Bugs in VNav, To Davide, for information Options

[Cyril Murat]

Hi Davide.

For information, I’ve noticed 2 bugs that I think haven’t been reported yet:

1- VNAV in descent: Let’s say the successive points in legs are XXX, YYY and ZZZ.

If I put a speed restriction on XXX (220 for example), it is copied in YYY and ZZZ so the speed restriction should be applied to all the next points. The problem is that after passing XXX (when YYY becomes the next point), the restriction is forgotten and the speed increase from 220 to 250 again. I have to put the restriction manually to all the next points to keep the speed.

2- In VNAV too: it often happens that as the aircraft descends, the VMO limit pointer descend suddenly bellow the actual IAS and that an overspeed occurs. I guess that descending in the real a/c in VNAV never leads to overspeed… I may be corrected.

That said, may I ask you confirmation that you’ve read this and can you confirm us customers that Leonardo is back to work and will try to correct the know issues ?

Happy new years, best regards, happy flights and safe landings.

Cyril

[massimo]

Hi Davide.

For information, I’ve noticed 2 bugs that I think haven’t been reported yet:

1- VNAV in descent: Let’s say the successive points in legs are XXX, YYY and ZZZ.

If I put a speed restriction on XXX (220 for example), it is copied in YYY and ZZZ so the speed restriction should be applied to all the next points. The problem is that after passing XXX (when YYY becomes the next point), the restriction is forgotten and the speed increase from 220 to 250 again. I have to put the restriction manually to all the next points to keep the speed.

2- In VNAV too: it often happens that as the aircraft descends, the VMO limit pointer descend suddenly bellow the actual IAS and that an overspeed occurs. I guess that descending in the real a/c in VNAV never leads to overspeed… I may be corrected.

That said, may I ask you confirmation that you’ve read this and can you confirm us customers that Leonardo is back to work and will try to correct the know issues ?

Happy new years, best regards, happy flights and safe landings.

Cyril

1 - It's a bug

2 - VNAV

The followings captions can be displayed on the Climb, Cruise and Descent Page Title Line:

-ACT LIM SPD CLB (Limited by speed envelope or flap placard)
-ACT LIM SPD CRZ (Limited by speed envelope or flap placard)
-ACT LIM SPD DES (Limited by speed envelope or flap placard)

NOTE: when a speed (either IAS or MACH), greater or lower than the max/min speed allowed by speed/buffet envelope or airplane configuration, is inserted in the FMS, MCDU will accept and show that particular speed, but the title line indicate “LIM” to alert crew that the FMS is controlling the speed limiting to the max/min value permitted by the situation.
PROGRESS Page will show in field 5L (LIM SPD) the exact limited speed value that the FMS is maintaining.

When the acft is tracking the descent path, system is designed not to violate established speed limits. If above the transition altitude or first wpt speed constraint,should it be necessary to maintain the vertical path, the system will increase the descent speed until approaching the VMO. Then the acft will leave the path and maintain a limiting speed below VMO.This can result in undesired speed values during descent. Below the 10000ft speed transition altitude, the acft will never exceeed 255 Kts. Below the speed transition altitude, 240 Kts is used as the target speed. The MCDU message “DRAG REQUIRED” is displayed when the acft exceeds the target speed by 15 Kts above the first speed/altitude constraint or 10 Kts when below the first speed/altitude constraint.

Notes: in Terminal areas with VNAV engaged, the use of FMS SPD OVRD mode is reccommended. This will preclude speed target changes resulting from NAV/VNAV editing or leg sequencing. When the acft gets significantly off the lateral path in descent or attempts to fly against the path, the FMS will inhibit the descent patch and a message “DESCENT PATH INHIBITED” will be issued.
In Terminal areas, when under vectoring or under extensive deviations from original lateral/vertical path, it is suggested to exit VNAV and to continue vertical navigation by means of traditional Flight Guidance controls (VERT SPD or IAS).

As soon on skype

[Cyril Murat]

As soon on skype

Thanks a lot Massimo. It is very interesting and there were many things that I didn't know and that you learned me. I'll train them in my next flights.
But nothing explains that VNAV can lead to OVERSPEED if I let it do the path with defaults settings and I still thing about a simulator issue.
Regards,
Cyril

[Omaniac]

Are these quick, momentary overspeeds? It's a well known problem with some weather programs like ASX and happen because of large changes in airspeed. I use a registered version of FSUIP and have managed to set it up to avoid this. It is the same with all add on aircraft.

[Cyril Murat]

Are these quick, momentary overspeeds? It's a well known problem with some weather programs like ASX and happen because of large changes in airspeed. I use a registered version of FSUIP and have managed to set it up to avoid this. It is the same with all add on aircraft.

Hi.
I guess that you are right. I didn't think about it.
smoothing the wind changes will certainly solve the problem.

Best flights.

Cyril

[TWVA MDs]

Are these quick, momentary overspeeds? It's a well known problem with some weather programs like ASX and happen because of large changes in airspeed. I use a registered version of FSUIP and have managed to set it up to avoid this. It is the same with all add on aircraft.

Hi Omaniac...I also have a registered version of FSUIPC. What settings are you using to stop the overspeeds, etc?

Thanks in advance to anyone who has some good settings for this.

Cheers!