Ground/Wheel friction too high?

[Ahmed]

During taxi a considerable amount of thrust is needed to maintain the speed. Idle thrust results in a massive deceleration. Seems like ground friction is exaggerated in the current flight model :

 

EDIT: Example of real taxiing. Notice power is needed to start rolling but then it can easily coast for a while, as any other jet (skip to 7:00)

 

本帖最后于2014年10月1日，由Ahmed编辑

[Razor5-1]

I've just got into the module today and noticed the exact same issue. I'm almost at AB to just get rolling. Am I missing a parking break or something similar or is this just the models behavior?

[Frederf]

As in most simulated planes the nose gear is modeled much too loose in castering. Almost always the nose gear is rotated to the side when beginning to move. That increases the resistance to move.

 

I find the airplane moves initially at 65-70% N1 and keeps moving at about 60%. No idea if those numbers are good or not but if your install needs totally different numbers then it would be worth it to figure out why.

 

https://ntrs.nasa.gov/search.jsp?R=19930091658 Here it looks like reasonable rolling resistance values are 0.01 to 0.02. Given a 9800kg (961kN) airplane and say 0.015 coeff. this needs 14.4kN to roll. Engine provides 44kN at maximum static dry thrust (sources vary 33-55). Is 60-70% RPM equal to 32.7% thrust output? It very well might be.

 

Sanity spot check http://code7700.com/images/variation_of_thurst_with_rpm_hurt_figure_2.10_middle.png shows 70% RPM giving 30% rated thrust. The shape of the graph makes for a very sensitive thrust per RPM as RPM increases.