Altitude drops during flight...

[Helijoc]

I have noticed slight drops in altitude with my P3 . Usually noticed when flying fast and doing hard turns, no where near as drastic as 10 feet. I attributed it to blade stall based on direction of travel and blade vortices . Someone above kinda touched on it but I think it is a result of the aerodynamics of the new design.

Maximum flight speeds of helicopters are limited by what is called retreating blade stall. As you approach velocity never exceed Vne the rotor blade retreating towards the rear of the aircraft will become less efficient and stall causing the aircraft to turn in the direction of the stall and loose altidude. Multi rotor aircraft with counter rotating blades are not affected to the same degree as the stall is counter balanced. It is the reason the Chinook was the fastest helicopter for a while.

I could be wrong but I suspect the new design is experiencing some sort of vortex disturbance causing one or more rotors to become less efficient based on flight direction and orientation .

 

[gtpark]

I have noticed slight drops in altitude with my P3 . Usually noticed when flying fast and doing hard turns, no where near as drastic as 10 feet. I attributed it to blade stall based on direction of travel and blade vortices . Someone above kinda touched on it but I think it is a result of the aerodynamics of the new design.

Maximum flight speeds of helicopters are limited by what is called retreating blade stall. As you approach velocity never exceed Vne the rotor blade retreating towards the rear of the aircraft will become less efficient and stall causing the aircraft to turn in the direction of the stall and loose altidude. Multi rotor aircraft with counter rotating blades are not affected to the same degree as the stall is counter balanced. It is the reason the Chinook was the fastest helicopter for a while.

I could be wrong but I suspect the new design is experiencing some sort of vortex disturbance causing one or more rotors to become less efficient based on flight direction and orientation .

If that is the case rather than a barometer issue, then their purported firmware solution would probably not correct a motor efficiency issue.

 

[robdigphot]

If the IMU was calibrated in an upstairs room instead of on the ground floor would this cause an issue with the barometer?

 

[N017RW]

No

 

[sar104]

If the IMU was calibrated in an upstairs room instead of on the ground floor would this cause an issue with the barometer?

I guess you don't live in the mountains.

 

[robdigphot]

I guess you don't live in the mountains.

You are correct, almost sea level!

 

[ianwood]

I have noticed slight drops in altitude with my P3 . Usually noticed when flying fast and doing hard turns, no where near as drastic as 10 feet. I attributed it to blade stall based on direction of travel and blade vortices . Someone above kinda touched on it but I think it is a result of the aerodynamics of the new design.

Maximum flight speeds of helicopters are limited by what is called retreating blade stall. As you approach velocity never exceed Vne the rotor blade retreating towards the rear of the aircraft will become less efficient and stall causing the aircraft to turn in the direction of the stall and loose altidude. Multi rotor aircraft with counter rotating blades are not affected to the same degree as the stall is counter balanced. It is the reason the Chinook was the fastest helicopter for a while.

I could be wrong but I suspect the new design is experiencing some sort of vortex disturbance causing one or more rotors to become less efficient based on flight direction and orientation .

Vortex state is most prevalent in straight down flight as the props sit mostly in disturbed airflow. The P3 and P4 have canted motors to compensate for this. And any approaching blade stall would be immediately noticed in the change in pitch (sound). I haven't heard anything sounding like a stall.

I can almost guarantee you the increased power of the P4 motors is creating a pressure bubble in fast flight causing the barometer to think it is higher up than it really is. X8s have this problem in fast flight because they have larger props on shorter booms. Many flight controllers compensate for it. Not all DJI flight controllers do.

 

[John Locke]

I calibrated my 4 sensors last night. The newly updated Digital assistant works on a PC now. I don't think I have the altitude drop problem anymore. Has anyone else calibrated theirs with similar results? Seems like a sensor calibration could only help at 30' and below since that's the range of the downward facing sensors. However, for me I've only noticed this phenomenon at less than 30'. Does everyone else notice it drops unexpectedly only at low altitudes? Or is that just me?

 

[Kman]

I calibrated my 4 sensors last night. The newly updated Digital assistant works on a PC now. I don't think I have the altitude drop problem anymore. Has anyone else calibrated theirs with similar results? Seems like a sensor calibration could only help at 30' and below since that's the range of the downward facing sensors. However, for me I've only noticed this phenomenon at less than 30'. Does everyone else notice it drops unexpectedly only at low altitudes? Or is that just me?

Only at low altitudes for me too.

 

[MikeK]

Good news.....thanks for coming back on this.

That's encouraging.

Thanks.

 

[gtpark]

Only at low altitudes for me too.

Or is it that you more readily notice it when you are close to the ground. A five foot drop when flying at 10 feet is much more apparent than the same drop when flying at 300 feet.

 

[G-K]

Just an update guys.

My new P4 doesn't have altitude dropping issue in P and Atti mode anymore after a proper IMU calibration.

I realise very minor but consistent flight height dropping (maybe 1 degree or 2) when I fly full throttle in Sport mode. Which is not important at all for my flying purpose.

I can say that I am 100% happy with P4 now.


Sent from my iPhone using PhantomPilots mobile app

 

[Kman]

Still have the altitude dropping issue even after an IMU calibration.

 

[John Locke]

I still have too. I thought the sensor calibration fixed it, but today I noticed it was back. Where I noticed it most is flying along fast then let go of the stick, which puts on the brakes to stop. The craft stops quick, then slowly descends about 5 to 8', then it ascends back up 5 to 8'. This will happen above 30' AGL I've noticed.

 

[Kman]

I still have too. I thought the sensor calibration fixed it, but today I noticed it was back. Where I noticed it most is flying along fast then let go of the sick, which puts on the brakes to stop. The craft stops quick, then slowly descends about 5 to 8', then it ascends back up 5 to 8'.

Mine doesn't climb back up I don't think.

 

[gtpark]

I still have too. I thought the sensor calibration fixed it, but today I noticed it was back. Where I noticed it most is flying along fast then let go of the sick, which puts on the brakes to stop. The craft stops quick, then slowly descends about 5 to 8', then it ascends back up 5 to 8'.

Sound like a barometer issue (pressure bubble) as mentioned before. If so it would seem that sensor calibrations would not solve it unless they also involve the barometer which I have not seen reported.

 

[John Locke]

Sound like a barometer issue (pressure bubble) as mentioned before. If so it would seem that sensor calibrations would not solve it unless they also involve the barometer which I have not seen reported.

Yes, I agree. In post #25 of this thread is my theory about that.

 

[Humberto Caldas]

After a chat with DJI - where they told me to calibrate it, after calibration made first flight, P Mode, see what happens in the second 14 after made the move to the left and completely take my fingers from the command

 

[John Locke]

So you're saying the calibration DJI told you to do didn't work, correct? Mine still does this too. I've calibrated the IMU and 4 sensors and this anomaly still exists.

 

[will.moindrot]

After a chat with DJI - where they told me to calibrate it, after calibration made first flight, P Mode, see what happens in the second 14 after made the move to the left and completely take my fingers from the command




]

That's nothing to do with being low down over water in P mode right? I'm probably wrong but when I first watched it I thought that your drop coincidences with going over a river of the water. Mine does this too but I was hoping on calibration imu