[NSRCA-discussion] Arming Switch

[Scott McHarg]

I would definitely like to point out that Peter's examples are exactly why
the proposed rule was written.  We aren't as concerned about when the pilot
has control of the aircraft in the ready box or on the flight line but what
happens after the flight when the pilot is distracted by the judges wanting
to talk or a fellow competitor asks how you did.  The pilot is no where
around the plane and the caller has control of the aircraft.  Some of us
have dedicated callers and know the airplane as well as you know your own.
Most folks run around trying to find someone to call for their next
flight.  When this is the case, rarely will that individual stand there
with their hands on your plane waiting for you to come over and disarm it
nor will they reach inside your plane to disconnect your batteries for fear
of doing it wrong or causing damage.  When the pilot is distracted and not
fully paying attention to their aircraft is when something tends to go
wrong.

Y'all know the saying, "It's not me I'm worried about, it's the other
people"?  This easily applies to the "other people" around you at every
competition.  There's enough nerves going on at a competition to rattle
anyone.  We all make mistakes.  We are trying to find a way to prevent one
that could really do some damage to human lives.

On Mon, Feb 13, 2012 at 9:30 AM, Peter Vogel <vogel.peter at gmail.com> wrote:

> From the accidents I've seen or heard of, the issue is not a failure
> before takeoff, but rather a failure after landing (ESC already armed) or a
> pilot mishap that results in an unintentional bump of the throttle lever
> (neck strap, coat, etc)
>
> Peter+
>
> Sent from my iPhone4S
>
> On Feb 13, 2012, at 7:18 AM, Bob Richards <bob at toprudder.com> wrote:
>
> Keith,
>
> My gut instinct is to agree with you on this, but I have to wonder what is
> the possibility that there would be a failure mode where the controller
> could go full throttle without an input from the receiver. For the
> brushless controllers, the micro in the controller must be working properly
> for the motor to run - period - since it has to sense the feedback from the
> motor and operate the outputs in proper phase for the motor to run at all
> (this would be a different discussion if we were talking about *brushed*
> controllers). The more likely failure would be that it applies power to one
> or more motor wires - not pulsed - that would do little more than heat up
> the motor and burn a winding, but not turn the motor over.
>
> Is it possible for the micro think there is a full-throttle input when
> there isn't? Most controllers that I know of will not arm if it powers up
> with anything other than a low-throttle signal from the receiver. It has to
> sense a low-throttle signal that then transitions to something else before
> it starts the motor turning. Is this a possible failure mode for an ESC - I
> don't know since I don't know any specifics of the circuitry or firmware
> programming of ESCs, but I seriously doubt this can happen and if it can,
> the likelyhood would be extremely low.
>
> Of course, not having the battery connected to anything is safe. Safer yet
> is to just stay at home, but we have to decide what is an acceptable risk.
>
> Bob R.
>
>
>
>
> --- On *Sun, 2/12/12, Keith Black <tkeithblack at gmail.com>* wrote:
>
>
>
> Dave, you're points are correct, but you're not taking into account a
> malfunction of the speed controller itself. They have been know to
> malfunction, so the safest approach, as Earl suggests, is to assume that
> anytime the battery is connected to the controller the motor may go to full
> throttle. Until you unplug the battery the thing is hot and dangerous
> regardless of your fail safe or switches on the transmitter.
>
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-- 
*Scott A. McHarg*
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