I have recently been having issues with the autothrottle on the 737-700. After about 10,000 feet the autothrottle stops working and doesn't increase or even maintain speed. It drops my engines to about 88% which slowly drains my speed and unless I manually increase the throttle I will eventually stall. I think it has something to do with my N1 Limit setting in my FMC, but since the FMC is still kind of new to me I'm not completely sure if that is the problem and if it is how to fix it. I have double checked that my A/T is armed, Speed Hold set to .73 mach and is on, Autopilot is on, flaps are all the way up, and Speed Brake is off. Any help would be much appreciated as I have been researching this problem both on this forum and many other sites and haven't had any luck finding a solution.

The speed control on an aircraft can be done in 2 ways, one is modifying thrust, the second one is done by modifying pitch.

If you reach the maximum N1 (the one you set on FMC or manually) the only way to add speed is by reducing vertical speed. If you are in speed mode, you are using VS. Reduce VS.

As a check, verify your TAT when climbing, sometimes active sky can create some thrust problems because it will give you unreal high temperature when at cruise altitudes.

PS: If you cannot reach your desired climb rate, change your N1 limit value.

Thanks, I figured it had something to do with my N1 Limit. How do I change my N1 Limit though? I tried doing it through the FMC but didn't have any luck and I'm not sure how to set it manually.

Upload a pic of your displays (especially the primary engine display) to figure out what is going on.

 

Changing N1 limits is easy, just press the N1 button on the CDU and choose the setting you want, also make sure the N1 limit dial above the upper centre scree is in auto. Confirm what mode your engine limits are in by checking what mode it is above the N1 indications on the centre display.

 

It might not be a n1 limit issue is could very well be TAT temp is unrealistically too high (as mentioned by Andrea above) so post a pic of your displays.

 

 

Oh and please sign your real name in your posts or sig as it is the rules. :)

Thanks, I figured it had something to do with my N1 Limit. How do I change my N1 Limit though? I tried doing it through the FMC but didn't have any luck and I'm not sure how to set it manually.

If you want to set the N1 limit manual. Set the inner knob of the N1 SET control selector on the Engine Control Module above the engine display from AUTO to "BOTH" for both engine's or "1" for engine 1 only or "2" for engine 2 only, and than set the N1 limit manually with the outer knob of the N1 SET control selector, The selected N1 limit will be displayed above the N1 indication.

Yes but note that manual N1 limit selection has no effect on A/T operation.

~ FCOM vol. 2, Engines, APU section

Ok here are the screenshots of my panel. I tried replicating this problem in single player free flight but couldn't, this only happens to me when I'm flying on the VATSIM network so it might not be the plane at all. However, I can't think of anything on VATSIM that would cause this. I also set my weather to Clear Skies to make sure that the weather wasn't affecting it.

 

Panel:

http://www.flickr.co...in/photostream/

 

N1 Settings:

http://www.flickr.co...in/photostream/

 

Payload (although it doesn't seem to affect my throttle issue):

http://www.flickr.co...in/photostream/

 

And not sure if this is helpful but here is the N2 and oil readings:

http://www.flickr.co...in/photostream/

Hmm blistering hot temperature on the top of Mount Everest! Weather is effecting it.

 

Your thrust settings are fine. TAT of +43C at FL280 is your problem, do you have some external software controlling anything, like some sort of server/client thing for Vatsim (I don't fly Vatsim so I don't know what software is involved)

I have FSInn which is the software I use to connect to VATSIM so the weather is what ever it the VATSIM server sets it to. It must be due to what ever the server sets the weather to.

This is a well-known issue with FSInn weather. The solution is to disable any weather options in FSInn and instead use some other source.

 

 

Oliver Branaschky

Don't you need to have the same weather setting as the server so that if the ATC tells you to set your altimeter or something else that is weather related it matches the ATC's weather?

After even more research I found this and it fixed my problem.

http://forum.avsim.net/topic/344335-problem-with-fsinn-on-vatsim/

 

Once I get to about 20,000 feet I turn my CAVOK on then load weather from FSX. Real World weather that updates every 15 minutes seems to work fine and it doesn't seem that far off from the weather in the VATSIM server. Thanks for the help guys.

I am glad it solved your problem, this is why pictures are very handy when explaining your problem. :)

Generally, you can use any source/program that gives you realtime weather. Generally they all have the same weather within minutes (well the same METAR anyway, interpretation can be a bit different, but nothing major.

 

I recommend Active Sky, I use that for weather, ever since I started looking at alternatives when IVAO weather started giving problems at altitude. I think this will even let you use VATSIM servers as source of weather information.