Rotor Fatigue

[herman2992]

I didn't find a discussion focused on rotor fatigue. Rotor failure, but not expected or reasonable rotor life. So I decided to start one.

I'm retired Army. Comfortable with the idea of preventive maintenance on critical components. I've seen some conversation about rotor failure. These are simple plastic parts. At some point they have to fail. I would rather replace my rotors at some reasonable milestone than send my aircraft (if I can find it) to DJI after rotor failure.

Does anyone mark their rotors (sharpy?) with the date they put it in service? Or add a sharpy dot for every flight? What would be a reasonable number of flights or minutes/hours before retiring a rotor?

It seems that if we don't replace rotors at some flight milestone, we are simply asking for rotor failure in flight and all the associated consequences.

I'm a newbie, so I'll just shut up and listen ...

 

[rjl0000]

New here too but after reading a couple horror stories about rotors spinning off mid flight and inspecting my own I developed a theory that the Mavic having the folding rotors has a lot to do with it. By leaving the rotors on and sliding the Mavic in and out of a storage bag and moving that bag around (bumping things) it's stressing the mounting tabs and the rotor hub itself as they get pressure and impacts from different directions. This is compounded by them being left on all the time as there is no inspection or even significant manipulation prior to flight in most cases. I agree that rotors can and probably should have a service life but suspect most of the wear is likely happening on the ground. DJI markets it as just unfold and fly but it needs to be treated like an aircraft with thorough inspections pre-flight. Just my thoughts on it.

 

[Former Member]

OP, you can expect hundreds of flights from one set of blades if you have not crashed and the blades have not been subjected to undue stress, as RJ mentioned above, such as pulling the Mavic with blades on, in and out of the tiny DJI FM bag.

I still have one original set of blades I use to test fly repaired birds, and they have at least 200 flights on them. Aside from some grass stains, the blades are solid, and the tabs inside the rotor hub are fine.

 

[Robert Mitchell]

I am ex USAF aircraft maintenance, and I also believe in routine maintenance.

That said, as stated above, absent any unusual strikes or adverse stresses, I believe these OEM props
have been designed with margins way beyond normal use stress. Think about it. Due to centrifugal force, there is virtually no movement relative to itself in the horizontal plane, nor is there any at the hub, once properly locked into place.

Blade flex up and down is inevitable but apparently has been engineered into the materials.

I do preflight checks on the props, but have been using the original set for over a year with no sign of deterioration.

I’m thinking many prop “failures” are the result of improper installation, or erroneous interpretation of an strike accident as being “minor”.

 

[Former Member]

I’m thinking many prop “failures” are the result of improper installation, or erroneous interpretation of an strike accident as being “minor”.

 

[vertrider]

question: do you all unmount the props each time before transport?
what’s best practice here?
I fix the props in place with a adjustable wide velcro strap before storing in the bag (strap with just so much tension that the props don’t move around) and have seen others doing this as well. but I understand the point on putting some “load” on the motor etc while storing...

 

[ftttu]

DJI delivered me a set of undamaged 8331 LNPs, but the set I got from B&H were damaged in USPS transport. The boxes were crushed so the blades were deformed, however, I fly them anyway since there are no negative flight characteristics.

Because those props were deformed when pressure was applied, I remove my props when transporting my MP in its case so they don't don't get deformed or damaged at the pivot points. It may be overkill removing them during transport, but I REALLY don't want prop failure.

 

[Youser]

question: do you all unmount the props each time before transport?
what’s best practice here?
I fix the props in place with a adjustable velcro tape before storing in the bag (there just so much tension that the props don’t move around) and have seen others doing this as well. but I understand the point on putting some “load” on the motor etc while storing...

I normally take the top two (when folded) off as I find them catching on the Fly More Combo bag when removing the Mavic. With them off, the Mavic seems to fit into the bag better.

 

[Former Member]

I leave my props on during transport. However, removing and reinstalling the props are part of my preflight inspection. I just like to hear them snap in to place, and it takes all of 30 seconds for all 4 props. Even in between flights, after I install a fresh battery, I try to check the props again.

 

[Big Fil]

It's never a bad idea to look over your blades every so often, but the reality is that the way these style drones fly is not putting any extreme stresses on the blades. The flight controllers limit what can be done so much and the blade RPMs are relatively low.

 

[Marko9219]

I often inspect the blades , top, bottom and middle for anything not normal, then, every single flight, I anchor each motor between my thumb and forefinger of one hand and with the other hand give each prop a good twist to make sure they are locked in like they should be. I won't replace them without cause

 

[Lake_Flyer]

Props are made of plastic and any kind of plastic is prone to drying out or get brittle from UV over time.

Although they still might look OK, it is wise to toss them away after say 200 flights. That's what I do anyway.

 

[Glenn Goodlett]

I replace my props every million feet flown as preventative maintenance. Have never hit anything except for the occasional bug.

 

[Midway]

As soon as i see a nick chip or crack I scrap them and also do preventative maintenance. .

 

[Callum]

I check mine before each flight and with the amount of flying I get in will probably replace them after 12 months.

Maybe my OCD kicking in here but you mentioned writing on them with a marker, depending on the material used this can actually make the plastic more prone to failure.
Same goes for hard hats and safety harnesses. If you write on a harness with marker pen it's supposed to be scrapped.

 

[BossBob]

Correct, marker pens contain solvents that can compromise some plastics, obviously not the plastic the pens are made of but we don’t know what the Mavic’s blades are made from.