Does P-GPS (in Litchi) Always Stop Movement

[aburkefl]

This morning I was executing a Litchi "mission." As my Phantom approached the end of the mission, I moved the function switch from "F" to "P."

Instead of stopping, my P3P started drifting downwind - toward a huge tree! Instinctively (and incorrectly) I pulled gently back on the right stick. My bird moved just a tad faster in that same direction - i.e., downwind and still toward that tall tree. Fortunately, before disaster struck, I realized (a great deal of ATTI practice really helped out!) what I had done. The phantom was pointing at my last waypoint - which was directly opposite that nasty tree. For about two seconds I watched the phantom continue drifting toward the tree. Then I pushed forward - very gently! - on the right stick and the phantom moved slowly away from the tree.

Once I was convinced I was safely away from the tree, I maneuvered (yawed) the phantom until it was obvious it was pointing at me, rotated it 180 degrees (so it was pointing away from me), then lowered it, backed it up and few feet and hand-caught it.

When I reviewed the recorded Litchi screen (love that screen record function) I saw that my mode was in P-GPS, which is what I expected it to be when I ended the mission and flipped the switch back to the P-position. So why did my phantom drift downwind instead of just "freezing" in place?

I forgot to look at the recorded screen and see how many satellites I had captured. My assumption is that if I had enough for the display to show me "P-GPS" I should have had more than enough satellites working.

Art - N4PJ
Leesburg, FL

 

[Fly Dawg]

Are you 100% sure you didn't flip the switch to "A" instead of "P", at least momentarily? Look at your flight log, that will tell you.

 

[aburkefl]

Are you 100% sure you didn't flip the switch to "A" instead of "P", at least momentarily? Look at your flight log, that will tell you.

Yes. After the fact, it dawned on me that it might have momentarily been in ATTI (A instead of P) but there is absolutely no occurrence of ATTI in that column (column AJ in the csv file).

Fortunately, my experience saved the day, but it's still puzzling.

Art - N4PJ
Leesburg, FL

 

[aburkefl]

Are you 100% sure you didn't flip the switch to "A" instead of "P", at least momentarily? Look at your flight log, that will tell you.

Well, I answered this once, but then I did more research.

I can't see the flightlog analysis on my PC - yet. I can see the actual csv file and see the individual data columns. ATTI doesn't appear anywhere in the csv during the flight. However...

I uploaded the csv file at PhantomHelp.com - thanks for posting that site on a related link - and the puzzle begins. In the log on that site, the ATTI shows up *everywhere* except during the "waypoints" (i.e., the actual mission). Wow - what's that supposed to mean. I mean, even when I started and was in P-GPS mode, the log (after uploading to PhantomHelp) shows ATTI. I went back to the video of the screen recording. *That* evidence shows ATTI mode immediately after the mission end - which is what I actually experienced. The screen apparently shows that as well. I guess I just wasn't seeing it in the glare of the sun this morning.

I saw a related post below and examined it. He describes pretty much the same thing I've experienced. Despite moving the switch to "P" it acted as if I had moved it to "A" and let the phantom drift in the wind. Frankly, I think I can tolerate this happening once in a while and being prepared for it, just in case. I don't remember this happening previous flights, but I wasn't looking for it either.

Still can't figure out why the raw flightlog shows no ATTI but the screen and PhantomHelp both show that mode - big time.

Art - N4PJ
Leesburg, FL

 

[Fly Dawg]

Post a link to your Phantom Help Log. That sounds very odd.

 

[aburkefl]

Post a link to your Phantom Help Log. That sounds very odd.

I tried a couple of times to upload the log to PhantomHelp.com but it blows up. I contacted someone at the web site and sent them a copy of the flight log. Might take a day or two (or more) before there are any results.

Based on a couple of related threads, this is apparently not the only time something like this has happened. As long as it's not sufficiently serious to cause a crash, I guess I can live with it - but a solution would be really nice.

Art - N4PJ
Leesburg, FL

 

[aburkefl]

I tried a couple of times to upload the log to PhantomHelp.com but it blows up. I contacted someone at the web site and sent them a copy of the flight log. Might take a day or two (or more) before there are any results.

Based on a couple of related threads, this is apparently not the only time something like this has happened. As long as it's not sufficiently serious to cause a crash, I guess I can live with it - but a solution would be really nice.

Art - N4PJ
Leesburg, FL

UPDATE: been working with Jacob at FlightReplay. Went flying this morning and successfully uploaded my csv flightlog to PhantomHelp (the log viewer) and also to FlightReplay. The load went just fine and the playback is what I expected to see, etc. There does seem to be an irregularity here and there - as Jacob pointed out, it may be platform differences. He's pursuing some extra analysis. I have found one really strange event(s).

Looking at the "raw" csv file (in Excel) I see no evidence of an ATTI flight mode. I recorded the screen (a built-in function of Litchi) on my iPad Mini 4. The screen shows P-GPS on startup, then F-GPS when I switched on the mission in Litchi. Then it shows F-WPT during the actual mission and then back to P-GPS when the mission is over and I'm bringing my P3P back home. When I look at the raw csv file from the flightlogs (retrieved from my iPad via iTunes app sharing - thanks to whomever steered me in the right direction on that!), the flight modes all reflect what i see on the screen. However...

After uploading the file to the log viewer at PhantomHelp.com, there are essentially only two flight modes shown - ATTI and F-WPT. Go figure.

At least, when addressing the problem that started my thread in the first place, when the mission ended, I moved the switch from "F" to "P" and the phantom hovered there, locked in place to the GPS. The wind this morning was even stronger than the other day when I got scared of the drifting. Consequently, I got my P3P down rather quickly. I think it could handle the wind, but I definitely like the better-safe-than-sorry approach.

Now, for those who really care about the raw data, how do I post a link so someone else (anyone else) can see my flight log?

Just to make sure anyone understands, all the above (my flying this morning) was done with Litchi and an iPad Mini 4.

Art - N4PJ
Leesburg, FL

 

[Sagebrush]

How much battery was left? What was the bird programmed to do after it ended the mission?

SB

 

[aburkefl]

How much battery was left? What was the bird programmed to do after it ended the mission?

SB

Remaining battery was around 70% (mission was only a little over 3 minutes). At the end of my missions, I just have the phantom hover where the mission ends and then I take over from there. Typically, I have the last waypoint set 100 - 200 feet from the starting point. And the starting point is generally not very far from the home point.

Art - N4PJ
Leesburg, FL