2DH doesn't hold altitude, but Loiter and RTH are fine - RC Groups
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Jun 21, 2017, 11:40 PM
Registered User
dsal's Avatar
Question

2DH doesn't hold altitude, but Loiter and RTH are fine


I was out flying my mini talon today and found that 2DH just wouldn't hold altitude. It'd just sink relatively slowly at a reasonably high speed. However, loiter would hold altitude just fine. Also, RTH would climb to the correct altitude, hang out there, come in, switch to the home altitude and hold that fine.

Is there something that would cause 2DH to behave differently?
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Jun 22, 2017, 07:29 AM
because rust never sleeps....
HugoRogers's Avatar
Quote:
Originally Posted by dsal
I was out flying my mini talon today and found that 2DH just wouldn't hold altitude. It'd just sink relatively slowly at a reasonably high speed. However, loiter would hold altitude just fine. Also, RTH would climb to the correct altitude, hang out there, come in, switch to the home altitude and hold that fine.

Is there something that would cause 2DH to behave differently?
I have had a couple of support discussions with EagleTree on this, which indicate that whoever wrote the messages believed that 2DH should use altitude hold. A number of helpful forum users corrected me on this, and after trying it recently (I didnt have this mode programmed for regular use) I agree that it does not maintain altitude. Rather than discovering this empirically, I think it would be helpful if Eagletree would communicate this when asked and possibly review the documentation.

I assume therefore that the H in 2DH refers only to Heading.
Jun 22, 2017, 10:05 AM
Registered User
dsal's Avatar
That's odd. The documentation says:

Quote:
Same as 2D Mode, except that altitude and heading hold are enabled. Heading hold uses the ailerons or elevons to hold the present heading, and altitude hold uses the elevator.
I've observed this happening, but it was not on my latest flight. The documentation seems fairly clear that it's intended to use the elevator to maintain altitude. My cruise throttle is a bit low, but I'm able to maintain altitude myself (in the same mode by just pulling up a bit more).
Jun 22, 2017, 10:11 AM
I'd be mad without a Taranis!
Quote:
Originally Posted by HugoRogers
I have had a couple of support discussions with EagleTree on this, which indicate that whoever wrote the messages believed that 2DH should use altitude hold. A number of helpful forum users corrected me on this, and after trying it recently (I didnt have this mode programmed for regular use) I agree that it does not maintain altitude. Rather than discovering this empirically, I think it would be helpful if Eagletree would communicate this when asked and possibly review the documentation.

I assume therefore that the H in 2DH refers only to Heading.
2DH should maintain altitude and heading. What we went back and forth with you on prior was whether or not the Vector would manage the throttle in 2DH mode (it doesn't, you have full control of the throttle).

I mainly cruise around at distance in 2DH mode, and in this mode the Vector has always maintained altitude for me, while I can control the throttle setting manually for optimal efficiency.
Jun 22, 2017, 12:14 PM
Registered User
dsal's Avatar
Quote:
Originally Posted by Rups63
2DH should maintain altitude and heading.
What would cause this to not work, but would not affect RTH or Loiter?
Jun 22, 2017, 12:52 PM
I'd be mad without a Taranis!
Quote:
Originally Posted by dsal
What would cause this to not work, but would not affect RTH or Loiter?
Don't know. Open a support ticket on the Eagletree website and they'll help.
Jun 22, 2017, 05:42 PM
JohnET's Avatar
Hey Guys,

Yes, 2dh is definitely 2d leveling and altitude hold. You can adjust your climb throttle position during the RX Wizard and adjust the altitude gain if it is not holding the altitude well enough. Also, if it is an issue during loiter only, make sure you don't have your loiter radius too small. If you can not get it to work correctly please open a support ticket.

Regards, John
Jun 23, 2017, 04:14 PM
Registered User
dsal's Avatar
Quote:
Originally Posted by JohnET
Hey Guys,

Yes, 2dh is definitely 2d leveling and altitude hold. You can adjust your climb throttle position during the RX Wizard and adjust the altitude gain if it is not holding the altitude well enough. Also, if it is an issue during loiter only, make sure you don't have your loiter radius too small. If you can not get it to work correctly please open a support ticket.

Regards, John
I did open a support ticket. I think it's still being researched. I don't fully understand what's expected, though. From my OpenTX logs, I can see that my elevator stick was sending a value 0.4% below "zero" (i.e, 1497 instead of 1500, which almost exactly equals one trim tick, though no trim was applied). It's possible that this is enough to make it think I wanted to cancel AH. None of it's clear to me at this point, though. Hopefully there's clarity in the ticket.

I'd expect the following:
  • 2DH to hold altitude and heading at current throttle value with other sticks in the middle ( some deadband)
  • elevator input to control altitude (rather than pitch)
  • some notification when 2DH is making no attempt to hold altitude

In particular, loiter and RTH were both working fine, so if that 0.4% is enough to cancel AH, it's not enough to cancel RTH or affect loiter in a noticeable way. If it's something else, I don't know what yet, but it's a bit of a safety concern at this point, because I was hoping to be able to rely on 2DH.


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