VNAV, Descend Via and Embray'ers

ctab5060X said:
Well...

Most of the time :)

I love listening to those that complain about the "piece of crap" airplane not making a restriction when they are doing 300+ knots with a 50+ knot tailwind and they start down at the computed top of descent on a 3.0 path.
Click to expand...

Airbus can make it at 320 kts with 100 kt tailwind.
 
ctab5060X said:
Well...

Most of the time :)

I love listening to those that complain about the "piece of crap" airplane not making a restriction when they are doing 300+ knots with a 50+ knot tailwind and they start down at the computed top of descent on a 3.0 path.
Click to expand...

You're telling me. I fly with guys all the time who say, "VNAV on this airplane is a piece of crap." Well, any automation will bite you in the ass if you don't know how to use it. So maybe it isn't the automation that is crappy...
 
PhilosopherPilot said:
You're telling me. I fly with guys all the time who say, "VNAV on this airplane is a piece of crap." Well, any automation will bite you in the ass if you don't know how to use it. So maybe it isn't the automation that is crappy...
Click to expand...

I've had the VNAV give up on me once or twice, but it was so obvious that it wasn't going to do what it was intending that you'd have to be a fool who isn't paying any attention to the aircraft to not realize there's a glitch.

99% of the time, the plane does exactly what you've programmed it to do. Now what I CAN'T figure out is why the boxes will draw completely different paths sometimes, where one makes sense (usually the side it's coupled to), and one gives you a VTA chime every 60 seconds without dropping down the carrot.

Again, when this happens, it's incredibly clear that something is wrong and that the box isn't working AT ALL.
 
jtrain609 said:
I've had the VNAV give up on me once or twice, but it was so obvious that it wasn't going to do what it was intending that you'd have to be a fool who isn't paying any attention to the aircraft to not realize there's a glitch.

99% of the time, the plane does exactly what you've programmed it to do. Now what I CAN'T figure out is why the boxes will draw completely different paths sometimes, where one makes sense (usually the side it's coupled to), and one gives you a VTA chime every 60 seconds without dropping down the carrot.

Again, when this happens, it's incredibly clear that something is wrong and that the box isn't working AT ALL.
Click to expand...

I've seen it malfunction, but that's not what people complain about. They program it to do something, and then complain when it does EXACTLY what they programmed it to do. If you have more than 25 knots of tailwind, you better not descend at 3.0 degrees and expect to make a slow-down restriction.

You're right though, sometimes it gets a little confused, especially if you're making multiple changes at once, or doing a complete reroute.

(Sorry for the off-topic sidebar. Back to regularly scheduled complaining.)
 
PhilosopherPilot said:
I've seen it malfunction, but that's not what people complain about. They program it to do something, and then complain when it does EXACTLY what they programmed it to do. If you have more than 25 knots of tailwind, you better not descend at 3.0 degrees and expect to make a slow-down restriction.

You're right though, sometimes it gets a little confused, especially if you're making multiple changes at once, or doing a complete reroute.

(Sorry for the off-topic sidebar. Back to regularly scheduled complaining.)
Click to expand...
Making hard altitides helps sometimes too ;)
 
PhilosopherPilot said:
You're telling me. I fly with guys all the time who say, "VNAV on this airplane is a piece of crap." Well, any automation will bite you in the ass if you don't know how to use it. So maybe it isn't the automation that is crappy...
Click to expand...

Yeah but you expect an airplane built and designed in 2003 to be able to descend via and take into account winds and airspeed changes. Just building a vnav that calculates a generic 3.0 glide slope is in my opinion a huge oversight.

Best option is to change the default to 2.5.
 
Last edited:
The VNAV is better in the e190 than airbus IMO. The ability to do vertical direct to, changing the programmed decent angle, and starting down on it's own are all positives for the e190.
 
Kingairer said:
The VNAV is better in the e190 than airbus IMO. The ability to do vertical direct to, changing the programmed decent angle, and starting down on it's own are all positives for the e190.
Click to expand...
Would you rather be in an airbus or e190 doing the sevu in LA or the Ivane in CLT?
 
skyw82 said:
Would you rather be in an airbus or e190 doing the sevu in LA or the Ivane in CLT?
Click to expand...
Does the Airbus hold a higher N1 at flight idle when the anti ice is on? Helps answer the question. The rnav arrivals are great in the -175 unless the anti ice function is on. Then it is at least half boards the whole way down.
 
amorris311 said:
Does the Airbus hold a higher N1 at flight idle when the anti ice is on? Helps answer the question. The rnav arrivals are great in the -175 unless the anti ice function is on. Then it is at least half boards the whole way down.
Click to expand...

Not that I can tell.

The thing about the bus vs. the 190 is that when you initiate the descent on the bus it will make all speeds and alts easily without pretty much any inputs at all (except the 321).
 
skyw82 said:
Yeah but you expect an airplane built and designed in 2003 to be able to descend via and take into account winds and airspeed changes. Just building a vnav that calculates a generic 3.0 glide slope is in my opinion a huge oversight.

Best option is to change the default to 2.5.
Click to expand...
It's rare for me to do that; I'm usually going to make a strategic "between" into an "at (bottom of altitude window)" somewhere down the line. 2.8 down works pretty well (on the 175, at least).

Start down early!

skyw82 said:
Would you rather be in an airbus or e190 doing the sevu in LA or the Ivane in CLT?
Click to expand...
Which gets me more than 9 days off a month?

Polar742 said:
I think certain individuals (ok just one) who got the express ride to #tier1 always forget that today's "historic hiring" is a single event to cataclysmic stagnation.

Those of us old farts (even #tier2 for lifers like me) that have seen several cycles have the cynicism for a reason.

While past performance doesn't indicate future results, it's myopic to ignore historical patterns in a cyclical industry. Just ask the 22 year-old hired at US Air in 1989.
Click to expand...
It doesn't, but studying history is quite instructive; ignore it at your own peril.
 
skyw82 said:
Not that I can tell.

The thing about the bus vs. the 190 is that when you initiate the descent on the bus it will make all speeds and alts easily without pretty much any inputs at all (except the 321).
Click to expand...

Yea, I like the bus vnav much better. 190 was pretty good except that weird issue that @jtrain609 mentioned where 1 side is out of whack. It was always the uncoupled side, but I never could figure out why it would do that. Speed control is way better on the bus as well.
 
Snuggle said:
Yea, I like the bus vnav much better. 190 was pretty good except that weird issue that @jtrain609 mentioned where 1 side is out of whack. It was always the uncoupled side, but I never could figure out why it would do that. Speed control is way better on the bus as well.
Click to expand...
I've found going to FPA, waiting for things to "settle," and going back into VNAV PTH makes that go away...sometimes.
 
skyw82 said:
Yeah but you expect an airplane built and designed in 2003 to be able to descend via and take into account winds and airspeed changes. Just building a vnav that calculates a generic 3.0 glide slope is in my opinion a huge oversight.

Best option is to change the default to 2.5.
Click to expand...

The plane's default is 3.0, but you can program whatever you want in the perf init page when you initialize the box.
 
jtrain609 said:
Now what I CAN'T figure out is why the boxes will draw completely different paths sometimes, where one makes sense (usually the side it's coupled to), and one gives you a VTA chime every 60 seconds without dropping down the carrot.

Again, when this happens, it's incredibly clear that something is wrong and that the box isn't working AT ALL.
Click to expand...
Actually this is because the uncoupled side has an altitude that is off by more than 80 feet. The altimeters are within RVSM limits, but they're far enough off that the uncoupled box is constantly recalculating a new descent profile. That top of descent is within a minute of your current position (because you're damn close in altitude) but it's just far enough off that I gives you that warning chime that the uncoupled FMS wants to start down in less than 1 minute.

They only way to settle this is to unpair the FMSs (not an authorized procedure) or just write up the altimeters on the ground and have them re calibrated.

Btw cross checking altimeters upon leveling in RVSM and writing it down is a requirement. It could be rather eye-opening sometimes. Those Delta birds are getting old and cranky.
 
jtrain609 said:
I've had the VNAV give up on me once or twice, but it was so obvious that it wasn't going to do what it was intending that you'd have to be a fool who isn't paying any attention to the aircraft to not realize there's a glitch.

99% of the time, the plane does exactly what you've programmed it to do. Now what I CAN'T figure out is why the boxes will draw completely different paths sometimes, where one makes sense (usually the side it's coupled to), and one gives you a VTA chime every 60 seconds without dropping down the carrot.

Again, when this happens, it's incredibly clear that something is wrong and that the box isn't working AT ALL.
Click to expand...

The big and medium Boeing will do the same thing.
 
You must log in or register to reply here.
Back
Top