Flight mode names, a little help please

[psuedoman]

Hi,

I am having a play round with a 450 sized quadcopter and Multiwii, so far I can make it hover. Now I wish to expand my understanding of the software a little further and I have one basic stumbling block, what do all the different flight modes do ? (wrt r1311). I can find either partial documentation, conflicting information, or outdated info on this subject.

For instance this page: http://www.multiwii.com/wiki/index.php? ... lightmodes suggests in the table of sensors used for "headfree" mode only the magnetic is used, but then goes on to say it uses GPS and altitude hold modes, but these sensors are not marked as used in the table. I can probably guess that all of the suggested sensors are used in "headfree" mode but I'd rather not be guessing. I can piece together a reasonably clear picture of what is going on from the snippets I have found but I'd like to know for sure.

The several name changes the various modes have had are not helping either. I realise keeping documentation up to date is always the last job, guiltily of it myself. Please don't get me wrong I'm not picking fault, I understand the situation fine.

My guesses at the current flight modes are, please correct me !

. ANGLE -- Uses gyro and accelerometer ? Provides a stable flight mode ?
. HORIZON -- Uses gyro only ? A more aerobatic flight mode ?
. BARO -- Uses accelerometer, baro, and sonar ? What if sonar isn't present does it still work ? Tries to maintain a commanded height ?
. MAG -- Not a clue
. ARM -- Arms your motors.
. GPS HOME -- Uses compass and GPS only ? No stabilization and only GPS altitude ? Returns copter to point of origin.
. GPS HOLD -- Uses compass and GPS only ? No stabilization and only GPS altitude ? Hold current position
With both the GPS modes what happens if you have no GPS lock at time of arming ? Does it just ignore the flight mode ?
. HEADFREE -- Uses gyro, accelerometer, and compass ? No matter the orientation (yaw) of the copter it will always move in the same 2D direction for the same (roll-pitch) stick movement ?
. HEADADJ -- Sets a new yaw origin for HEADFREE mode ?

Humble apologies if I have missed the page where this is all explained, I have given it a good Googling and searched here to.

Thanks !

[QuadBow]

My guesses at the current flight modes are, please correct me !

. ANGLE -- Uses gyro and accelerometer ? Provides a stable flight mode ?
. HORIZON -- Uses gyro only ? A more aerobatic flight mode ?
. BARO -- Uses accelerometer, baro, and sonar ? What if sonar isn't present does it still work ? Tries to maintain a commanded height ?
. MAG -- Not a clue
. ARM -- Arms your motors.
. GPS HOME -- Uses compass and GPS only ? No stabilization and only GPS altitude ? Returns copter to point of origin.
. GPS HOLD -- Uses compass and GPS only ? No stabilization and only GPS altitude ? Hold current position
With both the GPS modes what happens if you have no GPS lock at time of arming ? Does it just ignore the flight mode ?
. HEADFREE -- Uses gyro, accelerometer, and compass ? No matter the orientation (yaw) of the copter it will always move in the same 2D direction for the same (roll-pitch) stick movement ?
. HEADADJ -- Sets a new yaw origin for HEADFREE mode ?

Humble apologies if I have missed the page where this is all explained, I have given it a good Googling and searched here to.

I put in my changes/answers.
- ACRO -- Neither ANGLE nor HORIZON means only gyros are used for stabilisation. It allows acrobatic flights e.g. allowing flips.
- ANGLE -- Yes, it should be stable in case the PID values are correctly adjusted, and the gyro and the accelerometers have been calibrated and trimmed.
. HORIZON -- In fact it is a mixture between ACRO and ANGLE combining the stabilising effect in case of calm rc sticks are available and acrobatics e.g. flips in case of busy rc stick.
. BARO -- Only the barometer is used for the purpose of keeping a certain height unless there is no other command from rc sticks.
. MAG -- Considers a magnetometer/compass as a prerequesit of HEADFREE.
. GPS HOME -- Uses compass and GPS for the purpose of returning home to the starting point. Stabilisation is done in accordance to the flight mode (ANGLE/HORIZON/ACRO). The GPS altitude is not very accurate and therefore not usable for holding the height.
. GPS HOLD -- Hold current position using GPS and baro (if available).
. HEADFREE -- It is not impacting the flight mode (ANGLE/HORITON/ACRO) only holding the orientation (yaw) of the copter and will always move in the same 2D direction for the same (roll-pitch) stick movement.
. HEADADJ -- Sets a new yaw origin for HEADFREE mode ? Yes.

[psuedoman]

OK, the smoke is clearing a little. A couple of questions:

1) r1311 doesn't seem to have an ACRO mode, am I missing something ? Is it the default mode if none of the others are selected ?

2) What exactly is the point of MAG mode then ? What would be the difference I would notice when flying ? MAG mode must be enabled for the HEADFREE mode to work ?

3) Does GPS HOME use the baro or sonar sensor if available ? and for that matter does GPS HOLD use sonar if available ?

4) How do you set the return altitude ?

3) ANGLE, HORIZON, (and ACRO) are primary flight stabilization methods, and can/should be selected along side the secondary modes which are: MAG, GPS HOME, GPS HOLD, HEADFREE ? Or is MAG considered a primary mode ?

4) If ANGLE, HORIZON, (and ACRO), all use gyro and accelerometer sensors for stabilization then what is the difference in terms of how the sensors are used ?

[Alexinparis]

Hi,

The wiki is not accurate about this. we should correct this.

some replies:

1) r1311 doesn't seem to have an ACRO mode, am I missing something ?

ACRO mode is the default mode when HORIZON or ANGLE are not activated

2) What exactly is the point of MAG mode then ? Does it fly like HEADFREE ?

MAG mode means: head lock mode.
That is to say, when there is no yaw input, the multi will point forever to the same direction.
without this mode, you will still have a light deviation (like a tail gyro in heli)

3) Does GPS HOME use the baro sensor if available ?

GPS mode does not rely on baro sensor.
GPS POS HOLD of GPS HOME is generally used in coordination with ATL HOLD, but this is not mandatory.
You can imagine a GPS POS HOLD navigation inside a column.

4) How do you set the return altitude ?

This is currently not supported.
You can activate ALT HOLD and the GPS mode will use the same altitude. But you can't set a specific RTH altitude.

3) ANGLE, HORIZON, (and ACRO) are primary flight stabilization methods, and can/should be selected along side the secondary modes which are: MAG, GPS HOME, GPS HOLD, HEADFREE ? Or is MAG considered a primary mode ?

MAG can be activated in all flight stabilization methods
HEADFREE can be activated with MAG mode
GPS HOME, GPS HOLD can be activated in ANGLE or HORIZON mode

4) If ANGLE, HORIZON, (and ACRO), all use gyro and accelerometer sensors for stabilization then what is the difference in terms of how the sensors are used ?

the gyro sensors are in all cases mandatory
ANGLE and HORIZON MODE need: gyro + acc sensors
HORIZON MODE= ANGLE MODE mode when PITCH/ROLL sticks are centered
HORIZON MODE= ACRO MODE mode when one of the PITCH/ROLL sticks are fully on one side (allowing flips)
I would say ANGLE MODE is obsolete. HORIZON MODE is preferable in most cases.
MAG MODE needs: gyro + acc + mag sensors (acc is needed also because it is used in heading angle determination)
BARO MODE needs: gyro + acc + baro (acc is needed to estimate the Z acceleration in this mode)

GPS altitude is never used in a control loop (only for display)

With both the GPS modes what happens if you have no GPS lock at time of arming ? Does it just ignore the flight mode ?

yes

. HEADFREE -- Uses gyro, accelerometer, and compass ? No matter the orientation (yaw) of the copter it will always move in the same 2D direction for the same (roll-pitch) stick movement ?

as the mag orientation is not accurate if the tilt is too important, MAG MODE correction is deactivated after 25deg inclination

[psuedoman]

ACRO mode is the default mode when HORIZON or ANGLE are not activated

Understood, this occurred to me when you were writing you reply, hence my edited post.

MAG mode means: head lock mode.
That is to say, when there is no yaw input, the multi will point forever to the same direction.
without this mode, you will still have a light deviation (like a tail gyro in heli)

So isn't this the same as HEADFREE mode ? How do MAG and HEADFREE modes differ ?

GPS mode does not rely on baro sensor.
GPS POS HOLD of GPS HOME is generally used in coordination with ATL HOLD, but this is not mandatory.
You can imagine a GPS POS HOLD navigation inside a column.

So using the GPS functions without ALT HOLD (BARO mode ?) could be disastrous as the copter is not regulating it's height in any way ?

You can activate ALT HOLD and the GPS mode will use the same altitude. But you can't set a specific RTH altitude.

Understood

GPS HOME, GPS HOLD can be activated in ANGLE or HORIZON mode

Understood, I see the #defines NAV_CONTROLS_HEADING, NAV_TAIL_FIRST and NAV_SET_TAKEOFF_HEADING effect yaw operation during GPS modes, yes ?

Also your statement implies that GPS HOME and GPS HOLD exclude the use of ACRO mode ?

the gyro sensors are in all cases mandatory
ANGLE and HORIZON MODE need: gyro + acc sensors

Therefore ACRO mode only uses gyro sensors, yes ?

HORIZON MODE= ANGLE MODE mode when PITCH/ROLL sticks are centered
HORIZON MODE= ACRO MODE mode when one of the PITCH/ROLL sticks are fully on one side (allowing flips)
I would say ANGLE MODE is obsolete. HORIZON MODE is preferable in most cases.

Got it perfectly understood. But is this not similar to the RATE setting in MultiWiiConf ?

MAG MODE needs: gyro + acc + mag sensors (acc is needed also because it is used in heading angle determination)
BARO MODE needs: gyro + acc + baro (acc is needed to estimate the Z acceleration in this mode)

So if using ACRO+MAG or ACRO+BARO in these instances the acc sensor is only used for sensor fusion with mag or baro sensors, and does not contribute to roll or pitch stabilization. (This assumes I am correct in saying ACRO mode only uses gyros.)

GPS altitude is never used in a control loop (only for display)

Easy to understand.

as the mag orientation is not accurate if the tilt is too important, MAG MODE correction is deactivated after 25deg inclination

So best to use MAG mode only with HORIZON or ANGLE mode ? What happens if you exceed the 25deg limit, is there a failsafe approach ?

[Alexinparis]

MAG mode means: head lock mode.
That is to say, when there is no yaw input, the multi will point forever to the same direction.
without this mode, you will still have a light deviation (like a tail gyro in heli)

So isn't this the same as HEADFREE mode ? How do MAG and HEADFREE modes differ ?

MAG MODE is for head lock
HEADFREE MODE is different and is explained by QuadBow: HEADFREE -- It is not impacting the flight mode (ANGLE/HORIZON/ACRO) only holding the orientation (yaw) of the copter and will always move in the same 2D direction for the same (roll-pitch) stick movement.

GPS mode does not rely on baro sensor.
GPS POS HOLD of GPS HOME is generally used in coordination with ATL HOLD, but this is not mandatory.
You can imagine a GPS POS HOLD navigation inside a column.

So using the GPS functions without ALT HOLD (BARO mode ?) could be disastrous as the copter is not regulating it's height in any way ?

It's not disastrous if you manage to control the alt.

GPS HOME, GPS HOLD can be activated in ANGLE or HORIZON mode

Understood, I see the #defines NAV_CONTROLS_HEADING, NAV_TAIL_FIRST and NAV_SET_TAKEOFF_HEADING effect yaw operation during GPS modes, yes ?

yes, I forgot to add that mag sensor is mandatory for GPS control.

Also your statement implies that GPS HOME and GPS HOLD exclude the use of ACRO mode ?

yes, activating a GPS MODE without ANGLE or HORIZON will have no effect.

the gyro sensors are in all cases mandatory
ANGLE and HORIZON MODE need: gyro + acc sensors

Therefore ACRO mode only uses gyro sensors, yes ?

yes

HORIZON MODE= ANGLE MODE mode when PITCH/ROLL sticks are centered
HORIZON MODE= ACRO MODE mode when one of the PITCH/ROLL sticks are fully on one side (allowing flips)
I would say ANGLE MODE is obsolete. HORIZON MODE is preferable in most cases.

Got it perfectly understood. But is this not similar to the RATE setting in MultiWiiConf ?

PITCH/ROLL rate is used in ACRO mode, so yes.

MAG MODE needs: gyro + acc + mag sensors (acc is needed also because it is used in heading angle determination)
BARO MODE needs: gyro + acc + baro (acc is needed to estimate the Z acceleration in this mode)

So if using ACRO+MAG or ACRO+BARO in these instances the acc sensor is only used for sensor fusion, and does not contribute to roll or pitch stabilization. (This assumes I am correct in saying ACRO mode only uses gyros.)

Exactly. In those cases, acc sensors are used indirectly for MAG & BARO, not to compensate PITCH&ROLL inclination.

as the mag orientation is not accurate if the tilt is too important, MAG MODE correction is deactivated after 25deg inclination

So best to use MAG mode only with HORIZON or ANGLE mode ? What happens if you exceed the 25deg limit, is there a failsafe approach ?

If you exceed the 25deg limit, the heading won't be used anymore to correct the orientation, but the yaw gyro will still maintain the heading. It's not a problem if this situation is short (ok for a flip or looping for instance)

[psuedoman]

Ah this is very good information, we are nearly out of the woods I think !

I now understand the difference between MAG and HEADFREE !
HEADFREE holds the pilots 2D perspective as reference, MAG does not, both give a drift free tail.
MAG compared to no MAG offers a drift free tail, just like the difference between heading hold and conventional helicopter gyros, yes ?

yes, I forgot to add that mag sensor is mandatory for GPS control.

mag sensor is mandatory but not MAG mode, yes ?

PITCH/ROLL rate is used in ACRO mode, so yes.

Does PITCH/ROLL rate only work in ACRO mode ?

All other points perfectly understood. Quite a complex relationship between them all.

[Alexinparis]

Ah this is very good information, we are nearly out of the woods I think !

I now understand the difference between MAG and HEADFREE !
HEADFREE holds the pilots 2D perspective as reference, MAG does not, both give a drift free tail.
MAG compared to no MAG offers a drift free tail, just like the difference between heading hold and conventional helicopter gyros, yes ?

yes, that's it

yes, I forgot to add that mag sensor is mandatory for GPS control.

mag sensor is mandatory but not MAG mode, yes ?

exactly, but as the GPS MODE controls the yaw direction, the activation of MAG MODE has no effect in GPS MODE.

PITCH/ROLL rate is used in ACRO mode, so yes.

Does PITCH/ROLL rate only work in ACRO mode ?

In HORIZON MODE also, because it's a mix between ACRO and ANGLE.
So you will see the effect of PITCH/ROLL rate in HORIZON MODE if you try to make a flip.

[psuedoman]

Perfecto !! I am surprised this question doesn't crop up more. I will now see if I can condense this information into something more Wiki friendly for you.

Thanks.
Cam

[In-Flight]

Make a chart! Us visual learners would LOVE it.

I'm still trying to figure out what options are dependent on each other.
IE: If i don't enable ACC with GPS Home, is there a potential for the copter to fall out of the sky? (EDIT: Or would ACC and GPS HOME actually fight each other?)
...or can most of the AUX options be used alone, and none really rely on each other?

Another example I just thought of would be GPS Hold and ACC. Wouldn't ACC be somewhat redundant while GPS Hold was active?

I have at least learned that GPS altitude is never used in controlling the copter. That answered a lot of my questions about use of the barometer and some of the GPS functions together.

[In-Flight]

Maybe to sum up my last post...
Are there any modes that should be used together? (A problem can arise if one mode is enabled without another)
Are there any modes that should NOT be used together? (A problem can arise by two modes fighting each other)

[Alexinparis]

Make a chart! Us visual learners would LOVE it.

I'm still trying to figure out what options are dependent on each other.
IE: If i don't enable ACC with GPS Home, is there a potential for the copter to fall out of the sky? (EDIT: Or would ACC and GPS HOME actually fight each other?)
...or can most of the AUX options be used alone, and none really rely on each other?

if you activate GPS without ACC (one of ANGLE or HORIZON mode) and without MAG, nothing will happen.
if you activate GPS with ACC but without MAG, the heading control of the GPS won't be active, but the angle correction of GPS will be active
if you activate GPS with ACC and with MAG, you will have the full functionality of GPS

some other hints:
HORIZON MODE + ANGLE MODE = HORIZON MODE
GPS HOME + GPS HOLD = GPS HOME
ARM MODE = no way to arm/disarm via stick
BARO MODE = totally independent with other MODE
HEADFREE can be used with or without MAG MODE

Another example I just thought of would be GPS Hold and ACC. Wouldn't ACC be somewhat redundant while GPS Hold was active?

no as the GPS itself needs one of ACC mode to work.

Are there any modes that should be used together? (A problem can arise if one mode is enabled without another)

we could in fact auto activate function when one is selected. for instance, it's a nonsense to activate GPS without ACC.
but you have the choice of ACC mode with way

Are there any modes that should NOT be used together? (A problem can arise by two modes fighting each other)

maybe this one will have strange effect: GPS + no ACC + MAG (which is not logical at all). we should maybe prevent it.
otherwise, nothing is critical and every combination should be crash free.
in all situations, you continue to have the stick control

I know the documentation is poor on this...

[In-Flight]

we could in fact auto activate function when one is selected. for instance, it's a nonsense to activate GPS without ACC.
but you have the choice of ACC mode with way

Ding Ding Ding... Thats what I was thinking.
Have the GUI auto-select or unselect options that are dependent on each other. (selecting GPS Home will auto select ACC and MAG)

Stuff like that is my biggest confusion, but I think you helped out.

[psuedoman]

if you activate GPS with ACC but without MAG, the heading control of the GPS won't be active, but the angle correction of GPS will be active

So the copter will still get home but it could be facing in any direction ?

[In-Flight]

if you activate GPS with ACC but without MAG, the heading control of the GPS won't be active, but the angle correction of GPS will be active

So the copter will still get home but it could be facing in any direction ?

Thats how I understand it.
I wasn't aware until now that the GPS function didn't already have some sort of ACC function associated with it. Didn't realize we had to make sure it was enabled. I kinda thought it did that in the background for you.

[psuedoman]

I was sort of lost in a sea of modes until these posts, I hadn't considered the interactions either. Damn glad I asked I guess a few people will be wondering why GPS doesn't work, but it's because it doesn't play with the default stabilization mode of ACRO.

[bulesz]

I was sort of lost in a sea of modes until these posts, I hadn't considered the interactions either. Damn glad I asked I guess a few people will be wondering why GPS doesn't work, but it's because it doesn't play with the default stabilization mode of ACRO.

Indeed mate!!!

I have started a topic in Multi Rotor UK forum why the GPS is not working at all...

Now I hardly wait to could go outside and try my new mode mixes...

Many thanks guys!!! This topic is truly helpful for all MW users!
I think the same time mode usage should be more highlighted for the new born MW users like me...
Spec I came from MPNG where you could select/use the flight modes separately and I just followed that logic...and suprised why the GPS HOME or ALT HOLD not working...

Thanks again!

[Sac D]

The more I read this thread, the less sense it makes.

Maybe I'm just getting frustrated finding so much conflicting information all the time with MultiWii stuff. It would be nice to find some solid and current documentation for everything, but I guess that would take the "fun" out of it all.

[Tvixen]

The more I read this thread, the less sense it makes.

Maybe I'm just getting frustrated finding so much conflicting information all the time with MultiWii stuff. It would be nice to find some solid and current documentation for everything, but I guess that would take the "fun" out of it all.

Hi Sac
This is because the thread is old, and the new software version 2.2 (from march 2013)has updated some of these things mentioned here, in the GUI



/Tvixen

[Sac D]

Hi Sac
This is because the thread is old, and the new software version 2.2 (from march 2013)has updated some of these things mentioned here, in the GUI



/Tvixen

I guess I should search for a similar thread that's more recent. Or wait for 2.3 to appear. Failing that, by the end of the month, the NAZA that I ordered will be here, and I can take the easy way out.

[Tvixen]

Hi Sac
This is because the thread is old, and the new software version 2.2 (from march 2013)has updated some of these things mentioned here, in the GUI



/Tvixen

I guess I should search for a similar thread that's more recent. Or wait for 2.3 to appear. Failing that, by the end of the month, the NAZA that I ordered will be here, and I can take the easy way out.

I think that would be the easiest way ... I have been searching the net for days now, and no concrete info on 2.2 is written down. Not even the Wiki is updated. Been searching for info on multiwiiWingui too, and there is no info here too. Guess thats the backside of these projects, we have to learn it the hard way

/Tvixen

[fotophanatic]

I noticed there's not much activity here lately but I just have a quick question. I am mainly interested in the HORIZON mode and a GPS mode with altitude hold and maybe a third mode that I haven't decided on (Any suggestions?). What toggles do I need to set up for these modes? Using a MultiWii PRO EZ3.0 board from Witespy with GPS (obviously). Any help is much appreciated.

[austntexan]

What's is the application? What are you trying to do with the multi? AP? For setting switches up, it's going to depend on what type of transmitter you're using. I'm using and ER9x on a FlySky Tx. The aux switches are pretty easy to enable in ER9x. Then, it's just a matter of preference I should think. I'm just now working through the work flow on switch setup for myself, but it's really going to depend on what and how you're flying, I think. If you're doing FPV only, your aux switches will likely be different from a craft flying only LOS. You might consider setting up a base model for each type of craft (one for FPV and one for LOS).

I was thinking of using my 3 way switch as a progressively more GPS switch with each tick. Then, I'll set up a 'master' switch that can disable everything and bring me back to plain ole acro (only gyros, no GPS, BARO, or MAG).

[fotophanatic]

What I meant by toggles is in the multiwii GUI itself not the actual switches on the tx. Sorry I wasn't clear. Made sense to me I'm probably going to set up horizon mode, gps mode and acro on my 3way switch. I'm using the turnigy 9x with the newest firmware. What I'd really like to know is what needs to be checked in the GUI for each to be active? I have the multiwii pro ez3.0 from witespyquads with the gps unit all per configured. Someone said that I don't need to turn the mag on for any of these modes so what exactly does the mag do? For the gps mode I want altitude hold as well as the gps hold. There's so many options to choose that I'm confused and after googling I'm even more confused so much contradictory info out there or outdated info. I'm pretty stoked to get this bird in the air. It's my first complete custom build that I designed and built from the ground up. I usually design and build the quads and run DJI NAZA or WKM on them so I don't have to do too much thinking but this is new territory for me and I don't want to screw it up. Paul, from witespy has been super helpful even though he's crazy busy so I'm going to be a return customer from now on.

[Javier Garcia]

How to change betwen Horizon and Angle modes?

If you see the RC Control Settings in the MultiwiiGui 2.1, I see Level (Angle), but not Horizon. Or is it done in config.h file or another one?

Thanks!

[scrat]

How to change betwen Horizon and Angle modes?

If you see the RC Control Settings in the MultiwiiGui 2.1, I see Level (Angle), but not Horizon. Or is it done in config.h file or another one?

Thanks!

Use MWii v2.2 and you'll get Angle in MWii GUI.

[Javier Garcia]

Use MWii v2.2 and you'll get Angle in MWii GUI.

I use MW 2.2 and MMWGUI 2.1. I supose Angle is the same as Level.

But I can´t find anything like Horizon. Is the same as Acrotrainer?

From config.h:

/************************ Assisted AcroTrainer ************************************/
/* Train Acro with auto recovery. Value set the point where ANGLE_MODE takes over.
Remember to activate ANGLE_MODE first!...

A Value on 200 will give a very distinct transfer */
//#define ACROTRAINER_MODE 200 // viewtopic.php?f=16&t=1944#p17437

[iWolf51]

Hi,
I've recently built my first quad and had questions about the different flight modes in MultiWii 2.2.
I found what I wanted to know in this topic, thanks to pseudoman for asking the questions and Alex for the detailed answers.
From Alex's answers I've put together the following summary explaining flight modes, their interactions and the sensors required to use them.

I hope other MultiWii 2.2 users find this useful.

-----------------------------------------------------------------------
MultiWii V2.2 Flight Modes
- A number of flight modes are defined and can be assigned to transmitter AUX switches in the MultiWiiConf GUI.

Motor Control:
. ARM - Arms motors, can be used as an alternative to the transmitter stick controls.

Main flight modes, only one of the following can be active at any time:
. ACRO - is the default mode when HORIZON or ANGLE are not activated.
- Uses: gyro only.

. ANGLE - stable mode if the PID values are correctly adjusted and the gyro and the accelerometers have been calibrated and trimmed.
- According to MultiWii developers ANGLE MODE is virtually obsolete, HORIZON MODE is preferable in most cases.
- Uses: gyro and accelerometers.

. HORIZON - A mixture between ACRO and ANGLE modes. Combining the stabilising effect with calm rc sticks and acrobatics with busy rc sticks.
- ANGLE MODE mode when PITCH/ROLL sticks are centered. ACRO MODE mode when full PITCH or ROLL sticks are applied, allowing flips.
- Uses: gyro and accelerometers.

Additional flight modes that can be activated in combination with main flight modes and each other:
. BARO - The barometer only is used, for the purpose of keeping a certain height. While there is an no other command from rc sticks.
- Needs: gyro + acc + baro (acc is needed to estimate the Z acceleration in this mode)
- You can activate BARO (ALT HOLD) and the GPS modes will use the same altitude.

. MAG - Heading lock mode. Can be activated in all flight stabilization methods.
- The multi will continue to point in the same direction until there is a yaw input. Without this mode, you will still have a light deviation (like a tail gyro in heli).
- compared to no MAG offers a drift free tail, just like the difference between heading hold and conventional helicopter gyros.
- Needs: gyro + acc + mag sensors (acc is needed also because it is used in heading angle determination)

. HEADFREE - Does not impact the flight mode (ANGLE/HORIZON/ACRO). It only holds the orientation (yaw) of the multi and will always move in the same 2D direction for the same ROLL/PITCH stick movement.
- Can be activated with MAG mode
- Holds the pilots 2D perspective as reference, MAG does not, both give a drift free tail.

. HEADADJ - Sets a new yaw origin for HEADFREE mode.

GPS Modes:
- GPS modes can be activated in ANGLE or HORIZON flight modes.
- will be ignored if there is no GPS lock at time of arming.
- are generally used along with ALT HOLD, but this is not mandatory.

- the mag sensor is mandatory for GPS control, but MAG mode is not.
- Activation of MAG MODE has no effect in GPS MODE.
- GPS altitude is never used in a control loop (only for display).

. GPS HOME - Uses compass and GPS for the purpose of returning home to the starting point.
- Stabilisation is done in accordance with the flight mode (ANGLE/HORIZON). The GPS altitude is not very accurate and therefore not usable for holding the height.

. GPS HOLD - Hold current position using GPS and baro (if available).


Additional information:

PITCH/ROLL rate is used in ACRO and HORIZON modes. You will see the effect of PITCH/ROLL rate in HORIZON MODE if you try to make a flip.

If using ACRO+MAG or ACRO+BARO the acc sensor is only used for sensor fusion, and does not contribute to roll or pitch stabilization.
In these cases, acc sensors are used indirectly for MAG & BARO, not to compensate PITCH/ROLL inclination.

If you exceed the 25deg PITCH/ROLL limit, the heading won't be used anymore to correct the orientation, but the yaw gyro will still maintain the heading.
It's not a problem if this situation is short (eg. for a flip or looping).

The mag orientation is not accurate if the tilt is too high, MAG MODE correction is deactivated after 25deg inclination.
-----------------------------------------------------------------------

[Charliechan]

Very good post, all info in one spot...