Today's Message Index:
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1. 05:41 AM - Re: hypothetical question (Eric M. Jones)
2. 06:24 AM - Re: Accident library addition (racerjerry)
3. 01:44 PM - Re: Contactors (Bill Allen)
4. 01:48 PM - Re: Re: EXP 2 Bus workaround (Sacha)
5. 02:02 PM - Re: Contactors (Eric M. Jones)
Message 1
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| Subject: | Re: hypothetical question |
Rob,
If you tried to fly from NY to Paris using a magnetic compass in 1927, you'd probably not make it. Lindbergh's primary navigation device was an "Earth Inductor Compass" see: http://en.wikipedia.org/wiki/Earth_inductor_compass
I stand by what I said. A magnetic compass is a pretty weak tool for long-distance
navigation. On aircraft, the pilot steers compass courses, but aerial navigation
depends on making corrections to account for all sorts of disturbances
from the straight line course.
As you approach the magnetic poles, the magnetic compass becomes worthless, when
you cross the equator, the compensators have to be flipped. Then there are the
dozen compass errors they teach in ground school.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=411576#411576
Message 2
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| Subject: | Re: Accident library addition |
Simplicity does have its virtues, especially when things start going to hell.
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=411581#411581
Message 3
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Erics suggestion that a mechanical master switch be considered over a
"solenoid" contactor seems to have merit.
On small OBAM aircraft one is always looking for ways to introduce a weight
saving synergy.
I am reworking the panel on my LongEz with a Dynon Skyview and can see
that my current consumption will reduce using modern avionics.
This then opens up the possibility of removing the 40amp alternator from
the aft of my Lycoming (worst place for weight on a pusher) and replacing
it with a 20amp unit in place of one magneto, and with a (B&C SD20) 20amp
unit, one scrutinises all consumers to reduce appetites where possible.
While populating my electrical load schedule, I was taken aback to see that
the master contactor takes a constant 2amps. That would make it the most
hungry consumer of watts in my aircraft, 10% of my alternators output going
to keep the master latched.
Thus I'm struggling to see why I should not use a mechanical master along
the lines of that suggested by Eric; (
http://www.flamingriver.com/index.php/products/c0015/s0001/FR1013) particularly
as I'm at the "clean sheet" stage. And I've had an electrical master fail
on a certified aircraft (PA30).
Am I missing something here?
Bill Allen
LongEz160
N99BA
On 27 October 2013 17:52, Eric M. Jones <emjones@charter.net> wrote:
> emjones@charter.net>
>
> The requirement for a main battery contactor comes from the FAA's
> requirement to have the main battery disconnected "by one hand" in the
> event of a forced landing. Cutting off the main source of electrical energy
> should reduce the chance of ignition one supposes.
>
> NASCAR and various racing groups have the same problem but they usually
> have decided that a contactor failure is to be avoided by the elimination
> of electrical coil-type contactors, instead choosing rugged mechanical
> switches like "Flaming River Battery Switches".
>
> So keep in mind:
>
> 1) A contactor won't fail if you don't have one.
> 2) A contactor by regulations only has to open, not close. Sort of like a
> parachute.
> 3) Really big switches can be used instead of small switches and
> contactors. My Grandfather's Chevy had a starter footswitch. Still seems
> like a good idea.
>
> --------
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge, MA 01550
> (508) 764-2072
> emjones(at)charter.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=411531#411531
>
>
Message 4
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| Subject: | Re: EXP 2 Bus workaround |
If the prop is windmilling then the starter isn't needed for a
restart. All you need is to provide fuel and spark, it already turning.
OK, thanks, it makes sense to me now.
Sacha
Do not archive
Message 5
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Bill,
Be aware that the main contactor is best replaced by a big switch in the same location.
That is, a remote actuator (like a long actuator rod) is best. Flaming
River sells these, but you can make one. Since flaps and ailerons and rudders,
etc. use remote mechanical actuators, most builders can do something like this.
Remember you only have to have the ability to turn OFF the battery.
Harbor Freight sells the big switches too. Roll your own actuator.
There comes a time in designing a big airplane when contactors are necessary, but
small single engine homebuilts probably don't need them.
Since FAA regulations are to turn OFF the battery in an emergency, one might add
some contacts to turn ON the ELT, turn off the fuel, etc. when one emergency
T-handle is pulled.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=411630#411630
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