Is This The Dumb Question Department?

[Former Member]

Yes - I think you are right w.r.t. the ESC, but still - you are going to get to that point in the sky where the rev's on the motors are max'd out, and the amount of air available is just enough to keep the Mavic at the hover on full up-stick ... The motors won't actually get much hotter, because though they may be spinning faster, the lack of air means that they are still 'working' the same as if they were spinning slower, in more dense air. There may be some issues with bearings coming under load due to higher rpm, but that would cause minor effect. There's also a marked temperature decrease with altitude. In clear skies, temperature drops 9.8 degrees celcius per 1,000 metres. That means that when flying at high altitudes, the motors are going to be in an environment that will keep them cooler anyway!

In response to your post about the motors reaching max RPM, and wont get much hotter, I wouldnt want to reach that point! It's like redlining a tach on a racing car. Your statement about bearings causing minor effects might be true in a perfect world, but in reality, if your berings are worn, if your props are not perfectly balanced, and motor shafts are not perfectly straight, running a motor flat out open is not a good long term or short term strategy. At high RPM, especially on a rotary wing aircraft, vibration is your enemy, and vibration can increase with increased RPMs.

 

[FoxhallGH]

A previous flight log would be just fine.

Argh! - I thought I knew how to do that ... Can you point me a t a good how-to for Android please?

 

[sar104]

Argh! - I thought I knew how to do that ... Can you point me a t a good how-to for Android please?

How to retrieve a V3.DAT from the tablet

 

[FoxhallGH]

Thanks for that ... I think I've found a log file for a flight that was a short part of a hover duration test - so the height and position was fairly constant. This flight took place in my back garden, which according to Google Maps, is 22 metres ASL. I had larger 25 minute files, but the Forum site won't accept files that large ...

 

[FoxhallGH]

I first want to say that I always appreciate and respect your statements and opinions. Sometimes we differ, but it's always to get to the bottom of the truth, and disspell any myths or rumors that might be perpetrated by people who either dont really know, or that have come to believe in something that just doesnt ring true. IMHO, You are one of the most knowledgeable people on this board, and have helped me and many fellow members figure out what the truth is on many issues. You are also a gentleman, in the true sense of the word.

In response to your post about the motors reaching max RPM, and wont get much hotter, I wouldnt want to reach that point! It's like redlining a tach on a racing car. Your statement about bearings causing minor effects might be true in a perfect world, but in reality, if your berings are worn, if your props are not perfectly balanced, and motor shafts are not perfectly straight, running a motor flat out open is not a good long term or short term strategy. At high RPM, especially on a rotary wing aircraft, vibration is your enemy, and vibration can increase with increased RPMs.

Thanks Rob - please don't be afraid to challenge me if I've got something wrong ... I'm here to learn and appreciate everything that is given here so freely. So I'd rather be picked up on something that's not correct, than have it go on to cause somebody else a problem because I've said something I shouldn't. I won't take offence, but will want to learn ...
In regard to this one - agreed 100% - not something I'd want to do either ... I was presenting more from a theoretical point of view, where you are [correctly] being practical ... Making my Mavic hang on its prop's on the edge of the Stratosphere is the last thing I'd want to do ... Can't be healthy for it!

My thoughts about the motors not being loaded at high rpm comes from this [theoretical] line of thinking ...
If you put the Mavic in a vacuum chamber with no air at all ... there may be some issues regarding temperature etc. that would not be healthy for it - but that aside ... the motors would spin the prop's at the same rpm as the shafts would spin if you had no props on them at all i.e. there would be no air resistance for the prop's to spin against and therefore, max. rpm would be limited by DJI electronics (ESC circuits). I'd assume, as you've mentioned above, that the ESC's would limit the rpm to a level that prevents damage - but I think there would also be a theoretical maximum due to the way the motor is driven by an oscillating waveform making a reaction between the fixed coils on the stator, and the ring of magnets that are fixed to the spinning-can part of the motor assembly. There has to be a maximum frequency that will drive the motor before it just literally can't keep up! With no air in the vacuum chamber though, the Mavic will not fly ...
If you gradually bring air pressure up in the chamber, there will be a point where the Mavic prop's will bite into enough air, and it will lift.
I'm pretty sure that this air pressure is the equivalent of the 'Max Service Ceiling Above Sea Level' altitude specification that DJI quotes, which is 16,404 ft (5,000m) for my Mav' Pro Platinum, and 6,000 metres for the Mav' 2 Pro.

 

[sar104]

Thanks for that ... I think I've found a log file for a flight that was a short part of a hover duration test - so the height and position was fairly constant. This flight took place in my back garden, which according to Google Maps, is 22 metres ASL. I had larger 25 minute files, but the Forum site won't accept files that large ...

That's a Mavic Pro - not a Mavic 2 - yes?

 

[FoxhallGH]

That's a Mavic Pro - not a Mavic 2 - yes?

Correct ... Mav Pro Platinum. (Not sure what prop's would have been on it on that flight segment).

 

[sar104]

Correct ... Mav Pro Platinum. (Not sure what prop's would have been on it on that flight segment).

I need a Mavic 2 file for the the comparison to be equivalent. I only have the Mavic 2 Pro and the Mavic Pro, both of which have different props and motors than the MPP.

 

[brett8883]

Any idea what the max tilt to RTH would be with and without OA on?

Tired it today and there was no difference in speed(in this case velocity) between OA on and (OA off+RTH OA off).

The max tilt would be whatever the max tilt of the drone is because the drone will tilt to whatever angle it needs to achieve the RTH speed. This is the one time where it's not using a tilt input as the forward speed output, the opposite, its using a speed input to determine the tilt output.

 

[Former Member]

Tired it today and there was no difference in speed(in this case velocity) between OA on and (OA off+RTH OA off).

The max tilt would be whatever the max tilt of the drone is because the drone will tilt to whatever angle it needs to achieve the RTH speed. This is the one time where it's not using a tilt input as the forward speed output, the opposite, its using a speed input to determine the tilt output.

Excellent. Any idea what your RTH speed was? Funny I did the same test today with a Mavic Pro. Did you use a Mavic 2 in your test? My RTH speed with and without sensors was exactly the same, which is what you described in your test.

My RTH speed was 22mph. Im thinking that even though it is returning to home, the sensors stay active, which is why the speed is limited to Pmode max speed.

Did you try RTH with the controller switched to sport mode?

 

[brett8883]

I'd be very interested to see the flight log for a Mavic in level flight at 60° pitch.

Obviously anything approaching 90° is physically impossible, racing quad or otherwise.

And of course the parameter is related to wind - what it is not is the tilt that the aircraft will apply to resist wind. That's trivially obvious. 60 is the default setting. At just 35° in sport mode, which is its maximum tilt in that mode, the Mavic will achieve an airspeed of 40 mph. If it could use 60° to resist wind then it would be able to hold in winds of much higher than 40 mph, when in fact the Mavic 2 maximum wind resistance is 24 mph.

Ask and thou shall receive.
Google Drive

I even screen recorded for you so you could see what I was seeing. I didn't mean for it to be but ended up being a pretty epic flight.

 

[brett8883]

Excellent. Any idea what your RTH speed was? Funny I did the same test today with a Mavic Pro. Did you use a Mavic 2 in your test? My RTH speed with and without sensors was exactly the same, which is what you described in your test.

My RTH speed was 22mph. Im thinking that even though it is returning to home, the sensors stay active, which is why the speed is limited to Pmode max speed.

Did you try RTH with the controller switched to sport mode?

No its just that the RTH speed parameter is 10 meters per second. Thats why when I upped mine to 11 m/s it goes home at 24 MPH. I actually recorded this in the video I made for @sar104 above. Skip to 17mins 40 secs if all you want to see is the RTH tests.

 

[brett8883]

Did you try RTH with the controller switched to sport mode?

Yea it didn't make a difference.

 

[sar104]

Ask and thou shall receive.
Google Drive

I even screen recorded for you so you could see what I was seeing. I didn't mean for it to be but ended up being a pretty epic flight.

Nice flight, and interesting data.



Did you say that you had maximum tilt set to 60°? The maximum pitch achieved during that flight was 45°, transiently, and all the excursions over 40° led to uncommanded altitude loss - as expected. These aircraft will not hold stable flight at 60°.

Horizontal speeds were reasonable, briefly reaching a maximum of 22.5 m/s (50 mph) at one of the 45° pitch excursions.

 

[brett8883]

Nice flight, and interesting data.

View attachment 66103

Did you say that you had maximum tilt set to 60°? The maximum pitch achieved during that flight was 45°, transiently, and all the excursions over 40° led to uncommanded altitude loss - as expected. These aircraft will not hold stable flight at 60°.

Horizontal speeds were reasonable, briefly reaching a maximum of 22.5 m/s (50 mph) at one of the 45° pitch excursions.

View attachment 66105

Very interesting thanks for the break down!

 

[Firejay27]

It would use whatever power was necessary to accomplish the goal set for it whether you're in tripod, normal or sport mode. We've had some up and down weather here so I was flying one day and a very large block of heavy wind came in. I was already attempting to fly slowly against the wind and found myself pushing the stick forward all the way to keep my slow pace against that wind. At one point I got a message that the motors were at maximum though I wasn't moving much at all. Basically it was telling me that it knew that I was trying to move with full forward on the stick and it was not going anywhere. It was trying to tell me it was doing what it could to keep going but couldn't. Wouldn't have mattered if I was in sport mode at the time either because the motors were already at max. Tripod mode vs normal mode only slows things down a bit to help you make a more steady shot. [Eventually my wind stopped and I was back to normal again.]

 

[Oneball 1971]

I want to know because I have a dumb question.

When in "Tripod" mode will the M2P use all available power to stabilize it's self in strong winds. When I say all available power I mean will it use the same amount of power in Tripod mode as it is capable of in Sport mode if that is what is necessary to stabilize it? Inquiring minds want to know!

See it wasn't a dumb question after all

 

[brett8883]

It would use whatever power was necessary to accomplish the goal set for it whether you're in tripod, normal or sport mode. We've had some up and down weather here so I was flying one day and a very large block of heavy wind came in. I was already attempting to fly slowly against the wind and found myself pushing the stick forward all the way to keep my slow pace against that wind. At one point I got a message that the motors were at maximum though I wasn't moving much at all. Basically it was telling me that it knew that I was trying to move with full forward on the stick and it was not going anywhere. It was trying to tell me it was doing what it could to keep going but couldn't. Wouldn't have mattered if I was in sport mode at the time either because the motors were already at max. Tripod mode vs normal mode only slows things down a bit to help you make a more steady shot. [Eventually my wind stopped and I was back to normal again.]

In that situation what I would have done is ascend to a higher altitude and then full stick forward and full stick down. This allows the aircraft use less power to maintain the same pitch angle forward since it doesn’t need to use as much vertical power due to your command to descend at the same time.

You could also fly diagonally to the wind instead of right into it and then turn to fly diagonally the other direction to get back on course. It’s kind of like tacking a sail boat.

 

[Firejay27]

In that situation what I would have done is ascend to a higher altitude and then full stick forward and full stick down. This allows the aircraft use less power to maintain the same pitch angle forward since it doesn’t need to use as much vertical power due to your command to descend at the same time.

You could also fly diagonally to the wind instead of right into it and then turn to fly diagonally the other direction to get back on course. It’s kind of like tacking a sail boat.

Agreed. I was trying to get a test shot to see what it could do and was caught off guard by the wind and the message on screen. That multi layer effect of the wind caught me on this day as we had been having some strange weather.

 

[Drgnfli]

I want to know because I have a dumb question.

When in "Tripod" mode will the M2P use all available power to stabilize it's self in strong winds. When I say all available power I mean will it use the same amount of power in Tripod mode as it is capable of in Sport mode if that is what is necessary to stabilize it? Inquiring minds want to know!

15 MPH WIND GUSTS !!! If my Dark Sky weather app says the wind is higher, I park my MP until the next day. I have had a couple of 'near misses' flying in "high" winds & it scared the shet our of me & almost crashed my MP into a tree, so I have "SMARTENED" up and just curb my desire to fly when the winds are above 15 MPH. Kind of like the same rule about flying above the highest tree, pole, bridge, tower, or antenna in your flight area - you cannot go wrong with those simple self induced rules... IMHO!