I figured out how to disable SAS!

[Pocket Sized]

For the longest time I found that messing with the autopilot panel didn't affect SAS and assumed it was a bug. It turns out the solution has nothing to do with the autopilot panel. (For those of you that don't know, SAS is why the craft will right itself when you center the cyclic)

 

During the startup you are told to select a gyro and give it a few minutes to align until the barberpoles go away.

 

Turn the switch between these indicators one notch to the left of center. (If the helo was already running just left click it once) The barberpoles should come back, indicating the SAS is NOT working and you should not lift off under any circumstances. This is the perfect time to lift off and get a feel for the helicopter.

 

It's a different beast to fly without SAS, much less predictable. But it makes holding forward flight much easier because the nose doesn't want to creep back up to the horizon. If the cyclic response speed was higher this would allow for some truly ridiculous aerobatics.

Edited May 5, 2016 by Pocket Sized
"and circumstances" "response peed"

[fjacobsen]

Turning off the Gyos will render the SAS inop.

But i don´t think that this is the right way to turn the SAS off, though it celarly show how the Gazelle fly's with or without SAS.

 

What would be nice would be more deteiled description of the SAS/AP system.

I´m not stating it is wrong, but it´s hard to figure out.

 

Try to turn on autohover..

You can disable autohover by turning off the AP, but then You loose control, since the controls won´t move.

 

When in an Autohover, try to turn off the pitch channel, and whil still keeping ina steady hover the helicopter might drift back or forward.

 

Try the same with the roll channel, and You will start drift sideways.

 

Turning off the yaw channel does not seem to do much.

 

If controls for these channels would be brought back to the stick and pedals when the relevant channels where turned of in an autohover, then this could be used to adjust You poistion ie. back, forth - lateral right left, heading right left. But this isn´t the case.

 

So question is..

 

How does the real SAS/AP work and how do they interact.

Is it possible to turn SAS off without turning the gyros off ?

Wat are the real function of the pitch, roll and yaw channels ?

Is the Main AP switch meant to turn off both SAS and AP or just AP functions ?

 

To understand this, we need more indepth ino regarding the SAS/AP system.

 

FinnJ

[Pocket Sized]

But i don´t think that this is the right way to turn the SAS off, though it celarly show how the Gazelle fly's with or without SAS.

 

[. . .]

 

How does the real SAS/AP work and how do they interact.

Is it possible to turn SAS off without turning the gyros off ?

Wat are the real function of the pitch, roll and yaw channels ?

Is the Main AP switch meant to turn off both SAS and AP or just AP functions ?

 

I know there's probably a better way but maybe the craft isn't made to be flown with the SAS off at all.

 

In real life it probably works a bit like this:

 

The stick/pedals are connected directly to the swash plate/tail rotor with force sensors somewhere along the line.

 

There are hydraulic actuators that can move the stick and pedals. The SAS uses the force sensors to figure out what the pilot wants to do to prevent it from fighting the pilot. (When no force is detected it will gently level the craft)

 

When the autopilot is turned on the hydraulic actuators take full control of the stick/pedals. (The pilot could override them with elbow grease alone, but it could be designed to disengage when it detects a certain amount of force) Turning off channels should probably make the associated actuator go limp/back to SAS mode, allowing for manual control.

 

I'm speculating right now, so don't take my word for it just yet.

[Geskes]

In this article is some information:

 

https://books.google.nl/books?id=2iPpBN29ezMC&pg=PA72&lpg#v=onepage&q&f=false

[fjacobsen]

Here is an article about helicopter autopilots and expedit describing the autopilots from SFIM inc., which is the manufacturer of the unit we see in the Polychop Gazelle.

 

http://www.aviationtoday.com/rw/training/ratings/No-Hands_1458.html#.VytkgXqjBp0

 

 

My finding (coupled with finding by "Pocked Sized") is that SAS is always ON and only turning off the gyros will rebder it inop and clearly show the difference between SAS and non-SAS.

The Autopilot control pilot then becomes more of a mystery. The AP master does not seem to affect the SAS, but only Autohover, Slave and Altitude/Airspeed modes.

The Pitch, Roll and Yaw channels can be used to de-couple those channels during autohover, Slave and Altitude/airspeed modes, but not giving control back to the stick renders them to cause problems when decoupled.

 

Since I don´t knw the inner workings, I cannot state that the current way it works is buggy, but questions surely arise how it should work.

 

Apart from this I find the Polychop Gazelle to be a very fine product and it feels more finsished than other modules when they where at this early beta stage.

It makes fun to fly, but I also find some of the issues regarding the flightmodel being a bit strange, which might be due to the SAS/AP as it works now.

 

For instance maing a simple turn, SAS should help keeping stable and not fight Your maneuvres. With my findings from f.ex the Mi-8, some "rubberbanding" is expected, but not like what we see now.

 

But regardless - Thank You Polychop to ring this very interesting helicopter to life in DCS :)

 

 

FinnJ

Edited May 5, 2016 by fjacobsen