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nuckolls.bob(at)aeroelect
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 Posted: Tue Jul 03, 2012 6:28 am Post subject: Old hangar tales . . . |
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-------------------- Original Query to Garmin -------------------
Good morning,
By way of introduction, I'm an electrical engineer retired
from a 45 year career in aviation related electrics and
electronics. My last 13-year stint was with Hawker-Beechcraft
where most of my job focused on environmental robustness and
DO-160 certification issues. The last 5 years at HBC included
the duties of Lead Subject Matter Expert for Electrical Systems.
A client of mine forwarded an email from your address wherein
it was suggested that certain 'spikes' present on the electrical
system during engine cranking might be damaging to your SL-40
product.
I was surprised by this assertion for two reasons:
(1) DO-160 Qualification Protocols have evolved over the last 50+
years to assist designers and manufacturers in the production
of products immune to the worst case stresses that one might
expect on the DC power system of an airplane (or any other vehicle).
(2) In years of watching instrumented DC power conditions under
all operating conditions on everything from Cessna 150s through
the Hawker 800, I've never had occasion to capture a transient event
(other than gross over-voltage) that would offer a threat
to an artfully crafted and qualified piece of avionics. During
engine cranking, the bus is remarkably free of transients that
exceed energy levels to which every qualified device is subjected
during DO-160 testing.
The assertion made in your email to my client gives one pause
to wonder if Garmin is (1) aware of some design deficiency that would
make the product vulnerable to normal and expected DC bus transients
or (2) some new and heretofore undiscovered threat has been identified
that exceeds DO-160 qualification requirements.
I've been teaching my students that we no longer need be
concerned about such matters for devices qualified to DO-160.
Indeed, I've either designed or been cognizant of dozens of
'fragile', micro-processor based devices which are connected
to the ship's main bus under all conditions including
engine cranking. None of these devices requires extra-ordinary
protection for start-up transients. I'm curious about differences
in the SL-40 that prompts Garmin to assert some value in
disconnecting the radio during engine cranking.
The idea is contrary to my own understanding of the physics
involved and argues with what I have been teaching in my
classes for the last 25 years. If I'm in error, I'd really
need to be aware of any enlightenment one of your engineers
might offer. Thanks!
Kindest regards,
Robert L. Nuckolls, III
AeroElectric Connection
P.O. Box 130
Medicine Lodge, Kansas 67104
(316)209-7528
--------------- Response received 7-3-12 ------------
Service Record Details
Service Record Number: 88142
Subject: Service Record Number 87343
Last update: 07/02/2012 08:03:23
Name:
Phone:
Email: nuckolls.bob(at)aeroelectric.com
Brief description of the problem:
It is true that system is designed to operate through all DO-160 testing However I would recommendd not running the radio during engine start unless you need to for some other requirement.
During engine start you typically want as much battery power available to the starter motor as possible, so unless you need the radio at that time, it make more sense to turn it off.
Cranking the engine reduces the buss voltage significantly; in some extremes, this could cause a brown out condition, which causes the radio to reset This is not a big deal since the boot time is about one second in the SL40.
It is not likely that any failure of the system could be traced back to an odd voltage spike, hence if the system were under warranty Garmin would pay to repair it, but if it was out of warranty the customer would need to pay that bill.
This is similar to adding a FAN to some of the other Garmin equipment, like the GTX330 transponder. It is not required, but it is a good idea.
If any of the above information is incorrect, please reply to this email with corrected contact information. You may also contact Garmin Aviation Product Support at 866-739-5687 and provide the information to the agent who assists you. For the latest news about Garmin products and services, please visit our Web site at www.garmin.com.
----------------- Commentary -------------------
I was initially tempted to engage this writer in further
conversation but really don't have time for it. Garmin's
response is typical of exchanges I've had with avionics
OEMs in years gone by, "Yeah, we're fully DO-160 compliant
but there's nothing like the belt/suspenders approach to
protecting one's radios from the "odd voltage spike".
To date, none were willing/able to come forward with an
origin, amplitude, duration, or source impedance for any
"odd voltage spike" that would (1) exceed DO-160 requirements
or (2) justify negating a warranty.
Similarly, I've been aware anecdotally of dozens of claims
by some bench technicians who have asserted that "a spike
got it" but without offering a clue as to where that spike
came from and just how large it had to be to trash the
radio.
'nuf said
Bob . . .
[quote][b]
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Tue Jul 03, 2012 9:43 am Post subject: Old hangar tales . . . |
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Bob, It seems it's still easy to baffle with BS rather than blind with brilliance. Garmin's answer is pretty much what I used to get when I questioned some edict by my Grandmother, "Because I said so, that's why".
Rick Girard
On Tue, Jul 3, 2012 at 9:27 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | -------------------- Original Query to Garmin -------------------
Good morning,
By way of introduction, I'm an electrical engineer retired
from a 45 year career in aviation related electrics and
electronics. My last 13-year stint was with Hawker-Beechcraft
where most of my job focused on environmental robustness and
DO-160 certification issues. The last 5 years at HBC included
the duties of Lead Subject Matter Expert for Electrical Systems.
A client of mine forwarded an email from your address wherein
it was suggested that certain 'spikes' present on the electrical
system during engine cranking might be damaging to your SL-40
product.
I was surprised by this assertion for two reasons:
(1) DO-160 Qualification Protocols have evolved over the last 50+
years to assist designers and manufacturers in the production
of products immune to the worst case stresses that one might
expect on the DC power system of an airplane (or any other vehicle).
(2) In years of watching instrumented DC power conditions under
all operating conditions on everything from Cessna 150s through
the Hawker 800, I've never had occasion to capture a transient event
(other than gross over-voltage) that would offer a threat
to an artfully crafted and qualified piece of avionics. During
engine cranking, the bus is remarkably free of transients that
exceed energy levels to which every qualified device is subjected
during DO-160 testing.
The assertion made in your email to my client gives one pause
to wonder if Garmin is (1) aware of some design deficiency that would
make the product vulnerable to normal and expected DC bus transients
or (2) some new and heretofore undiscovered threat has been identified
that exceeds DO-160 qualification requirements.
I've been teaching my students that we no longer need be
concerned about such matters for devices qualified to DO-160.
Indeed, I've either designed or been cognizant of dozens of
'fragile', micro-processor based devices which are connected
to the ship's main bus under all conditions including
engine cranking. None of these devices requires extra-ordinary
protection for start-up transients. I'm curious about differences
in the SL-40 that prompts Garmin to assert some value in
disconnecting the radio during engine cranking.
The idea is contrary to my own understanding of the physics
involved and argues with what I have been teaching in my
classes for the last 25 years. If I'm in error, I'd really
need to be aware of any enlightenment one of your engineers
might offer. Thanks!
Kindest regards,
Robert L. Nuckolls, III
AeroElectric Connection
P.O. Box 130
Medicine Lodge, Kansas 67104
[url=tel:%28316%29209-7528](316)209-7528[/url]
--------------- Response received 7-3-12 ------------
Service Record Details
Service Record Number: 88142
Subject: Service Record Number 87343
Last update: 07/02/2012 08:03:23
Name:
Phone:
Email: nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)
Brief description of the problem:
It is true that system is designed to operate through all DO-160 testing However I would recommendd not running the radio during engine start unless you need to for some other requirement.
During engine start you typically want as much battery power available to the starter motor as possible, so unless you need the radio at that time, it make more sense to turn it off.
Cranking the engine reduces the buss voltage significantly; in some extremes, this could cause a brown out condition, which causes the radio to reset This is not a big deal since the boot time is about one second in the SL40.
It is not likely that any failure of the system could be traced back to an odd voltage spike, hence if the system were under warranty Garmin would pay to repair it, but if it was out of warranty the customer would need to pay that bill.
This is similar to adding a FAN to some of the other Garmin equipment, like the GTX330 transponder. It is not required, but it is a good idea.
If any of the above information is incorrect, please reply to this email with corrected contact information. You may also contact Garmin Aviation Product Support at [url=tel:866-739-5687]866-739-5687[/url] and provide the information to the agent who assists you. For the latest news about Garmin products and services, please visit our Web site at www.garmin.com.
----------------- Commentary -------------------
I was initially tempted to engage this writer in further
conversation but really don't have time for it. Garmin's
response is typical of exchanges I've had with avionics
OEMs in years gone by, "Yeah, we're fully DO-160 compliant
but there's nothing like the belt/suspenders approach to
protecting one's radios from the "odd voltage spike".
To date, none were willing/able to come forward with an
origin, amplitude, duration, or source impedance for any
"odd voltage spike" that would (1) exceed DO-160 requirements
or (2) justify negating a warranty.
Similarly, I've been aware anecdotally of dozens of claims
by some bench technicians who have asserted that "a spike
got it" but without offering a clue as to where that spike
came from and just how large it had to be to trash the
radio.
'nuf said
Bob . . .
| Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
|
|
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
[quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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_________________
The smallest miracle right in front of you is enough to make you happy.... |
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JLuckey(at)pacbell.net
Guest
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| Posted: Tue Jul 03, 2012 10:47 am Post subject: Old hangar tales . . . |
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These non-answer CYA responses are kind of frustrating. It seems as though these answers get filtered thru the legal dept before getting to us – thus omitting the details we are seeking. We all know that there are several engineers on their staff who designed the power supplies and have intimate knowledge of this subject. Why can’t we get a response from one of them.
Anecdote:
I recently queried a manufacturer regarding performance of one of their products in a specific environment (I’m being deliberately vague). The person on the other end of the phone kept saying “we have not tested for that condition”. This person was obviously technical in nature, and I got the feeling that he knew more info but was restricted by corporate policy from giving me anything more than the canned response. Frustrating!
Referring back to the previous topic “What’s wrong w/ this circuit..”. It occurs to me that using isolation diodes in that manner would help mitigate “brown-out” condition on the main bus. If you are cranking w/ Batt A and feeding the bus w/ both Batts A & B, the Batt B would be able to maintain bus voltage when Batt A’s voltage sags during crank. Food for thought…
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Richard Girard
Sent: Tuesday, July 03, 2012 10:43
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: Old hangar tales . . .
Bob, It seems it's still easy to baffle with BS rather than blind with brilliance. Garmin's answer is pretty much what I used to get when I questioned some edict by my Grandmother, "Because I said so, that's why".
Rick Girard
On Tue, Jul 3, 2012 at 9:27 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
-------------------- Original Query to Garmin -------------------
Good morning,
By way of introduction, I'm an electrical engineer retired
from a 45 year career in aviation related electrics and
electronics. My last 13-year stint was with Hawker-Beechcraft
where most of my job focused on environmental robustness and
DO-160 certification issues. The last 5 years at HBC included
the duties of Lead Subject Matter Expert for Electrical Systems.
A client of mine forwarded an email from your address wherein
it was suggested that certain 'spikes' present on the electrical
system during engine cranking might be damaging to your SL-40
product.
I was surprised by this assertion for two reasons:
(1) DO-160 Qualification Protocols have evolved over the last 50+
years to assist designers and manufacturers in the production
of products immune to the worst case stresses that one might
expect on the DC power system of an airplane (or any other vehicle).
(2) In years of watching instrumented DC power conditions under
all operating conditions on everything from Cessna 150s through
the Hawker 800, I've never had occasion to capture a transient event
(other than gross over-voltage) that would offer a threat
to an artfully crafted and qualified piece of avionics. During
engine cranking, the bus is remarkably free of transients that
exceed energy levels to which every qualified device is subjected
during DO-160 testing.
The assertion made in your email to my client gives one pause
to wonder if Garmin is (1) aware of some design deficiency that would
make the product vulnerable to normal and expected DC bus transients
or (2) some new and heretofore undiscovered threat has been identified
that exceeds DO-160 qualification requirements.
I've been teaching my students that we no longer need be
concerned about such matters for devices qualified to DO-160.
Indeed, I've either designed or been cognizant of dozens of
'fragile', micro-processor based devices which are connected
to the ship's main bus under all conditions including
engine cranking. None of these devices requires extra-ordinary
protection for start-up transients. I'm curious about differences
in the SL-40 that prompts Garmin to assert some value in
disconnecting the radio during engine cranking.
The idea is contrary to my own understanding of the physics
involved and argues with what I have been teaching in my
classes for the last 25 years. If I'm in error, I'd really
need to be aware of any enlightenment one of your engineers
might offer. Thanks!
Kindest regards,
Robert L. Nuckolls, III
AeroElectric Connection
P.O. Box 130
Medicine Lodge, Kansas 67104
[url=tel:%28316%29209-7528](316)209-7528[/url]
--------------- Response received 7-3-12 ------------
Service Record Details
Service Record Number: 88142
Subject: Service Record Number 87343
Last update: 07/02/2012 08:03:23
Name:
Phone:
Email: nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)
Brief description of the problem:
It is true that system is designed to operate through all DO-160 testing However I would recommendd not running the radio during engine start unless you need to for some other requirement.
During engine start you typically want as much battery power available to the starter motor as possible, so unless you need the radio at that time, it make more sense to turn it off.
Cranking the engine reduces the buss voltage significantly; in some extremes, this could cause a brown out condition, which causes the radio to reset This is not a big deal since the boot time is about one second in the SL40.
It is not likely that any failure of the system could be traced back to an odd voltage spike, hence if the system were under warranty Garmin would pay to repair it, but if it was out of warranty the customer would need to pay that bill.
This is similar to adding a FAN to some of the other Garmin equipment, like the GTX330 transponder. It is not required, but it is a good idea.
If any of the above information is incorrect, please reply to this email with corrected contact information. You may also contact Garmin Aviation Product Support at [url=tel:866-739-5687]866-739-5687[/url] and provide the information to the agent who assists you. For the latest news about Garmin products and services, please visit our Web site at www.garmin.com.
----------------- Commentary -------------------
I was initially tempted to engage this writer in further
conversation but really don't have time for it. Garmin's
response is typical of exchanges I've had with avionics
OEMs in years gone by, "Yeah, we're fully DO-160 compliant
but there's nothing like the belt/suspenders approach to
protecting one's radios from the "odd voltage spike".
To date, none were willing/able to come forward with an
origin, amplitude, duration, or source impedance for any
"odd voltage spike" that would (1) exceed DO-160 requirements
or (2) justify negating a warranty.
Similarly, I've been aware anecdotally of dozens of claims
by some bench technicians who have asserted that "a spike
got it" but without offering a clue as to where that spike
came from and just how large it had to be to trash the
radio.
'nuf said
Bob . . . | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-Listtp://forums.matronics.com_blank">http://www.matronics.com/contribution |
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
0123456789 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
0 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
1 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
2 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
3 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
4 | Quote: | | ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List |
5
No virus found in this message.
Checked by AVG - www.avg.com
07/03/12 [quote][b]
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