FW takeoff docs improvements

[sfuhrer]

FW takeoff (and landing) docs are outdated. Major changes on the PX4 side came in lately through PX4/PX4-Autopilot#20537 and PX4/PX4-Autopilot#20557. This PR reflects the changes on the Takeoff side, the Landing side is still todo.
I've moved all the takeoff docs/hints/param description to the Takeoff mode section (currently have also a section under the "flying 101" that is to a big part duplicated info). Maybe we can make it even clearer that this section applies to both takeoffs via mission and without mission in manually entered Takeoff flight mode. Also up for other ideas on where to place it @hamishwillee.

@tstastny please check if the current controller logic is correctly resembled in the docs, and if you agree with the level of depth I propose here (there are ofc many more parameters that affect takeoffs, but listing them all removes focus from the important ones).

[hamishwillee]

@sfuhrer Excellent. I am very happy with the removal of the FW landing standalone doc and the integration into Takeoff mode doc.

Maybe we can make it even clearer that this section applies to both takeoffs via mission and without mission in manually entered Takeoff flight mode. Also up for other ideas on where to place it

I am not so sure about the mixing of mission mode takeoff information in the takeoff mode doc. It certainly isn't "clean" right now.

From this I cannot tell

• how to plan a mission takeoff
• whether I can do a runway takeoff in a mission
• whether I can do a catapult takeoff in a mission - and how I plan
• What configuration is required that is common to both mission and takeoff mode.

I think we at least need a "planning an FW mission takeoff" section to cover this, which we can cross link from mission mode, and which might cross link to the takeoff mode you have written - depending on how much duplication there is.

I suspect that once you have created "planning a mission takeoff" that answers the above questions it will be obvious how mixed these should be.

We can have a call to chat through if you want.

[sfuhrer]

how to plan a mission takeoff
whether I can do a runway takeoff in a mission
whether I can do a catapult takeoff in a mission - and how I plan
What configuration is required that is common to both mission and takeoff mode.
I think we at least need a "planning an FW mission takeoff" section to cover this, which we can cross link from mission mode, and which might cross link to the takeoff mode you have written - depending on how much duplication there is.

Yes agree that we need this section, where all the 4 points above should be addressed. And then link to the Takeoff section for details (I would keep configuration details in the Takeoff section, and focus on the interface differences in the Mission one).

[sfuhrer]

@hamishwillee I've added a mini section in the Mission section as well now, let me know if that makes the operation clearer. Maybe we can extend it a bit more.

[sfuhrer]

Need to fix the link once we get the landing part merged #2245)

[hamishwillee]

@sfuhrer @tstastny Just to be very clear here:

• In takeoff mode a catapult launch is triggered by acceleration detection - either throwing or shaking to start the throttle ramping up.
  • What this implies is that in a mission mode you do not need acceleration detection for catapult launch - is that correct? That does not make sense to me - I'd expect the vehicle to arm, but would still expect it to require throwing.
  • However for runway mode I'd expect it to just take off. Can you still "nudge" as in takeoff mode?
• I assume all the parameter setup for catapult/runway are required whether using mission or takeoff?

[sfuhrer]

Actually the launch detection is only an additional feature, that's not necessary for hand-launch. If it's not enabled the motor will just immediately ramp up on arming.

What this implies is that in a mission mode you do not need acceleration detection for catapult launch - is that correct? That does not make sense to me - I'd expect the vehicle to arm, but would still expect it to require throwing.

Mission mode doesn't change the procedure - you arm the vehicle, and if launch detection is enabled it needs to detect an acceleration before it starts the motor.

However for runway mode I'd expect it to just take off. Can you still "nudge" as in takeoff mode?

You can only nudge if in runway takeoff mode.

I assume all the parameter setup for catapult/runway are required whether using mission or takeoff?

Correct, there is no difference in required params.

[hamishwillee]

@tstastny @sfuhrer Getting pretty close. I've added some confirmations and then I'll do a final subedit. If you can answer the questions today I should be able to get this in tomorrow.

[hamishwillee]

Is this true? That's not what it says here: http://docs.px4.io/main/en/flight_modes/land.html#fixed-wing-fw

[sfuhrer]

Working on a fix, we should remove this line (or once the fix is in).

[hamishwillee]

Do you have a PR for this fix?

[hamishwillee]

FYI, I added these bits for MC and VTOL takeoff landing for "symmetry". We could reasonably expand on them too.

[hamishwillee]

FYI So here you see the mission mode all separated into own paragraph.

[hamishwillee]

@sfuhrer I'm going to merge this now - I think it is OK.

My main concern is that we are mixing the takeoff mode and mission mode takeoff, as discussed. I think we could do a better job here, but maybe as a post process.

What we could do is:

1. Duplicate just this section in mission mode FW takeoff, and make it mission mode specific.
2. Then reference the catapult and runway sections in takeoff mode for the "common stuff".
3. Remove the mission mode specific stuff from here.

We might then put the stuff currently in mission mode into the "Planning" doc.

Let me know what you think?

[sfuhrer]

So where would the catapult and runway sections live? In the mission or the flight modes docs, or on a new, neutral ground?