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Downed EAA Plane

 
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deej(at)deej.net
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PostPosted: Sat Mar 13, 2010 12:07 pm    Post subject: Downed EAA Plane Reply with quote
On 3/13/2010 2:26 PM, John Markey wrote:

Quote:
“At least that is the theory at the moment, and I can’t find anything
else wrong. I won’t know for sure for at least several days but will let
ya’ll know when I know,” Jon told us.

Jon followed up later with:

Hi all,

I have confirmed the cause of my power failure last weekend. Long story
short - it was builder error. When you install a locknut on a bolt, you
MUST ensure that there is at least a thread or two coming all the way
thru the nut. If not, it will eventually vibrate free. I am guessing
that I did not look at these nuts after installation due to the
difficulty of seeing anything in this area. No excuse - get a mirror or
whatever is required and visually confirm this type of thing.

Longer story: To mount my EFI controller (computer in a metal box), I
mounted two bolts on the underside of my header tank, two holes in the
controller box, and then put locknuts on each of these bolts. One of
these nuts (and washer) came off the bolt and got down into the
electronics. I assume they bounced around in there for awhile before
finding the ideal location to cause a short which shut everything down.

I have changed my mounting method and now have nutplates inside this "box".

Please; learn from other's mistakes cause you don't have enough time to
make them all yourself!!

Jon Finley

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khorton01(at)rogers.com
Guest
PostPosted: Sat Mar 13, 2010 12:48 pm    Post subject: Downed EAA Plane Reply with quote
On 2010-03-13, at 15:05 , Dj Merrill wrote:

Quote:


On 3/13/2010 2:26 PM, John Markey wrote:

> At least that is the theory at the moment, and I cant find anything
> else wrong. I wont know for sure for at least several days but will let
> yall know when I know, Jon told us.

Jon followed up later with:

Hi all,

I have confirmed the cause of my power failure last weekend. Long story
short - it was builder error. When you install a locknut on a bolt, you
MUST ensure that there is at least a thread or two coming all the way
thru the nut. If not, it will eventually vibrate free. I am guessing
that I did not look at these nuts after installation due to the
difficulty of seeing anything in this area. No excuse - get a mirror or
whatever is required and visually confirm this type of thing.

Longer story: To mount my EFI controller (computer in a metal box), I
mounted two bolts on the underside of my header tank, two holes in the
controller box, and then put locknuts on each of these bolts. One of
these nuts (and washer) came off the bolt and got down into the
electronics. I assume they bounced around in there for awhile before
finding the ideal location to cause a short which shut everything down.

I have changed my mounting method and now have nutplates inside this "box".

Please; learn from other's mistakes cause you don't have enough time to
make them all yourself!!

Jon Finley


I'd also suggest that if a single short can lead to an engine failure that he should review his system design. Even if he wishes to assume that this short cannot physically occur, this occurrence suggests there are possibly other single failures than can kill all power to critical components.

--
Kevin Horton
RV-8
Ottawa, Canada
http://www.kilohotel.com/rv8

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nuckolls.bob(at)aeroelect
Guest
PostPosted: Sat Mar 13, 2010 1:04 pm    Post subject: Downed EAA Plane Reply with quote
Jon followed up later with:

Hi all,

I have confirmed the cause of my power failure last weekend. Long story
short - it was builder error. When you install a locknut on a bolt, you
MUST ensure that there is at least a thread or two coming all the way
thru the nut. If not, it will eventually vibrate free.

<snip>

I have changed my mounting method and now have nutplates inside this "box".

Please; learn from other's mistakes cause you don't have enough time to
make them all yourself!!

I would like to follow up with the idea that
on a TC aircraft, there are NO plain nuts or
combinations of plain nuts and lockwashers used.
Non-locking, threaded fasteners are often supplied
on accessories from the outside world . . .

http://www.aeroelectric.com/Pictures/Contactors/Kilovac_EV200_contactor.jpg

http://www.aeroelectric.com/Pictures/Contactors/s701-2.jpg

http://aeroelectric.com/Pictures/Switches/Toggle_Switch_with_Mold-Captured_Terminals.jpg

http://aeroelectric.com/Pictures/Switches/Flap_Switch.jpg

Every time the system integrator picks up such
devices, there's supposed to be an evaluation of
risk due to "loose hardware". If the risks are
deemed great enough, non-locking fasteners will
be replaced with locking devices -or- doped with
Loc-tite on final assembly.

The tree-visible-threads rule has much more to do
with strength of the assembled fastener (indicates
that the screw is long enough) than with anti-
loosening. The same rule applies to all threaded
fasteners including the locking style nuts and
nutplates.

Where locking threads are not possible or practical,
consider still longer screws with a jamb-nut installed
on top of the structural nut. Further, a thread locker
that can be easily disassembled can go a long way
toward insuring joint integrity. Super-glue works
nice. It's thin and wicks into an already assembled
set of threads.

Bob . . .

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