cant keep a perfect turning

[muamshai]

use FD mode or better buy a Force feedback stick :D

[sobek]

Originally posted by EtherelN

How do you all calculate this 3 degrees/s yaw rate per second?

Are you estimating it? or are you watching some instrument? because I cant find it.

 

Skkuda

 

We just estimate.

[AlphaOneSix]

A turn rate of 3 degrees per second corresponds to 2 minutes for a 360 degree turn. A 2-minute turn is also referred to as a "standard" turn, and many aircraft are equipped with a turn and slip indicator which shows the angle of bank required for a standard turn. Of course, the Ka-50 has no turn and slip indicator (just two slip indicators on the primary and standby attitude indicators), so the only way to really tell is to see how long it takes you to turn. A standard turn (3 degrees per second) will take 30 seconds to turn 90 degrees, 15 seconds to turn 45 degrees, etc.

[Frederf]

Duh. Yes i know that, i just wanted to emphasize that the autopilot does not work that simple, of course there is backcoupling and damping in the control system, also full AP authority occurs well below 180° deviation from the trimmed course. There's a differential equation of at least 1st order involved into such a circuit, to counter overshoot.

 

I wouldn't count on friction though, the Shark weighs in at roughly 8 to 10 tons, which gives it quite the fair amount of moment of inertia. Considering the low tangential velocities that would occur in a yaw oscillation, i'd say if it was only for friction, it would go on for hours on end. Dunno what you mean about the deadzone, or how that would counter oscillation.

 

I was just saying that even a simple proportional AP input didn't have to lead to an oscillation even though your thinking is sound. There are way that even a simple system can avoid this pitfall... not that I'm saying that the Ka-50 is so simple, just a theoretical simple AP could avoid this.

 

By deadzone I mean that small deviation is not corrected for so once any theoretical osculation died down to some small amount the AP would stop trying to be perfect and the osculation loop breaks. This is just theory though on how the AP could work if it wanted to, not how it really works. How it really works is something I don't know, but it would be nice to find out!

 

Standard rate (3°/sec) is a rather lazy turn even in a Cessna 172. It actually takes some patience to not turn faster in the Ka-50 so I assume your trim-for-yaw-rate tests were fast enough. Still it's good to check all our processes :D