Let my recent schoolboy mistake be a lesson for others to heed so it doesn't happen to them.

I'm always pretty safety conscious and I always considered that making sure the throttle was raised while disarmed was a good enough safety mechanism to prevent accidental arming. Lapse of concentration and not remaining focused led to the following sequence of events occurring.

So, I powered up my quad, switched on the transmitter ready to take off and then realised the angle of my FPV camera had got knocked out of position in the last hard landing. Instead of doing the sensible thing of unplugging the quad and switching off my transmitter, I stupidly just turned round and crouched down to get a hex driver out of my backpack with the transmitter still hanging around my neck.

The next thing I know is that I hear a few beeps followed by the roar of props. It took a few seconds to register in my brain what was actually happening but I turned back round to see my quad had shot way up into the air and seemed to be disappearing fast into the sky. Blackbox data shows throttle got knocked to 53% and it went to a height of almost 30 metres (100 feet). You can also see from the log that even after the throttle was cut (21 seconds into the video below), the quad had so much upwards momentum that it went up another full 13 metres in 2 seconds with no thrust from the props (as shown by the Barometer reading on the right of the video). That's how fast it was going up into the sky.

Panic immediately set in with some choice censored words spoken, but thankfully I fairly quickly managed to get everything back under control before I ended up my quad on the railway line behind me. It was lucky I hadn't manage to also knock the pitch/roll stick so at least it had only shot straight up and not flown off somewhere and ended up crashing out of control. For a split second I did consider just flipping the kill switch but I didn't really want to voluntarily drop it from that height onto the hard concrete surface of the skateboard park below, so after a bit of grappling and fumbling with the transmitter I managed to get the quad back into Angle Mode, drop the throttle and then get it safely back down to Terra Firma which it should never have left in the first place.

Needless to say, the whole episode scared the out of me and everything happened so quickly that I hardly had time to think. I'm lucky I wasn't standing over the quad when that happened otherwise I'd probably be writing this from a hospital bed. I certainly won't be making that same mistake again in a hurry. I'm generally really careful with procedures but it just goes to show that a small lapse in concentration or discipline could result in some catastrophic consequences. I could never see any real need for a pre-arm switch but after this, I'm now seriously considering adding one to my models just an an extra safety measure.

Lessons to be learned from this are:-

1. ALWAYS stay focused and remain disciplined with what you're doing.
   
2. NEVER walk around with a switched on transmitter dangling from your neck.
   
3. UNPLUG your quad immediately and also SWITCH OFF your transmitter if you need to abandon take-off for any reason.
   
4. Don't assume that putting the throttle stick up when disarmed is a good enough safety measure to prevent accidental arming because it's NOT.
   
5. Consider configuring a PRE-ARM SWITCH for added safety/security.
   

This is a running video of the Blackbox data log:-

Glad you were able to get it under control. I'll have to check mine and see what happens if I try to arm with the throttle up.

(11-Mar-2019, 01:31 AM)Sugs Wrote: I'll have to check mine and see what happens if I try to arm with the throttle up.

The flight controller won't arm with the throttle in the up position, which is a safety feature built into Betaflight and is why I thought I was OK because I always keep my throttle up then disarmed in case I accidentally knock the arm switch. As per always, I had the throttle up to prevent arming, but I had managed to knock the throttle down to zero, then knock the arm switch to on, then knock the throttle back up again after it had armed !!!

Something similar happened to me time ago...
After a crash I've went for my quad and I didn't unplugged the battery while I was returning with it in my hand, and with the transmiter hanged in my neck...
Then accidentally the arming switch turned on and the throttle raised a little, so the props start spinning and made me a cut on one finger (It was nothing serious, but painful....)
I'm glad you have controlled the situation with no incidents

In my last build, I have configured prearm with the momentary switch of the taranis. And I'm going to configure it in my other quad too

I am glad you are still with us. You could have been seriously hurt.

Glad you and the quad are ok.  Way to keep a cool head to save the quad.  Sometimes hard lessons like this are the best.  I'm betting you won't make that mistake again.

Reminds me of when my girlfriend wanted to try my quad LOS in angle mode. I showed her how it was done and how little you have to use the throttle and fly with very gentle movements… After a couple of seconds she was descending fast towards the ground and panicked and punched it full throttle and screamed while my quad disappeared straight up in the air..

I took the controller and regained control after a while.. lessons learned: try on a whoop the first time you fly, not a 5" race quad

Glad it worked out OK!

I had a scare like that when I had my TX dangling around my neck and it spun around and knocked my arm switch while I was picking the quad up. Whenever I land now I first turn off DVR, lift the goggles and the *very next thing* I do is unclip my TX and put it on the ground before I go near my quad.

Wow, that could have ended badly, glad you're OK!

I had a pre-arm switch set up on my FS radio but despite that i had one accident which almost cost me a nail... I ordered a momentary switch to do a mod, but got the taranis before it arrived

TL;DR - prearm setup without a momentary switch is USELESS.

Uff sounds scary, glad you managed to save it like that. On my Flysky radio I always just relied on the raised throttle as a safety measure, but on the new QX7 I set up a pre-arm on a momentary switch. I still combine it with the raised throttle, but I feel much safer now.

Thanks people.

Yes, pre-arm will definitely be getting configured on my transmitter's momentary switch. My beeper which is already on that switch will be getting moved to another switch.

I haven't been out since this episode but it will all be reconfigured before my next outing.

So next time anyone sees someone powering up their quad on the bench with props attached, you can just redirect them to this thread so they have something to think about 

ha. This is why i love prearm. One of my quads has not been updated in a while so it didnt have prearm setup. It was wicked cold so I was heating up some lipos and waiting for gps to get a signal in my car so my quad was on the dash at an angle. While waiting I reached over to the passenger seat  to get my phone with the controller in one hand and accidentally hit arm. It was in auto so it started to level out and spool up but luckily it kept falling and made its way between the dash and steering wheel. I disarmed after I shit my pants and went home lol.

   

I asked on the bf rcgroups about what exactly triggers the msp flag on the flight controller. I was thinking that maybe a small resistor on the rx/tx lines to trigger a flag. That way its always left plugged in so that even when accidentally pre-arming and arming it wont flyoff or spinup. Just an extra added level of safety

Glad everything worked out okay for you. Good post as well. Good safety practices can always be improved on.

Deal

Yes, I configured pre-arming last night so hopefully everything should now be as idiot-proof as it can be  For anyone familiar with Betaflight and their transmitter setup, it's intuitive enough to set up without needing to read any instructions on how to do it, but for anyone who does prefer walk-through guides then just follow JB's tutorial video below.

If you have an FrSky transmitter, you also just need to remember to ensure that you've configured your chosen switch to be output on a channel in the Mixer & Outputs page of the model you want it set up for.



Alternatively, if all channels are already in use and you don't have a spare channel (can happen when binding in D8 mode as you're limited to 8 channels), or if you don't want to waste a channel, then on the Taranis transmitters it can also be done on the transmitter itself using logical switches instead...

I think most, if not all of us go through scary things like that. Thankfully most of us can walk away with the only thing being hurt is their pride.
I too, have had a similar experience and thankfully all i got was a nasty cut on my finger...could have been much worst because I was too close the quad.

Before my next flight I added a momentary switch for pre-arm.
In another reply someone mentioned that a pre-arm is useless if not put on a momentary switch... I totally agree!

Glad you didnt get injured.

Roger74