High altitude flight ...

yamahu · Dec 2, 2019

Hello
Yesterday with Mavic Mini I got this msg.
High altitude flight, aircraft braking distance is extended, flight time is shortened, Fly with caution (code 30238)
I have to mention I was in Mexico City at altitude 2230m
I wonder what this mean.
I found Mini has 3000m max but I was under that limit,
Appreciate any comments
Thanks

WooZie · Dec 2, 2019

maybe you was at 3000m above level sea or almost

guinness · Dec 2, 2019

It means that you are at high altitude, air is thinner and the drone has longer break distance and lower flight-time due to higher speed on engines due to the thinner air..

yamahu · Dec 2, 2019

guinness said:
It means that you are at high altitude, air is thinner and the drone has longer break distance and lower flight-time due to higher speed on engines due to the thinner air..

I wasn't 2300m I'm sure about that.

But why flight time is shorter? I did 20min max

moncefj · Dec 2, 2019

exact

old man mavic · Dec 2, 2019

the MM has a max altitude of 3000m above sea level ,so if you take your starting ASL, and add your height from your take off point , then you were approaching the service ceiling for the drone ,it is not as powerful as other mavics due to its size and power train

yamahu · Dec 2, 2019

old man mavic said:
the MM has a max altitude of 3000m above sea level ,so if you take your starting ASL, and add your height from your take off point , then you were approaching the service ceiling for the drone ,it is not as powerful as other mavics due to its size and power train

I'm 2200m above see level Mexico City so Im still under 3000m right. I guess this msg should pop up when I'm at 3000m, no ?

Like yesterday I was 2200m start MM and did 100m up so aprox MM altitude was 2300m still under 3000m limit.

old man mavic · Dec 2, 2019

not really there are other factors at play here such as wind , in the thin air the mav will be working much harder to stay airborne,so the message is just that, it is a warning to let you know that the drone is having a hard time, these messages air on the side of caution so you have a chance to react to them they are not written in stone

PhantomFandom · Dec 2, 2019

yamahu said:
I'm 2200m above see level Mexico City so Im still under 3000m right. I guess this msg should pop up when I'm at 3000m, no ?

Like yesterday I was 2200m start MM and did 100m up so aprox MM altitude was 2300m still under 3000m limit.

No that is not correct. The message did not say that you have reached the service ceiling. Only that you are at high altitude (which you certainly were). As @guinness properly stated above, the air density decreases as altitude increases. When the air is less dense, the propellers are less efficient. This means that the motors need to do more work for the same output you would get at sea level. The end result is shorter flight time, lower top speed, increased breaking distance, and generally more sluggish performance overall.

This is the same reason you don't see propeller driven airplanes and helicopters at very high altitudes.

JS1600 · Dec 2, 2019

PhantomFandom said:
No that is not correct. The message did not say that you have reached the service ceiling. Only that you are at high altitude (which you certainly were). As @guinness properly stated above, the air density decreases as altitude increases. When the air is less dense, the propellers are less efficient. This means that the motors need to do more work for the same output you would get at sea level. The end result is shorter flight time, lower top speed, increased breaking distance, and generally more sluggish performance overall.

This is the same reason you don't see propeller driven airplanes and helicopters at very high altitudes.

Very well explained, Just like I learned for my Part 107 Certification.

Bman22 · Dec 2, 2019

I got the same message when I'm flying my drone. I live in a town with an elevation of 6200 ft asl. It's just a warning to you that the drone might not be as responsive to fly compared to flying near sea level.

Flyicaptain · Dec 3, 2019

yamahu said:
I'm 2200m above see level Mexico City so Im still under 3000m right. I guess this msg should pop up when I'm at 3000m, no ?

Like yesterday I was 2200m start MM and did 100m up so aprox MM altitude was 2300m still under 3000m limit.

Your density altitude was probably the problem. Other factors that play into the altitude limit are temperature and humidity and when factored in create a higher density altitude. This is the altitude all aircraft and humans too experience. Thinner air means propellers have to spin faster to create the lift to get your drone flying and the motors are the ones working harder to spin them. The harder they work the more battery they use.

Rockycat · Dec 3, 2019

yamahu said:
I wasn't 2300m I'm sure about that.

But why flight time is shorter? I did 20min max

Thin air.

yamahu · Dec 3, 2019

Thank you all for your answers. I knew about 3000m limit but actually I didn't expect it will trigger that kind of message at 2200 already.
I wonder how wind is thinner here 2200m or sea level. What I wonder is at which altitude will start trigger this message like 1000m or so

Airborne_Aircrew · Dec 3, 2019

No that is not correct. The message did not say that you have reached the service ceiling. Only that you are at high altitude (which you certainly were). As @guinness properly stated above, the air density decreases as altitude increases. When the air is less dense, the propellers are less efficient.

You're very close.. It's called "Density Altitude". It's the relationship between air pressure and it's temperature. Simply put, when you get high the pressure tends to decrease. Similarly, when you get high the temperature tends to decrease. But if you get high in the Arctic the air stays "thicker" at the same altitude and pressure than the air would be at the same altitude and pressure in the Sahara Desert.

It's how "thick" the air is that gives the rotors a "bite" into the air. As the density altitude gets lower the less "power" a rotary aircraft has - thus the less lift is available to the aircraft. The opposite is true too. You can be at sea level at 1013mb at 32f and have a much higher density altitude than being at sea level at 1013mb at 80f.

Flying rotary wings in hot and high situations is a recipe for a disaster.

Are the drones you fly as susceptible to the disastrous effects of weight versus density altitude? No, but if you are close to things below you and are hot and high you could experience a lack of power that drops you down onto something you didn't want to meet.

PhantomFandom · Dec 4, 2019

Airborne_Aircrew said:
You're very close.. It's called "Density Altitude". It's the relationship between air pressure and it's temperature. Simply put, when you get high the pressure tends to decrease. Similarly, when you get high the temperature tends to decrease. But if you get high in the Arctic the air stays "thicker" at the same altitude and pressure than the air would be at the same altitude and pressure in the Sahara Desert.

It's how "thick" the air is that gives the rotors a "bite" into the air. As the density altitude gets lower the less "power" a rotary aircraft has - thus the less lift is available to the aircraft. The opposite is true too. You can be at sea level at 1013mb at 32f and have a much higher density altitude than being at sea level at 1013mb at 80f.

Flying rotary wings in hot and high situations is a recipe for a disaster.

Are the drones you fly as susceptible to the disastrous effects of weight versus density altitude? No, but if you are close to things below you and are hot and high you could experience a lack of power that drops you down onto something you didn't want to meet.

While density altitude and pressure altitude have their place in determining lift and propeller efficiency, I tried to keep it simple in this case. The OP was getting an error indicating that he was flying at a high altitude, which he was. It was the altitude that was causing the low air density, compared to other locations that we all fly from. He is in Mexico City where the average temperature in December is in the mid 70's F, so it was not brutally hot which would have caused even lower density and further issues.

Airborne_Aircrew · Dec 4, 2019

PhantomFandom said:
While density altitude and pressure altitude have their place in determining lift and propeller efficiency, I tried to keep it simple in this case. The OP was getting an error indicating that he was flying at a high altitude, which he was. It was the altitude that was causing the low air density, compared to other locations that we all fly from. He is in Mexico City where the average temperature in December is in the mid 70's F, so it was not brutally hot which would have caused even lower density and further issues.

Ok, that's fair... I just think that a full explanation is always a good thing and the reader can take what they want or need from it. Since rotary wing flight can get a tad complex I don't think it hurts to try to explain the science and let the readers take what they need from it.

In this case the error message came from the App only, (via GPS), since the Mini has no pressure and temperature sensors aboard so it has no idea of either the pressure or density altitudes. So the App is throwing out a warning based only on the geographic location not the actual, measurable, parameters.

Just my 2c...

PhantomFandom · Dec 5, 2019

Airborne_Aircrew said:
In this case the error message came from the App only, (via GPS), since the Mini has no pressure and temperature sensors aboard so it has no idea of either the pressure or density altitudes. So the App is throwing out a warning based only on the geographic location not the actual, measurable, parameters.

Wait, what??

Where did you see that DJI has changed the method of establishing altitude? I have not seen anywhere that the Mavic Mini has no on-board barometer or air pressure sensor. Establishing altitude via GPS would not be anywhere as accurate and would also cause major problems for the drone if GPS signal was lost.

I can't see why DJI would do this and see no indication anywhere that this is the case. As far as I know, the MM uses air pressure to determine altitude just like every other DJI product.