Propellor guards

Hi everyone,

I have the opportunity of doing some photographic flights inside a cathedral. However there are some concerns being raised regarding the downwash disturbing dust and entering the fire sensing array.

My question is, do you think fitting propellor guards will have any effect on the downwash from the drone, a Mini 2.
My argument is the downwash from a sub 250g drone is negligible, but if fitting guards reduces it even more by dissipation, that could clinch the deal.
I know guards add extra weight therby reducing flight time. I have taken that into account.

I checked today with UAVForecast and DJIFly app in the venue and was notified of 18 locked satellites, so although I have practised manual flying in other indoor areas, I don’t think I will have a problem with lack of control in the proposed venue.

What are your thoughts about reducing the downwash ?


Just remember that indoors prop wash is magnified so the chance of disturbing dust is highly likely


I don’t think that the guards will do much. They may help with the side wash. But not a lot.
With regards to down wash, the higher you are the better. At least 2 ft.

Be careful with indoor locked satellites. You will get problems.

Isolate the sensors on the fire system or put it in test.


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Nice idea, but not very practical when the ceiling is 120 ft up :grinning:

I’ve flown indoors on a couple of occasions already, but thanks :+1:

Thank you. It is a huge building, so not a small area.

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Looking into disabling the sensors whilst flying. Thanks for your reply.

Indoors, in a cathedral, relying on GPS satellites, at least for me, is an accident waiting to happen. When fitting pro guards you would also need to switch the mode, to let the drone know, is is carry thing extra weight. Downwash is not only a problem where dust is concerned, it will also affect the drone… Truth is, I wouldn’t even consider it… satellite coverage inside a cathedral, prop wash, zero collision detection, so pro guards would be a must… I’m all for trying new things, but for me, unless they are designed for that specific job, drones belong in the outdoors… but hey good luck and I hope it works out well… Don’t forget to post some shots and video if you pull this one off without any hassle… I tried flying indoors once, in a sports hall a very empty sports hall… and prop wash is quite significant, even with a tiny little drone like the Mini 2, get yourself an anemometer and you’ll discover for yourself, remember it has to generate enough thrust, to combat grade 5 winds… and in a confined space, even if it is a cathedral, all those surfaces are going to play havoc with the poor little drone, especially if you hope to reply on satellite positioning…

Still like I say, good luck with this one, fit the prop guards for sure and fingers crossed the little mini 2 comes out of it in the same condition it went in… Not a risk taker myself, although you could say that you are taking a risk every single time

**** happens as they say

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A cinewhoop and fly FPV may be a much better option, you would still have the propwash problem though.

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The Mini 2 changes to payload mode when it detects extra weight i.e. prop guards. This changes it’s max height & range so could be an issue depending where you’re filming in the cathedral.

Thanks. I am aware of this and I know through prior testing in open air, that I can reach the desired height with prop guards on. Range is not an issue.

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Thanks for your reply. Prop wash is my main concern.

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Thank you for your reply. As said above I have flown several times indoors, with lower than 5 satellites, under full manual control. So I know I am able to control the drone and am not relying on GPS coverage. The Mini 2 recognises the load automatically and informs you. So there is no switching mode to worry about. I’ll remember all you have said.

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If propwash is a real issue how high do you need to film from? Would a camera pole be an option?

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Try covering the downwards sensors with tape. This should put it into ATTI mode and then you wont have a situation where the drone suddenly loses satellite lock and decides to do its own thing.

You can buy rc zeppelins. No downwash on these

Not quite sure why you keep mentioning how many satellites you get, when the mini 2 with prop guards fitted, switches to atti mode, so satellites are meaningless. anyway as I said good luck and don’t forget to post an update with pics/vid.

Probably going to be the loudest thing (inside) the cathedral has ever experienced

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To prevent accidental activation of the fire/smoke sensors you could ask for them to be disabled in the areas you intend to fly in.

You say you had 18 satellites locked or did you mean that 18 satellites were in view? There is a big difference. What neither APP tells you is the HDOP (Horizontal Dilution Of Precision), VDOP (Vertical Dilution Of Precision, and PDOP (Position Dilution of Precision).

When flying in open areas these factors, other than HDOP, are not that important unless absolute precision is needed. However in enclosed spaces where multi-path reflections will occur there could be sudden fluctuations in the drones position. A much better and safer method would be to rely on the Mini2’s Vertical Positioning System, assuming there’s enough ambient light for it to work reliably.

Personally, if I were to fly in a similar situation I would be more inclined to use a drone that I could disable the GPS and Magnetometer so as to prevent any un-commanded corrections.