Another dead stick landing. Same old
causes. Fortunately no fatalities....this time.
Let's pretend you are the copilot. You've been
flying along for 10 minutes. When the pilot says: "Hey Bob, how about giving
me 150 times as much fuel right now." You'd say:"WHAT?!! You are
crazy, that will shut down the engine!"
Pilot:" Oops, my bad. O2 and egt's are normal.
My mistake"
Does that sound far fetched? Nope. It happens a
couple times a year. Often it's a case where the pilot inadvertently drives
the ecu to super lean condition. Engines suddenly quits. Let's use your
home pc as an example. You tell the pc to delete all files on your hard
drive. It recognizes this is most unusual and could be catastrophic. So it
says:"Are you sure you want to wipe out hard drive? This could be
fatal"
Every failure has more than one cause. Yes, the
pilot inadvertently flipped the "cold start" switch when he was reaching for
his gps. Was it Ed last year who inadvertently rotated the mixture to full
lean? Last year Keith's passenger bumped the ecu mixture knob
while getting in the plane. So, yes, Ed, Keith, and Dave all made the
same mistakes. They placed a switch capable of shutting down the engine in
the wrong area of the instrument panel. End of story? NO!
As soon as one of these ECU suppliers adds the
"Are you sure?" logic, then all of these failures disappear. Pretty simple
logic statement. Actually, there are a whole bunch of ways this can be
handled. I had to do this type of programming with industrial plc's because
these same "oops" were so common. Think about this. If engine has been
running for more than 5 minutes, only allow small mixture changes. Never
enough to shut down engine. So let's say that 100 will shut down engine,
then we only allow a change of 20 each minute.
I think the ECU providers recognize builder
error. "Whew! Not MY problem." They don't ask: "Is there something I
can do to save lives?" If they make these simple changes, then
every single plane is no longer sensitive to these common "oops" scenarios.
So yes, if Dave moves his switch, HE will be safer. But if the ECU
supplier makes this simple programming change, then every single plane will
be safer. Real world mistakes will no longer shut down the engine.
I want these suppliers to be successful. I want
fewer plane crashes. But it's not going to happen unless you guys
(privately) encourage these simple changes.
This group is making good progress on failure
reduction. There are a handful of ecu changes that will really make a
difference. Please pursue! Question question question.
-al wick
----- Original Message -----
Sent: Sunday, March 14, 2010 7:10
AM
Subject: [FlyRotary] Re:
Ut-Oh...
I know Dave or Jon wouldn't phrase it this way but I've
already received a number of messages from others about these two recent
in-flight power failures due to EC2 issues.
Jon's was due to
a loose mounting nut inside the EC2 that shorted the main power input
filter to ground and burned open both foils from the 2 power input
pins. How lucky was that.
Anyway, at the risk of
sounding defensive, I thought I'd share my response to one of them that
suggested changing the EC2 case to an external mount of some sort.
I'm sure there are scores of messages on the way urging me to place switch
guards on the cold start switch : )
REPLY
Hello
----------
I'm aware of the failure and have the unit here for
repair.
Like a thousand other critical details in
building an aircraft, it is not possible to explicitly spell out all of
them. The precise method and hardware used to accomplish it are not
part of the EC2 or the instructions. The first paragraph of the
installation guide does say the following:
"Needless to
say, the quality of installation is just as important as the quality of
the hardware itself. It is not practical to include a
course on proper electrical wiring practices in these installation
instructions, but it is imperative that proper wiring techniques be
employed during the installation of the EC2."
It was my thought
that avoiding the presence of loose metal objects inside an electrical
device that your life depends on fell into the category of "needless
to say".
Nevertheless, a cautionary note might well be worth
adding. As also stated in the first paragraph of the
instructions,
" I want your project
to succeed and your life to be a long and happy one. "