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driftdown over the indian ocean

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driftdown over the indian ocean

Old 13th Nov 2011, 07:55
  #1 (permalink)  
Thread Starter
Join Date: Jul 2010
Location: france
Age: 47
Posts: 255
driftdown over the indian ocean

hello folks

for those of you more familiar with that area flying along the routes from the middle east to southern india, sri-lanka and the maldives, what is the correct procedure for a driftdown from an operational standpoint taking into consideration that:
aviate first - fly the aircraft, apply rudder, mct, identify, verify, checklist
navigate second - to your drftdown altitude at the driftdown speed: i presume you offset your course laterally ( of how much? 15nm left or right?) first and then you descend ( the higher between your driftdown altitude and the altitude applicable to the course to the enroute alternate basd on the EPT) unless you have a rapid decompression, which in that case you start descending as you turn to the offset!
communicate: inform the atc on the active frequency and the surrounding traffic on the 121.5 emergency frequency about your intentions.
is this the right sequence?
how many nm do you offset your altitude?
if, for instance, the driftdown altitude for the current mass is let's say 26350ft, and you are turning towards mumbai, would the correct procedure call for offsetting your track - in which direction - and then only once established on the offset to descend to the correct altitude - FL260 in our case for a westerly track or you level off at the altitude plus, minus 500ft as over the atlantic? is that portion of the indian ocean rvsm?
many thanks and sorry for the silliness of the question.

baobab72 is offline  
Old 13th Nov 2011, 20:50
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Join Date: Mar 2007
Location: Havana
Posts: 600
Jepp. Supplementary



(Ref Regional Supplementary Procedures, DOC 7030/4 - MID/ASIA, Part 1, Rules of the Air, Air Traffic Services and Search and Rescue.)

Hopefully this is what you are looking for....just look up ME-11 and this should set you straight, and hopefully you won't need it!
Yes, it is RVSM.
Che Guevara is offline  
Old 14th Nov 2011, 04:22
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Join Date: Jul 2010
Location: france
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Posts: 255
drift down

thanks for your response.
the only document that i could come across -i have no access to the ME volume at this particular moment in time -, it states that if unable to maintain altitude turn 90 either left or right from the assigned track to acquire and maintain a track parallel to the assigned track and offset by 25nm. Once established on the offset track descend to an altitude 500ft above the the normally used one (and lower than the applicable drift down altitude): only once at the proper altitude turn towards the enroute alternate based on the position of the aircraft with respect to the ETP.
What if your drift down altitude is below 290, the lower limit of the RSM airspace, do you still level off 500 above the normally used altitude?
in case of wx encounter, for deviation of less than 10nm maintain CFL, for deviations greater than 10nm climb or descend 300ft based on eastbound-westbound track and direction of turn - similar to NAT -, if a revised clearance can not be obtained.
ME rnp5
ASIA rnp10

are those info still applicable? 25nm offset?

many tks

baobab72 is offline  
Old 14th Nov 2011, 05:31
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Join Date: May 2009
Location: Home
Posts: 133
Drift down only comes into play, or becomes a concern when terrain is a factor.
When no terrain, or terrain not a factor you are only descending to your engine out altitude.

Of course you can always drift down if you like.

Contingency procedures can also be found on the back of the Indian Ocean Chart.

CAVnotOK is offline  
Old 14th Nov 2011, 20:27
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Join Date: Mar 2007
Location: Havana
Posts: 600
You have to descend below 290 because you are no longer RVSM compliant etc. Our procedure is to maintain the + 500' because more than likely you will have to cross other airways during your diversion.
Che Guevara is offline  
Old 16th Nov 2011, 02:55
  #6 (permalink)  
Join Date: May 2001
Location: A few degrees South
Posts: 813
You do not have think about descent to below FL 290...the plane will do that by itself.
latetonite is offline  
Old 16th Nov 2011, 14:38
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Join Date: Sep 1999
Posts: 30
Almost correct....


The initial offset until below RVSM airspace over the Arabian Sea/Persian Gulf/North Indian Ocean is 10nm. The rest of it is essentially up to your company SOP's but your general procedures and order seem to be right. Of course on the day, your mouth will become full of cotton wool and your hands will not go to the place you expect them to go.
In terms of the weather deviation procedure without being able to get a clearance first ( which I have never managed to get from "Mumbai Mumbai") when in the Northern hemisphere, if you turn towards the nearest pole i.e. North, then descend. (If you imagine that pole is greasy, then you slide down it) Vice versa for turning away from the pole.

Hope this helps
Luckyguy is offline  
Old 17th Nov 2011, 07:49
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Join Date: Jun 2007
Location: London
Posts: 384
Cripes, get it right chaps. I might be coming the other way. Love Boeings but my Airbus mates were recipients of fabbo instructors, one in particular who said; "Just look at your Nav Display...ND............get it ? North, Descend............ The rest you can work out. Boeing boys just have our lower screen, can't work out a suitable mnemonic. Keep a good look-out fellas.
slowjet is offline  
Old 17th Nov 2011, 20:56
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Join Date: Mar 2007
Location: Vesterbronx
Age: 43
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One once told me SAND:

South Ascend North Descend
Vesterbronx is offline  
Old 18th Nov 2011, 09:22
  #10 (permalink)  
Join Date: Jun 2007
Location: London
Posts: 384
Damn, you guys are good ! That is a really good'n & one that I will use.
slowjet is offline  
Old 18th Nov 2011, 11:35
  #11 (permalink)  
Join Date: Sep 2009
Location: Bombay
Posts: 48
i just remember it as climb towards the ocean and descend into karachi
Speed Freak is offline  
Old 9th Dec 2011, 09:50
  #12 (permalink)  
Join Date: Apr 2001
Location: here and there
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Relevant section of the Indian AIP here:

Large Dave is offline  
Old 9th Dec 2011, 10:26
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Join Date: Jun 2007
Location: London
Posts: 384
Thanks LD. Reading it gives me eye ache. I prefer Vester's "SAND" mnemonic which I am actually teaching ...AND. I am claiming that I invented it.
slowjet is offline  

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