Humming sound after startup

[mtbkrdrone]

After updating new firmware, I took my little mtbkrdrone out for a flight over a frozen lake. I kept batteries and spark ext to my body while hiking in, along with a small hand heating pad. Batteries never gave me a low temp warning during the flight. Upon returning for a new battery, when I landed and motors shut off, there was still an audible humming sound coming from my Spark. Changed out batteries, restarted and the hum was still there.
Could it be the cold weather, it was 10F during the flight but as I said, never did I have a low temp warning on the controller. Does the little guy need to be looked at by DJI??

 

[msinger]

Got a video so we can hear the humming sound?

 

[mtbkrdrone]

Sorry, I do not. When I landed, I turned off camera not hearing the humming until motors shut off. I am going to start it up in the house here in a little bit to see if it is still doing it. I will post audio if it is.
Thanks
Don

 

[Spark 317]

Upon returning for a new battery, when I landed and motors shut off, there was still an audible humming sound coming from my Spark.

Is it possible that you are hearing the internal cooling fan?

It runs when the Spark is powered up even when the flight motors are shut down.

 

[mtbkrdrone]

Started my little mtbkrdrone up this AM and NO Audible Humming sound! I tried it with all 3 batteries and no Hum. I guess I will chalk that up to extreme cold, as it was under 10F yesterday.
I only have a little over 10 hours of actual flight time, but I have never heard the Hum as audible as it was during my flight yesterday.
Funny thing also.....when I turned it on today, I was prompted to install new firmware. Yesterday, 2:00pm eastern time when I flew, the prompt wasn't there. Huh....

 

[Spark 317]

I was prompted to install new firmware.

I'm kidding but I think DJI does it on purpose.

I'm not the only pilot that checks everything at home before a flight and then get ready to fly that an update pops up then and there.

 

[REMUS1]

I also noticed that I can hear the Fan when its cold ( 20's). Warm it up in the house and it sounds normal. I suspect the internal fan blades are hitting the housing due to some part contracting when cold.

 

[Virtual1]

I also noticed that I can hear the Fan when its cold ( 20's). Warm it up in the house and it sounds normal. I suspect the internal fan blades are hitting the housing due to some part contracting when cold.

That would be my guess. The fans may simply get a bit noisy when cold due to thermal contraction in the bearings or other areas of the cooling fan. Or the fan may be off balance. I don't know if the internal fan is variable-speed (one would hope so), and fans can have "sweet spots" where they hit a harmonic of vibration and get noisy when running at certain RPMs. Being cold outside may cause the fan to slow down because the spark doesn't need cooling, and that is dropping it into an RPM range where it starts to vibrate.

 

[s2 Web Parrot]

After updating new firmware, I took my little mtbkrdrone out for a flight over a frozen lake. I kept batteries and spark ext to my body while hiking in, along with a small hand heating pad. Batteries never gave me a low temp warning during the flight. Upon returning for a new battery, when I landed and motors shut off, there was still an audible humming sound coming from my Spark. Changed out batteries, restarted and the hum was still there.
Could it be the cold weather, it was 10F during the flight but as I said, never did I have a low temp warning on the controller. Does the little guy need to be looked at by DJI??

Perhaps it "hums" because it doesn't know the words.

 

[Spark 317]

T

Perhaps it "hums" because it doesn't know the words.

That is why a Humming bird hums .

 

[Ophidia Snaketongue]

If could be that the lubricant in the fan bearings has got cold and much thicker than normal, thus you hear the fan. You get a similar thing in failing computer fans- they make a lot of noise on startup, but once the lubricant has warmed up and thinned, they become quiet.

Not that I think your cooling fans are failing- it's just the very low temperatures making the fans work against harder lubricant than normal.

 

[clouseau]

My Sparks fan has a mind of its own, when My Sparks fan make noises it never seems to make the same exact noise consistently from one flight to the next . There are times it sounds like its geeting ready to die any second and other times it just hums loudly until it warms up. The only good thing about the fan making noise is that I can tell the fan is actually working.

I have had laptops with exactly the same looking fan, and they often had made some noises simular to the Spark, so I kinda thought this to be normal.

 

[DesertWindAero]

After updating new firmware, I took my little mtbkrdrone out for a flight over a frozen lake. I kept batteries and spark ext to my body while hiking in, along with a small hand heating pad. Batteries never gave me a low temp warning during the flight. Upon returning for a new battery, when I landed and motors shut off, there was still an audible humming sound coming from my Spark. Changed out batteries, restarted and the hum was still there.
Could it be the cold weather, it was 10F during the flight but as I said, never did I have a low temp warning on the controller. Does the little guy need to be looked at by DJI??

The manual states 32F is the minimum operating temperature. You could probably go a few degrees lower and get away with it...but, 10F is probably too low and things can go wrong. Hence, the hum, more than likely.