Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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There are a number of parameters listed on the RTL flight mode wiki page that may help.  So for example, to stop the vehicle from  descending during the land phase of RTL, set RTL_ALT_FINAL to a number > 0.  like 10m and it will stay up there.

I think everyone understands, but just in case, the failsafe radius of 5m is only used to make the decision whether the vehicle should RTL (as the failsafe parameter specifies) or whether it should instead LAND.  So if the vehicle is within 5m of home when the failsafe happens, it will trigger a LAND instead of an RTL.  If an RTL happens, it will still attempt to land at the takeoff location.

The feedback I've received on the previous 2m radius (from a few people) was that it was too small.  There's some discussion of a more complicated decision involving altitude and distance from home but sadly that will need to wait for Copter-3.4.

I think 5m (or 15feet) is really quite a short distance but I must admit when Luis and I discussed it I thought to myself it was perhaps too large.  How about 3m or 4m?  I'm not keen on using WPNAV_RADIUS because I think most people will not expect this parameter to affect the failsafe behaviour so I'd prefer a hardcoded distance if we can agree on one.

Wilson,

Sorry, I actually downloaded your log when you first posted but didn't complete the analysis.

I think the lean is caused by the poor GPS location.  The NSat is really very low at only 5 or 6.  I think the GPS position was drifting around but it wasn't bad enough to trigger the glitch protection.

The EKF also reports a spike in velocity and position variances around that time.  I'm not very familiar with the units of these variances so I've asked Paul Riseborough (EKF expert) and we shall see what he says.

I don't think it's caused by the low battery itself because the desired and actual roll/pitch values stick together.

Use X and it should be front left motor goes clockwise then front right goes counter clockwise then rear right goes clockwise and rear left goes counter clockwise and are ordered as it shows Starting front left  and going clockwise around the frame 3-1-4-2 

Thanks Randy for looking into my issue~ ^^

My landing/take-off point has poor GPS reception. This location is surround by tall buildings and a hill of 100~200 meters height. So I switch to alt-hold mode when I attempt to take-off and landing, expecting to be unaffected when my copter is flying through this "bad GPS air-space".

Does autopilot or EKF continue to use GPS information in alt-hold mode or land mode, maybe for correcting X-Y coordinate? 

Thanks a lot for your help again~~ 

I must say my initial tests with 3.3-rc10 running totally stock everything on my beater quad with a Hawk Lite is one of the better firmware revisions I have run in a really long time. Rock solid. Alt-Hold is working well, Loiter is back to being like it is hanging from a string and RTL worked flawlessly each time I used it. Awesome work!

Use of WPNAV_RADIUS does make sense to me, especially since the other WPNAV_ parameters control the return speed, etc.   But I think the more important issue is *why* is land being performed at all if RTL is the selected failsafe action?  As you mention, land may not even be configured as a part of RTL if RTL_ALT_FINAL is not 0.  So if it's not zero, why land just because the failsafe happened to occur within a 5m radius of home?  Shouldn't we be going to RTL_ALT_FINAL instead?

I'm guessing the motivation for land if inside WPNAV_RADIUS was just an easy way to avoid wasting power climbing to RTL_ALT only to decend and land again later (in the default case where RTL_ALT_FINAL=0)

I see this as a safty issue.  If RTL_ALT_FINAL is greater than 0, it may be because it's pilot control is the only safe way to land.  If so, failsafe should not land, no matter where it happens to be when failsafe kicks in.

--Brad

Hi! This is a question specially for Leonard and I think and the answer might be a good addition to the Wiki.

Let say I have a copter that I know the PID should start at 10 for stabilize Pitch and Roll and 0.25 for Rate Pitch and Roll. I remember that those values are near the previous ones that I had on the same copter but I had to clear the eeprom and I forgot to back up :-(.

Does it help and speed up the process if I start with that?

Maybe this can be extended to a second autotune if the values that are setted in a previus one are not too accurate?

Thanks so much for the help

I had a very violent crash today while flying my 750 size quad.   I am currently using 3.3rc8 on this one.

I have flown it about 3 times on this firmware and it was very stable.  The wind conditions were light and variable.  

this time, I began to wonder when I first tool off, a slight gust came up and It tipped over backwards.  on a second try, it lifted off and seemed very stable (in stabile mode).  I switched to Alt-Hold at about 10 feet, it seemed to be fine so I went to PosHold.

Also fine, but I was showing friends how it could hold position then it started loosing stability in the Z axis.  It dropped i altitude pretty quickly and I took a bit of stick to stop the descent.    I stopped so I tried to get it to stabilize, flipped it back to Althold.

then I decided to land, and forgot it was in AltHold. It landed and I reached to switch it back to stabile, and the copter spun up again, tipped back, then went to full throttle.  I was about 20 feet away and I started to duck, but it went but me so fast I didn't had time to take cover, I was just blessed that it missed me.  (this is a 6s powered system with 15 inch carbon props, and 380 Pancake motors and it is lethal at full power.  It then headed towards my group of 5 friends and just by the grace of God missed them too. it was all over the place, ended up reversing course several times, barely missed me again on the way to destroy my ground station and finally hit some pavement, flipping a few times until it slung the battery off.  

All this happened in about 2 seconds..

Once I was able to declare it officially dead, I started picking up the pieces.

I feel that the beginning of this sudden destruction was cause by landing in Alt-Hold.  Is that possible?

here is the log, I hope someone can help me understand what pissed this copter off.  I'm afraid to power this beast up again..

(there is a lot of dead time where I am waiting for GPS lock and getting the ground station set up)

Attachments:

Hi

Besides what has been said by Trent Russell there's something very strange on your vibration log that occurs right after you said you changed to PosHold. If you see the clipping that jumps at that time, I would say that something physical came loose and from that point forward the copter was trying really hard to keep up. 
I know that now might be almost impossible to trace back where the physical fault might have occurred but look carefully at what might not be crash results.

Sure, plain APM Planner 2.0.18

There are other issues on the flight but from what you told us, I believe this was the moment things began to act strange. Also to note, that the controller appears to have some brownouts, but I didn't look at this with care.

Luis, are the brownouts that you are referring to the red spikes downwards?  I seem to have always seen these, so much that I thought maybe it is just a sensor glitch, they are never more than a sharp spike.

Also, I know that other than the unexplained climbing and descending motion, the vehicle didn't got to full throttle and fly around like crazy for 2 or 3 seconds until the very end of the log. The last mode change was from stabile to alt-hold, and then when it touched down, all heck broke loose. I agree, it seems like a sudden displacement of the CG, like something falling off could have the vehicle reacting in this way.  It makes me wonder if it was the camera and gimble.  It will be hard to determine now, they were thrown from the wreckage..

I'm pretty sure this is not a 3.3 issue now, so sorry I brought it up here. 

thanks for the help.

RE

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