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Inductive Spike from Starter Solenoid

 
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john(at)totten.com
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PostPosted: Wed Feb 08, 2006 2:08 am    Post subject: Inductive Spike from Starter Solenoid Reply with quote

If anyone has a Cessna 185 alternator that goes off line
when the start the engine or retract the (amphib) gear -
then here is why. Your plane does not comply with ACS
SB92-01 and Cessna SEB91-5R1

http://www.caa.is/datadir/bsdata/img/adnotes/93-05-06.pdf

The parts needed to comply are available here

http://www.aircraftspruce.com/pdf/catalog/Cat06413.pdf

The $7 diode abolishes the starter solenoid inductive spike
and starter switch arching that trips the overvoltage relay
in the regulator. Most people that face this problem
misinterpret the problem as 'Load Dump' cause by drop in
the bus voltage from high starter loads. Not so. Disconnect
the starter and operate the solenoid alone - same problem.

The entire plane from the pilot seat forward is supplied
from the firewall solenoid positive terminal so the
solenoids inductive spike goes throughout the plane
including the panel and the regulator. It burns out not
only your avionics (if you don't have an avionics master
switch) but also the contacts in your starter switch so you
can't ground the mags. Thats why your mag check doesn't
drop the rpm - Not good.

The fix is a $7 dollar diode. Of the three C185's that I
have inspected besides mine - none comply with this SEB.

I also put the diode across the solenoid on my hydraulic
pump for the Amphib Floats which also threw the alternator
off line when the gear operated. So thats not a 'Load Dump'
problem either, its an inductive spike.

Call ACS at 602 855 8613. Save yourself the cost of that new
regulator, alternator, battery and huge mechanic bills for
a non-fix..

JohnT


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nuckollsr(at)cox.net
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PostPosted: Wed Feb 08, 2006 6:14 am    Post subject: Inductive Spike from Starter Solenoid Reply with quote

For additional background on this phenonmenon see
http://www.aeroelectric.com/articles/spikecatcher.pdf

Bob . . .
At 01:02 AM 2/8/2006 -0900, you wrote:

Quote:

If anyone has a Cessna 185 alternator that goes off line
when the start the engine or retract the (amphib) gear -
then here is why. Your plane does not comply with ACS
SB92-01 and Cessna SEB91-5R1

http://www.caa.is/datadir/bsdata/img/adnotes/93-05-06.pdf

The parts needed to comply are available here

http://www.aircraftspruce.com/pdf/catalog/Cat06413.pdf

The $7 diode abolishes the starter solenoid inductive spike
and starter switch arching that trips the overvoltage relay
in the regulator. Most people that face this problem
misinterpret the problem as 'Load Dump' cause by drop in
the bus voltage from high starter loads. Not so. Disconnect
the starter and operate the solenoid alone - same problem.

The entire plane from the pilot seat forward is supplied
from the firewall solenoid positive terminal so the
solenoids inductive spike goes throughout the plane
including the panel and the regulator. It burns out not
only your avionics (if you don't have an avionics master
switch) but also the contacts in your starter switch so you
can't ground the mags. Thats why your mag check doesn't
drop the rpm - Not good.

The fix is a $7 dollar diode. Of the three C185's that I
have inspected besides mine - none comply with this SEB.

I also put the diode across the solenoid on my hydraulic
pump for the Amphib Floats which also threw the alternator
off line when the gear operated. So thats not a 'Load Dump'
problem either, its an inductive spike.

Call ACS at 602 855 8613. Save yourself the cost of that new
regulator, alternator, battery and huge mechanic bills for
a non-fix..

JohnT

--



Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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