FMC: No descent path after ....

[Gerardius 20]

Wow Ryan! That's an explanation! Thank you very much! This is another reason to love PMDG, the great customer service... keep this great work!

The UNABLE 250 KTS AT CLE-34 is because you are crossing that point at 10,000 feet, and by default there is a 240 kts speed restriction at or below 10,000. Delete the speed at CLE-34, or remove the restriction from the DES page. Not sure where D222K is, so that one I cannot explain. Might be a ripple effect from the speed problem.

Tom, thank you very much for your explanation!Cheers!

[Tabs 2,790]

You guys can thank Vangelis for the explanation, I just turned it into plain English

[wreck1463 0]

You guys can thank Vangelis for the explanation, I just turned it into plain English

Well Thanks to both of you then. I agree with the above comment, you all have excellent customer service. At least from me, it will pay off for you. I'm hooked on your aircraft now...

[kjjj11223344 48]

Well Thanks to both of you then. I agree with the above comment, you all have excellent customer service. At least from me, it will pay off for you. I'm hooked on your aircraft now...

Same here.

[Gabriel Teles 172]

I saw this when inserting my approach to Sion... expected, I guess.

[fakeflyer737 992]

Ok so now that we know what it is, what do we do about it? Ignore it?

[RYR738 9]

Ok so now that we know what it is, what do we do about it? Ignore it?

It is an FMC Advisory message !! See FCOM Vol 2 page 1134 for the corrective action.( very bottom of the page) Fred.

[Tabs 2,790]

Ok so now that we know what it is, what do we do about it? Ignore it?

Quite simple - you are the pilot, fly the airplane. Real pilots don't just use VNAV "on rails" like this - if you really want it to do something, take over manually and use speed intervention, V/S, LVL CHG, throw out speedbrakes etc to get the result you're looking for. VNAV isn't a perfect system, in fact most real NG pilots will tell you it's far from it. Sometimes it flat out may not be possible to meet a path depending on the exact restrictions and your gross weight. The 800 is a very slippery airplane as I said and some restrictions may not be doable. In real life you hear pilots say things to ATC like "I can do the altitude or the speed, not both, which do you want?" That's perfectly reasonable - ATC is there to accommodate and facilitate what pilots need, not the other way around. (common misconception in the simming world where everyone thinks SID/STAR charts are absolutes and that you do fully automated descents all the time - not true in real life) You will find the 700 in particular MUCH easier to descend and slow down with once we release it - it feels much more "normal" than the 800 does in that respect.

[RYR738 9]

Just to add a little bit more on this ! In the RW we would see what the corrective action is for this " Advisory Message " and if we thoughtthat nothing needed to be adjusted/altered then it would just be ignored.For example " Drag Required " is also an Advisory Message so the corrective action would be to use thespeed brakes to help keep the plane on the VNAV PATH.( the second you deploy the speed brakes the Advisory Message goes away ) " Alerting Messages " on the other hand relate to operationally significant conditions which can affect the FMC's operation. Fred.

[badderjet 181]

Here's the technical explanations: NO DES PATH AFTER XXXXX: [...]

You guys can thank Vangelis for the explanation, I just turned it into plain English

Although a little old already, still a great read and valuable info! Never knew about the 6/7 degree thing too.

[Rickie Welsh 27]

Hi, I was under the impression that FlightLevel Change wasthe best for descent purposes as the system gives you the ability to correct/control the speed whereas Vnav usually means the speed tape will speed up past the selected speed and you might end up throwing everything at your disposal, flaps,spoilers and even landing gear to try and regain selected speed, i got this info from reading Capt. Mike Ray. richard welsh.

[Spin737 102]

Hi, I was under the impression that FlightLevel Change wasthe best for descent purposes as the system gives you the ability to correct/control the speed whereas Vnav usually means the speed tape will speed up past the selected speed and you might end up throwing everything at your disposal, flaps,spoilers and even landing gear to try and regain selected speed, i got this info from reading Capt. Mike Ray. richard welsh.

There's many ways to skin this cat. Speed intervention in VNAV will give you the same effect. If you're high, you're high and you'll need to dirty the plane up or speed it up regardless of the mode.

[badderjet 181]

Speed intervention in VNAV will give you the same effect. If you're high, you're high [...] speed it up regardless of the mode.

Ok, I'm very embarrassed to ask this question, but I feel I have to. Why do I have to speed it up, that means the faster I go, the steeper my glide angle? I am aware of best C_L/C_D, which usually results in best glide (that is, farthest distance per altitude loss). Does that in any way imply that VNAV would usually fly around best glide (plus or minus CI corrections obviously)? If that were true, I could actually go faster or slower, at least leave best glide speed somewhat to steepen the angle, no?I remember the 'buses have that "green dot speed", which is I believe exactly that speed, minimum drag. Guess there's no way to find that quickly on a Boeing?

[Spin737 102]

Ok, I'm very embarrassed to ask this question, but I feel I have to. Why do I have to speed it up, that means the faster I go, the steeper my glide angle?

I didn't say you have to speed it up. You can add drag by other means, as well. However, going fast is a good way to get back on profile if you're high. Let's say you had planned on a .78/280 descent and you got high on path because of ATC. When you get clearance to descend, you can just go down at 300kt, and you'll get back on path. You go down steeper, and I suppose you have more drag due to the higher airspeed. This works very well if you're a ways from the the airport (maybe >30nm?) and you've got smooth air. I'd rather go fast than use the speedbrakes.

[badderjet 181]

Ok, thanks. Yeah I remember Jack Colwill had posted that insanely helpful video of going fast instead of putting the panels up during descent. Makes a lot of sense.