Revo 3.3 & no Failsafe... WHY!!!!!

[Nitro4910]

You cannot adjust the FS in the Traxxas radio system.
And that's all the built in FS will do, move it back to neutral.
It's all the 2.4 I use does and I have not had a problem out of it, the truck stops soon enough when the throttle servo goes into neutral position.
The one time the battery door dropped off and popped some of the battery's loose it worked like it should, the truck didn't roll very far once the servo went to the idle position.

 

[Rolex]

The one time the battery door dropped off and popped some of the battery's loose it worked like it should, the truck didn't roll very far once the servo went to the idle position.

If the batteries dropped out, the fail safe didn't do anything. It needs the power to work, even if that power is very low.
The only thing that happened in your case is that the return spring pulled back a servo with no power going to it.

 

[Nitro4910]

The battery door "incident" was on the Transmitter so the RX saw it as a loss of signal.
On the truck yah it would have been the TRS that saved it, I went to rechargeable packs for the RX long ago.
I've been thinking of going with a lipo for the TX's but haven't yet as I don't yet have a lipo capable charger.

One thing I've gotten in the habit of doing before I start mine is to turn the TX on and off just to verify the FS moves the servo to neutral in case of lost signal.

 

[Rolex]

The battery door "incident" was on the Transmitter so the RX saw it as a loss of signal.

Gotcha'. Then it worked.
Likewise, always test the servos and the fail safe before running.