777 VS Mode Fluctation

[Flamin_Squirrel 71]

Take a look a few pages before.  There's a page with three diagrams illustrating initial descent and associated parameters for a level-off.  If it stayed there for 60nm, it was probably working in some of the DES NOW logic and hanging out at the new level until it recaptured an ECON path.  I'm on my other computer so I don't have the manuals in front of me.

 

If you do the tutorial flights, you'll see it work in GP for the entire descent after the first restriction.

 

You might be right there. I may have placed too great a distance between altitude constrains and it took FL200 as my new cruise alt. More investigation required!

[Paul_Smith 92]

 

 

Imagine this scenario:

You're in VNAV in the descent. ATC says "reduce speed 220 knots or less for spacing, if able." The latter is added in by controllers for two reasons: to reassert that pilots should still maintain safe speeds, and to concede that the restriction in the descent is known to be difficult. Had they wanted to reduce speed immediately, they would have said "reduce speed 220 knots or less, immediately (or similar)" or "amend your altitude to [higher intermediate altitude], at [higher amended altitude] reduce speed 220 knots or less..."

Thank you Kyle, that settles the argument as it is a scenario where V/S is clearly better then any of the other available modes.

 

 

 

...at low altitude where FLCH is prohibited...

That is the second time you have made that claim. I do not doubt that you know people who know things, but since the manuals written by Boeing that the rest of us have access to actually recommend the use of FLCH in a number of low altitude situations, perhaps you could tell us mere mortals why you believe that it has been prohibited?

[FLEX1978 373]

Wow, you don't quit do you? It Seems only one mere mortal needs an explanation.

 

Have you ever heard of a company SOP paul? Do you understand that Boeing/Airbus and every other manufacturer will provide the template for operating their aircraft, however 'every' airlines training department will modify aspects of those guidelines to ensure their flight crew operate those aircraft in a way they see fit, often these changes are a result of internal incidents or recommendations.

 

In short, real world aviation is not as rigid as it seems you would like to believe.

 

In case you still don't get it paul here a few other examples, putting aside certain company policy's regarding the use of certain A/P modes in various stages of flight.

 

Use of Auto thrust

 

Hand flying above a certain altitude (Not talking about RVSM airspace)

 

Accepting or requesting 360 orbits at low altitude.

 

F/o being allowed to taxi or call abort

 

Minimum Flap setting allowed on approach.

 

I could go on and on.... Pretty sure someone on this very thread even mentioned a restriction on the use of V/S, not something I have ever come across In the past 15 years however I have no reason not to believe that was a part of that companys SOP.

 

As I mentioned previously, it is all fine and dandy that you like to read FCOMs, however actual line flying for an airline requires a bit more then downloading the original Boeing FCOM & FCTM off the internet and believing that every operator blindly follows it in the same way.

[xkoote 57]

FLEX is correct, manufacturer FCOM's regarding flight techniques are guidelines only. Companies can add what they want to the satisfaction of their regulatory agency.

 

Another area where I always use V/S is when getting "descend now" clearances. You can use the DESC NOW feature and adjust the throttles to get the rate of descent you want. But it is just a very complicated way to get a fixed vertical speed. So what I do is type in the new altitude into the CRZ page. A new TOD is calculated for your next crossing restriction. I then use V/S and adjust to reach the assigned altitude right at the new FMC calculated TOD. Thus creating a constant descent, without level off towards the first hard crossing restriction.

 

 

Xander

[mjd7419 2]

Guys - PMDG got back to me and are looking into this for the SP1 update.

[777simmer 117]

Guys - PMDG got back to me and are looking into this for the SP1 update.

Oh no....that means it will take longer to finish SP1.....all on you!!

 

Just kidding ;-)

[Paul_Smith 92]

 

 

Wow, you don't quit do you?

Not usually, no.

Yes, I do know what a SOP is. I also know that you seem to have forgotten that Standard Operating Procedures vary between airlines and airframes, and evolve over time. They reflect the thoughts and opinions of the authors at the time they where written and only apply to their  intended target audience.

 

Boeing's FCOM recommends the use of FLCH in certain low altitude situations, but you have twice claimed that it is prohibited. You have not qualified it to say, for example, "such and such an airline recommends against it use in the following situations because of concerns about...", you have simply said it is flat out not allowed. And when asked for details, all you have done is bluster. So you would please be kind enough, on the third time of asking, to tell us why we should believe you over Boeing? 

[FLEX1978 373]

What on earth are you on about? Are you really that much of a troll!

 

Ok, let me spell it out, unfortunately I cannot draw you any pretty pictures. And for obvious reasons (likely not obvious to you) I am not going to name the particular airline on a public forum.

 

Now, myself and others have mentioned potential issues of using FLCH in the approach phase at low altitude so I am not going to repeat myself.

 

In case you really are being that ----- I am not talking about FLCH on departure...

 

I am going to give you an example of one Airline, pre Asiana... After a number of incidents including unstable approaches whilst using FLCH a senior Captain also using FLCH busted stable approach criteria, engines unspooled & landed heavy below Vref causing extensive damage to the aircraft, captain fired! policy put in place and training reviewed.

 

Paul, I have had enough of you, stick to flying your desk and trawling the internet for snippets of information about real world operations, Most importantly keep out of my way and I will most definitely continue to stay out of yours.

[pete_auau 1,164]

Rob maybe  you should  take your own advice  as per # 38  you  posted

[FLEX1978 373]

Yeah your right if it wasn't so sad it would actually be quite funny in a way. Anyway I am done with schooling 6000 hour virtual airline captains. Time to find Kyle's post on setting up an ignore, should have done it 5 years ago.

[777simmer 117]

Guys - PMDG got back to me and are looking into this for the SP1 update.

For what its worth, I did a climb to FL330 with Vs mode today.

 

Setting +3000ft/min resulted in the AP maintaining 2850 - 3150ft/min.

Setting +1500ft/min resulted in AP maintining 2950 - 3050 ft/min.

And it would be going up/down between those two values constantly...not just once and in a while.

 

Nothing I would call irritating or a big problem though.

 

The real 777 does not constantly exactly keep the set VS either.

 

I only tested this on this one flight, so hardly enough to draw any coclusions!

 

But it seems to me that PMDG has tried to simulate the slight variance of the real thing in a little bit too simplistic manner. As in, a constant tiny pitch fluctuation that results in a certain percentage of up/down VS.

Too much of a pattern, not random enough!

 

I say again: only one test done....and not a real problem (for me) anyway.

[Paul_Smith 92]

What on earth are you on about? Are you really that much of a troll!

 

Ok, let me spell it out, unfortunately I cannot draw you any pretty pictures. And for obvious reasons (likely not obvious to you) I am not going to name the particular airline on a public forum.

 

Now, myself and others have mentioned potential issues of using FLCH in the approach phase at low altitude so I am not going to repeat myself.

 

In case you really are being that ----- I am not talking about FLCH on departure...

 

I am going to give you an example of one Airline, pre Asiana... After a number of incidents including unstable approaches whilst using FLCH a senior Captain also using FLCH busted stable approach criteria, engines unspooled & landed heavy below Vref causing extensive damage to the aircraft, captain fired! policy put in place and training reviewed.

 

Paul, I have had enough of you, stick to flying your desk and trawling the internet for snippets of information about real world operations, Most importantly keep out of my way and I will most definitely continue to stay out of yours.

Yet again, lots of bluster but very few facts. Read your own posts again, you have not mentioned potential issues, you have said that they exist but not what you think they are.  

 

Even in this latest post, you have not said who bans FLCH or why, so I ask yet again, why should we believe you over Boeing?  At least you have qualified your self a little in that now you are only claiming FLCH is prohibited at low altitude while descending. Earlier you did give the impression that it was completely verboten (though come to think of it, you never did mention what altitude it was banned from).

 

And sorry, but your latest example is only good for showing how you talk about stuff without actually saying anything. Why would a senior pilot get busted for following procedure, even if it is subsequently changed. If there was heavy damage to the airframe then there is probably a public domain report on the incident which that you would have no problem referring to, and of course, it would implicate FLCH so proving your point outright.  There is such a report, isn't there?

[FLEX1978 373]

Last post here paul.... Yes obviously there is a report, I have no idea if it is in the public domain, highly unlikely since I know of at least 5 hard landings in a month involving one carrier on the 777 that is not public domain, only mentioned in the monthly internal safety memos.

 

Re read my post (you do have problems don't you?) The captain in question busted the stable approach criteria resulting in a hard landing. Now obviously in your world that should not be a sackable offence...

 

I guessed correctly, you are incapable of understanding that someone would not wish to mention the name of a particular operator on a public forum, especially when they are not posting anonymously.

 

You have shown yourself to be a troll of the highest degree, even beyond my expectations.

 

However I am going to play this silly game one last time, and to finally shut you up I will contact you via PM Within the next 48 hours with the exact details and the name of the operator. now crawl back under that rock

[777simmer 117]

Come on now guys....this is just plain silly.

 

Paul stop provoking.

 

Rob stop wanting to prove you are right.

 

Each time you guys post here, the thread lights up.

And I go there to see if there is something new, or someone needs help.

 

To find out I am wasting my time reading nothing but you guys bickering with each other is really annoying!

[Tabs 2,790]

This has run its course. We will look into it. As Rob mentioned (we saw this ourselves too in the level D 777 sim), the real airplane does not fly on rails with a perfectly constant V/S while in this mode (nor in any of the other modes including FBW hand flying) - you will not get that sort of effect out of our simulation because it isn't realistic.