VNAV issues - P3D V3

[GCBraun 2,392]

Hello, today I have experience for the second time in a row some strange issues with my VNAV upon descent. After about 1 or 2 minutes into the descent, the auto throttle would just set 100% power until the plane overspeeds and the climb like crazy to reduce the speed.

 

I have checked all the speed infos on the FMS, and they were correct. There were no stall warnings or anything unusual before this thrust issue occurred. The only way to continue my descent was using FLCH or manual V/S.

 

Has anyone experienced a similar issue?

 

I`m using P3D V3 and last 777 version.

 

Thanks

[Peter Webber 339]

Where was your physical throttle set? Did you leave it at full throttle during the VNAV descent? I found this was causing the same issue that you describe..

[scandinavian13 5,192]

 

 

Hello, today I have experience for the second time in a row some strange issues with my VNAV upon descent. After about 1 or 2 minutes into the descent, the auto throttle would just set 100% power until the plane overspeeds and the climb like crazy to reduce the speed.

 

The default throttle setting for your hardware is AT OVERRIDE: ONLY IN ARM.

 

This means that, when your AT mode drops to ARM in the descent, it defers to your physical throttle position, which, guessing by your text, was left at the firewall since takeoff. The ability to adjust the throttles in ARM mode is true to the real aircraft, as well (which is why the option is offered).

 

You can either reduce the throttle yourself prior to T/D, or you can change the setting to AT OVERRIDE: NEVER.

 

Note: This may not happen every time as the sim may ignore the hardware throttle position until an "updated" position is sent. For example, if your hardware has been reporting 100% since takeoff, the sim is ignoring it because the position hasn't changed. If the signal varies even slightly, this is seen as an update. So, if the data stream is:

100.0, 100.0, 100.0, 99.9, 100

...the sim sees the change at 99.9 and "wakes up" to the hardware and firewalls the throttles.

 

In the real aircraft, the throttles have servos in them such that when IDLE is commanded, the physical levers move back. Your hardware likely doesn't have servos, so you have to manually move them back as the throttles roll back to IDLE at T/D.

 

 

 

Thanks

 

Full names in the forum please - first and last.

[GCBraun 2,392]

Where was your physical throttle set? Did you leave it at full throttle during the VNAV descent? I found this was causing the same issue that you describe..

 

 

Yes, my throttle was set to full as I usually leave it like that after takeoff. Will try to set it back next time.

 

 

Thiago Braun

The default throttle setting for your hardware is AT OVERRIDE: ONLY IN ARM.

 

This means that, when your AT mode drops to ARM in the descent, it defers to your physical throttle position, which, guessing by your text, was left at the firewall since takeoff. The ability to adjust the throttles in ARM mode is true to the real aircraft, as well (which is why the option is offered).

 

You can either reduce the throttle yourself prior to T/D, or you can change the setting to AT OVERRIDE: NEVER.

 

Note: This may not happen every time as the sim may ignore the hardware throttle position until an "updated" position is sent. For example, if your hardware has been reporting 100% since takeoff, the sim is ignoring it because the position hasn't changed. If the signal varies even slightly, this is seen as an update. So, if the data stream is:

100.0, 100.0, 100.0, 99.9, 100

...the sim sees the change at 99.9 and "wakes up" to the hardware and firewalls the throttles.

 

In the real aircraft, the throttles have servos in them such that when IDLE is commanded, the physical levers move back. Your hardware likely doesn't have servos, so you have to manually move them back as the throttles roll back to IDLE at T/D.

 

 

 

 

Full names in the forum please - first and last.

 

Thanks a lot! Will do that!

 

 

Thiago Braun