Hi everyone,

I'm leading some acoustic measurement on the DJI Phantom 4. I would like to record the acoustic of the propellers for differents configurations. First with all propellers, the second with 3, the third with 2 and the fourth with 1.

All the measurement are made with the drone fixed on the ground and not flying.

My problem is the follow : When I use only 3 propellers or less, I got the following message "DJI Motor Idling (Losse of Missing Propellers)" and the motors cut off automatically. I was wondering if there is a way to keep the motors on eventhough only 3 propellers are fixed ?

Thank you very much.

Not a smart thing to do.  It should have flipped.

From my understanding it’s not advisable to run the motors at anything but idle with no props on. You run the risk of damaging them.

Record the acoustic db level of the propellers for all 4 propellers,
Mulitply by 75% for the db level of 3 propellers,
Multiply by 50% for the db level of 2 propellers,

Thank you for your answer.

I m actually making a spectral analysis for different configuration of the drone with different number of propellers. I saw in article that they do that with the Phantom 2.

You would have to add some (little) resistance to the motors without props in order to limit the speed, they don't like to be spinning free.
Think it somehow should match the resistance from the props in order to avoid a security shutdown as you get now.

To987, it is not recommended to do that since the motor could be possibly damaged.

TBH there is only two configurations, one with the props installed and one without. These machines log everything and if you cause damage in your experiment warrant will not cover it.

I can only re-iterate what others have said here.  If the CPU is sensing no load on the 4th motor - then it'll stop as a safety measure.  It's telling you to "I'm not flying until you fit the right number of props".


Why don't you try buy four 3 bladed props - and then see what the dB level are like?