What it shows, is that the vertical speed does not jump as high as 5000-6000.So the problem with high vertical speed is weather. On those videos the weather is default.

Ehh, no. I watched 5 minutes of the first video and what I saw was a pilot that seemed to know what they were doing and didn't have a problem. I don't think you can say "here is a video showing no problem, therefore the problem must be..."

Come on give me a break. Were talking about normal not a rare repositioning or a flight that was low on pax. I am talking about normal day to day ops. There is no way airlines are taking off with 20 pax in a 162 seat layout. If they are then thats why the idiots had to file bankruptcy in the first place. If they are taking a loss on certain routes you can bet they will start cutting back the number of flights so they can fill the planes more.

Here in Europe our low cost boys (easyJet, Ryanair) would simply cancel the flight! Iain Smith

A simple guide would be, if you are not flying with a full load and full fuel, then use Thrust Reduction.(There is a very good example of this in the tutorial flight.)In your example I would put in much more passengers and use Derate 2 for the takeoff and Climb 2 for the initial climb. ( it will return to normal CLIMB at 15,000 ft )By doing this, I would be amazed if you see more than 3,600 - 3,900 fpm.The Assumed Temperature thrust reduction method is the best but you will need a good dispatch type program.I have looked at Topcat but not fully convinced as yet !!A cost index of between 20-40.Fred.

Thank you very much!!!

As far as passengers not noticing steep descents is not true. I fly 4 to 5 times a month on commercial airliners and I can tell when we are in a steep decent even if I'm watching a movie or listing to music, you have the feeling of leaning forward like your diving into the earth and this usually never happens sure enough on my last flight from KJFK to KIAH It happened and it was uncomfortable the other passengers seemed to notice as well. Sure enough I got on flight aware after the flight and saw that we hit a 3,900 fpm descent for a minute or so but I definitely noticed. If you look at flight on flight aware for 737's the most VS they usually get is 2,800. But certainly not 6500!

Trying being a Flight Attendant and walking down the aisle and feeling like your about to float to the ceiling.. I hate it when we have steep descent in an aircraft. The worst I ever felt it in was in the 757...Carlitos Colon

Again, that is a function of rate change, not rate. If pilots gradually make airplane descend at 10 000 fpm but kept her level, you would not know.Iain: Come on now. Do you have any idea how expensive it is to cancel a flight?

My company still has U10.7, so I guess we've opted out of the Full Geo Path for the App-only Geo Path.

A lot of companies went back to U10.7 after the U10.8 problems. ( U11 is due next autumn sometime. )(The NGX is the latest U10.8a update.)Fred.

Guys,This thread shows a terrible understanding of CIs. First, sounds like a lot of you have it set too high. Second, some in here say CI is always this way or another and it's not. Some CIs are fixed across the operation, some are not. Some CIs are fixed in most circumstances, and changed in IRROPS (delays to attempt to make up time, etc). Some CIs are changed for climb, cruise and descent.It is all based on company SOP. It varies, both in value and applicability.

I... don't think. In descent you are in VNAV PTH mode, so the FMC should primarily track pre/computed descent path and only then should it speed up by the way of thrust.

Wrong. In VNAV, the throttles are set using A/T to a particular thrust setting, with pitch to maintain speed. For this reason, an increase in CI, demanding an increase in speed, results in an increase in pitch to maintain that higher speed.

What it shows, is that the vertical speed does not jump as high as 5000-6000.So the problem with high vertical speed is weather. On those videos the weather is default.

Sorry, but it was hard to tell the point you were trying to make when you just said "Have a look". Anyway the second video shows a rate of descent in the 5000-5500 ft/min range. You can't say the problem is weather without ruling out other factors like weight and CI. However I think it's quite possible to say that what it isn't is anything to do with the NGX simulation.Kevin Hall

Wrong. In VNAV, the throttles are set using A/T to a particular thrust setting, with pitch to maintain speed. For this reason, an increase in CI, demanding an increase in speed, results in an increase in pitch to maintain that higher speed.

I am sorry, but I have to disagree. That part is only true with VNAV SPD. VNAV PTH will maintain path, and either add thrust or request drag if speed varies too much from expected.FCOMv2 page 4.10.6 (190)

Descent –•VNAV SPD descent•autothrottle holds idle•AFDS holds FMC target speed.•VNAV PTH descent•autothrottle holds idle but can command FMC SPD mode if ground speed becomes too low to maintain FMC vertical path•AFDS tracks FMC descent path.

I am not able to find a statement that clearly states that VNAV PTH is default descent mode, but this statement from page 11.31.27 supports it.

[Option – With common VNAV]VNAV performs descents using pitch control to maintain a vertical path. Thrust is used to control speed, similar to a glideslope in three dimensions.

11.31.32 also supports that.

Here in Europe our low cost boys (easyJet, Ryanair) would simply cancel the flight! Iain Smith

Indeed, and easyJet would trust that no passenger will be able to find out how to circumvent the automatic answering machine when phoning to get back their money.

VNAV SPD = pitch for speed with constant thrust setting (climb N1 limit or idle in descents) - always. There was a comment earlier about it not following the path well in VNAV SPD. There's a reason for this - it isn't trying to follow it at all. VNAV SPD is a completely different mode from PTH.VNAV PTH = idle thrust from T/D to first waypoint using pitch to meet the econ speed (which the idle path is calculated with), after the first waypoint, it goes into power-on geometric descent (you'll see the A/T mode go from ARM to FMC SPD). If you drop too far below the target speed, even in the idle PTH mode, it will add thrust to get you back up to target and then retard to idle again.

As far as passengers not noticing steep descents is not true. I fly 4 to 5 times a month on commercial airliners and I can tell when we are in a steep decent even if I'm watching a movie or listing to music, you have the feeling of leaning forward like your diving into the earth and this usually never happens sure enough on my last flight from KJFK to KIAH It happened and it was uncomfortable the other passengers seemed to notice as well. Sure enough I got on flight aware after the flight and saw that we hit a 3,900 fpm descent for a minute or so but I definitely noticed. If you look at flight on flight aware for 737's the most VS they usually get is 2,800. But certainly not 6500!

Sorry, this is either an illusion because of what you're seeing visually or there actually are slight accelerations happening that let you know about it. Certainly you feel the onset of the descent, because that's an acceleration.Think about how you're standing on the earth right now with respect to "up" at the north pole. Very likely you're actually standing "sideways", the degree to which depends on your latitude. Do you feel this? No. Same idea here. At 1G, you cannot discern things like this - it's fundamental physics. Check out Einstein's "equivalence principle" and the part of Special Relativity about objects in motion at a constant velocity.Also - a descent at a high IAS/Mach is going to produce a higher rate of descent at a given angle than a slower one will over the same distance. You could be descending at 4000-6000FPM up in the higher altitude portion of the descent and it won't look like much at all out the window as far as the angle you're seeing due to the speed involved. Flightaware themselves btw say not to trust their data for speed, V/S etc - it's interpolation off the radar, slant range and all of that comes into it and it's just not accurate.

Sorry, this is either an illusion because of what you're seeing visually or there actually are slight accelerations happening that let you know about it. Certainly you feel the onset of the descent, because that's an acceleration.Think about how you're standing on the earth right now with respect to "up" at the north pole. Very likely you're actually standing "sideways", the degree to which depends on your latitude. Do you feel this? No. Same idea here. At 1G, you cannot discern things like this - it's fundamental physics. Check out Einstein's "equivalence principle" and the part of Special Relativity about objects in motion at a constant velocity.Also - a descent at a high IAS/Mach is going to produce a higher rate of descent at a given angle than a slower one will over the same distance. You could be descending at 4000-6000FPM up in the higher altitude portion of the descent and it won't look like much at all out the window as far as the angle you're seeing due to the speed involved. Flightaware themselves btw say not to trust their data for speed, V/S etc - it's interpolation off the radar, slant range and all of that comes into it and it's just not accurate.

I must admit since SP1B i don't get this anymore per say. But i use PFE ATC and i wait for them to call the shots on decent and manually decend via VS and to be honest works for me .. Not sure if im correct proberly not. But when the captain starts to decent if he is being instructed my ATC to decend to flight level 23.000ft from 32.000ft would'nt he use this procedure any how because if you use alt intv it causes steep decents because the VNav is trying to catch up yeah that right Ryan...

Thank you very much!!!

If I may add to Fred's post, (whose posts I really enjoy reading, thanks!), you say you arm LNAV and VNAV on the ground. That means you should have the respective flight director indications on the PFD. Follow those and keep the cross centred. Trim out the pitch to maintain the vertical path bar in its central position and engaging the AP should be a smooth transition. I have not had any jerk on AP engagement since I have made sure that the FD is centred and the aircraft trimmed out. Andrew

Hi I use 25 which seems to be a good number Chris