Hand Launch after Crash

[Reconnaissance Squadron]

I took my full set of drones and accessories out for a flight yesterday. Because I live near a major airport I have to drive at least a couple of miles to find somewhere to fly where I can't be arrested on sight. I had planned to do some clever stuff. However, when I arrived and started to fly it immediately became clear that the wind was too strong for what I had in mind. The screen popped up that red band warning about dangerous conditions and my analogue wind speed warning indicator was blown off my head and rolled rapidly away on its brim. The wind was strong but there were bursts of extra strong gusts. So I decided to do something else instead. I would fly around in a clearing and orbit a tree to hone my skills. I would be deliberately putting the drone at risk of crashing but not a long way off, over water, at the far side of a field full of cattle, or into my other drones. I decided to stick with the Anafi as it is the best for handling wind and I had prop guards which made for lower risk of serious damage while orbiting around trees, flowers and my head. The plan worked very well. The prop guards did actually prevent one crash as the Anafi bounced off a tree trunk. I did have two small crashes which ended up with the Anafi on its back making that pathetic noise that it does. Both of these involved fine twigs being brushed back by the prop guards and then springing back into the path of one of the props. Fortunately, I only needed to replace one pair later, the damage was not enough to ground the Anafi but I noticed the video showed fine vibrations which ruined the shot.

After one crash I straightened out the arms, looked it over and decided to hand launch it. It whirred into life gave me a countdown and half a second after telling me to go for a launch I gave it a tiny throw upwards and phut it fell to the ground. That's not a good look. I was immediately reminded of another crash when I was out with my son. It had crashed while videoing the underside of a viaduct, quite a drop, but into long grass which cushioned the fall quite well, I suppose being light is a real advantage here. After that undignified experience, I wanted my son to be impressed with the Anafi so I decided to hand launch it after checking that there was no damage. This had a real impression on him as he watched his father hand launch the Anafi and it went phut and fell to the ground. From this experience I have now decided that whenever the Anafi shuts down its motors and starts to tweak and bleep the drill needs to be:-

1] shut down
2] check for prop damage, major prop damage must be repaired at once, minor damage may lead to loss of video quality
3] check arms are clicked properly in place
4] do a LAUNCH FROM THE GROUND and a test at less than waist height, up, down, rotate in both directions
5] only after this ground launch has been done is it safe to try a hand launch again

Can anybody else confirm that this is in line with their experiences? It seems an obvious set of precautions even if it is just a coincidence.

 

[MustangPhil]

Well... I never had a problem with hand launch.

I was less successful with hand land.
I know it is not officially supported by Parrot, but each time it lands in my hand, I grab it to prevent from dropping on the ground, then fight it to shut it down and finish with the ‘90° Roll of protest’ to stop the engines.

After I saw your video (and your shadow of you doing the hand launch), shall I suggest you should do the following for hand launch :
Launch it with a more ‘up and forward’ motion so the drone understands you are hand launching (see the user’s manual).
In your video, you seem to ‘remove your hand from above the Anafi’ which it understands like ‘the ground has collapsed below me ?’ and it ends logically on the ground.
Just try the firmer ‘up and front’ method and you should reach a 100% with this procedure.

 

[Reconnaissance Squadron]

When you have told it you are hand launching and it has told you to launch 3, 2, 1 NOW! surely it should be expecting to get launched! I have launched from my hand dozens of times. TWICE it has immediately crashed. On each occasion this was after the last flight had resulted in a crash.
From the video you can't see that I have pressed the launch button and got the instruction to launch, but I have. This is not my first hand-launch or my first failed hand-launch. A more vigorous up and away gesture would perhaps just mean a more spectacular and embarrassing crash.

Well... I never had a problem with hand launch.

Have you tried a hand launch immediately after recovering from a crash? I have. Twice. And twice that particular hand launch resulted in the drone going phut.

I agree with your experience of hand landings. It is hard to get the Anafi to land flat on your open palm so the bottom sensor thinks it has landed. Several times I have had it balancing precariously on my fingertips. I resort to a rather dangerous move of grabbing the top of the back of the battery with my thumb. This works very well but involves putting the thumb closer to the spinning props than anybody would be comfortable with. As the thumb grab must be followed up with the flick-of-death/‘90° Roll of protest’ it will count on your record as a crash, but not a proper crash that triggers the twitching and bleeping. It does mark the video (intentionally?) with a stripe of noise across the image when the motors cut out. Many times I have just grabbed the Anafi out of the air without giving it any clue that I was about to do so. That is always tagged as a crash, but it just results in a very brief roll of protest and then the drone shuts down completely and does not then screw up the next hand launch. This is best achieved by having the drone in front of you looking forward while you take it from behind. This has the added benefit that my left and the drone's left mean the same thing.

The next time I go out I will test to see if it is possible to launch it on cue so feebly that it just falls down. I will do it over some long grass so it won't come to any harm whatever happens.

 

[Dirk_ANAFI]

After a crash with no visible damage it's a good idea to ...
- Turn the drone off.
- Turn it on again with fresh battery.
- Make a reset.
- Make a calibration.
- Start with hoovering at low altitude.

 

[PascalG]

Not sure why anyone would want to launch a drone in high winds to just circle around trees...

From the video it looks like you were holding the drone with your fingers instead of having it resting on your open palm. I also believe it needs more upward motion.

 

[Reconnaissance Squadron]

Not sure why anyone would want to launch a drone in high winds to just circle around trees...

The explanation has been given.

I went back again today and I decided to prove my point. I made about ten hand launches and hand landings. I have proved, to my own satisfaction at least, that you can't go wrong by not launching vigourously enough. It makes no difference how gentle the launch is, even just moving your hand out of the way, if the Anafi is expecting a hand launch it will launch. BUT if it has crashed in the previous flight this is not necessarily the case. I tested a launch after a crash and the result was that the Anafi BOUNCED! It hit the ground as the motors began to bite. All the hand launches that didn't come immediately after a crash worked flawlessly whether I tossed the drone up hard, soft or just let it slip off my hand.

 

[MustangPhil]

You may be right regarding the post-crash-hand-launch failure (I did not test it after a crash, though the 90° roll of protest is considered as a crash ... and I still do the hand-launch without any problem).

What I just wanted to point ( and you wrote ‘it has told you to launch 3, 2, 1 NOW! surely it should be expecting to get launched!’) is what exactly Anafi seems to expect to be sure it is ‘officially launched’ (if I were working for the software dpt at Parrot) :

- Before the launch, the bottom cam should expect to be in ‘complete darkness’, covered by your hand or the ground then after it should be seeing a ‘sort of ground scene’
- Before the launch, the ‘proximity sensor’ or ‘Ultra-sound sensor’ if any, should give the information : I’m in touch with something reaaal close to my @ss. After the launch it should not feel anything with its proximity sensor (and could probably sing a song like ‘Liberté, Liberté chérieeeeuuu’)
- Before the launch, the accelerometer sensor, gravity sensor or equivalent should feel a steady position, peace and quietness during the countdown that must serve as a ‘steady reference time’. After the launch, the accelerometer and its brothers should feel a front-upward motion (easy to calculate in a processor view), and thus a form of panic.
- Before the launch, the inboard barometer sensor should be at a constant altitude (particularly during the 3,2,1 countdown that may also be used for ref altitude setting). After the hand launch, a raise in altitude may occure.
- The hand-launch should be done at a relatively slow paced motion for all above parameters to be analyzed by the drone (I mean not ‘tchac’ but more like ‘Yeeepeee’).

If all these parameters were sent to the processing unit after the hand-launch countdown, then I would be confident in the fact the Anafi would be sure to get what it expects to feel ‘launched’

But of course, I am not sure of it, I work in Bio-Mechanics (orthopedics).

My technique is the following : I hold the Anafi in one open flat hand, relatively low (at hip level, probably a professional deformation...), avoid moving during the countdown, and throw upward and in front of me slowly, releasing it when at bust level (so if it should fall, it’s not that high).

Of course, like you suggested, it is wise to do it above grass or a soft surface.
If the ground is made of a hard surface (concrete or else)... then I take off normally from the ground and do not need to hand launch it.

Hope this helps

 

[Reconnaissance Squadron]

I did a lot of launches today to prove that it doesn't matter how feebly or purposely you launch, a launch is a launch is a launch. Every launch went just fine whether I threw it feebly or quite purposefully or even just let it slip off my hand. There was one exception, the time that I did a hand launch immediately after a crash. Of course if you let it slip off your hand before it is telling you to launch it is likely to crash, I didn't feel the need to prove that point.

After proving these points to myself I had to put the Anafi away and fly my Mavic Pro instead. I can't believe that it didn't occur to me to use expendable prop blades. I had bought some coloured blades but I lost confidence in them for proper long-distance flights after a serious crash that came without warning. I should have used those props for these experiments. I am running low on spare props now.