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How to get in and out of canyon airports

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I did some reading on the Majola Wind and can’t see how it could create a downdraught which exists at all points in the valley. How does one assess the risk and plan a departure from Samedan?

However, this is not related to engine management, which one would assume would be limited to setting up the engine for best power.

Administrator
Shoreham EGKA, United Kingdom

Peter,

the main problem of the Maloya wind is that in a departure on 21 you have a positive wind component only until you turn 180° into downwind, when it turns into a negative component. This can lead to quite a lot of speed loss and has in the past led to hairy situations and even accidents.

It can be beneficial to take off towards the east even with a slight headwind in such conditions, as terrain there does not demand any turns. On 21, you have to fly a right turn of about 30° followed by a left turn in the bassin of Pontresina into downwind, all of which fairly close to the ground and with a possible wind component change which is quite considerable.

The downdrafts which are relevant here are those caused by the terrain west of the airport, which rises quite sharply towards St Moritz. (On that slope the world famous bobsleigh run as well as the Cresta run are located) . St Moritz is some 400 ft higher than Samedan airfield and therefore terrain rise is quite steep and normally a straight out departure out of 21 is not possible.

LSZH(work) LSZF (GA base), Switzerland

Mooney_Driver wrote:

he main problem of the Maloya wind is that in a departure on 21 you have a positive wind component only until you turn 180° into downwind, when it turns into a negative component. This can lead to quite a lot of speed loss

I don’t see how it can unless there is wind shear?

ESKC (Uppsala/Sundbro), Sweden
don’t see how it can unless there is wind shear?

Well there may well be. On the ground the wind may be 5 kts from west. At 300 to 500 ft it may be 20 kts or more. In any case during take off and initial turn you will have headwind which turns into a quite massive tailwind during the turn into downwind. That will cause a speed loss or height loss or both.

LSZH(work) LSZF (GA base), Switzerland

Mooney_Driver wrote:

In any case during take off and initial turn you will have headwind which turns into a quite massive tailwind during the turn into downwind. That will cause a speed loss or height loss or both.

No, that’s an old myth. Unless there is wind shear (which, as you say, it could be) a downwind turn doesn’t affect the aircraft in any way. The aircraft doesn’t know how the wind is blowing. It does affect the pilot’s perception of speed and may cause him/her to reduce airspeed to maintain groundspeed and thus stall the aircraft.

Last Edited by Airborne_Again at 01 Jan 16:03
ESKC (Uppsala/Sundbro), Sweden

I looked up what I could find over night and it does look like it qualifies as wind shear most of the time the Maloya wind is active. Wind on the ground and wind at 400-600 ft AGL may differ by up to 20 kts. This hits you right in the upwind turn and initial downwind.

There is a picture series available of a Jodel fighting this, he almost ended up touching down on downwind due to this.

Maybe my explanation is lacking but the problem is there, believe me.

LSZH(work) LSZF (GA base), Switzerland

This pic here gives a good idea of the terrain situation to the southwest of the airport and how a wind coming from that direction could give some problems to aircraft departing that way.

Mainz (EDFZ) & Egelsbach (EDFE), Germany

Are there some general tips on how to do these operations?

Obviously you need to be aware of engine management issues for altitude ops.

Another thing you get is that sometimes the canyon is not all that wide and after departure if you have to do a 180 then you may want to fly over to one side of the canyon before doing the turn, to give yourself extra space. But the published circuit may not allow that. I had that in Bolzano, visible here from 41:00 onwards



Administrator
Shoreham EGKA, United Kingdom

Airborne_Again wrote:

No, that’s an old myth.

I agree. It is not like the aircraft turns from departure heading to downwind at an instant. It does so by gradually hence the airspeed remains practically uneffected. The main problem here with 21 looks like the downdraft as soon as the aicraft crosses the leeward side of the terrain, while turning downwind. The airspeed would reduce because of pilot error while trying to keep level against the down draft. I have never been there but looking at their Pilot Briefing material, it seems to be a real danger.

They have a 1.8km runway. If there is a risk of Maloja wind, wouldn’t departing 030 with a bit of a tailwind of course assuming the whole calculation checks out with high altitude take off performance etc. be an option? Does anyone know if Samedan reports Maloja winds status and speed?

Switzerland

By9468840 wrote:

If there is a risk of Maloja wind, wouldn’t departing 030 with a bit of a tailwind of course assuming the whole calculation checks out with high altitude take off performance etc. be an option?

Yes. Normally in this situation, it is far less dangerous to depart with a bit of tail wind and follow the valley straight out direction of Zernez than to negotiate a turn in the Pontresina baissin. I’ve done this every time I could get away with it.

If there is sufficient headwind on 21, then of course your climb will be so that you are higher over the critical area already. So most of the time when the wind is too strong for a 03 departure, that would compensate for the risk a bit.

I am not sure if the Malyoa Wind is indicated on their Information Display which includes quite a lot of good information otherwise, but certainly the people at the airport know about it. Simply ask.

LSZH(work) LSZF (GA base), Switzerland
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