PPRuNe Forums Planning a descent

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 4th Feb 2005, 16:47 #1 (permalink) Join Date: Dec 2003 Location: Dorset Posts: 21 Planning a descent Hi Another quick question.... When say planning a descent "to be level by a certain point" whats the quick way of working out how many miles before to start the descent...? Sure there was a way involving speed and how many thousands of feet you needed to descend... Thanks
 4th Feb 2005, 17:39 #2 (permalink) PPRuNe Secret Agent!Moderator   Join Date: Nov 1999 Location: West Sussex / Stansted Posts: 1,360 Based on a constant ROD of 1500 fpm, the required altitude loss (divided by 1000) multiplied by 3 to obtain the distance from the bottom of descent point at which descent should be commenced! Hope that makes sense - sounds more complicated than it is! I prefer minutes to go = present altitude @ 1000 fpm! Cheers JB __________________ Regards JB007! Flight Ops,Crewing and Dispatch Moderator
 5th Feb 2005, 15:00 #3 (permalink) Join Date: Oct 2004 Location: Hunched over a keyboard Posts: 1,134 It does rather depend upon groundspeed and rate of descent. However, most airliners manage an average of 1000' of descent for every 3 nm travelled.
 5th Feb 2005, 17:37 #4 (permalink) Join Date: Jun 2001 Location: uk Posts: 434 or just tap in the FMC and see what it said!! BB
 6th Feb 2005, 08:23 #5 (permalink) Join Date: Jun 2002 Location: Wor Yerm Age: 57 Posts: 1,950 Three times table, ish... You have to loose nine thousand feet - therefore three times nine equals 27 miles. Groundspeed 400 kts, ROD required equals 2000 fpm or so. Apparently this is OK unless you are flying an A330, which requires the four times table. Unless of couse you have an FMS when your tap in your request and it does the rest (or heaven forbid, you use V/S and use the BOD arc on the ND. Flying jets etc.. is not rocket science (you might say it's jet science). They are designed to be flown by plonkers (and there are many of them out there, myself included) on bad night. PS: If you then have to loose speed, more distance has to be added
7th Feb 2005, 08:23   #6 (permalink)

Join Date: Oct 2003
Location: Deutsch-Wagram, Austria
Posts: 19
Hi!

Quote:
 or just tap in the FMC and see what it said!!
Before I do that, I let my co-pilot do it manually without any technical equipment .

Bye,
Bernd

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