGS). Are there any experienced pilots able to help me prepare for this? I'm definitely not in the experienced category. I've already noticed the ILS beacon is actually separated from the runway and the mountains could require a somewhat steep approach, but some hints and suggestions would be very welcome.

 

Cheers,

Bert

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i'm also not an experienced pilot, but I tried to get down into SION several times, and with success!!!

I fly a PMDG 737NGX, and can say that there are some things to keep in mind. First of all : the plane tends to speed up during the Sion IGS-approach (a special effect ILS)

Second is that the instrument guided system has indeed a displaced descent path. (SIO-VOR, 243°radial) and is extremely steep on the first part.(6° instead of 3°)

And there is a less steep visual approach (3.5° instead of a normal 3°) on the bottom of the pit.

To get there : fly to GRANA @17000ft and start the hold if required. Wait for ATC clearance furtheron.

Next fly the rest of the approach : turn to the right, fly downwind along the valley for some miles.

Turn to base 63° and final 353°over the ALETCH glacier, still at 17000ft, max. 25° bank angle and max. 210kts.

The turn on final is towards the MASAB waypoint on a 243° VOR-radial towards SIO. Try to get as SLOOOOOWWW as possible there allready.

Next on the line is the ALETO final approach fix, on the 246°radial. You MUST be fully configured (gear down, landing flaps, approach speed, Terrain radar ON!!!) at this point. Keep in mind that slowing down during the descent is impossible in a heavy or even light 737!!!

At Aleto you drop into the valley. 6° down or 10,5% so 160kts = 1760 ft/minute down... This is very steep!!!

Almost at the bottom at the valley the Rhône river passes from right to left. Try to follow the river straight above. Look towards the runway. Once you get aligned, follow the papi-lights downwards and hit the SION-RWY25-pavement... Welcome to SION...The way out is easier! :)

 

Chart @ http://www.vacc.ch/file/60

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Do get configured before starting the final descent - so gear down, flaps down on GRANA.

 

Then be prepared that there is a bit of a problem with IGS in FSX - FSX has a hardcoded range limit, that is not quite enough for Sion. The NGX should make it with IAN though. Good luck, it's a nice approach when you make it!

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The STAR and approach are in the airac-files. If you fly this approach with the NGX, you end up way too high in the valley for a good touchdown.

So fly according to the charts, and make the correct descent.

The errors in the FMC approach that is loaded from the airac is that every altitude is stated as 'at or above', and it should state 'at'.

And the last fix is not at 5163ft but at 4120ft@7DME to SIO

 

@Fabo, the GRANA fix is way ahead of the ALETO... If you keep in mind that a good fuel consumption is something that is highly recommended by higher management of airlines, it's better to be slow when required, and not ahead of schedule... So wait as long as possible, slow down before MASAB, get everything configured at ALETO, as it is also described on the chart in the link...

 

The hardcoded range is indeed a pain in the @$$, but I don't see it changed now anymore :)

 

Maybe some guys flying prepar3D can say if this is still the case in that software, since I am really eager to change over to Lockheed soft... but then I will probably buy another aircraft-soft as well, and stop flying the NGX... (maybe a 777)

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Something I forgot to mention : don't fly VNAV or Level change... Use the Vertical speed function... Otherwise you may also drift of too high during the descent, and not be able to touch down.

I have just flown a round trip LSGS-LSGS, and am trying to upload my blackbox-log, so you can follow in Google Earth if you can...

 

I took off from LSGS/Sion on the ROCCA 1J SID, and connected with a VADAR 1N STAR. Configuration was 174 pax, fully loaded in the cargo hold. Takeoff was TO-thrust, flaps 25, trim 4.78. Weather was a calm and clear.

I went towards ROCCA fix, but cut the corner just before getting there, and went towards VADAR fix.

Upon arrival at GRANA I entered the hold (67°, Right turn), but was able to arm the hold exit before the first crossing of GRANA. and continued on the IGS Rwy25.

 

Because of the heavy plane, I was already slowing down, using airbrakes, even before the GS602 point on the chart.  Speed went below 210 for the first corner. Before the GS603 I put the gear down. This adds a great dragfactor, since speed is 210 this is not a problem! So it was easy to get slower to 150kts.

 

Then flaps went down, getting at 40° before ALETO (during the descent I retracted by accident, so had to put them down firmly again, somewhere around 14000ft)

 

The full plane came down nicely at 150kts, flaps 40, gear down, max. autobrake set, spoilers armed. something like a 1700ft/min downwards... I use the FMC to check the required vertical speed, and adjust accordingly.

I don't use VNAV or level change, because depending on windgusts, your V-speed may vary a lot, getting you too high on the path.

At 4200ft I went to hand flying, checking continuously for the papi-lights and my alignment.

Beware: you will get some terrain warnings or sink-rate-warnings which are coherent with this IGS-approach (you turn towards the mountains at the end, and you DO come down fast the last few thousand feet). You can otherwise ignore, or turn them off.

 

At 3200ft I started the S-turn over the Rhone river, to get aligned.

And had a not so soft touchdown (350ft/min) at LSGS... (Just 350lbs below the max. landing weight at this time)

Max. Braking, no reverse thrust, and I stopped at the last exit from the runway...

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There are a number of videos on youtube showing the approach to Sion. Make your turn as the hospital goes under the nose.

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Came into the descent yesterday before other duties called. Amusing to see the CDU message "No DES Path after MASAB" change to "STEEP DESCENT..." when sufficiently slowed. Are you sure the FMC can't handle it?

 

Bert

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Sometimes FMC can, sometimes it can't... Depends on winds. If you suddenly get a windgusts from the front, or a suddenly changing windspeed, and your indicated airspeed increases, the plane will pull back on the stick, to make the speed drop. This causes you getting deviated from the path and getting you too high. In this type of descents, it's almost impossible to recover that difference.

If you fly CAVOK, it should work.

Just check the FMC LEGS-data for the 'At or Above' differences from the chart, since those will also get you too high.

16000 at or above ALETO, means that 20000 is also okay for the FMC. This is an extra 4000ft drop on al already very steep descent!

 

Get it right, and you will be able to land...

And keep in mind that an slightly too high airspeed (keep below max. speed for flaps position!) will bleed of on the last part of the descent, since that is only 3.5°, so flaps 40 gear down will slow you down over there...

 

Another detail I would mention : you are as a pilot still responsible for the behavior of the plane. You should monitor this descent, and keep track of things happening. So depending on the FMC to get your plane down to ground, is not correct, especially on this type of DANGEROUS approach.

 

This morning I was watching a guy flying the PMDG737 down the Rhone valley. The plane started the descent way too fast, and not steep enough. What he did to correct : he made a 360° turn in the valley, he got constant RED terrain warnings... Just because he descended to slowly... If that guy becomes a real life pilot, it will not be for this type of flying... :)

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I've seen similar mistakes with videos of Innsbruck. Too many simmers trying it out at far too high a speed. In fact most jet a/c will fly the whole approach with flaps and the whole descent as far as Absam with gear down. And usually the downwind leg is at full flaps.

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Ok, thanks for all the help. The descent worked beautifully. Somehow I got kicked out of Auto-Throttle when I arrived at the bottom of the slide, and it took a while to detect this as I was busy (and not very experienced in these kind of unexpected things) so I landed a bit early, but definitely not a crash, so I'm happy. Will try again (and again...) to get better.

 

Cheers,

Bert

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