How-To: Easy setup for perfect (bail-out) self-level

[soko]

Hey guys,

As I wasn't satisfied with the accuracy of SL (self-level) I was achieving with the methods described here I wrack my brain to find a (better) solution...

I'm glad to anounce that I've found a perfect solution!
But let's start with my story and needs for SL as this solution might not work for every purpose!

If you want something like the following, this solution is for you:
I'm just beginning with 3D: trying to get my flips, rolls, loops, and stall-turns right.
I bought the SK720 for its SL feature, to use it at bail-out.
I dislike to practice on the simulator. I like to try&error with real helis.
I want to flick a switch on the Tx when I'm loosing orientation and the heli hovers as good as possible and as long as possible. So I can get my nerves back

Requirements, restrictions, preperations and hints
Bad things first:

• You loose one flight mode (but be honest here: who does really NEED 3 flight modes?)
• You need an advanced Tx (I use a DX8)

The good side:

• Your heli will go into "hover-level" with the flick of a switch
• Easy trim of SL with the trims on your Tx
• You don't have to mess with the Setup Software servo trims
• You don't have to mess with the linkage lengths of the cyclic servos
• Your mechanical setup and SK720 setup stays perfect for normal flight

What you have to do first is to mount the SK720 as close as possible to the center of grafity (CG, CoG) of your heli.
My SK720 is mounted directly under the main shaft on the bottom plate: So as perfect as possible
AND (of course) make sure the SK720 is mounted in level (all 3 axis) with the heli as stated in the SK720 manual.

Second make sure that your vibrations are as low as possible to support the SL function of the SK720 as much as possible. To achieve that see the other threads arround here.
My vibes on my 550E are 0.7 in Playback Log and the spikes in the Vibration Log are max. 2.5.
Skookum states that the vibes should never exceed 7.0! If they do SL will shut itself down (=the heli will fly in normal mode) The SK720 led will flash red+green if that happens.

Third make sure that your heli hovers nicely (hands-off!) on a calm day with SL disabled!
To achieve that each of this points should be completed successfully:

• Your heli should fly and you should have flown your bell gains (point 6 on page 55 of the SK720 manual).
• Do the "BasicTuning" as stated in the SK720 manual page 55f
• Do point 4 (200% hiller decay trim) in section "Advanced Tuning for 3D Pilots" on page 58 of the manual

My problem after all that was, that the heli still drifted significant out from stable hover when I activated SL.
The important thing is:
It drifted always into the same direction!. To make things clear: It hovered great w/o SL!
If your heli doesn't do that (i.e. drift in complete other directions each time) in SL there is probably something else wrong and you won't get what you want with this solution!

Finally you should understand the basic setup procedures of your Tx (i.e. DX8) and the SK720 (i.e. how to switch between cyclic banks). If you don't know it read other threads or do it like I did: try & error

What does "hover-level" mean
This guide is no magic! It can't do anything more than the SL feature is able to do. It just an easy way to get the maximum out of the SL!
So if you in a roll in FFF (fast forward flight), you loose orientation and flick the switch don't expect that the heli gets in stable hover!. We will get that with the GPS module (if we ever get hands on it )
What will happen is, that your heli will keep the speed and direction! It will go in hover position (="hover-level") though.
So after that you can easier stop the heli. You also have to do the pitch right as the self level only affects elevator & aileron.

Here's the How-To
As I'm not familiar with other Tx I'll explain it using the DX8 procedure. Hope your Tx will be able to do the things coming
Furthermore, to keep it simple, I'll explain my setup. I'm sure there are many ways to achieve the same result. So feel free to alter...
The result is as follows:

• "hover-level" SL is activated with the F-Mode switch
• F-Mode 2 (switch in "close to you" pos) will get normal flight mode
• F-Mode 1 (switch in middle pos) will get idle-up 1
• F-Mode 0 (switch in "away from you" pos) will activate SL

SK720: Setup Software interface switch
Click on the main menu - "Preferences" - "Interface" - "Advanced"

SK720: Setup for cyclic bank switch
In the "Control" tab set "Cyclic Gain Ch:" to "Gear"

SK720: Setup cyclic bank 2 for SL
Assumption: You did all your setup and tuning with cyclic 1!
# Click with the right mouse button on the "Cyclic 1" tab and select "Copy Cyclic 1 to Cyclic 2"
# Disable "Self Tune Bell Gains" if enabled
# Set "Hiller Decay" to 75
# Set "Self Level" to "Always on" and 100% (EDIT- 200% is now the maximum %, it was 100% at the time of writing)

DX8: preparation & hints
Make sure you've loaded the setup that is bound to your heli.
The following setup will give you a reverse order of the flight mode! So be sure that you set up the pitch & throttle curves accordingly!

DX8: set trims per flight mode
# Turn off your DX8
# Turn it on while pressing the roller
# Goto "Trim Setup"
# Select "F Mode" for "Type:"
# Press the "BACK" button 2 times

DX8: Assign flight mode switch to gear channel
# Goto "Governor" menu (your DX8 is in "ready" mode after last step)
# Choose "F Mode" (equals "Sw:" = "F Mode" if it wasn't Inhibit before)
# Set "Ch:" to "Gear"
# Set "Hold" "Stunt 2", "Stunt 1" to "-50%"
# Set "Normal" to "+50%"
# Press the "BACK" button 2 times

Test the settings
# Power you heli (SK720 & Servos only!)
# Connect the SK720 to your PC & start the setup software
# The software should indicate "Cyclic 2" when switching F-Mode to 0 (away pos). All other positions should be "Cyclic 1". If you don't get to "Cyclic 2" be sure to release throttle hold!
# The software should show in section "Live Data" - "Inputs from receiver" - "Elevator" and "Aileron" 0% in all Flight modes (don't touch the sticks of the Tx!).
# Now switch to F-Mode=0 (away pos = SL active): Use the trims on your Tx close to the stick (w/o moving the stick itself!). The "Live Data" should show the change accordingly.
# If you switch to any other F-Mode the "Live Data" value should be 0 again.
# If you switch back to F-Mode=0 the "Live Data" values are the once you saw before
# Set the values back to 0 in F-Mode=0.

Real life test & setup
# Check everything again and be sure that you've "reversed" the throttle & pitch curves!
# Go to a stable hover in F-Mode=1 (middle pos).
# Switch to F-Mode=0 (away pos). If the heli stable drifts use the Tx trims to compensate for that drift.
# Repeat the last both steps so that the heli doesn't move anymore when switching to F-Mode=0

!!CONGRATS!! you have a stable hover level with SL

Whenever you're in trouble wipe with your left hand the F-Mode switch to F-Mode=0 and your heli is hopefully rescued!
That is why I reversed the F-Mode orders: Its faster to wipe the switch down as to go under it und flick it towards you

If you've read until here you should have get the principle behind this setup and should be able to adapt it to your needs and to another Tx.
In short: With the flick to F-Mode=0 you do two things: activating "Cyclic 2" (hence SL!) and a trim on aileron & elevator to compensate the static drift.

Last thing to say:
It's a good idea to get used to flick to SL. So train it! Furthermore check the trims from time to time especially when you're trying some new stuff and are likely to need the SL. The sense of the SK720 may change during flight and conditions.
So:
# getting warm with some basic flights maneuver
# retrim your SL (see "Real life test & setup" above)
# Do the dangerous stuff

Soko

[NRPY]

I just dedicate a bank for an SL bailout mode, which I programmed to the left hand shoulder switch on my DX8. When the crap hits the fan, I just flick that switch and the heli rights itself. All I need to do is make sure it has enough collective to stay aloft. IMO, its not that important whether the heli drifts in SL because all you really need is the bailout. After you've recovered, flip back to non-SL mode and do it again. I don't like to fly with SL active because l don't like how it interferes with my normal control.

[georgi UK]

=] Soko its a great post, I keep reading it and need to re-read it many more times, to absorb its value!

[soko]

Thanks, I appreciate it

And what a nice way to say that I'm really able to write complicated sentences.
I know that I'm tending to put as much details as possible in as few words as possible

Soko

[phenault]

When you say drift, do you mean drift left or to the right, or drift as in elevator and aileron input drift? I thought if its perfectly level it will drift right (or left i cant remember).

[soko]

I mean drift to the right/left/front/back.
No static drifts on the aileron/elevator! With souch a drift your heli will be performing a roll/flip automatically.

Soko

[jhamel]

Soko,

Please, post pictures of how you mounted the SK-720 on your T-Rex 550E. The bottom plate has lots of holes. Did you mount it fore/aft or left/right? Thanks.

[soko]

Hey,

My SK720 is mounted at the top side of the bottom plate so it is protected during crashes.
The Servo connectors are facing to the front. The position on the bottom plate is so that the SK720 is directly under the main shaft.

So I think this should. lear the exact position.

If you still need/want pics let me know and I'll take some...

Soko

[soko]

Hi John,

First I had a typo in my last post: Servo connectors facing to the front, not to the back...
Here are the pics:
First the position of the SK720 looking from the back. You can see the USB connector there...


With this tools i connect/disconnect the usb cable. For connecting the USB-cable I insert the metal rod from the front and the usb cable to the back. Then I push both against the SK720 so the USB-cable snapps in.
For disconnecting the cable i insert the round plastic thing from the back. Push it gently to the SK720 and pull at the cable. DONE


Finally here's the detail of my tail-servo-mounting:


hope that helps

Soko

[jhamel]

Just like with your under-mount tail servo setup, I also needed a servo spacer between the servo and the mount to have proper geometry with the carbon tail pushrod. However, I do not know if it is an issue with the stock plastic mount, but with the KDE tail servo mount, I had to shave off some of the width and the corners of the spacers (the ones closest to the motor) in order for them to fit properly. I see that you used the 4 arm servo horn. I already configured the 6 arm servo horn with the link in the center hole. I'll try the 4 arm horn if this 6 arm horn does not agree with the SK-720. Thanks for posting your photos. They are tremendous help.

[ds1rc]

Full credit for the original thought-out process goes to soko of Auckland, NZ . I have modified the procedure to fit my JR 11X and flying style.

Thank you Andreas for a great method, Don S., Aloha, OR.

You need to read the first post in this sticky if you haven’t because it explains the theory. Remember this setup is applied to a JR 11X and a 700e.

The Transmitter:

This post describes the programming and modification made to the JR 11X Transmitter based on my flying style including how I hold the transmitter.

I am a thumb flyer and this means I hold the mode 2 Transmitter with my thumbs on the sticks, palms gripping the sides and the forefinger of the left hand under the F.MODE SW and the forefinger of the right hand under the RD.D/R SW above the MIX/HLD SW.

In its standard configuration the 11X F.MODE SW in the down position = NORMAL, the center = ST-1 and the up position = ST-2. I want the SW positions reversed so up = NORMAL, center = ST-1 and down = ST-2. The 11X F.MODE SW cannot be electronically reversed so remove the F.MODE SW, turn it upside down, replace it and you have the SW reversed. All I have to do is pull my left forefinger up with the F.MODE SW in any position and I am in NORMAL flight mode with Cyclic Gain 1 at 100% self-level.

The MIX/HLD is the normal HOLD SW. Since my right forefinger is positioned above this SW accidently activating the SW is difficult. To activate HOLD the right forefinger needs to be moved under the SW and the SW pulled up.

Programing:

From the standard SK720 placards SET Cyclic Gain Ch = GEAR and Tail Gain Ch = AUX-2. From the SYSTEM LIST DEVICE SELECT SET GEAR: = FMOD SW ACT and AUX2: = GEAR SW ACT. All the other SW is SET to INH. FLIGHT MODE = FMODE SW. EXTRA = INH. From the SYSTEM LIST WARNING SET THRO STK:ACT, POS: 10, AREA:HIGH. Select SW SELand SET ST-1 = ON, ST-2 = ON and HOLD 0=ON.
From the FUNCTION LIST D/R & EXP SET AILE, ELEV and RUDD @ 100%, EXP to +20%. NORM: P0, ST-!: P1, ST-2: P2 and HOLD: SW. REVERSE the GEAR SW and the AUX2 SW. SET THRO HOLD = ON, HOLD POS -5% SW SEL = HOLD 1. SET the TRIM SYSTEM to 1 and L.S.T., STUNT TRIM: COM. This differentiates between the NORMAL and STUNT trims allowing the transmitter trims to control the NORMAL F.MODE. Remember when you change the SK720 trim it effects all flight modes so you will have to adjust the transmitter trims for NORMAL.

Throttle and Pitch Curves:

I am running the SK720 Governor Mode with a CC ICE2 HV set to OFF with a release of the CC Firm Ware that works with an external Governor. The throttle curves are NORMAL 40-40-40, ST-1 60-60-60 and ST-2 100-100-100. The Pitch Curves are HOLD 0-50-100, NORMAL 50-50-100, ST-1 0-50-100 and ST-2 0-50-100. Note: In NORMAL with a throttle curve 0-40-40-40-40 if you pull the throttle stick to far negative you can get a Governor disconnect and Governor Disconnect is not Heli Friendly.


Flight Envelope:

For the theory of the dead on self-level at 100% go back to Soko’s post. After preflight and main power connect SET F.MODE = NORMAL, HOLD = ON, throttle at 50%, flip HOLD = OFF, spool up will start. As the head RPM comes up switch F.MODE to ST-1 and let the Governor engage and then lift off. If you have transmitter trims set in NORMAL you DO NOT want to lift off in NORMAL because the SK720 will accept the trims as stick input. Once you have altitude switch to ST-2 and go “fly it like you stole it.”

Self-Level:

Cyclic Gain 1 = NORMAL @ Self-Level ALWAYS ON @ 100% and Cyclic Gain 2 is SET to OFF or anything you want to make it. ST-1 and ST-2 AUTO-SWITCH to Cyclic Gain 2.

Landing:

On approach to Landing F.MODE = NORMAL. The Governor maintains head speed regardless of the throttle stick position, remember the throttle curve is 40-40-40. At five to three feet flip the HOLD SW = ON and auto rotate to land like a feather.

Video: [ame]http://www.youtube.com/watch?v=LR-_BMR5hgI[/ame]

[ds1rc]

Component locations.

https://www.helifreak.com/attachment...0&d=1328990710

https://www.helifreak.com/attachment...4&d=1329507066

[soko]

nice work Don

[Avi_Y]

Originally Posted by soko

...
What you have to do first is to mount the SK720 as close as possible to the center of grafity (CG, CoG) of your heli.
...

Thanks for the effort Soko.

Please note regarding the system placement considerations - Mounting the gyos and accelerometers at the center of gravity does not make any difference. The angular velocity, sensed by the gyros, and the accelerations (= forces = "sense of level"), sensed by the accelerometers, will be measured the same anywhere on the helicopter. This is not only with regard to the center of gravity, but also with regards to the roll / elevator / yaw axis of the helicopter.
The important thing is to have the system aligned with the axes.

[soko]

OK, thats the theory part.

Anyway in Rev 3.00 of the SK720 manual page 16 middle: "If you plan to use the SK720’s self-levelling / bailout feature, it is better to mount the unit close to your helicopter’s centre of gravity"

Soko

[georgi UK]

=] the real reason for this is to reduce the lateral vibrations, the nearer the mast the better, in terms of SL performance.

the physical location makes no difference were it not for this factor.

[Avi_Y]

Originally Posted by gmcallister

=] the real reason for this is to reduce the lateral vibrations, the nearer the mast the better, in terms of SL performance.

...

This indeed makes a lot of sense.
Thanks.

[Luvmyhelis]

Geez, once again I just learned something profound and new. Thanks G!

[Husqua]

Hi Soko!

A few questions,

After following all your instruction for bail out what is your control rates value with the SL on?
also with the SL off and do you activated the Self Tune Bell gains with the SL off


Thank you very much
Denis

[soko]

Hi Denis,

Here's what I did...
I load 3D defaults to cyclic-bank1. Flew then a few times with "self tune bell gains" to let them tune in. After that I deactivated self-tune, copied cyclic-bank1 to bank2 (SL bank).
In cyclic-bank2 I changed:
control rates=360° for both values
self-level="always on", 100%

thats it
Soko