Changed props - very scary flight behaviour

Flydigital

Flydigital

Member
I have 6 stock DJI props 10" x 3.8 on a F550. I decided I needed some spares and without properly looking into it bought some more 10" blades off eBay. They were in fact 10" x 4.5 type but that didn't mean much to me. I swapped them over and took it for a test flight. The behaviour was very odd and dangerous as if the Naza or transmitter were completely screwed up.
On start up as I increased throttle on the ground the revs felt like they were jumping up suddenly so by the time I got it off the ground it would shot up uncontrollably. I would quickly try to bring it down only to have it crash hard. Keeping it in one place too was almost impossible.

All the time it was with 8+ satellite lock. At first I had no thoughts of it being prop related and was thinking I needed to look into my naza and tx / rx configuration. Then for the hell of it I put the old props back on and it flew perfectly.

Is this normal? I'm about to buy some more DJI plastic 10"x3.8 props as back up. They seem really good and reliable. I've had loads of crashes with damaged legs and gimbal but never any problem with the props. They seem indestructible and very forgiving to the point that I think they can reduce damage elsewhere as they flex and absorb impact.

This observation I know is contrary to a lot of comments I have read saying stock props are terrible and that carbon fibre is the way to go. But my experience so far goes against that route.

Did I do something wrong fitting the 10"x4.5? How can that kind of flight behavious be explained?
 

Benjamin Kenobi

Benjamin Kenobi

Easy? You call that easy?
Easy, the 4.5 is 4.5°. You have increased the angle of the props thus increasing the amount of lift they have per rotation and their sensitivity in reaction.

You could probably make them work by lowering the gains quite a bit but you might as well stay with the props that work.

What lipos are you using (3S/4S)?
 




MadMonkey

MadMonkey

Bane of G10
Sounds to me like the new props were badly out of balance. My old F550 flew perfectly on RCTimer 10" props I had spent a couple of hours balancing, but when I switched to the same brand 8" props (unbalanced) it went completely batty. Would barely climb, was extremely unstable, would sometimes drop a foot or two for seemingly no reason, etc.

Checking it with Gemfan 8's resulted in normal flight behavior.
 

Flydigital

Flydigital

Member
Yes they were probably way out of balance - the holes had to be made bigger and very likely not aligned. I've never balanced the stock 550 props before but have seen slight jello now and again on footage. From what I've read that would disappear with proper balancing. So from your experience extreme off balance sounds like the main cause, not the change in prop pitch.
 

kloner

kloner

Aerial DP
i recently went ahead with the newer naza firmwares to get the mac part of it and mine is doing this too...... i'm making bigger prop swaps but none the less, i thought it was naza sorting out the prop difference but now i'm at a loss cause yesterday it did it without a swap...... shoots up, if you do nothing it comes crashing down then it'll rev back up and consistently lock in the altitude after that....

watch this at like :36
 
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