Descending in a hold question

[buzzc152]

My instrument knowledge is a bit rusty : when instructed to descend in a hold do you do so immediately or next time over the beacon/fix ??

Thx

Buzz

[blackmail]

descending in holding

hello buzzc152,

when instructed to descent while in the hold, you do this immediately. remember that generally, when atc issues holding instructions, it is because there is too much traffic that wants to land at the same time. it's kinda rush hour as with your car. to accommodate the traffic situation most of the aircraft are stacked in holdingcircuits at 1000feet intervals. then, when the lowest aircraft gets it's clearance to start the approach, it leaves the holdingpattern, usually on radar vectors. then atc issues a descent clearance for the aircraft 1000ft above & all other aircraft are then descended in steps of 1000ft, kind of a cascade effect. it is vip you follow strictly descend clearances so as not to disrupt the system. atc will issue a clearance like this:" speedbird123 descent 6000ft, call when leaving 7000ft". so, you acknowledge the clearance & you use vertical speed, rod 1000ft/min & at 6700ftdescending you call:"sb123 leaving 7000 for 6000ft".(an altitude or fl is considered "occupied", +/-300ft in non rvsm airspace).
vertical speed is preferred to level change in order not to play havoc with the tcas systems.
also, when a lot of aircraft are stacked up in the holdings, atc radar screens are blurred with to many overlaying symbols & thats the reason they ask you to report "call when leaving".
there is a lot more to be told about holding procedures, but thanks to the fms, if programmed properly, it's relatively easy. a last thing i think about, if in the sim you get holding instructions, don't forget to ask for an expected approach time(eat), otherwise the devil in the back(the sim instructor), will be springloaded to give you a complete radio failure while in the hold.
hope this satisfies your question?

[vancouv]

So would ATC give each plane in the hold a descent clearance simultaneously? Or would they make sure the guy at 7000ft has left that level for 6000 before clearing the guy at 8000 down to 7000.

Also, I presume the bottom of the stack is published, so for example once you're at 6000 you know the next clearance will be for your approach?

[HEATHROW DIRECTOR]

Vancouv... Separation must be maintained at all times so an aircraft will not be instructed to descend to a particular level until the one below has either a) reported vacating the level, or b) is observed on SSR to have left the level, be at least 400 ft from that level and continuing descent.

In the UK the lowest level in the stack varies so is not published (to my knowledge!). Also, it may not necessarily be the lowest aircraft which is next to commence approach. MAny factors decide the order and these are taken into account by ATC in formulating the landing sequence.

Hope that helps...

[keithl]

HD, the lowest level is published, and appears as "Mnm Hold". What varies is that for some, the Min Hold is reserved for the Missed Approach procedure, with the Approach starting from the level above that.

[HEATHROW DIRECTOR]

keithl.. OK sorry for my ignorance. As usual I was thinking of Heathrow where the lowest level in the hold varies according to the QNH and the lowest level is not kept for missed approaches, except in severe weather conditions. I really ought to get out more!!

[FlapsOne]

I wouldn't if I were you...........it's a jungle and it's cold!

[issi noho]

i remember being tought descent in hold was 750+/-150 fpm ie 600-900. at least that was the way ATC would re allocate levels if an a/c had RT failed once it was assumed to have vacated last cleared level dependant on whether EAT issued or ETA acknowledged. All assuming procedural or c unverified. might still be true.