Altitude not holding when over 35mph

Dunginhawk · Jul 27, 2015

So here is a video i just put together, because rich and I are having the same issue.Among other similar issues.

Anything about 35mph, nose down loses a TON of altitude FAST.
i dont have the overlay, but you can easy see the drop in the video.

184 ft to start
125 when done.
pitches up a bit to about 140 and holds.

45mph downwind.

Dunginhawk · Jul 27, 2015

FYI, posted to the 3dr solo UG on facebook 2 minutes ago and already have another person citing the same thing.

Acroduster · Jul 27, 2015

In Fly mode, set to full speed, I saw no drop in altitude but only a max speed of 30mph. If you are not in Fly mode, I would expect it to lose altitude at full translation speed...

Andrew Tarleton · Jul 27, 2015

Were you in fly or manual/stabilize?

Dunginhawk · Jul 27, 2015

In fly mode you likely wont.. ive modified my fly mode parameters to allow a higher speed in that mode.
Even in manual mode though, the quad is designed to hold alt... the fact that it doesnt, is not good

Andrew Tarleton · Jul 27, 2015

Dunginhawk said:
In fly mode you likely wont.. ive modified my fly mode parameters to allow a higher speed in that mode.
Even in manual mode though, the quad is designed to hold alt... the fact that it doesnt, is not good

I notice the same yesterday in manual almost cut grass. I am a rookie but have been flying in manual and stabilize to get used to it. It is a different animal in stabilize. But manual I was losing alt. as well.

rrmccabe · Jul 27, 2015

Acroduster said:
In Fly mode, set to full speed, I saw no drop in altitude but only a max speed of 30mph. If you are not in Fly mode, I would expect it to lose altitude at full translation speed...

Why? In manual it should hold altitude.

ChrisM101 · Jul 27, 2015

Acroduster said:
In Fly mode, set to full speed, I saw no drop in altitude but only a max speed of 30mph. If you are not in Fly mode, I would expect it to lose altitude at full translation speed...

I also lost altitude in FLY at full, went from 400 down to 250 over a short distance on a 1 mile flight.

Eric Sheehan · Jul 27, 2015

Is it normal for copter to loose altitude at over 35mph in manual mode?
Do you recommend one request support for this issue?

I am seeing this big time.

ChrisM101 · Jul 27, 2015

all i can say is dont use sport unless you have lots of altitude, but yes, it typically should hold altitude in fly

Eric Sheehan · Jul 27, 2015

Should it hold in manual?

Rich · Jul 27, 2015

I think this has been a shortcoming of the Pixhawk for some time now.

I don't think they have put much priority into a fix yet.

rrmccabe · Jul 27, 2015

I think its a bug. Alt hold should fly just like GPS fly mode with slight drift.

Either it doesn't have the power to fly 55mph forward like they said it would and maintain elevation or at the pitch required to make speed 35mph and above there is pressure changes (turbulence) inside the body. Pretty sure most baro sensors for altitude are susceptible to turbulence. Just my guess(es)

Eric Sheehan · Jul 27, 2015

Once they answer my question about level calibration after every battery change, I'll start working on this one.

Thanks gents

rrmccabe · Jul 27, 2015

I started a support ticket yesterday. So will probably get an answer tomorrow.

Adimuzio513 · Jul 27, 2015

Mine was losing alt yesterday sitting still in Manual it was foggy and dense air but that's the first I've seen that. It's always lost altitude at speed since day one I've just compensated for this but when filming once we finally get a gimbal this is going to be a real draw back.

Did help some re calibrating level with a four foot level so it's precise. Seems that after a week or two level needs done again from what I've noticed flight wise which seemed odd to me. Seemingly fixes most issues but is a pain and shouldn't be necessary.

Man the more I think and post the more issues I've been ignoring and fixing myself being dead set on solo success. I really hope they get things together before its time to make the final call cause there's a lot I love but for the money it should work as it's supposed to at least. It's killing me especially with all I have into it that's not from 3dr but today's the first I've even debated not keeping it, problem is I don't want another phantom and after spending on all these extras couldn't afford or justify at least buying anything more expensive now.

Adimuzio513 · Jul 27, 2015

rrmccabe said:
I started a support ticket yesterday. So will probably get an answer tomorrow.

Likley one saying fly in better air though.lol

Adimuzio513 · Jul 27, 2015

Eric Sheehan said:
Once they answer my question about level calibration after every battery change, I'll start working on this one.

Thanks gents

Just saw your post so does it force you to do this or you just noticing like I am it improves things to do it often?

ChrisM101 · Jul 27, 2015

i will assume the weight of the gimbal will make this altitude drop issue worse or occur at a lower speed

Jubalr · Jul 27, 2015

Dunginhawk said:
So here is a video i just put together, because rich and I are having the same issue.Among other similar issues.

Anything about 35mph, nose down loses a TON of altitude FAST.
i dont have the overlay, but you can easy see the drop in the video.

184 ft to start
125 when done.
pitches up a bit to about 140 and holds.

45mph downwind.

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Hi Hawk, I tested this several time on Sunday and couldn't get it to vary by more than 2-3' Went a longer distance too, 1000' at 39mph. Going to go out this evening and see if I can get it to drop by increasing the speed and see if it starts to drop and at what speed/angle. Physics will kick in at a certain pitch angle, when the props are generating more forward thrust than lift. Same as a helicopter and the wing of a plane. There is also a setting in pixhawk for how much you will allow it to compensate. This can be easily verified by flying in manual at a speed it drops and see if you can compensate with throttle. If you can, then it hit a pre set limit. If not, then you have reached the point of diminishing returns, same as a full size aircraft.

I'll report back my findings..