VNAV Overspeed Descent, is it Part of the System?

[IAF747 8]

On descent in VNAV mode the 777 was doing over -5000FPM BUT when the overspeed zone was touched the A/P did nothing.

Why? I took a screenshot to show it. I'll possibly upload it next post if someone also queries this.

[Don t moderate me this way 882]

I had an 'overspeed (=actual speed higher than the magenta speed) for altitude' situation myself but haven't checked the overspeed protection yet.

Edited September 5, 2013 by olli4740

[scandinavian13 5,192]

 

 

Why? I took a screenshot to show it. I'll possibly upload it next post if someone also queries this.

 

Check your AT setting in your PMDG Setup > Simulation setting.  Post what it says here, please.

 

Additionally, that screenshot would be very helpful - never hesitate to post those when requesting support.  It saves a lot of time, and I potentially could've solved the issue by now.

[IAF747 8]

Check your AT setting in your PMDG Setup > Simulation setting.  Post what it says here, please.

 

Additionally, that screenshot would be very helpful - never hesitate to post those when requesting support.  It saves a lot of time, and I potentially could've solved the issue by now.

 

Well I took it with my iphone so ill have to get it off it. So not a 'screenshot' such as. I don't like flipping in between apps while flying. :-)

[scandinavian13 5,192]

 

 

I don't like flipping in between apps while flying. :-)

 

You can always just hit the V key and FSX will dump a BMP file into your My Pictures folder in an folder named something related to FSX.  You'll have to convert it to JPEG to link to it here, but at least it avoids all of the switching or poor quality / fuzzy camera pictures.  :wink:

[3-2-1-Now 126]

I had VNAV apparently completely ignore altitude constraints last night. I'm just wondering if it was because OFFPATH DESCENT was active? I noticed it drawing around the destination.

 

The system claimed it was on path, despite being 7000 ft too high, and didn't ask for drag. It managed the speed OK.

 

Does simply looking at the OFFPATH DES page activate it??? I did look at it earlier in the flight out of curiosity, but I didn't type anything into it.

 

Best regards,

Robin.

[StarBlue 27]

Also are you setting your flaps and speed into the FMC? For me that corrected a lot of my overspeeds. You can also set your speed on the MCP, click the middle and set the speed and it will override the FMC unless it has a hard set speed. Usually better once you are closer to landing. The tutorial has a good example of all of this.

[scandinavian13 5,192]

Does simply looking at the OFFPATH DES page activate it???

 

OFFPATH DES isn't a mode, it's an advisory feature like the FIX page to the best of my knowledge...

 

You sure your hardware throttle was at IDLE and the required altitude was entered on the LEGS page?

[IAF747 8]

You can always just hit the V key and FSX will dump a BMP file into your My Pictures folder in an folder named something related to FSX. You'll have to convert it to JPEG to link to it here, but at least it avoids all of the switching or poor quality / fuzzy camera pictures. :wink:

Thanks. After reading the introduction manual it is actually normal to get over speed in descent.

[downscc 1,327]

Daniel, it is normal to be a few knots over target but not what I would call "over speed." That would normally only happen if thrust was in HOLD mode and your throttle settings allowed you to activate your controller throttle and it is not in the idle position. That's why Kyle questioned your setting.

[scandinavian13 5,192]

 

 

After reading the introduction manual it is actually normal to get over speed in descent.

 

Above speed, but overspeed?  As in red arc?

 

 

Daniel, it is normal to be a few knots over target but not what I would call "over speed."

 

EDIT:

Dan beat me to it again 

[Alaaar 34]

I am sorry I had what it looks like an auto-throttle issue I think might be related to the above issues.......during my fifth flight or so with the T7, during TO phase, I pressed the hidden TO/GO button on MCP as usual, plane accelerates and took off, gears retracted,  after passing the acceleration  height,  the speed stays on the V2 setting I entered earlier, it wouldn't do what it is normally doing which is accelerating to 250kts ...no SIDs were used so there was no restrictions ...V speed were fed to the FMC as always ......any ideas ??

 

By the way it didn't stall only the speed was at the top of the yellow ribbon (representing the minimum maneuvering speed I guess) @ the bottom of the speed ribbon all the way. Then I interfered and assigned speed higher speed via MCP speed knob ????

[Alaaar 34]

I am sorry, but on a second flight same issue happened ....a question........ For the auto throttle to function does the VNAV has to be active even when AP is off ??

[E6BAV8R 88]

I am sorry, but on a second flight same issue happened ....a question........ For the auto throttle to function does the VNAV has to be active even when AP is off ??

 

No.  They are separate systems.

I am sorry I had what it looks like an auto-throttle issue I think might be related to the above issues.......during my fifth flight or so with the T7, during TO phase, I pressed the hidden TO/GO button on MCP as usual, plane accelerates and took off, gears retracted,  after passing the acceleration  height,  the speed stays on the V2 setting I entered earlier, it wouldn't do what it is normally doing which is accelerating to 250kts ...no SIDs were used so there was no restrictions ...V speed were fed to the FMC as always ......any ideas ??

 

By the way it didn't stall only the speed was at the top of the yellow ribbon (representing the minimum maneuvering speed I guess) @ the bottom of the speed ribbon all the way. Then I interfered and assigned speed higher speed via MCP speed knob ????

 

Did you have VNAV armed on the departure?  If not, you never told the plane to activate climb thrust and accelerate.

 

Without VNAV Armed the Auto-Throttle will still function but the airplane will not go proceed into the next phase of flight after take-off (Climb Thrust and Acceleration) without you manually telling it to.  If VNAV is Armed than Climb Thrust and Acceleration will activate at the altitude specified in the FMC, and that will also be reflected by the Flight Directors pitching the aircraft lower for it to accelerate.

[http404 22]

I am sorry, but on a second flight same issue happened ....a question........ For the auto throttle to function does the VNAV has to be active even when AP is off ??

 

That explains your issue. When VNAV is off, the A/T will not take you on it's own to the 250kts restirction, and in that case, you will have to manually set the target speed on the MCP. Pitching down will not work as the engines will reduce thrust to maintain your V2+20.