43 replies to this topic

[Jack_C]

[Vonyc]

Could you help me to ask this Question (see this post : http://forum.avsim.n...es/page__st__50) Never heard of this FSX issue before.On the PMDG 747x, PMDG MD11 , Iflyng , Level-D 767 .... never had this " issue" before.Would say , its a NGX issue ?!Every other plane before:Manually "disengage" the autobrake on the know released the autobrake. But not in the 737ngx. Why?!

[badderjet]

Nice one, thanks. Really impressive.

[denboy]

Can I ask once you descended steeply, interecepted and then went below the VNAV path at 320knts, how did you know to wait start to recapture the path when you were ~1400ft underneath it so you could kill your speed back to 256knts whilst comfortably settling back into the correct vnav descent path. Is there a simple formula saying that, for instance, every 10 knots of speed you need to kill whilst descending and rejoining the VNAV profile you will need to start your speed intervention 250 feet below the path? Or do you just do it empirically? Btw great vids, adds another dimension to descent planning rather than just slamming on the speed brakes.

[yurekk]

Great videos. No doubt the best ones I've seen!  Request, and maybe I won't be alone here - could you do a demo of noise abatement procedures during takeoff? Just to explain how it is carried out in real world, I am a bit confused how to properly program this in FMC. Thanks!

[Turboblower]

Vonyc, on 14 August 2011 - 02:08 PM, said:

Could you help me to ask this Question (see this post : http://forum.avsim.n...es/page__st__50) http://img41.imagesh...31/fsxissue.jpg Never heard of this FSX issue before. On the PMDG 747x, PMDG MD11 , Iflyng , Level-D 767 .... never had this " issue" before. Would say , its a NGX issue ?! Every other plane before:Manually "disengage" the autobrake on the know released the autobrake. But not in the 737ngx. Why?!

Thank you for hijacking this thread with a suppot issue.

[Alaaar]

Dear Jack,Thank you very much, that was to me the flight lesson of 2011 no doubt, I had such annoying problem trying to slow the plane down, I used to do things that I knew deep inside that it wast right, like using the air breaks starting FL200 and using flaps at a higher speed than indicated and deploying gear at high altitudes and speeds, I knew it wasn't right because on a real plane it wasn't happening, I followed your instructions in a small flight and it worked like magic, speed was no concern for the first time, I was busy rather than bored through out the descend phase, it felt so different and real, so thank you so much for those wonderful videos.Simple question; is there an altitude limitations for those procedures ?Best regards

[Jack_C]

denboy, on 14 August 2011 - 03:47 PM, said:

Can I ask once you descended steeply, interecepted and then went below the VNAV path at 320knts, how did you know to wait start to recapture the path when you were ~1400ft underneath it so you could kill your speed back to 256knts whilst comfortably settling back into the correct vnav descent path. Is there a simple formula saying that, for instance, every 10 knots of speed you need to kill whilst descending and rejoining the VNAV profile you will need to start your speed intervention 250 feet below the path? Or do you just do it empirically? Btw great vids, adds another dimension to descent planning rather than just slamming on the speed brakes.

No, i just use past experience on the airplane. After a while you know where to ballpark it. But sometimes the first try might not work so I might have to reopen the SPD INTV window and try again but usually it works our.

Alaaar, on 14 August 2011 - 04:48 PM, said:

Dear Jack,Thank you very much, that was to me the flight lesson of 2011 no doubt, I had such annoying problem trying to slow the plane down, I used to do things that I knew deep inside that it wast right, like using the air breaks starting FL200 and using flaps at a higher speed than indicated and deploying gear at high altitudes and speeds, I knew it wasn't right because on a real plane it wasn't happening, I followed your instructions in a small flight and it worked like magic, speed was no concern for the first time, I was busy rather than bored through out the descend phase, it felt so different and real, so thank you so much for those wonderful videos.Simple question; is there an altitude limitations for those procedures ?Best regards

Nope, no altitude restrictions for going fast in normal operations EXCEPT ones imposed by ATC or chart depicted restrictions.

yurekk, on 14 August 2011 - 04:01 PM, said:

Great videos. No doubt the best ones I've seen!  Request, and maybe I won't be alone here - could you do a demo of noise abatement procedures during takeoff? Just to explain how it is carried out in real world, I am a bit confused how to properly program this in FMC. Thanks!

We dont use vnav below 3000 feet at our company so up to 3000 feet we use LVL CHG. On the other video I demonstrated a NADP 2. Is a NADP 1 what you are wondering about?

[Tabs]

Vonyc, on 14 August 2011 - 02:08 PM, said:

Could you help me to ask this Question (see this post : http://forum.avsim.n...es/page__st__50) http://img41.imagesh...31/fsxissue.jpg Never heard of this FSX issue before. On the PMDG 747x, PMDG MD11 , Iflyng , Level-D 767 .... never had this " issue" before. Would say , its a NGX issue ?! Every other plane before:Manually "disengage" the autobrake on the know released the autobrake. But not in the 737ngx. Why?!

Because the NGX is the first addon to fully model modulated autobrakes that work like the real thing does - that's why.  I'm not going to go into the technical reasons, but this will not be changing - you need to double tap the brake key/switch or press and hold it to disengage.

[SSSILVABR]

I noted this but in my mind it was a problem here.............. Thanks Ryan!!

[LZaman]

denboy, on 14 August 2011 - 03:47 PM, said:

Can I ask once you descended steeply, interecepted and then went below the VNAV path at 320knts, how did you know to wait start to recapture the path when you were ~1400ft underneath it so you could kill your speed back to 256knts whilst comfortably settling back into the correct vnav descent path. Is there a simple formula saying that, for instance, every 10 knots of speed you need to kill whilst descending and rejoining the VNAV profile you will need to start your speed intervention 250 feet below the path? Or do you just do it empirically? Btw great vids, adds another dimension to descent planning rather than just slamming on the speed brakes.

There is no magic formula but it has to be noted that in general airplanes with highly efficient wings (such as the 737, A320, A330, actually all thin airfoiled wings) don't like to 'descend + decelerate', it's either 'descend' or 'decelerate' but never really combined. I used to fly an airplane which was able to do both but then again the name 'brick with wings' was a used nickname for it... ;) This entire debate is about 'energy management' btw. you need to consider your potential and kinetic energy level, being altitude(potential) and speed (kinetic) and combined they give you your 'energy level'... the trick is playing around with that... trading speed for altitude or opposite ...f.e. when hitting a turbulent layer of air... often we are climbing at an ECON speed around 310kias... but it never hurts to 'zoom up' through the turbulent layer by trading in your kinetic energy (310kias) for potential energy (higher altitude) (respecting minimum speeds of course, it should be noted that climbing at green dot speed gives you the best rate of climb but it will not be the most economical way of climbing as you will need a lot of time and power to regain your 'optimum cruise speed' after leveling off... so really it's a mix of a lot of factors but as Jack says, experience will bring most of the answers... try it out, if you miss it... so be it you learn from it. cheerz

[Alec]

Tried it today, delayed the start of descent. Man, you make it look easy! I ended up high and fast lol. But I can see what the problem was, I didn't let the airspeed conservation, or whatever is the name, do it's stuff. So after the TOD, I had the airplane mantain it's cruise speed, when I started the descent I had too much energy to bleed, both high and fast, not a good combination.

[mikea76]

Jack_C, on 14 August 2011 - 05:19 PM, said:

No, i just use past experience on the airplane. After a while you know where to ballpark it. But sometimes the first try might not work so I might have to reopen the SPD INTV window and try again but usually it works our.  

The NGX flies that close to the real thing..  IMPRESSIVE.. BTW nice flying and nice videos.  Wish I could handle the plane like that

[compressor_stall]

Thanks for making these videos! Before I would always use FL Change mode to descend (by dialing in a low speed and letting the plane sink past the descent path), which happens sometimes, but it's still unrealistic to use it all the time.

[yurekk]

Jack_C, on 14 August 2011 - 05:19 PM, said:

We dont use vnav below 3000 feet at our company so up to 3000 feet we use LVL CHG. On the other video I demonstrated a NADP 2. Is a NADP 1 what you are wondering about?

Yes, is NADP 1 always used with VNAV engaged? I do not understand under which circumstances NADAP 1 is used. Does NADP 1 involve throttle reduction at around 1000 ft and delaying flap retraction until 3000 ft? In this case acceleration altitude=thrust restoration altitude, or I am wrong?

[Jack_C]

No NADP 1 can be used with LVL CHG. With a nadp 1, at 1500 feet the fmc will select a climb thrust, flap retraction doesnt take place untill 3000 feet. A NADP2, the flap rettractn begins at 1000 feet.

[yurekk]

Jack_C, on 14 August 2011 - 09:41 PM, said:

No NADP 1 can be used with LVL CHG. With a nadp 1, at 1500 feet the fmc will select a climb thrust, flap retraction doesnt take place untill 3000 feet. A NADP2, the flap rettractn begins at 1000 feet.

OK, got it. Thanks! So basically NADP 1 allows you to attain 3000 ft at the shorter distance after takeoff. Is this a main difference between 1 and 2? And just to clarify, how do I program FMC: NADP 1: reduction height=1500; acceleration height=3000NADP 2: reduction height=1000; acceleration height=1000 Correct?

[Vonyc]

Tabs, on 14 August 2011 - 05:50 PM, said:

Because the NGX is the first addon to fully model modulated autobrakes that work like the real thing does - that's why.  I'm not going to go into the technical reasons, but this will not be changing - you need to double tap the brake key/switch or press and hold it to disengage.

Okay, thank you.But when the plane has stopped, i cant release the brakes anymore. Only by using the parking brake, but then there is no "normal" brake anymore.Also moddeld like the real ones ?!

[easyworldairlines]

Vonyc, on 14 August 2011 - 02:08 PM, said:

Could you help me to ask this Question (see this post : http://forum.avsim.n...es/page__st__50) http://img41.imagesh...31/fsxissue.jpg Never heard of this FSX issue before. On the PMDG 747x, PMDG MD11 , Iflyng , Level-D 767 .... never had this " issue" before. Would say , its a NGX issue ?! Every other plane before:Manually "disengage" the autobrake on the know released the autobrake. But not in the 737ngx. Why?!

Have you just worked that out ?

[gheeD]

Hey, thanks for the informative videos, i really appreciate them, add a lot more to the flight to take the speed off without speedbrakes. :) I was wondering though, how usual or allowed in real life this method is? You said speed isn't a problem, but how about a plane full of passengers? If you descent at 4100 ft/min it's quite a steep descent, is that allowed with passengers comfortability in mind? Or does that depend on the airline, who allows and who doesn't? I haven't been on a airplane many times, but as far as i recall all descents were quite "slow" at 1000-1200 ft/min. Do you have any insight on that?

[VIPERGTSR01]

gheeD, on 15 August 2011 - 03:04 AM, said:

but as far as i recall all descents were quite "slow" at 1000-1200 ft/min. Do you have any insight on that?

I doubt that, not for ay extended time, 1000-1200 ft/min is just wasteful in a airliner. Anyway passengers don't really feel set decent speeds especially they don't have much to reference it by, they feel accelerations (up, down, left, right, forward, back etc). If done in a smooth matter passengers will not likely notice.

[LZaman]

Jay is right. The only thing a pax will feel is the actual 'angle' at which you are descending as it's similar to putting a chair on a tilting slope... you do feel the way you are sitting. But the actual vertical speed is not really felt at all.I once had a VS over 10000fpm (negative of course) and my cabin crew never even noticed it was a steep descent! (this was in an Avro RJ btw)so sure, there is absolutely NO problem getting high descent rates, just keep your pitch within personal professional limits and you'll be fine...

[Jigsaw]

Does the pressurization keep up with a steep descent like that? I remember being on a DC-9 about 20 years ago that went into a steep descent on approach while dodging clouds left and right and that made my ears hurt quite a bit. But I suppose pressurization systems have come a long way since then. ;)

[patrickbc]

What do you do if you are under 10000 feet and can't follow the VNAV path?

[alvin]

VIPERGTSR01, on 15 August 2011 - 03:54 AM, said:

I doubt that, not for ay extended time, 1000-1200 ft/min is just wasteful in a airliner. Anyway passengers don't really feel set decent speeds especially they don't have much to reference it by, they feel accelerations (up, down, left, right, forward, back etc). If done in a smooth matter passengers will not likely notice.

On the other hand, I have heard somewhere that 4000ft/min is also not desirable - and it is not only g's, but also the speed of cabin pressure change. Could somebody confirm this? What speed is the most economic one on the one hand, and what is the upper limit for a descent on the other?