Use TRIM instead of pitch/rudder controls for SAS. Why? Read here!

[Human Person]

4 hours ago, The_Rocketeer said:

Considering your moniker, I'm surprised you ask. But on the assumption you're not trolling us...

I'm not trolling, I really didn't know this. Also, I don't think this is particularly useful (except for rovers maybe). Well, I mean I got along without it so far (I'm playing KSP for 800+ hours now)

I'm actually studying to become a physics- and chemistry teacher

Edited April 15, 2017 by Physics Student

[dr.phees]

A basic description is here:

https://en.wikipedia.org/wiki/Aircraft_flight_control_system#Secondary_controls

 

KSP also allows trimming your craft. Using that for SAS would allow combining user/pilot input with the trim, eliminating the weird bumps when you try to correct pitch while in SAS mode.

[The_Rocketeer]

On 15/04/2017 at 3:58 PM, Physics Student said:

I'm not trolling, I really didn't know this. Also, I don't think this is particularly useful (except for rovers maybe).

Uses for trim (off the top of my head):

Power setting for stock electric propellor craft.
Non-resonating attitude stability for aircraft (matters a lot for hypersonic atmospheric planes, and SAS doesn't cut it).
Rover throttle.
Low-power sustained RCS can semi-simulate gravity.
Gyroscopic launch stabilisation for rockets.
Landing busted aircraft, e.g. with a missing wing or engine.
Stock station centrifuges.
Anything you want to keep moving gently after you switch to another craft or astronaut nearby.

On 15/04/2017 at 3:58 PM, Physics Student said:

Well, I mean I got along without it so far (I'm playing KSP for 800+ hours now)

One of the many joys of KSP - the possibilities and ways to play are so diverse, you can discover something you never knew almost every time you play.

On 15/04/2017 at 3:58 PM, Physics Student said:

I'm actually studying to become a physics- and chemistry teacher

Kudos If you're familiar with how the major control surfaces act on an aircraft (principles of fixed-wing flight), you can think of a trim adjustment as a semi-permanent fine-calibration of that surface to account for environmental conditions. In the days before dynamic/reactive autopilot systems, trim was invented to help deal with the problem of exhausting sustained manual effort to maintain attitude or bearing. It was a bloody good idea too!

[Stoney3K]

On 23-3-2017 at 8:40 PM, dr.phees said:

An example: The autopilot settings in FlightGear do exactly that. You let your plane for example hold a course and turn off the autopilot. The trim stays, so the plane doesn't turn a bit in that moment and you take over a perfectly balanced and stable craft from the autopilot.

That's because a real autopilot does the exact same, at least when it comes to pitch trim where it matters most. Yaw and roll are only used for turning so they will usually return to zero, while pitch is used for speed control so it is generally a more persistent setting.

SAS behavior needs some attention. When you touch the controls now, SAS is temporarily disabled until you release the controls again, the controls are returned to zero and SAS tries to correct the rotation that results from it. Which results in the unwanted oscillation because SAS is totally oblivious to the dynamic behavior of the craft, and overshoots.

The best course of action would be to let SAS handle the trim controls while the pilot can add control inputs without affecting the action done by SAS. When the pilot disengages SAS, the flight profile should not change (it does not when you disengage an actual autopilot on an aircraft).

The other way to realize this action is to make the pilot control inputs the setpoint for SAS control when SAS is enabled. This way, the pilot can command a certain attitude (momentarily or persistently using the ALT+control keys) which SAS will hold in a similar manner to a maneuver node. This could be indicated as a separate marker on the navball. This is the way a 'fly by wire' autopilot like in an Airbus works.

When SAS is turned off, in any case, its last commanded control setting should be retained as trim so there is no sudden change in flight profile when it is turned off.

Edited April 20, 2017 by Stoney3K

[dr.phees]

On 20/04/2017 at 1:01 PM, Stoney3K said:

That's because a real autopilot does the exact same, at least when it comes to pitch trim where it matters most. Yaw and roll are only used for turning so they will usually return to zero, while pitch is used for speed control so it is generally a more persistent setting.

SAS behavior needs some attention. When you touch the controls now, SAS is temporarily disabled (...)

It would be soo great to do that. I am currently trying to build something like that in kOS, but am a bit short of free time.

I wonder if anyone knows if the autopilot/trimming/pilot input API's are open enough to build the correct autopilot behavior as an addon.

Does anyone know?

Edited May 4, 2017 by dr.phees

[Stoney3K]

1 hour ago, dr.phees said:

I wonder if anyone knows if the autopilot/trimming/pilot input API's are open enough to build the correct autopilot behavior as an addon.

I believe they are, since there are other addons that do it (MechJeb, Pilot Assistant, Atmosphere Autopilot), they override the stock SAS.

[Aeroboi]

I know this thread is quite old but I require such a stock function also (yes there are mods...)

Hereby a deserved bump

[herbal space program]

On 4/6/2017 at 10:04 AM, StahnAileron said:

My biggest gripe about the stock SAS is that with it engaged, ANY player input overrides ALL the SAS commands. So SAS can be holding pitch for you. Your craft can be rolled a bit and you want to level out. You inputting roll-only commands for some reason turns off the current SAS hold-pitch inputs. So now you're rolling manually while pitching down unless you input some pitch as well. You may or may not have to add yaw input as well. It's an absurd system that made fine-tuning attitude nearly impossible without mods to compensate (Pilot Assistant being the primary one I used until I found AA; using both now.)

Absolutely this. All of my long-range space planes tend to be low on lift and nose-heavy on takeoff, and keeping them pitched up enough early in flight using SAS is always a big struggle for this reason.

[Aeroboi]

5 minutes ago, herbal space program said:

Absolutely this. All of my long-range space planes tend to be low on lift and nose-heavy on takeoff, and keeping them pitched up enough early in flight using SAS is always a big struggle for this reason.

Funny that I replied in regard to that quote as I decided to bump the thread particularly on the same point made there. While trimming itself can do the job if your plane is properly balanced in roll and yaw natively. This isn't always the case so this feature should really be implemented or in any other way possible.

[dr.phees]

On 3/11/2019 at 9:36 PM, Aeroboi said:

Funny that I replied in regard to that quote as I decided to bump the thread particularly on the same point made there. While trimming itself can do the job if your plane is properly balanced in roll and yaw natively. This isn't always the case so this feature should really be implemented or in any other way possible.

There is a nice mod, called "Athmosphere Autopilot(Fly-by-wire)" which even allows for coordinated turns, which I would gladly fly myself, if keyboard controls would properly make it possible. That mod makes you love flying planes again.

I still think this should be stock, though. After all, plane/space plane parts are stock.