Today's Message Index:
----------------------
1. 07:02 AM - Strobe Switch - New evidence (Charles Brame)
2. 07:35 AM - Re: Strobe Switch - New evidence (R&J. Curtis)
3. 07:50 AM - Re: Strobe Switch - New evidence (Sprocket)
4. 12:03 PM - Re: Strobe Switch - New evidence (Bill Watson)
5. 12:30 PM - Re: Schematic Z-17 questions (Robert L. Nuckolls, III)
6. 01:05 PM - Re: Schematic Z-17 questions (Peter Pengilly)
Message 1
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Subject: | Strobe Switch - New evidence |
Bob, et. al.,
Once again my strobes quit working. Suspecting another Carling switch failure,
that's what I checked first. To my surprise, the switch and its connections were
pristine. However, the other end of the power line, a Molex connector at the
Whelen Strobe Power Pack, was the problem. The power pin had overheated to the
point where the Molex connector was blackened and melted around the pin. The
other pin on the connector, a ground wire, was not affected. Replaced the Molex
and the system is back in operation. The mystery deepens.
Charlie Brame
RV-6A N11CB
San Antonio
Message 2
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Subject: | Re: Strobe Switch - New evidence |
>
> Once again my strobes quit working. Suspecting another Carling switch
> failure, that's what I checked first. To my surprise, the switch and its
> connections were pristine. However, the other end of the power line, a
> Molex connector at the Whelen Strobe Power Pack, was the problem. The
> power pin had overheated to the point where the Molex connector was
> blackened and melted around the pin. The other pin on the connector, a
> ground wire, was not affected. Replaced the Molex and the system is back
> in operation. The mystery deepens.
Did you check the old connector to see if (1) there
were any broken strands on the connector going into
either side? (2) Were the wires on the pins
stripped properly and a nice gas tight crimped
connection? (3) Did there appear to be any corrosion
on the pins? Sometimes it is difficult to see these things
after the connection is burned up, but it is worth a look.
Roger
Message 3
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Subject: | Re: Strobe Switch - New evidence |
Not a mystery at all. The strobe power pack is a constant-power device, which
means that as the input voltage drops, the load current increases. If you have
a resistive switch or connection, you'll get what's called 'thermal runaway'.
This leads to burnt or charred switches, contacts or connectors.
When I first discovered the problem about 7 years ago, It was the Carling switch
rivets that were the root cause, but any deteriorating contact can cause it.
Make it an annual inspection item for the strobe connectors and switches. Check
your landing and taxi light circuits as well.
Vern
===================================================
Sent from my iThing. It is responsible for all gramma and typo terrors.
> On May 19, 2014, at 7:01 AM, Charles Brame <chasb@satx.rr.com> wrote:
>
>
> Bob, et. al.,
>
> Once again my strobes quit working. Suspecting another Carling switch failure,
that's what I checked first. To my surprise, the switch and its connections
were pristine. However, the other end of the power line, a Molex connector at
the Whelen Strobe Power Pack, was the problem. The power pin had overheated to
the point where the Molex connector was blackened and melted around the pin.
The other pin on the connector, a ground wire, was not affected. Replaced the
Molex and the system is back in operation. The mystery deepens.
>
> Charlie Brame
> RV-6A N11CB
> San Antonio
>
>
>
>
Message 4
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Subject: | Re: Strobe Switch - New evidence |
Not sure what strobe power supply you are using but I changed from one
that many homebuilders were using (Plane Power?) to a Nova Electronics
XPAK604X unit. It looks and mounts just like my old unit but it
separates the switch from the power circuit with what I assume is an
internal relay.
I burned out a switch terminal on my original installation. I didn't
fully understand the reasons but I swapped the original out for the Nova
unit. It significantly shortened the power leads from over 10 feet to
<2' (RV10).
Just a thought.
On 5/19/2014 10:01 AM, Charles Brame wrote:
>
> Bob, et. al.,
>
> Once again my strobes quit working. Suspecting another Carling switch failure,
that's what I checked first. To my surprise, the switch and its connections
were pristine. However, the other end of the power line, a Molex connector at
the Whelen Strobe Power Pack, was the problem. The power pin had overheated to
the point where the Molex connector was blackened and melted around the pin.
The other pin on the connector, a ground wire, was not affected. Replaced the
Molex and the system is back in operation. The mystery deepens.
>
> Charlie Brame
> RV-6A N11CB
> San Antonio
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
>
>
Message 5
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Subject: | Re: Schematic Z-17 questions |
At 10:27 AM 5/19/2014, you wrote:
>You mention a light weight lithium battery. This is the second time
>I have seen something about use of lithium batteries in airplanes. I
>would like to hear more about things like reliability, things to be
>aware of, the actual storage capacity (rather than just cranking
>amps) and of course, after the 787 battery issues, fire potential.
>The idea using a 3 or 4 pound battery is very appealing.
There's a 4-part series coming out in Kitplanes
about batteries with an emphasis on evaluation of
lithium products for suitability to task in aircraft.
Turns out that not all lithium products are the
same . . . and it goes deeper than selection of
the least-hazardous chemistry.
MOST commercial off the shelf examples have no
battery management system yet they claim to be
drop-in replacements for lead-acid. The claims
go even further to suggest that a 3# lithium battery
has an 18 ah 'lead acid equivalency' . . . when
the 18 ah battery weighs in at 15 pounds or more.
"Lead acid equivalency" speaks to engine cranking
ability and glosses over shortfalls in CAPACITY.
For a vfr airplane having an engine that is free
of electrical dependencies, one may down-size a
battery with little attention to capacity. If getting
the engine started is your only concern, then the
lithium chemistry can offer some enticing weight
savings.
But if you have any concerns for battery-only
endurance, then be sure the device you pick
has the capacity to meet your alternator-out
endurance requirements.
It also turns out that optimal battery service
life is achieved by cycling the battery's level
of charge between 30 and 90%. By artificially
limiting available energy on a cycle-by-cycle
basis (most hybrid cars do this), then they
battery can last a long time.
Ideally, one never runs the ship's battery
down . . . but it's there if you need it.
So if you set the bus voltage to limit the
battery to 90% of maximum capacity, then
it should last a long time.
But if you ever run it down on purpose or
accidently . . . then maximizing the battery's
serviceability usually calls for recharging
with a battery management system (BMS).
Folks flying the simpler, day-vfr airplanes are
encouraged to experiment with the current offerings
of lithium technology
http://tinyurl.com/nlamrrw
This battery claims to crank as well as a 16-18
a.h lead-acid at one 6th the weight. At that price,
it almost certainly has no internal BMS.
On the other hand, this 2.2 pound battery claims
400+ amps cranking ability . . . and I believe
it is fitted with a full-time, capable battery
management system.
http://tinyurl.com/lcegge5
Bob . . .
Message 6
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Subject: | Re: Schematic Z-17 questions |
There is also a gotcha in cold weather with lithium batteries - they
don't work well (sorry I can't be specific to the type). When the
battery has cold soaked at around freezing it will hardly turn over an
O-360. But, a minute or two after an attempted start - I'm told 5
seconds of trying and barely cranking - the battery will have warmed
itself up and happily spins the engine into life.
Batteries on the firewall will probably be happy for the rest of the day
(and also respond to the hair dryer in the oil door trick for 10 minutes
while pre-flighting). Batteries in the aft fuselage will require the
'failed start' technique each time. No very scientific data or
information on a minimum temperature when this technique doesn't work.
Peter
On 19/05/2014 20:27, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 10:27 AM 5/19/2014, you wrote:
>> You mention a light weight lithium battery. This is the second time I
>> have seen something about use of lithium batteries in airplanes. I
>> would like to hear more about things like reliability, things to be
>> aware of, the actual storage capacity (rather than just cranking
>> amps) and of course, after the 787 battery issues, fire potential.
>> The idea using a 3 or 4 pound battery is very appealing.
>
> There's a 4-part series coming out in Kitplanes
> about batteries with an emphasis on evaluation of
> lithium products for suitability to task in aircraft.
>
> Turns out that not all lithium products are the
> same . . . and it goes deeper than selection of
> the least-hazardous chemistry.
>
> MOST commercial off the shelf examples have no
> battery management system yet they claim to be
> drop-in replacements for lead-acid. The claims
> go even further to suggest that a 3# lithium battery
> has an 18 ah 'lead acid equivalency' . . . when
> the 18 ah battery weighs in at 15 pounds or more.
>
> "Lead acid equivalency" speaks to engine cranking
> ability and glosses over shortfalls in CAPACITY.
> For a vfr airplane having an engine that is free
> of electrical dependencies, one may down-size a
> battery with little attention to capacity. If getting
> the engine started is your only concern, then the
> lithium chemistry can offer some enticing weight
> savings.
>
> But if you have any concerns for battery-only
> endurance, then be sure the device you pick
> has the capacity to meet your alternator-out
> endurance requirements.
>
> It also turns out that optimal battery service
> life is achieved by cycling the battery's level
> of charge between 30 and 90%. By artificially
> limiting available energy on a cycle-by-cycle
> basis (most hybrid cars do this), then they
> battery can last a long time.
>
> Ideally, one never runs the ship's battery
> down . . . but it's there if you need it.
> So if you set the bus voltage to limit the
> battery to 90% of maximum capacity, then
> it should last a long time.
>
> But if you ever run it down on purpose or
> accidently . . . then maximizing the battery's
> serviceability usually calls for recharging
> with a battery management system (BMS).
>
> Folks flying the simpler, day-vfr airplanes are
> encouraged to experiment with the current offerings
> of lithium technology
>
> http://tinyurl.com/nlamrrw
>
> This battery claims to crank as well as a 16-18
> a.h lead-acid at one 6th the weight. At that price,
> it almost certainly has no internal BMS.
>
> On the other hand, this 2.2 pound battery claims
> 400+ amps cranking ability . . . and I believe
> it is fitted with a full-time, capable battery
> management system.
>
> http://tinyurl.com/lcegge5
>
>
> Bob . . .
>
>
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