N1 Limit page FMC

[sichars1968]

The values for N1 on the N1 limit page, are the values assumed at sea level?

I have done a couple of take offs from Las Vegas(2100' elev) and Reno(4110' elev) and the aircraft is barely able to lift off. This is at quite low weights also. The N1 value on TOGA is in mid 80's so I would assume these values are at sea level? Should the v-speeds not be increased as a consequence of this?

Any help with this would be much appreciated.

 

Simon

[Litjan]

I just tried at Flagstaff on a HOT day (+30C) and I get ca. 95% N1 for full takeoff power - so yes, what you are seeing seems low. Nominal Takoff N1 is ca. 90.5% for seal level and standard temp - anything higher/hotter than that should incrase N1...

Can you make a short video of your Takeoff page?

Jan

 

[sichars1968]

Hi Jan

I will try tomorrow.

I haven't been using the full FMC capabilities for doing the route etc, as I've been having problems, as per my post about Gizmo soft crashes. Could this be the reason why, I am obviously inputting weights etc, does it take the position info from the POS page or when you input a full route(if that makes sense!)?

Thanks

Simon

 

[sichars1968]

Hi Jan

Just did a quick flight prep, KRNO-KTVL and on the N1 page was showing approx 95% N1 for full power takeoff. However upon selecting TOGA the throttles advanced to 85% N1 and barely able to get airborne.

Could this be to do with packs? Should these be off to give more engine power?

Here are my logs for your info.

Simon

 

GizmoLog.txt

Log.txt

[Litjan]

Hi Simon,

are you sure your autothrottle can work without getting interference from your hardware throttle? We see a lot of people that try to move their hardware throttle "along" with the ghost throttle - this can cause an inadvertant disconnect of the autothrottle when they trigger the rejected takeoff mode or you can accidentially "grab" the throttles when they enter THR HOLD at 84kts.

To rule this out, just move your hardware throttles ALL THE WAY FORWARD right after you trigger TOGA.

Does this help?

Jan

 

[sichars1968]

Hi Jan

I will try this tomorrow and let you know how it goes.

Thank you for coming back to me so promptly on this, very much appreciated.

Simon

[sichars1968]

Hi Jan

I tried what you said regarding putting hardware throttle all the way forward, and to start with there was no difference. I then applied the latest hot-fix and thought I would try to make a video as you suggested and lo and behold the throttle worked as it should, it went to about 85% and then advanced further to 92% when thrust locked appeared. I hope this is now correct.

The AVI was a terrible resolution so you was no use anyhow.

Simon