Hi chaps,
Could anyone a little more experienced explain the behaviour I should expect if I performed the following WP sequence in a mission?
In short, what I am trying to achieve is an "on the spot" reduction in altitude: so the first waypoint is at the starting height and by the end of the 2nd it should be at the new, lower height, before moving on.
How will the plane interpret these commands? Will it:Start diving at TECS_SINK_MAX as soon as it heads for WP2? Its clear it won't be able to lose that much altitude that quickly, so what next?
Will it continue diving at SINK_MAX until it hits its 40m or will it spread its decent across the loiter duration? (20 seconds, 60m to lose = 3m/s)
If it descends as quickly as it can (as I suspect it will), does this mean I can safely calculate my loiter time to be altitude_change/sink_max? If my max sink was 4m/s in this example, I could lower the loiter time to 15 seconds?
I haven't got a HIL sim set up and working yet so thank you to anyone who can advise from their experience.
Replies
Please find the results of my "spiral climb" and "spiral sink" experiments in the attached tlog. I appreciate that Seattle International isnt the tightest airfield in the world but I think its good proof of concept.
The mission starts with a short auto take off with navigation starting at 20m. This is a 50m loiter for 60 seconds, just enough time to climb to 200m.
The plane then flies off (just to make the trace clearer) and hits two waypoints, one NAV at 200m and then another 60 second loiter descending down to 20m. I find the exits of loiters a bit unpredictable so I sent it north then had it U-Turn to set up for final glide in.
If you have to fly really really tight spaces I don't think auto landing is the right tool for the job, you could end the mission on a LOITER_UNLIM and take it down manually when its pointing into the wind.
2013-08-22 19-22-05.spirals.tlog
I have spent some time this evening getting XPlane working. With the exception of a few glitches it is mostly flying in the way you would expect so I have been able to test my own query.
With two waypoints set apart, any altitude delta will be met smoothly along the entire path.
If you put two waypoints on top of each other, with a big altitude differential, the plane will hit them both almost simultaneously and work to close the altitude error as quickly as possible, while it continues its mission.
I then tried the example above with a waypoint moving into a loiter. The vehicle starts descending when it hits WP 1, then immediately hits WP2. It tries to fix the resulting altitude error as quickly as it can, which is the behaviour I wanted to achieve.
I was also able to play with Land as I didn't find the wiki clear enough to assure me how it would work in practice. Setting the LAND waypoint to 0 alt causes the plane to move from its penultimate waypoint to the landing waypoint in a steady even descent (as above). Throttle cuts near the ground as the wiki documentation describes, touching the plane down very close to the target WP (albeit a bit quick). Hope someone else finds this helpful.