P4 took a dump 2 inches off the ground on take off..

[OldManInWva]

Was out yesterday morning killing a little time before work and had my P4 in the air for a while using a new iPad Air 2. Was using Litchi on that flight and had it in the air about 15 or so minutes.
Returned and exchanged battery and then closed out Litchi and opened Go4 for another flight. Fired everything up and when the bird acquired the needed GPS signal I started to take off, I let the motors idle a few seconds before pushing the left stick forward to lift off. Once it started in the air the bird immediately tilted backwards in place so far that the rear blades contacted the ground and broke. (I use carbon/plastic hybrid).. the split second prior to the complete tilt reminded me of the jerking in the hovering it has experienced since on of the summer firmware updates. None of those jerks ever equaled the the rearward tilt that this one experienced though.

Yesterday evening I put some new blades on and decided to play with some hovering inside the garage to see if it was going to do it again.
No issues and it hovered almost perfectly in place for 5 min with no jerking.
It’s like now I cannot trust the bird to fly right. Has anybody experienced any issue like this?
A review of the flight log shows only 5.5 seconds of data in 51 lines on the CSU file. On the last 10th of a second I see where it pitched a -11 degrees and then immediately back to -3.1 before stopping data recording. At that close to the ground 12 degrees is enough to let the blades hit the ground.

Anybody have any thoughts or experiences on this?

 

[lannes]

Have you upgraded to IOS 11.2

 

[Fly Dawg]

Sounds like a VPS issue to me. Not sure on a P4 but try turning the VPS off and see if that corrects the issue.

 

[msinger]

Once it started in the air the bird immediately tilted backwards in place so far that the rear blades contacted the ground and broke. (I use carbon/plastic hybrid)

3rd party props?

 

[OldManInWva]

Yes, I do have IOS 11.2, and have since it came out.

Carbon Fiber/Plastic hybrid blades are aftermarket, been using since April 17

Possible it could be a VPS erroneous sensor signal forcing a correction, I always lift off and hover for a few seconds (usually 5 to 10 ft in the air) before climbing and start my flight course.

As far as the jerking while hovering goes, I know I've seen many complain of this.. mine will do this "Most" of the flights, usually on take off, and usually fairly close to the ground so maybe the VPS could have something to do with it.

However, is VPS able to be turned back on while in flight? I know some features or adjustments used to be only made once the connection has been established.. Not during flight.
Never tried turning it off then back on.

Thanks for the replies folks

Roger

 

[sar104]

Yes, I do have IOS 11.2, and have since it came out.

Carbon Fiber/Plastic hybrid blades are aftermarket, been using since April 17

Possible it could be a VPS erroneous sensor signal forcing a correction, I always lift off and hover for a few seconds (usually 5 to 10 ft in the air) before climbing and start my flight course.

As far as the jerking while hovering goes, I know I've seen many complain of this.. mine will do this "Most" of the flights, usually on take off, and usually fairly close to the ground so maybe the VPS could have something to do with it.

However, is VPS able to be turned back on while in flight? I know some features or adjustments used to be only made once the connection has been established.. Not during flight.
Never tried turning it off then back on.

Thanks for the replies folks

Roger

The DAT file will show what caused the event, if you feel like retrieving it.

 

[OldManInWva]

The DAT file will show what caused the event, if you feel like retrieving it.

If you would like to look at it I will send it to you, the only radical events take place in the last 1/10th of a second of the logging, where it pitches. I do see that at this point the change in the OSD.Flystate column where it changes from AssistedTakeoff to GPS_Atti.

You are welcome to look at it if you would like.

 

[sar104]

If you would like to look at it I will send it to you, the only radical events take place in the last 1/10th of a second of the logging, where it pitches. I do see that at this point the change in the OSD.Flystate column where it changes from AssistedTakeoff to GPS_Atti.

You are welcome to look at it if you would like.

I'd be happy to take a look. It records sensor data at 200 samples per second and motor speeds and command data at 50 samples per second, so even events over 0.1 seconds should be clearly documented.

The best solution is to upload it to Dropbox or Google Drive and post the link here.

How to retrieve a V3 .DAT File from the AC

 

[OldManInWva]

Not a problem.... Dropbox - FLY536.DAT


Thanks

 

[sar104]

Unfortunately that event appears to have been caused largely by your take off technique. Gradually increasing throttle to only 30%, as you did, from 4.5 s to 5.25 s, does not lift the aircraft cleanly off the ground and it will tend to tip. With part of the landing gear still on the ground the FC has a very hard time correcting for that. As you can see from the DAT file data, the motors all responded appropriately but at 5.18 s the front left unstuck first and the FC overcorrected, leading to the tip over.

Manual takeoff should be a very positive action initiated by pushing the throttle fully forwards until the aircraft leaves the ground. That will prevent this type of problem.

 

[OldManInWva]

Yes, I did have a very slow takeoff on that attempt... I usually do lift off a bit quicker to clear the ground. I have done the slow takeoff before with no issues so never had any thoughts or concerns about it. Your analysis makes perfect sense though and I REALLY appreciate the time and feedback. This will prevent future prop damage!

Thanks Again.

Roger

 

[sar104]

Yes, I did have a very slow takeoff on that attempt... I usually do lift off a bit quicker to clear the ground. I have done the slow takeoff before with no issues so never had any thoughts or concerns about it. Your analysis makes perfect sense though and I REALLY appreciate the time and feedback. This will prevent future prop damage!

Thanks Again.

Roger

No problem. Sometimes a slow take off will work, but the risk of tipping over is not insignificant whereas it never happens on full throttle.

 

[JWH]

Thanks for posting. I always learn from threads like this. I am glad that the props were the only thing damaged.

 

[lannes]

Yes, I did have a very slow takeoff on that attempt... I usually do lift off a bit quicker to clear the ground. I have done the slow takeoff before with no issues so never had any thoughts or concerns about it. Your analysis makes perfect sense though and I REALLY appreciate the time and feedback. This will prevent future prop damage!

Any reason why you prefer a manual take off to the automatic take off ?

 

[OldManInWva]

To tell the truth I’ve NEVER used the auto take off and seldom let it auto land... I have never actually thought about it. May have to try it sometime I guess.

 

[JWH]

I use auto takeoff every time. It goes up a few feet, then waits for you to tell it where to go. I have never used auto land.

 

[sar104]

I used to takeoff and land manually and I have experienced tip-overs occasionally until I stated using auto takeoff and auto land. No more tip overs.

I'm sure that the auto options work well, but I've never used them and never experienced any problems. Take off should be full throttle until airborne and landing should be minimum throttle until the motors stop.

 

[sar104]

The auto land and takeoff functions work brilliantly. I'm happy for you that you have not had any tip-overs on your landings and takeoffs sar104. But I believe this thread was about a gentleman that did have a tip-over and ruined some props. Just saying.....

Yes - it was about that. However, if you read the thread you will have noted that the conclusion, from analyzing the DAT file, was that the tip over was due to taking off with only 30% throttle, and my point was that manual take off is perfectly safe provided full throttle is used.

 

[sar104]

I did read the thread sar104. My point was that the novice that had the tip over can use the auto take-off and land functions and he will never have that problem again. Use the technology that was built into the aircraft. Again, just saying.....

Agreed, and I wasn't disagreeing about the usefulness of auto take off and landing - just making sure that it was clear that manual operation will not cause problems if done properly.

 

[sar104]

sar104, I read the thread and what we have here was a novice that was asking for advice on what happened with his Phantom tipping over and the conclusion from the DAT that the tip-over was pilot error due to a low powered take-off. Yes, your solution to take-off full power will eliminate that, but your solution is but one solution. Why not use the technology that was built into the aircraft and completely eliminate any pilot errors until he has more time and experience under his belt?

I’m not disagreeing with you - it’s a fine suggestion. Again - I simply wanted to make sure that there was no mystery surrounding this issue and that no one gets the impression that manual takeoff can randomly cause problems, even when done correctly.