I'm Joshua Bardwell and you're going to
learn something today there's a claim
that's going around Facebook that
betaflight 317 has a failsafe bug that
if you're using air mode then failsafe
doesn't work right and people are
claiming that the props have spun and
injured themselves oh all kinds of
Horrors Horrors betaflight has a bug oh
my gosh yeah well you know what turns
out you can't believe everything you
read on Facebook and I'm going to prove
it
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folks I'm going to get right to the
point with this one be normally I would
go on and on for a long time but many of
you would tune out and I don't want you
to do that I'm going to get right to the
point of exactly what's going on here
and why betaflight does not have a
failsafe bug this is getting way blown
out of proportion if betaflight did have
a fail safe bug that would be a pretty
big freaking deal
but betaflight is getting unfairly
accused of something that is not true
and I'm going to put a stop to it right
freaking now what happened is a person
claimed that his receiver came
disconnected and when that happened his
quadcopter spun the motors fortunately
for him it was upside down at the time
it spun the motors digging a hole into
the ground and he was able to reproduce
it every time he unplugged his receiver
from the flight controller this time
with the props off on the bench the quad
cter would not go into fail safe the
motors would
Spin and he also dug further into this
and found that when he had air mode
enabled as a
mode then everything worked correctly
but when he had air mode enabled as a
feature in the command line then
failsafe didn't work now here's what
actually happened this is the bug report
that this person filed on GitHub and he
posted his command line dump and if we
look at his command L dump you'll see
right here feature minus fail safe this
person has disabled Fail Safe in His
quadcopter and if we look at this
comment you can see that he's asked
about that and he says I disabled stage
two fail safe since I wanted the quad to
just drop in fails safe I didn't see
anything in stage two that I needed so
what happened here is that this person
didn't fully understand how fail safe
Works he turned fail safe off and then
surprise surprise when the receiver
disconnected the quadcopter Motors kept
spinning he turned fail save off of
course the quadcopter did exactly what
it was told to do that's not a bug now
you could certainly argue why does betaf
flight even let you turn fail safe
should you ever even be able to turn
fail safe off I think that's a good
question but the fact remains that betaf
flight gives you the option to turn fail
safe off and if you choose to use that
option then don't be surprised when fail
safe doesn't work anymore but the
question that got everybody interested
in this topic and I think look what made
everybody convinced that this must be a
bug is why did fail safe seem to work
correctly when air mode was configured
in the modes tab but not work correctly
when air mode was configured as a
feature in the command line and I'm
going to tell you the answer to that we
got to go a little bit deeper into the
features here remember that fail safe
consists of two stages when the signal
is First lost the quadcopter goes into
stage one fail safe and in this setting
the channels are held and well the
default is that the role pitch and yaw
channels are centered and the throttle
is held low we go to low throttle the
idea of stage one fail safe is that if
you have a very quick interruption in
radio connectivity we don't want to just
dump the quad in the dirt the minute
there's a TIN Tiny microsc of disrupted
connectivity so we go into fail stage
one fail safe and during stage one if
the signal comes back the quadcopter
will go back to normal operation so we
get a little bit of Grace time to try
and recover the signal and then after
stage one fail safe time times out we go
into stage two fail safe and that's
where the quadcopter completely shuts
down and dumps itself in the dirt the
reason that fail safe appeared to work
correctly when air mode was set up in
the modes tab goes back to the fact that
the user was using motor stop now motor
stop is an option that causes the motors
not to spin when the quadcopter is armed
if the throttle is all the way down when
the quadcopter went into stage one fail
safe the default position for the
throttle channel was zero and and
therefore motor stop stopped the motors
it looked like the quadcopter
successfully went into stage two fails
safe but in fact it didn't because he
disabled it the reason that fail safe
appeared to work incorrectly when air
mode was enabled as a feature from the
command line goes back to the fact that
air mode overrides motor stop so as long
as air mode is active the motors will
not stop spinning regardless of the
throttle position so when the quad cter
went into stage one fail safe
the throttle went to zero but the motors
kept spinning because air mode was
active and the quadcopter never went
into stage2 fail safe because the user
disabled it therefore the motors just
kept spinning forever there's one other
question that stands out though which is
why did the why did air mode not
override motor stop when we had air mode
on the modes Tab and the reason for that
it just so happens that when the quad
cuptor went into stage one fail safe and
all the channels went to their of
default positions it so happens that the
default position for the aux channel
that this user had air mode on was to
disable air mode so the net effect was
that when the quadcopter went into stage
one fail safe air mode was disabled
therefore motor stop became active again
and the motor stopped spinning so the
takeaway of this is don't disable fail
safe you freaking
numbnuts and if you do disable fail safe
don't blame beta flight when your
quadcopter keeps spinning its Motors
after you disconnect the receiver that's
what you told it to
do happy
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flying