Hello,My question is about the Plan of decent and V/S.To know our v/s, we have firstly to calculate the plan of descent with this expression :Plan of descent (in degree) = (current FL

Does anybody know ?

Hi Daniel,Just as a rule of thumb, (without VNAV) when I used to fly 747 classic we use a G/S angle of 3 degrees and this is what we did:ALT to loose divided by 3 will give us TOD.Ex: Airport elevation 0 Ft cruise FL 330330: 3 =110 NM TODRate of descend (ROD) G/S: 2 + 100= ROD420 (G/S):2=2100 Ft/Min + 100=2200 Ft/MinNow having in view that we had no VNAV to take care of our speed restriction below 10,000 Ft we added 10 NM to our TOD. In our case we will start out descend at 120 NM,When approaching 11,000 we set V/S at about 1600 Ft/min to slow dawn to 250KTS by 10,000.Just to mention here that monitoring your G/S is very important taking in consideration the winds aloft, so you might have to increase or decrease your ROD. It is like descending on ILS, certain speed different ROD adjustments.This type of planning helped a lot, because we where always on a slop of 3 degrees and transition to almost any type of the approach was very easy.Now answering to the other issue you can apply the same rule when ATC is requesting you different altitudes crossing. See how much you have to loose: 3 that

Thank you for your reply.I don't like make a descent in VNAV. I find that tedious.I prefer manage the descent by using V/S or LVL CHG.Just another question.If ATC says to me to go down now to the FL110. I'm at the FL340, so I use V/S -1000 fts min. At FL340, the T/D is at 102+10 = 112 NM from the Airport and our G/S = 480 kts --> V/S = 2500fts/min.When I arrive at the T/D, I'm at FL280. So it's 6000 fts under the plan of descent.If we want to catch the correct plan of descent, we must start our descent of -2500 fts/min at 28x3 =84+10 =94 NM from the Airport.The problem is that we to go down with a V/S of -1000 fts/min.Continuing to go down with V/S of -1000 fts/min will be still change our calculated T/D at 100 Nm for a V/S of 2500 fts/min ?Thanks.

Correct

Oups, sorry, I made a mistake.I said :"Continuing to go down with V/S of -1000 fts/min will be still change our calculated T/D at 100 Nm for a V/S of 2500 fts/min ?".It's not 100 NM but 84 NM.So Continuing to go down with V/S of -1000 fts/min will be still change our calculated T/D at 84 Nm for a V/S of 2500 fts/min ?A little not ?Thanks.

Depends how you want to look at it.That distance difference is if you want to be at 250 KTS by 10,000 FT, or forget the 10NM, descend at high speed and when you get down to 10K just level off and wait for the speed to bleed down to 250KTS.And afterwards continue your descend, some speed brakes might be required but nothing to worry about.

Ok, thanks a lot Alex.Just an example and you say to me if it's correct.Cruise : Fl360G/S : 420 ktsT/D : 36x3 = 108 + 10 = 118NMRoD : 420 : 2 = 2100 +100 = 2200 fts/minATC say to us to go down now to FL065, so we take a V/S of -1000 fts/min. Arriving at our calculated T/D, we are at the FL280. So it's 8000 fts under our plan of descent. We must calculate a new T/D : 28x3=84+10= 94 NM. So we continue our descent at -1000 fts/min and at 94 Nm we start our descent at -2200 fts/min(G/S = 420 kts).If something is false or incomplete, do not hesitate to correct me.Thanks in advance.

Sorry, I forgot the speed reduction under FL100.V/S : -1600 fts/min and when we are at 250 kts, we adjust V/S according to the G/S.

Hi,Just wanted top add a small comment.V/S is regarded by Bill Bulfer and most experienced 737 jocks as 'Very Special' and it should be used only in particular circumstances. The standard des profile of 3 times + 10 is meant for use with LVL CHG which is a Flight Idle descent and pitch being used to maintain teh MCP Speed. Also remember that most people follow the Beoing recommendation and use VNAV.Rgds,

Daniel,That is correct.

Hi Brad,That is correct; Daniel is exercising the idea of not using the VNAV.To be honest with you, we use VNAV 90% outside of US until about 20 NM inbound to the FAF, in States this constant descend profile is not used so much and ATC likes to keep you down in and out of the airports. The best we did last month inbound JFK was on VNAV down to 12,000 Ft, afterwards we had to get on FLCH, and of course speed up or slow down. All that technology down to the toilet.The irony here is that you will see pilots using V/S from the TOD and not trusting VNAV, and you know why? Some of them do not understand how the system works or simply afraid of the box :-(Daniel excluded form the last statement, he is just curious and eager to know about the steam gages airplanes.