Ok, this is the story. I'm new to Betaflight and I've been happily flying my Nazgul 5 for a few weeks now.

After a couple of hard landings yesterday I can not now fly the quad. I can arm it but the motors don't spin.

Error message is "RPMFILTER".
I can see from the motor tab in the Configurator that I have E: 100.00% for telemetry received from the ESCs. I know I need this telemetry for RPMFILTER to work.
I've not changed anything in the configuration from stock (apart to do with swapping out the VTx a while ago which worked fine).
Quad has flown fine for weeks up until yesterday.
I've taken the stack apart looking for any obvious breaks or disconnections. No visible damage.
I've pulled and reconnected cables. No change.

I'm now having troubles just connecting to the Configurator. And when it does connect it occasionally hangs when I change tab with "Waiting for data..."

I'm thinking the FC or the ESC board/component has failed.

Anything easy/obvious I can try before I start replacing parts?

I've ended up replacing the ESC board. All back to working ok now.

So.. I chose a ready built quad for an easy way into 5" quads.. But I've now replaced:
1. The ESC board (due to failure)
2. The VTx (to reduce noise)
3. The camera (so I could use a 3.6mm lens)
Argh!! I suppose at least the FC, receiver and frame are still original.

BTW I was flying from longish wet grass when the ESC failed. I'm now thinking the failure was more down to water shorting out contacts rather than heavy landings. Do I need to do something to water proof my quad?

You can use conformal coating on the parts.

But foremost, avoid flying from wet grass.

Originally Posted by gorro

You can use conformal coating on the parts.

But foremost, avoid flying from wet grass.

Thanks for that conformal coating tip. Got some on order.

I fly from England. There is no dry grass

get or make a landing pad.
bam dry takeoff at least.
ESCs REALLY don't like water, even conformal coated they can freak out/short and die. conformal coating makes it less likely. really does wonders for proofing on everything else, but the esc it's more like water resistance instead of proofing.

I usually run two to three coats of conformal coating on my setups and verify coverage with a handheld UV light I picked up from Amazon.

Not idiot proof, but does help.

I've applied conformal coating and it seems to have done the trick. Only the one coat but I've flown from wet grass a few times and so far so good.. Maybe I'll apply another coat!

Anyway thanks for the info folks. Never even heard of conformal coating before.