P2 Crash - What Happened?

[NickB]

Hi everyone, i'm new here and new to flying. This is what i have :

- Phantom 2 with Zenmuse H3-2D, GoPro 3+ Black (everything new 1-2 days old)
- Black Pearl FPV, 600mW TX
- Do not have iOSD mini yet (on order)
- Prop Guard

On my test flight, the P2 crashed and i do not know why, I was hovering and suddenly it starts coming down (watch the video). I always have a fully charged battery before i fly and this happened about 5 minutes 15 seconds into the flight (based on the time of the gopro recording since i do not have iosd mini).

Please watch the video and listen to the sounds and let me know what you think happened? Thanks!!

Some notes:
- Battery was fully charged when i lift off
- This was pre 2.0 firmware update
- I did 4-5 flights before this and all went well
- I was just hovering and wasn't trying any manoeuvres
- There are no trees or power lines or such around the area as you can see from the video

I couldn't embed the video link but its here:

http://youtu.be/dL4uUOC9ta4

[youtube]dL4uUOC9ta4[/youtube]

 

[Big Ben]

Looks like you were descending... and a bit too fast without horizontal movement. A very well known problem with the P2's. What then develops is called Vortex Ring State.

Check this:

[youtube]http://www.youtube.com/watch?v=HrsGM0PzQFo[/youtube]

And this.

If you search this forum you'll find many threads about the subject already.

 

[hook3m]

That hurts to watch... I feel your pain. You said you were on a test flight. What were you testing out?

It does look like you were descending. Were you full stick down or close to it?

 

[NickB]

I was actually panning.. it does look like i was descending.. but definitely not full down. I said test flight as i just got the unit and still undergoing test flights.. this is probably my 5th flight.

One thing i didn't mention that when it started coming down, it seems like i lost all sense of control.

Thanks for your input big ben, will study that

 

[goldfishrock]

Definately looks like Vortex Ring State. If you experience it again just let go of the sticks, it'll take a second or two but it will stabalise and go back to the hover.

 

[NMG318]

It does look like you were descending pretty much vertical just before it became uncontrollable. If this is the case then this would be a classic case of Vortex Ring State. (You don't have to be descending full down to get into Vortex Ring State)

 

[goldfishrock]

(You don't have to be descending full down to get into Vortex Ring State)

Indeed! You get little currents and eddys which can cause pockets of dead air. Descending into one of those can trigger VRS. Looking at your video again, it seems you are flying in a location where I would imagine air would be unstable because of the movement of air around the buildings. In this case I think it's just a bad combination of factors.

You can induce VRS just by dropping too quickly in perfectly stable air, so the golden rule is put in a little forward motion as you descend. I normally descend in a large downward spiral... just push the left stick slightly down and slightly right. You can lose a lot of height quickly but without inducing any VRS.

You'll get used to the flight characteristics of the P2 in time so don't beat yourself up too much over this. We've all had accidents, it's all part of the learning curve.

 

[CJ31]

BTW - There is some speculation that prop guards enhance the effect.

 

[poostik]

It does look like you were descending pretty much vertical just before it became uncontrollable. If this is the case then this would be a classic case of Vortex Ring State. (You don't have to be descending full down to get into Vortex Ring State)

yep

I've gotten the wobbles from dropping slower than this video, in less time. I didn't lose it completely but it was definitely headed there.

When I descend now, I'll always give it a push in any direction so that it's coming down on an angle.

 

[Submariner]

I appreciate the education on this thread ... :ugeek:

 

[NickB]

I didn't quote everyone but many thanks for all your comments. I suppose when the majority says its VRS i will have to learn from this episode...

Damage: Scratched Go Pro Hero 3+ Black Lens (irreplaceable by gopro it seems), 2 broken propellers.

I gotta work on my landings first before i remove the prop guards. Sometimes when i land, or if the P2 lands itself (low batt) it topples over. The prop guard has saved my props on few occasions. Perhaps this is just a matter of practice....?

 

[Big Ben]

Does it topple over on landing or when you switch off the motors?

 

[NickB]

Does it topple over on landing or when you switch off the motors?

When i switch off the motors sometimes... am i doing something wrong?

 

[Big Ben]

That depends. If you switch off by doing a CSC then yes as this basically gives control inputs until you reach the 100% stick input positions. The control inputs are what causes it to topple over. You should switch off either by holding just the left stick full down a few seconds or immediately after giving such left stick full down THEN 'morph' that into a CSC by moving the left stick inwards and moving the right stick to a CSC position too. You can shut the motors off quicker that way than with the regular left stick down method. If you compare the two methods with props taken off the motors you can hear the difference. With a regular CSC you will hear motors speed up before they switch off which you won't hear with the 'compound' CSC.

 

[NickB]

That depends. If you switch off by doing a CSC then yes as this basically gives control inputs until you reach the 100% stick input positions. The control inputs are what causes it to topple over. You should switch off either by holding just the left stick full down a few seconds or immediately after giving such left stick full down THEN 'morph' that into a CSC by moving the left stick inwards and moving the right stick to a CSC position too. You can shut the motors off quicker that way than with the regular left stick down method. If you compare the two methods with props taken off the motors you can hear the difference. With a regular CSC you will hear motors speed up before they switch off which you won't hear with the 'compound' CSC.

Thanks. I will be trying this method out today. cheers

 

[jayhas]

I appreciate the education on this thread ... :ugeek:

Agreed. Helpful info.

 

[NickB]

That depends. If you switch off by doing a CSC then yes as this basically gives control inputs until you reach the 100% stick input positions. The control inputs are what causes it to topple over. You should switch off either by holding just the left stick full down a few seconds or immediately after giving such left stick full down THEN 'morph' that into a CSC by moving the left stick inwards and moving the right stick to a CSC position too. You can shut the motors off quicker that way than with the regular left stick down method. If you compare the two methods with props taken off the motors you can hear the difference. With a regular CSC you will hear motors speed up before they switch off which you won't hear with the 'compound' CSC.

Thanks. I will be trying this method out today. cheers

This method works. Will be shutting down this way moving fwd. Thanks.