Worst flight ever with p4p I'm still shaking, no control but got it landed

[Snowwolf]

Funny, I thought I had posted re "vexed" and his comments, TOTALLY uncalled for and unreasonable. Maybe it was moderated, though what I said wasn't nasty....

What I said on my original reply to him, which seems to have disappeared into cyber space somewhere, was:
"If you can't post something constructive or helpful, post nothing at all.
..and Professional what? I'm a professional airline pilot, what's that got to do with flying a Phantom, totally irrelevant."

Anyway, ignoring him, (probably the best thing to do) you'll get some confidence back and then have a lot of fun. I drowned my P3 some months ago, totally my fault, (flying sideways doing a panaroma shot and hit some low hanging tree leaves) in a fresh water river, luckily no harm done and it continues to work perfectly after a thorough clean and partial disassembly and long dry out. Yes, it smashed my confidence for a while, but part of the learning curve and still love flying my drone and have plenty of spectacular footage since then. Hopefully you'll have a new one soon and get back to it.

Cheers
David

Cheers for the heads up on the confidence point, I do hope I get it back, I'm looking forward to have a drone back in my life just hope it's not my old one back lol

 

[Snowwolf]

Took it for a good 10 minute flight and the thing is rock solid! Great signal, great GPS, I feel it even handles better.


Sent from my iPhone using PhantomPilots

I forgot to ask, how long did it take for the return new P4P to arrive? mine arrives with DJI on Tuesday

Mick

 

[Jason Porembski]

Mine came back pretty quick. They had it for three days and shipped me a new one. The mail took longer due to the holidays.


Sent from my iPhone using PhantomPilots

 

[ianwood]

Guys (and gals if any present), I am going to say this again for the cheap seats:

Despite what it says in the manual about not calibrating the compass unless it tells you to, there are better rules in the link below that you should follow. The most important thing about the calibration is getting it right. A bad calibration is much worse than none.

Compass Calibration, A Complete Primer

If I sound like a broken record on this, it's because I know a lot about how the compass works and how critical it is to basic flight control.

Also, cell towers have pretty much zero impact on flight characteristics. They may interfere slightly with the range of the controller but I've flown every kind of DJI drone in the most densely urban areas and seen only a handful of times where the was actual interference.

 

[Beebeach]

I had the same issues with my P4Pro, with multiple calibrations on four different locations away from anything except grass and trees:

• 17–20 GPS satellites on the ground, then "Weak GPS signal" at 45 meters altitude and automatic switching to Atti mode.
• It could never fly in a straight line. Sometimes it was worse than others.
• "Toilet bowl" hovers, sometimes 10–15 meters in diameter.

Just got the same machine shipped back to me, with a note saying DJI couldn't find any problems with it. I'm very disappointed, how can I ever trust this bird?

 

[gr8pics]

Just got the same machine shipped back to me, with a note saying DJI couldn't find any problems with it. I'm very disappointed, how can I ever trust this bird?

What? I feel you man, i wouldnt be happy either, after all youre not the only one experienced these problems. They should have routinely replaced it for you.

 

[Snowwolf]

What? I feel you man, i wouldnt be happy either, after all youre not the only one experienced these problems. They should have routinely replaced it for you.

Oh!!!! feel for you too matey, they may have changed things inside and if they have they are unlikely to say they have, have a fly when you can and see what it flys like, bet it will be stable.

 

[F3honda4me]

Best practice on the mavic, inspire 2, and P4/P4P is to calibrate compass the first time you ever fly it, then don't touch it after that unless the app tells you to or the bird isn't flying right. (you can also look at the compass to ensure it's in the "green") These newest drones use GPS to determine location and then load the magnetic inclination and deviation for the area. The purpose of a calibration is mainly to measure and compensate for magnetic distortions caused by the AC itself.

Contrary to popular belief, these drones don't discover or compensate for geomagnetic declination during compass calibration. The compass calibration procedure (the "compass dance") can't provide the data necessary to determine geomagnetic declination. A necessary step would be something like precisely aligning the AC along true north and then tell the AC that it's aligned true north. For that same reason, the compass calibration can not discover, know about, or compensate for local or regional geomagnetic distortions.

 

[John Locke]

Best practice on the mavic, inspire 2, and P4/P4P is to calibrate compass the first time you ever fly it, then don't touch it after that unless the app tells you to or the bird isn't flying right. (you can also look at the compass to ensure it's in the "green") These newest drones use GPS to determine location and then load the magnetic inclination and deviation for the area. The purpose of a calibration is mainly to measure and compensate for magnetic distortions caused by the AC itself.

Contrary to popular belief, these drones don't discover or compensate for geomagnetic declination during compass calibration. The compass calibration procedure (the "compass dance") can't provide the data necessary to determine geomagnetic declination. A necessary step would be something like precisely aligning the AC along true north and then tell the AC that it's aligned true north. For that same reason, the compass calibration can not discover, know about, or compensate for local or regional geomagnetic distortions.

Interesting to note, my Yuneec Q500 calibration process required pointing the craft to north. That's one of the things I didn't like about that craft. I'd have to pull out my phone to find exact north to do the compass calibration. And then the flips and spins I had to do was ridiculous, way more complicated than DJI's process.

 

[BudWalker]

Interesting to note, my Yuneec Q500 calibration process required pointing the craft to north. That's one of the things I didn't like about that craft. I'd have to pull out my phone to find exact north to do the compass calibration.

That was true north?

 

[John Locke]

That was true north?

Magnetic north, with compass.

 

[BudWalker]

Magnetic north, with compass.

Must be something different then. Was there some kind of compass dance? Or was it just point it magnetic north and tell the craft?

 

[ianwood]

Best practice on the mavic, inspire 2, and P4/P4P is to calibrate compass the first time you ever fly it, then don't touch it after that unless the app tells you to or the bird isn't flying right. (you can also look at the compass to ensure it's in the "green") These newest drones use GPS to determine location and then load the magnetic inclination and deviation for the area. The purpose of a calibration is mainly to measure and compensate for magnetic distortions caused by the AC itself.

Contrary to popular belief, these drones don't discover or compensate for geomagnetic declination during compass calibration. The compass calibration procedure (the "compass dance") can't provide the data necessary to determine geomagnetic declination. A necessary step would be something like precisely aligning the AC along true north and then tell the AC that it's aligned true north. For that same reason, the compass calibration can not discover, know about, or compensate for local or regional geomagnetic distortions.

You are confusing deviation and inclination with declination. Declination can be derived from a lookup table based on a location grid and/or it can be determined in flight by sampling the difference between heading and course across different vectors. The latter being the solution DJI put into the P2 after we complained about the lack of ability to correct for declination.

Deviation and inclination (to a lesser degree) are what the calibration is for. Hard and soft iron influences both vertical and horizontal magnetic fields which is why we measure it from different vectors.

And your Phantom cannot always determine when the compass needs to be calibrated. It can guess but it can be wrong. Therefore, waiting for the app to tell you that the compass needs to be calibrated is imperfect especially if you travel with your drone. If you are on the east coast and bring your drone to the west coast, recalibrate the compass regardless of what the app says.

 

[BudWalker]

..... Therefore, waiting for the app to tell you that the compass needs to be calibrated is imperfect especially if you travel with your drone. If you are on the east coast and bring your drone to the west coast, recalibrate the compass regardless of what the app says.

AFAIK, the only things that can be different from east to west coast are declination, inclination and strength. Declination and inclination can be derived from GPS coordinates. That leaves just strength as a reason to calibrate. Is there anything else?

 

[ianwood]

AFAIK, the only things that can be different from east to west coast are declination, inclination and strength. Declination and inclination can be derived from GPS coordinates. That leaves just strength as a reason to calibrate. Is there anything else?

Deviation. This is the "localized" field. For example, contents of the soil in the region. Mountains vs. plains. And there is hard iron, e.g. you added a tracker.

EDIT: It is not known if the P4 is looking up declination and inclination reference data at each power cycle. It is possible that it is part of the calibration process as was the case in early Phantoms.

 

[gr8pics]

You are confusing deviation and inclination with declination. Declination can be derived from a lookup table based on a location grid and/or it can be determined in flight by sampling the difference between heading and course across different vectors. The latter being the solution DJI put into the P2 after we complained about the lack of ability to correct for declination.

Deviation and inclination (to a lesser degree) are what the calibration is for. Hard and soft iron influences both vertical and horizontal magnetic fields which is why we measure it from different vectors.

And your Phantom cannot always determine when the compass needs to be calibrated. It can guess but it can be wrong. Therefore, waiting for the app to tell you that the compass needs to be calibrated is imperfect especially if you travel with your drone. If you are on the east coast and bring your drone to the west coast, recalibrate the compass regardless of what the app says.

Funny, i got my head chopped off and thrown out of the Dji forum for saying the same, quite fascinating how they run their forums over there, allowing Captains and First officers bashing people until the hijacked OPs loose their patience and try to fight back, then defending the guys that keeps starting conflicts and throw out the other instead, beats me!

Anyway, the earth's magnetic field has a dipole component that is roughly coincident with the spin axis. However, the north geographic pole (the spin axis) and the "north magnetic pole" are not found in the same place. This is because the Earth's magnetic field is a complex phenomenon, and the location where the inclination of the field is 90 degrees (the "poles") wander constantly due to fluctuations in the magnetic field.

A compass points in the directions of the horizontal component of the magnetic field where the compass is located, and not to any single point. Knowing the magnetic declination (angle between true north and the horizontal trace of the magnetic field) for your location allows you to correct your compass for the magnetic field in your area, or calibrate if you like.
A mile or two away the magnetic declination may be considerably different due to different geographical conditions, requiring a different correction. The figure below illustrates the variation in declination around the world.
This is how we relate to a magnetic compass in general aviation when navigating over longer distances...

As a thumb-rule, if i travel greater distances around the world which requires traveling with an airplane, i always recalibrate at first flight, not within my country, as the distances and deviations (differences) most likely are minor and not noticeable when flying a small drone.

 

[DavidN747]

Guys (and gals if any present), I am going to say this again for the cheap seats:

Despite what it says in the manual about not calibrating the compass unless it tells you to, there are better rules in the link below that you should follow. The most important thing about the calibration is getting it right. A bad calibration is much worse than none.

Compass Calibration, A Complete Primer

If I sound like a broken record on this, it's because I know a lot about how the compass works and how critical it is to basic flight control.

Also, cell towers have pretty much zero impact on flight characteristics. They may interfere slightly with the range of the controller but I've flown every kind of DJI drone in the most densely urban areas and seen only a handful of times where the was actual interference.

Thanks for that Ian, (AND gr8pics) very good advice.
I hadn't read that prior to now.

Having done at least ONE flight, (as mentioned previously, and which turned into a total nightmare), with the compass calibration out of whack, I am far more cautious about it all now.

Anyway, thanks again and cheers
David

 

[ianwood]

It's not just horizontal and it's not just declination. Inclination is not as consistent as the main field would suggest. And the localized variation is what is considered deviation.

Also, the compass isn't only used to identify a 2D heading. It is also used as a vector to the center of the earth which allows the craft to adjust for IMU drift and noise. The most obvious evidence of this is footage from Phantoms that have really bad horizon drift when their compass is out of whack.

 

[BudWalker]

Deviation. This is the "localized" field. For example, contents of the soil in the region. Mountains vs. plains. And there is hard iron, e.g. you added a tracker.

The tracker doesn't change with location. Certainly, if a tracker is added then a calibration should be done.

I'm assuming that regional effects such as a nearby mountain range loaded with iron could cause the declination to change. Within the confines of the compass dance the field isn't distorted because the scale of the regional effects are so much larger than the compass dance. It's just that the field is coming from the wrong direction. But this regional declination can't be determined from the compass dance for the same reason that the global declination can't be determined from the compass dance. To detect and compensate for any declination during a compass dance it would be necessary to place the AC in a true north heading and then tell it that it's heading is true north. Since this isn't part of the dance declination can not be determined from a compass calibration.

It's debatable if the geomagnetic inclination is used to correct IMU data. I would suppose the opposite is true. But, nevertheless, the same type of argument apples here. I.e. the craft would have to be placed in a known orientation while the magnetometer data is taken. This also is not part of the compass dance. At this point I always refer to an experiment I did where the P3 was calibrated upside down; first step inverted, second step nose up. Flew fine - didn't fly off to China upside down.

The only purpose of a calibration that consists of a P3-like compass dance is to detect and then compensate for the distortions caused by the AC itself; also called the hard iron effects. Detecting and compensating for regional effects just isn't possible with compass dance.

 

[BudWalker]

Thanks for that Ian, (AND gr8pics) very good advice.
I hadn't read that prior to now.

Having done at least ONE flight, (as mentioned previously, and which turned into a total nightmare), with the compass calibration out of whack, I am far more cautious about it all now.

Anyway, thanks again and cheers
David

I'm curious. What led you to believe the compass wasn't calibrated properly? The reason that I ask is that I've looked at a lot of actual data for flights where there was some reason to suspect compass issues. There was just one flight where the data supported the possibility of a bad compass calibration. Several incidents were caused by a compass problem other than a bad calibration. IMHO the vast majority of incidents attributed to a bad calibration were caused by something else. I say this having actually looked at real data.

Bad compass calibration incidents have been reported so many times, by so many pilots, for so long, and then repeated that pilots just assume that it just has to be true.