I'll do my limited best. You don't have to worry about the Iranians, it is our job to inform them that you might stray into their backyard. And they usually don't mind.
The increase in the rate of descent is to ensure you keep your spot in the stack and to make space for all the others approaching to take up the hold. If for example you are number 5 and already established in the hold at FL290, and other traffic approaches the hold at FL250, it may end up that he becomes number 5 and you, well, number 6. From the cockpit point of view it is good to stay high in the hold and conserve juice, but the higher you stay the more chances of somebody sneaking in below you. There is NO way to avoid this, as the dynamics and layout of the airspace dictates that this will occur. The best option would be to get as low as possible as soon as possible. The flipside of the above mentioned also happens. Because of the positioning and spread of traffic flying around its own arse at DESDI, you may go from #4 to #1. Then it would help to be low.
The unrestricted descent from FL280 to A100 is very situation specific and I cannot comment intelligently on it.
Start rant. Slightly off topic. If you are inbound to DESDI or BUBIN, don't for a second think that because you are presently in front of say Birdseed69, that you are going to stay in front. A lot of times the situation dictates that numbers 1, 2 and 4 run through but number 3 gets a hold to change places with number 4. This event is dictated by the DXB APP spacing requirements, there is nothing you can do about it and the best is to accept it and keep quiet. And don't play the "you are victimising us" card. The law of averages say that it will happen to EK more than the rest, for obvious reasons. And for Air Arabia: The correct readback to "route DESDI and hold" is "ABY123, route DESDI and hold", NOT "confirm hold, but we are inbound for Sharjah, are you sure?".Rant over.
Sorry for the VLP Thridle, but unfortunately their are so many factors that come into play that a short answer is a bit difficult.
Last edited by BlueSkye; 12th Mar 2009 at 12:06.