[NSRCA-discussion] Arming Switch

Mon Feb 13 07:15:31 AKST 2012

There are approximately 3 people that are an exception to my "rules" for
helping me at a contest or in practice.

My rules to helpers -

Hold the plane "here" and "here".

Don't touch anything else.

When you retrieve the plane and take it back to the pits, stand with 1 foot
in front of the wing next to the fuse, and one foot behind the wing next to
the opposite side of the fuse.

Don't touch anything.

I will disarm when I get back to the plane.

Very little chance for miscommunication.  No chance for the stabs ripping
off if the plane goes to full throttle.  If my helper has to wait for me to
get back to the pits, so be it, the plane is safe.  If my helper is needed
elsewhere, and I don't get to talk with judges or other pilots on the way
back to the pits, so be it, safety is more important.

The exceptions are to my rules are my Dad and Joe Z (I built their planes
identically to mine) and Ken V (who has built more Wistmodel planes than I
have, and uses the exact same methods).

Something no one has pointed out (directly at least) in this thread is that
the overwhelming majority of accidents are going to be caused by human error
(complacency being a big factor) and in many instances, these accidents are
not going to be prevented by any type of safety mechanism.  Most accidents
happen when safety procedures are not followed - intentionally or not.
Being safe requires both a good safety procedure and then using the
procedure.  We do not all think alike, and the "best" procedure is not
likely to be the same in every detail for every one of us.

Regards,

Dave Lockhart

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Scott McHarg
Sent: Monday, February 13, 2012 10:43 AM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Arming Switch

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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