MSA correction for wind

[NICK HEFF]

Our ops manual suggests that we make a correction to en route saftey altitudes if high ground is over 2000 feet,eg o to 20 kts of wind we add 500 feet.
Does this factor also need to be applied to the MSAs on arrival charts if near high ground ie Geneva.

[invalid entry]

Just a minor point, but if we work for the same airline, it is not the MSA that must be increased, but the MOA (Minimum Operating Altitude). In the case of Geneva I would say yes, it should be increased.

[brain fade]

Nick, from your post (and from the books of course) it seems that a correction is required for all wind speeds including 0 knots. therefore why not just increase the moa by 500' everywhere. I cant figure out why a wind of 0 or 1 kt requires any correction. or am i missing a trick somewhere?

[NICK HEFF]

Thanks for the info .I am still a bit confused,if on my Jepp plate the MSA is 3800 feet, do I assume from this that there is high ground over 2000 feet and then add 500 feet to the printed msa?.
Please help OPC in a few weeks.

[4g_handicap]

I speak under correction, but I would think the wind correction is to allow for mountain/standing waves. These can be very powerfull - I have had a colleague relate to me an experience going into Cape Town(9000ft Amsl @ 15DME) where he could not maintain the required altitude as he was caught in a down standing wave - pretty scary.

Anyway, I would have thought that the reason to add the extra height to the MSA, but really only applies when surface wind speed start reaching about 20 kts. Maybe one of the met boffins can fill us in on exact requirements.

Regards
4g
<img src="smile.gif" border="0">

[bluskis]

ARTICLE IN jAN 2001 pILOT, OUT NOW, CALLED HIGH SEIRRA DISCUSSES DOWNDRAFTS IN LIGHT AIRCRAFT CONTEXT.
SWISS 1/2 MILLION TOPO WOULD INDICATE MOUNTAIN AND OBSTACLE HEIGHTS, WHICH ARE VERY VARIED IN THE GENEVA AREA.

[MUNCH]

Hi Nick

you seem to be getting technical in your old age, i never realised you actually read the books.

[alosaurus]

Nick-Yes it does need to be added to arrival chart MSA(the rule is whenever you operate within 20NM of terrain &gt;2,000'AMSL).
It is actually more important that you apply the correction to approach MSAs as these only give 1,000' separation(Geneva NW spot alt 5,636 give app plate MSA 6,700').Route charts give 1,000' unless the area is defined by the state as mountainous in which case clearance is increased to 2,000'.
Although turbulence caused by mountain waves is not an issue,at light wind speeds,areas of local low pressure can be generated which cause the altimeter to over read.
In Geneva at this time of year you may need to apply an alt temp correction if colder than ISA-15
Good luck-Al

[ 01 January 2002: Message edited by: alosaurus ]</p>

[NICK HEFF]

Thanks for the replys Pruners, Happy new year!

[cpdude]

If your using jeppesen altitudes then they are good for up to 30Kts of wind. MSA does not need to be corrected for wind speed but does for cold temperature. Check the link below.

<a href="http://www.jerryflint.net/Minimum%20Altitudes%20ER.htm" target="_blank">web page</a>

[alosaurus]

CPDUDE-Checked your link it says MSA only gives 1000' obstacle clearance (which means you must apply wind correction 0-30 knots);Grid MORA (route info) is corrected for windspeeds of up to 30 knots)

[TopSwiss 737]

Just for info... Recently the MSA changed here in GVA. Instead of being based on the PAS VOR, it is now based on GVA VOR, and MSA has gone up to 7000' in the North... In the Southeasterly sector (002-245 bearing) it is 10600' (7000' within 10nm)

[alosaurus]

Topswiss-Thanx.