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Preventative Maintenance - A networking idea

As a RPA operator do you think collecting this data would be useful?

  • Yes and if it was in place I would use it.

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I am relatively new (about 9 months) into Remotely Piloted Aircraft (RPA) but I have been around aircraft in maintenance related matters since 1965 (Yes 51 years). I live in Perth, Western Australia. Purchased my Inspire 1 Pro a few weeks ago now. Had P3 since July 2015. The thought of losing either with no warning is a major concern even though both are well insured.

The basic question I would like to get my head inside is "Is it possible to better define how to mitigate the risk of crashing by some type of preventative maintenance program?".

Aside from the bleeding obvious - flying into trees, houses, power lines etc what are the key risks for the Inspire 1 RPA?

a) Engine failure
b) ESC failure
c) Propeller failure

Can we mitigate the risk for these?

In a normal aircraft one relies heavily on the various equipment manufacturers for such key data as "Mean Time Between Failures (MTBF)" and "Recommended Lives". But as stated in several other areas, for electrical components this can be a tad tricky.

Now to date I have been singularly unsuccessful in engaging DJI techs on such mundane things as MTBF's. If anyone might have a clue, based on sales of spares and reported crashes I would have thought DJI would.

So be it. Is there another solution to tracking/collecting these failures? Well I think there is. If suppliers and users could easily contribute to one data collection source perhaps over time some meaningful stats could be seen. Data needs to be tabulated so that it is good and easy to understand reports can be used. Is this forum the place for such a feature or would any readers feel interested in such a database if one were available?

In the short term I plan to commence the following data collection on both my RPA's.

a) Engine/ESC condition:
i) Within 1 min of last flight, measure and record each engines temp using an infrared thermometer. This is in addition to checking by hand for temp and ease of turning.
ii) Every routine inspection check engine rpm again using an infrared rpm gauge.

Q. At what temp and/or rpm should the engine and/or ESC be replaced. To leave it "On Condition" is just asking for serious trouble at some future point.

b) Propeller condition (Regardless of type):
i) At each removal check with extreme care for any cracks or other defects, including the attachment mechanism. Paying particular attention to the hubs and leading edges. If in doubt - chuck it out. Cheap option compared to a failure.

In both cases record the event in the RPAs maintenance log.
 
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In a normal aircraft one relies heavily on the various equipment manufacturers for such key data as "Mean Time Between Failures (MTBF)" and "Recommended Lives".
Now to date I have been singularly unsuccessful in engaging DJI techs on such mundane things as MTBF's. If anyone might have a clue, based on sales of spares and reported crashes I would have thought DJI would.
But the full scale equipment manufacturers are obligated to do the required large scale and real-time testing to determine those - no such thing in the hobby or UAS market yet so basically you build a thing and send it out with no idea of its long term reliability. They simply have no clue.And given there are no SN's for parts they won't be tracking anything or building a database from returns/repairs.

So be it. Is there another solution to tracking/collecting these failures? Well I think there is.
IMO without a centralized database (DJI) you won't get a meaningful sample size.

i) Within 1 min of last flight, measure and record each engines temp using an infrared thermometer. This is in addition to checking by hand for temp and ease of turning.
That's good

ii) Every routine inspection check engine rpm again using an infrared rpm gauge.
That's useless. RPM is regulated so you'll always measure the same. The ESCs would need to measure and provide their regulation parameters for us to be able to see the evolution (= see that the power required to reach a given RPM incresases), but they don't (or if they do we don't have access to that data). The closest thing now is temperature as above. And you can't really measure ESC temp (which is probably more important than the motor's) on the I1 given it's buried below the motor.
 

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I applaud your sentiment but as Kilrah states above, there is no regulatory mechanism in place and no way to trace parts via serial numbers (with the exception of a few)
I fly commercially and have a maintenance regime that I follow as well as always checking my motor temperatures by hand after every flight and the free running of the motors. This helps identify early problems with the bearings which I replace at 100 hours or sooner if required.
ESC's cannot be serviced and they either work......or they don't. Nearly every single esc fault is a FET failure and with the amount of current the arrays are switching it's no surprise that failures are sudden and non predictable.
I have found that multirotors follow the bathtub curve as regards to failure rate and if you do not have any problems in the early life of the machine you will follow this curve and probably have a reliable aircraft.
With a quad, inherently by design, if any one corner fails it's good night! It's just something we all live with but a comprehensive checklist before each flight together with sensible 'maintenance' regime helps mitigate any 'stupid' or preventable errors/failures.
 
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I applaud your sentiment but as Kilrah states above, there is no regulatory mechanism in place and no way to trace parts via serial numbers (with the exception of a few)
I fly commercially and have a maintenance regime that I follow as well as always checking my motor temperatures by hand after every flight and the free running of the motors. This helps identify early problems with the bearings which I replace at 100 hours or sooner if required.
ESC's cannot be serviced and they either work......or they don't. Nearly every single esc fault is a FET failure and with the amount of current the arrays are switching it's no surprise that failures are sudden and non predictable.
.

This is an old thread but I have a couple of questions for the Editor: My Inspire is going on 2 years and probably 200+ hours of flight time. In my opinion the electronics are pretty stable and, like you said, they either go or fail. Besides replacing all the electronics there really isn't any preventative maintenance to be done. However, the one thing that concerns me is the mechanicals, specifically the motors. So I am thinking of replacing them with 3510H (I have the original Inspire 1). They seem to be hard to come by and not cheap. Questions: 1) If I replace the stock motors with the 3510H, do I need to change the ESCs? Most are sold with the ESCs but one seller offers just the motors. 2) Should I even replace the motors? 3) You mention replacing the bearings. That sounds like a nice ineffective alternative. Are these readily available? 4)What else should I be doing to keep the Inspire flying in good form?

Forgot to mention, I do a periodic recalibration of the batteries.
 
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The Editor

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This is an old thread but I have a couple of questions for the Editor: My Inspire is going on 2 years and probably 200+ hours of flight time. In my opinion the electronics are pretty stable and, like you said, they either go or fail. Besides replacing all the electronics there really isn't any preventative maintenance to be done. However, the one thing that concerns me is the mechanicals, specifically the motors. So I am thinking of replacing them with 3510H (I have the original Inspire 1). They seem to be hard to come by and not cheap. Questions: 1) If I replace the stock motors with the 3510H, do I need to change the ESCs? Most are sold with the ESCs but one seller offers just the motors. 2) Should I even replace the motors? 3) You mention replacing the bearings. That sounds like a nice ineffective alternative. Are these readily available? 4)What else should I be doing to keep the Inspire flying in good form?

Forgot to mention, I do a periodic recalibration of the batteries.
The motors will not actually wear out.....EVER. There are no moving parts in them so they will pretty much last indefinitely.
However, what definitely will wear out is the bearings. These are easily replaceable (if you are confident in doing some self RC maintenance or have replaced brushless motor bearings before). They are readily available from pretty much any RC hobby store or you can go upmarket and put in hybrid ceramic or fully ceramic which will never run dry).
There are a few posts on the forum about which bearing fit etc and suppliers but they are nothing special in the RC world and generic good quality ones will be fine.
If you do want to go the route of replacing the motors then you do not need to replace the esc's. The existing ones are no different and will drive the 3510H's without any issues.
 
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The motors will not actually wear out.....EVER. There are no moving parts in them so they will pretty much last indefinitely.
However, what definitely will wear out is the bearings. These are easily replaceable (if you are confident in doing some self RC maintenance or have replaced brushless motor bearings before). They are readily available from pretty much any RC hobby store or you can go upmarket and put in hybrid ceramic or fully ceramic which will never run dry).
There are a few posts on the forum about which bearing fit etc and suppliers but they are nothing special in the RC world and generic good quality ones will be fine.
If you do want to go the route of replacing the motors then you do not need to replace the esc's. The existing ones are no different and will drive the 3510H's without any issues.

I like this idea a lot and I have no issues with actually doing the work. However, I am having trouble locating the bearings themselves. I called a few hobby shops in the US and they sell only complete motors. I called Boca Bearings and they indicated they may have them but they sell by size only, not application. Sooooo, can someone either provide a source and/or the actual bearing sizes? I don't want to tear my drone apart now without having the replacement bearings available.
 

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I like this idea a lot and I have no issues with actually doing the work. However, I am having trouble locating the bearings themselves. I called a few hobby shops in the US and they sell only complete motors. I called Boca Bearings and they indicated they may have them but they sell by size only, not application. Sooooo, can someone either provide a source and/or the actual bearing sizes? I don't want to tear my drone apart now without having the replacement bearings available.
Standard or ceramic hybrid dia: 5/11/5 (Bore 5mm, OD 11mm Width 5mm).
685ZZ's will fit (shielded)
Boca will definitely sell them. :)
 
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I never thought buying bearings would be so confusing. So I have a few final (I hope) questions. I ordered the hybrid ceramic from Boca (SMR685C-2-OS). They are the orange seal. The question is, do I oil these? Per the Boca rep, they are oiled from the factory but he said you can run them dry. So do I oil them as a regular maintenance item and if so, how frequently? Or, do I just run them until I swap them out again in 2 years?

You mentioned you change them out every 100 hours. Because they are ceramic, do you have a longer maintenance schedule?

As an aside, Boca seems to be a good company to deal with. I am swapping out bearings in 3 drones so I got a 10% quantity discount. Then they added an additional 10% discount for the heck of it. No tax and free shipping.
 

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