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 25 SYSTEMS & DYNAMICS (Read 7044 times)
Francesco Giacchetti
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Re: SYSTEMS & DYNAMICS
Reply #60 - May 19th, 2020 at 7:38am
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It is what it is, that's the product we are getting, i post the bugs that i found compared to the real airplane, just hope they can fix it and make the best of it. CS sayd the VNAV was descent enough, but compared to the real VNAV it does not look alike at allScholli04 wrote on May 19th, 2020 at 7:23am:
Francesco Giacchetti wrote on May 16th, 2020 at 11:47pm:
Airplane is planning bad its Descend Profile, it should do the descend on iddle thrust, CS767 is doing it with thrust pretty much the entire descend

AIIR#6


How is a customer supposed to calculate a formular for the descent? There are a thousand lines in the FCOM, and even your included manuals, saying that a VNAV PTH descent is an IDLE path descent.
Yours is not, yours constantly has thrust on.
That's all this report is about.

No numbers needed to proof yours has thrust on. That's clearly visible in any descent as you can see on this gentlemans picture

  
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #61 - May 19th, 2020 at 1:41pm
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Scholli04 wrote on May 19th, 2020 at 7:23am:
Francesco Giacchetti wrote on May 16th, 2020 at 11:47pm:
Airplane is planning bad its Descend Profile, it should do the descend on iddle thrust, CS767 is doing it with thrust pretty much the entire descend

AIIR#6


How is a customer supposed to calculate a formular for the descent? There are a thousand lines in the FCOM, and even your included manuals, saying that a VNAV PTH descent is an IDLE path descent.
Yours is not, yours constantly has thrust on.
That's all this report is about.

No numbers needed to proof yours has thrust on. That's clearly visible in any descent as you can see on this gentlemans picture


Honestly, no. Them asking for some more info is totally reasonable. They need some numbers (about his flight) to be able to do anything about it.

Bug reports should be reported here as if you were a pilot writing up an airplane, plus a lot more. This product is in beta as advertised so it's great there are so many reports, but if they say they wnat more info, that's totally reasonable. (A certain airbus developer does tht exact same thing)


VNAV PTH has two modes.. performance descent (idle path) and geometric descent (point-to-point).

They need to know whether:
He was in speed intervention mode?
He wasn't doing an ECON descent (SPD SEL)?
He input imporoper winds in the descent forecast page / the forecast winds were way different than planned?
Wat TAI supposed to be on according to the forecast page and it never came on?
If the computer descent path was somehow shallower than normal (was there a speed or altitude constraint behind him?)

I've never tried or seen a VNAV descent with such a high CI/Econ speed selected, does the  FMC perhaps calculate a shallower VPTH on purpose when doing such a high speed descent?
  
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trevors
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Re: SYSTEMS & DYNAMICS
Reply #62 - May 19th, 2020 at 2:58pm
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Alex T wrote on May 19th, 2020 at 1:41pm:
VNAV PTH has two modes.. performance descent (idle path) and geometric descent (point-to-point).

They need to know whether:
He was in speed intervention mode?
He wasn't doing an ECON descent (SPD SEL)?
He input imporoper winds in the descent forecast page / the forecast winds were way different than planned?
Wat TAI supposed to be on according to the forecast page and it never came on?
If the computer descent path was somehow shallower than normal (was there a speed or altitude constraint behind him?)



Alex is 100% correct. Sometimes the descent path between 2 waypoints is shallow and therefore the descent rate (vertical speed) must decrease - if this happens, then thrust has to be increased to maintain the KIAS/Mach - the opposite is also true.
  


Trevor
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #63 - May 19th, 2020 at 3:37pm
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I will also add from real-world experience (despite having lots of 757/767 knowledge, I don't fly that airplane, but another advanced jet) I'm not sure if the 75/76 constantly is recalculating its path to account for changes in air density as it descends (I doubt it) then the thrust required to maintain whatever FPA it calculated will ABSOLUTELY change as the aircraft descends.

Someone on the 75/76 please correct me if I'm wrong, but the company manuals I keep finding for the 75/76 tend to say "near-idle" when describing the logic to pilots to remind us that it changes as necessary and to override it if we need to.

In my airplane for example, if we start a descent in VNAV PTH, sure it may maintain idle to maintain the 300 or so KTS and the constant path, but idle at FL350 is way different than idle at FL180. The airplane slowly pitches up and up as it descends. Why? Because if you're maintaining a constant path, and your TAS (and therefore GS) is decreasing, you will eventually need to reduce your VS in order to maintain that constant path. The plane won't change speed since you're doing an ECON descent and probably maintaining a constant speed, so the only way to do this is by slowly increasing thrust all the way down, because simply: the path it calculated to be a good "average" decent is no longer working at that altitude. 

Maybe seems counter-intuitive that you'd need to increase thrust as you get lower since air is more dense, but that's what you get when you try and maintain a constant path. Think of an ILS on the GS: the slower you go, the less VS you need, plane pitches up to maintain that ~3 degrees, plane slows down more, you need more thrust.
  
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #64 - May 19th, 2020 at 8:26pm
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AABoeing wrote on May 16th, 2020 at 9:20pm:
v.95 P3D 4.512.30293

Insufficient decel logic in VNAV mode (CI of 111 and speed restrictions not complied with). Descent rate is kept to follow VNAV path when it *should* follow speed restrictions and prompt "DRAG REQUIRED" if not able to maintain speed+descent profile.

http://prntscr.com/si3y1l
http://prntscr.com/si3yo9
http://prntscr.com/si3yv0

AIIR#4, 6


You're absolutely right. Once you pass the first speed constraint, in your example the plane should done a speed reversion once it was +10 from target speed.

"If flight plan modifications or unknown winds occur when above the first speed
constraint, VNAV varies speed to maintain the path up to the following limits:
• With greater than 15 knots below the target speed, the autothrottle changes
from IDLE/HOLD to SPD to provide thrust to accelerate to the target speed. If
the autothrottle is not active, the scratchpad message THRUST REQUIRED
displays. The airspeed may decrease to minimum maneuvering speed.
Subsequently, VNAV commands the aircraft to fly below the path to stop the
deceleration. If VNAV can no longer maintain the aircraft within 150 feet
of the path without further deceleration, speed reversion occurs, the pitch
mode annunciation changes from VNAV PTH to VNAV SPD, VNAV resets the
target speed to 5 knots above the greater of best holding speed or minimum
maneuvering speed, and the scratchpad message THRUST REQUIRED
displays again.
• With greater than VMO/MMO minus 16 knots, the scratchpad message DRAG
REQUIRED displays. The aircraft may accelerate up to VMO/MMO minus
11 knots to maintain the path. If further correction is required, VNAV may
allow the aircraft to rise up to 150 feet above the path. If VNAV can no longer
maintain the aircraft within 150 feet of the path without further acceleration,
speed reversion occurs, the pitch mode annunciation changes from VNAV
PTH to VNAV SPD, VNAV resets the target speed to VMO/MMO minus 16
knots, and the scratchpad message DRAG REQUIRED displays again."


"If flight plan modifications or unknown winds occur when below the first speed
constraint, VNAV varies speed to maintain the path up to the following limits:
• With greater than 10 knots below the target speed, the autothrottle changes
from IDLE/HOLD to SPD to provide thrust to accelerate to the target speed. If
the autothrottle is not active, the scratchpad message THRUST REQUIRED
displays. The airspeed may decrease to minimum maneuvering speed.
Subsequently, VNAV commands the aircraft to fly below the path to stop the
deceleration. If VNAV can no longer maintain the aircraft within 150 feet of
the path without further deceleration, speed reversion occurs, the pitch mode
annunciation changes from VNAV PTH to VNAV SPD, VNAV commands
a speed 10 knots less than the transition speed for the destination airport
(not less than minimum maneuvering speed), and the scratchpad message
THRUST REQUIRED displays again
• With greater than 10 knots above target speed, the scratchpad message
DRAG REQUIRED displays. The aircraft may accelerate up to 15 knots above
target speed to maintain the path. The maximum speed excursion allowed
is 5 knots above the transition speed after the aircraft is below transition
altitude for the destination airport or 5 knots below the flaps placard speed
if flaps are extended. If further correction is required, VNAV may allow the
aircraft to rise up to 150 feet above the path to stop the acceleration. If VNAV
can no longer maintain the aircraft within 150 feet of the path without further
acceleration, speed reversion occurs, the pitch mode annunciation changes
from VNAV PTH to VNAV SPD, VNAV commands a speed 10 knots less than
the transition speed for the destination airport, and the scratchpad message
DRAG REQUIRED displays again."
  
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #65 - May 22nd, 2020 at 3:18pm
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In cruise, getting a new bug where on the VNAV crz page, it's showing an IAS instead of mach, even at FL360. This only after the last update.

Maybe the 250/10000 fix broke this?

If you're crusing above approx FL290 depending on the ambient conditions, the CRZ page will show a mach instead of an IAS. Like I said, this was working properly before.

The CRZ Page:


The CLB/DES pages look fine showing a transition MACH

  
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #66 - May 22nd, 2020 at 7:44pm
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Bug:
Predicted Distance to ETA or Altitude (PRED ETA-ALT) isn't working

Flight Phase:
Cruise

Manual Reference:
‘767 Captain II’ Manual Part II F – Flight Management System page 148

Issue:
According to the manual: "Entering an altitude or flight level displays the predicted along track distance
and altitude or flight level on this line. The predicted airplane position displays on
the HSI route line as a green circle with the entered altitude/flight level or time."

This is how we plot things for ETOPS. In my picture, in the HSI at near the 10nm mark there should be a little green circle that says "1405Z"
This is used to give pilots a quick glance at when on their route they're estimated to hit a certain time for planning purposes.

This is the 777 but it's exactly the same. In this case the person entered an altitude in the PRED ETA-ALT box instead of a time, both end up looking the same.
  
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Re: SYSTEMS & DYNAMICS
Reply #67 - May 22nd, 2020 at 7:56pm
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BEYOND THIS POINT PLS MAKE SURE YOU ARE ON VERSION 0.96
Pls do not report previously reported issues again, if they are not listed as fixed in the change log.
  
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fly cln
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Re: SYSTEMS & DYNAMICS
Reply #68 - May 23rd, 2020 at 12:02pm
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The FMC is unable to fly a proper DME Arc procedure.

Example: VANES2G arrival into LGRP. (current AIRAC)

It is supposed to fly a 13DME arc around PAR VOR. Then after DEXAS, join the localizer at D13.0 as well.

What it does instead: Fly a series of bizarre left and right turns that doesn't look like an arc at all. Then it tried to join the localizer at 8 DME (right where the GS starts).

AIIR#6
  
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Scholli04
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Re: SYSTEMS & DYNAMICS
Reply #69 - May 23rd, 2020 at 2:02pm
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Fuel Used is still not fixed in 0.96.
Block fuel on this flight was 46.3t.
https://imgur.com/1dTewDS

As you can see fuel on board plus fuel used adds up to 46.0t.

Furthermore there is a second bug visible.

The fuel Totalizer shows the fuel as per the fuel gauge. So far so good.
The CALCULATED fuel though is what the FMC determins by substracting the FUEL USED from the initial block fuel as entered on the PERF INIT page.
So in this example: 46.3-15.7=30.6.
The calculated fuel should therefore indicate 30.6 instead of 30.3.

What about APU? It could burn those 300kg
  
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Francesco Giacchetti
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Re: SYSTEMS & DYNAMICS
Reply #70 - May 24th, 2020 at 4:24pm
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Airplane is not respecting de 240kts below 10000ft

AIIR#6
  

2020-5-24_11-20-7-815.jpg ( 281 KB | 12 Downloads )
2020-5-24_11-20-7-815.jpg
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Francesco Giacchetti
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Re: SYSTEMS & DYNAMICS
Reply #71 - May 24th, 2020 at 4:34pm
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When doing a Go-around when trying to select CLB thrust at 1000ft on the TMSP in does not change to CLB it reamains on GA
  

2020-5-24_11-27-57-543.jpg ( 223 KB | 9 Downloads )
2020-5-24_11-27-57-543.jpg
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Francesco Giacchetti
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Re: SYSTEMS & DYNAMICS
Reply #72 - May 24th, 2020 at 4:42pm
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When doing an Instrument Approach using VNAV, 2nm from the FAF we set the MDA or DA on the MCP, select or verify VNAV is engaged on VNAV pth (FMC on approach mode is active). Once the airplane pases the FAF and is at least 300ft below missed approach altitude, we select the Missed APP altitude on the MCP, CS767 is reverting to ALT hold and is not allowing the airplane to re engage VNAV

Source 2020 767 QRH, Maneuvers, Flight Patterns, Instrument Approach Using VNAV
  

IMG_0124.jpg ( 492 KB | 8 Downloads )
IMG_0124.jpg
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Francesco Giacchetti
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Re: SYSTEMS & DYNAMICS
Reply #73 - May 24th, 2020 at 4:45pm
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FMC is not engagin On approach mode, meaning VNAV pth only even when speed intervention, airplane should remaint in VNAV pth when de following conditions are met
  
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Alex T
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Re: SYSTEMS & DYNAMICS
Reply #74 - May 24th, 2020 at 5:11pm
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Francesco Giacchetti wrote on May 24th, 2020 at 4:45pm:
FMC is not engagin On approach mode, meaning VNAV pth only even when speed intervention, airplane should remaint in VNAV pth when de following conditions are met


I already reported this a few pages back. They’re working on it.
  
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