Today's Message Index:
----------------------
1. 04:06 AM - Re: 14V or 28V (Carlos Trigo)
2. 05:09 AM - Re: Alternators on aircraft (racerjerry)
3. 05:16 AM - Re: 14V or 28V (R. curtis)
4. 05:29 AM - Re: 14V or 28V (Henador Titzoff)
5. 07:08 AM - Re: 14V or 28V (Charlie England)
6. 07:10 AM - Multi-hop wire sizing? (donjohnston)
7. 07:53 AM - Re: 14V or 28V (Eric M. Jones)
8. 09:12 AM - Re: Re: 14V or 28V (Robert L. Nuckolls, III)
9. 09:18 AM - Re: Multi-hop wire sizing? (Robert L. Nuckolls, III)
10. 11:57 AM - Re: COM radio/intercom wiring problem... (Peter Pengilly)
11. 12:42 PM - Re: COM radio/intercom wiring problem... (Michael Burbidge)
12. 02:25 PM - Re: Low voltage indicator with dual alternators (Bill Watson)
13. 03:11 PM - Re: Multi-hop wire sizing? (donjohnston)
14. 03:14 PM - Re: COM radio/intercom wiring problem... (Daniel Hooper)
15. 03:25 PM - Re: Multi-hop wire sizing? (Bill Maxwell)
16. 04:19 PM - Re: COM radio/intercom wiring problem... (Robert L. Nuckolls, III)
17. 04:36 PM - Re: COM radio/intercom wiring problem... (Daniel Hooper)
18. 04:39 PM - Re: Multi-hop wire sizing? (Robert L. Nuckolls, III)
19. 05:09 PM - Heathrow 787 lithium event (Robert L. Nuckolls, III)
20. 05:49 PM - Re: Heathrow 787 lithium event (Henador Titzoff)
21. 05:52 PM - Re: COM radio/intercom wiring problem... (Robert L. Nuckolls, III)
22. 06:06 PM - Re: COM radio/intercom wiring problem... (Michael Burbidge)
23. 09:57 PM - Re: Heathrow 787 lithium event (Robert L. Nuckolls, III)
Message 1
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Bob
and all
Still didn't get any answer about the second part of my initial query.
How about keeping the 14V system and using a 14/28 voltage converter to feed
the radio?
Carlos
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: domingo, 28 de Julho de 2013 04:27
Subject: RE: AeroElectric-List: 14V or 28V
--> <nuckolls.bob@aeroelectric.com>
At 09:34 AM 7/27/2013, you wrote:
><bbradburry@bellsouth.net>
>
>In an experimental plane, you will save a few ounces, maybe even a
>pound or two in smaller wires, but you will add 10-15 pounds for the larger
battery.
not strictly true. When going to a higher voltage system
a battery with 1/2 the a.h. capacity has the same stored
energy as the lower voltage battery.
>If you decide you should install two batteries...WOW! You will not
>find any automotive parts that are 28V. I suggest you will need a
>reason better than weight savings to go 28V.
The weight savings are pretty small . . . we did
some calculations on it way back when here on the
list. Not very impressive until you considered
a sea-plane with very long + and ground leads.
Many of the compelling reasons for 28v circulating
in the wild are more fantasy or error than face. See
page 12 and on in this document.
http://tinyurl.com/k9v2rfw
A 28v battery at 1/2 capacity will not be as roubust
to the effects of cranking events.
Cessna went 100% 28v for manufacturing conveniences
and before the advent of the higher efficiency, geared
light weight starters.
It would be interesting to see those economics
re-evaluated but in the certified, heavy iron
business, it's not likely to happen.
The most compelling reason cited for 28v here on
the list was "my engine came fitted with 28v hardware
and I didn't what to change it out."
Bob . . .
Message 2
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| Subject: | Re: Alternators on aircraft |
If you swapped to a different alternator pulley and are experiencing a vibration,
that MIGHT be the source of your problem. If you wish, you can do a rough
balance check by disassembling the alternator, mounting the pulley on the armature
and check for a heavy spot by supporting the armature on its own bearings.
Alternatively, you can support the armature on level knife edges on the bare
armature shaft. Or just retract/remove the brushes and if the armature spins
freely in its case, you should be able to detect a heavy spot.
This procedure will only check for a static imbalance; which will probably suffice.
Most balancing correction marks that I have seen have been directly on the
pulley (heavy) end. Besides, anything rigid and dynamically balanced will
also always be in perfect static balance and exhibit no signs of a heavy spot.
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=405487#405487
Message 3
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> Still didn't get any answer about the second part of my initial query.
> How about keeping the 14V system and using a 14/28 voltage converter to
> feed
> the radio?
You could use something like this. Just make sure that you
size it to supply enough 24 volt power for your needs.
This will connect to your 12 volt system and supply 24 volts
to your radios.
http://aconinc.com/index.php?route=product/product&path=1_12400_12402&product_id=136
Using this would mean that there is no other mod required
to your aircraft electrical system thus maintaining a standard
12 volt system.
Roger
--
Do you have a slow PC? Try a Free scan http://www.spamfighter.com/SLOW-PCfighter?cid=sigen
Message 4
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Carlos,=0A=0ACheck out this 14V to 28V converter at Aircraft Splice:=0A=0A
---- http://www.aircraftspruce.com/catalog/elpages/lsStepUpCon.php?
clickkey=87526=0A=0A-=0AThings you might want to consider are:=0A=0A
* Cost:- $450 plus shipping=0A* Weight: 0.7 lbs, which is pretty low i
n my opinion, given it's TSO'ed=0A=0A* Reliability: 100K hrs MTBF, not b
ad=0A* Output: 27.5V, 8 Amps or 220W, enough for your 16W transmitter po
wer. The radio will probably pull 2.5 times that, so 40W isn't so bad and w
ill be good for the converter's MTBF=0A* Heatsink: may require that you
mount it to a metal surface, which is no problem in your RV=0A* Ripple:
25 mV P-P. This and the switching frequency may affect your radio's audio o
utput and also ride on the transmission modulation. Depending on your insta
ll, your problem may benever or forever.=0ASeems like a lot of hassle for v
ery little, but if you gotta have it, it may be the solution=0A=0A=0AHenado
r Titzoff=0A=0A=0A________________________________=0A From: Carlos Trigo <t
rigo@mail.telepac.pt>=0ATo: aeroelectric-list@matronics.com =0ASent: Sunday
, July 28, 2013 7:05 AM=0ASubject: RE: AeroElectric-List: 14V or 28V=0A =0A
pac.pt>=0A=0ABob=0Aand all=0A=0AStill didn't get any answer about the secon
d part of my initial query.=0AHow about keeping the 14V system and using a
14/28 voltage converter to feed=0Athe radio?=0A=0ACarlos- =0A=0A=0A-----O
riginal Message-----=0AFrom: owner-aeroelectric-list-server@matronics.com
=0A[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Rober
t L.=0ANuckolls, III=0ASent: domingo, 28 de Julho de 2013 04:27=0ATo: aeroe
lectric-list@matronics.com=0ASubject: RE: AeroElectric-List: 14V or 28V=0A
> <nuckolls.bob@aeroelectric.com>=0A=0AAt 09:34 AM 7/27/2013, you wrote:=0A
bellsouth.net>=0A>=0A>In an experimental plane, you will save a few ounces,
maybe even a =0A>pound or two in smaller wires, but you will add 10-15 pou
nds for the larger=0Abattery.=0A=0A- not strictly true. When going to a
higher voltage system=0A- a battery with 1/2 the a.h. capacity has the s
ame stored=0A- energy as the lower voltage battery.=0A=0A>If you decide
you should install two batteries...WOW!- You will not =0A>find any automo
tive parts that are 28V.- I suggest you will need a =0A>reason better tha
n weight savings to go 28V.=0A=0A- The weight savings are pretty small .
. . we did=0A- some calculations on it way back when here on the=0A-
list. Not very impressive until you considered=0A- a sea-plane with ver
y long + and ground leads.=0A=0A- Many of the compelling reasons for 28v
circulating=0A- in the wild are more fantasy or error than face. See=0A
- page 12 and on in this document.=0A=0Ahttp://tinyurl.com/k9v2rfw=0A=0A
- - A 28v battery at 1/2 capacity will not be as roubust=0A- - to t
he effects of cranking events.=0A=0A- - Cessna went 100% 28v for manufa
cturing conveniences=0A- - and before the advent of the higher efficien
cy, geared=0A- - light weight starters.=0A=0A- - It would be intere
sting to see those economics=0A- - re-evaluated but in the certified, h
eavy iron=0A- - business, it's not likely to happen.=0A=0A- - The m
ost compelling reason cited for 28v here on=0A- - the list was "my engi
ne came fitted with 28v hardware=0A- - and I didn't what to change it o
ut."=0A=0A=0A- Bob . . .
Message 5
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It will work, if you really want to do it. I've got a Garmin 430 28v
model on the shelf that I'll install in my RV-7 (12v system) with a
14-28v adapter. But the only reason to do that is that I got a 'deal' on
the radio. The adapter adds weight & costs efficiency. As I said in my
previous response, it's unlikely that you'll be able to tell the
difference in range between a 6 watt radio and a 16 watt radio.
Charlie
On 07/28/2013 06:05 AM, Carlos Trigo wrote:
>
> Bob
> and all
>
> Still didn't get any answer about the second part of my initial query.
> How about keeping the 14V system and using a 14/28 voltage converter to feed
> the radio?
>
> Carlos
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
> Nuckolls, III
> Sent: domingo, 28 de Julho de 2013 04:27
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: 14V or 28V
>
> --> <nuckolls.bob@aeroelectric.com>
>
> At 09:34 AM 7/27/2013, you wrote:
>> <bbradburry@bellsouth.net>
>>
>> In an experimental plane, you will save a few ounces, maybe even a
>> pound or two in smaller wires, but you will add 10-15 pounds for the larger
> battery.
>
> not strictly true. When going to a higher voltage system
> a battery with 1/2 the a.h. capacity has the same stored
> energy as the lower voltage battery.
>
>> If you decide you should install two batteries...WOW! You will not
>> find any automotive parts that are 28V. I suggest you will need a
>> reason better than weight savings to go 28V.
> The weight savings are pretty small . . . we did
> some calculations on it way back when here on the
> list. Not very impressive until you considered
> a sea-plane with very long + and ground leads.
>
> Many of the compelling reasons for 28v circulating
> in the wild are more fantasy or error than face. See
> page 12 and on in this document.
>
> http://tinyurl.com/k9v2rfw
>
> A 28v battery at 1/2 capacity will not be as roubust
> to the effects of cranking events.
>
> Cessna went 100% 28v for manufacturing conveniences
> and before the advent of the higher efficiency, geared
> light weight starters.
>
> It would be interesting to see those economics
> re-evaluated but in the certified, heavy iron
> business, it's not likely to happen.
>
> The most compelling reason cited for 28v here on
> the list was "my engine came fitted with 28v hardware
> and I didn't what to change it out."
>
>
> Bob . . .
>
>
Message 6
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| Subject: | Multi-hop wire sizing? |
When sizing wires, do you use the total distance or segment distance?
For example: The starter is a total of 15' from the battery. But that total distance
is made up of a 1' battery-to-master contactor, 12' master contactor-to-starter
contactor and 4' starter contactor-to-starter.
So do we use a 30' round trip distance when sizing all the wires? Or do we size
each segment based on its distance (i.e. 8' for the starter contactor to starter)?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=405493#405493
Message 7
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(from my Z-100 paper) Choosing a Voltage for Your Airplane Project.
Bob's Nuckolls (AeroElectric guru) often makes the point about the relative costs
of using 14V automotive components, and I have to agree. If you went to buy
your electrical system from the 28V-Store, you'd find that most of the stuff
was expensive, for certificated a/c (remember that they certify the milk, but
they certificate the cow) and the selection would not be all that large. The
14V-Store has all the bargains and selection to be sure.
In short, the advantages of 28V don't seem to warrant the added expense. Although
28V is very handy for producing the high currents needed to start big diesel
truck engines, many get along fine on 14V. Super-capacitors are also finding
use in starting diesels.
Is the auto industry going to 42V? (Arguments applicable to 28V too.)
I was spreading that rumor once. More recent rumors show advantages in staying
at 14V; because LED lighting systems, microprocessors, and mosfets solid-state
switches, are more efficient at lower voltages, while the use of single-wire
power busses makes the argument about smaller wire gauges less important for small
aircraft (higher voltages still do make sense for large aircraft). The integration
of the starter and alternator works fine at 14V too.
The extinguishing of electrical-contact arcing is a difficult problem at 42V, and
problems of load dump and transient voltages are much more severe. Higher voltage
motors are smaller but they use smaller gauge windings too, thus the cost-per-watt
of the motor goes up. A 42V system can injure or even kill mechanics
and tinkerers. Trying to jump 14V and 42V vehicles can destroy the 14V vehicles
electrical system.
Then too, 42V and 28V systems corrode faster than 14V systems. Its a no-brainer
that more volts is better from a motive-power standpoint, but many in the automotive
field now say the move to 42V systems will never happen.
Big, really big aircraft use bunches of voltage buses, 12, 28, even 120VAC, and
more to accomplish their various needs.
But for the small experimental a/c, Go with 14V. Use PerihelionDesign.com CCA to
reduce the Fatwire weight.
--------
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=405497#405497
Message 8
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>
>
>Big, really big aircraft use bunches of voltage buses, 12, 28, even
>120VAC, and more to accomplish their various needs.
The B-52's I cut my avionics teeth on sported 400Hz,
208 3-phase systems for all but the lowest power
systems and those that HAD to run on batteries for
emergency situations.
Getting a 400Hz system to play well required constant
speed drives between the variable speed engine and the
alternator that really need to run at 12,000 or 6,000
RPM all the time. I think the B-52 had hydraulic
drives - a variable displacement pump plumbed to
a variable displacement motor. A governor modulated
the wobble plates such that for any RPM at the input
shaft, the output shaft speed was constant.
Nowadays, wild frequency systems are becoming more
prevalent. This is made practical by the advent of
high horsepower, brushless DC motors and a constellation
of high-voltage switching technologies to go with it.
The need for constant speed drives goes away.
Now the large system designer can carry much greater
flows of energy around the airplane on twisted trios.
The frequency of the ac no longer drives rotational
speed off the motors because the AC is rectified locally
to relatively smooth 270VDC with the same, acceptably
low ripple (5%) we enjoy from our 3-phase a 14v alternators.
The high voltage ac is easier to control in solid state
components with triacs so arcing issues associated with
mechanical contacts goes away.
The simple ideas are unchanged, the deck of cards has
be reshuffled to exploit technology advances in
high voltage semiconductors.
DC systems on large aircraft tend to be localized,
like the forward battery on the B787 is used for emergency
backup in the cockpit, the mid-ships battery primarily
used to crank an APU. In neither instance is the DC battery
power shipped very far on wires.
Local DC requirements are easily addressed with switchmode
power supplies not unlike those we find in our computers
and cell phone chargers. Pipe POWER around the airplane
on 115/208 VAC and convert it to DC locally as needed.
Bob . . .
Message 9
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| Subject: | Re: Multi-hop wire sizing? |
At 09:09 AM 7/28/2013, you wrote:
>
>When sizing wires, do you use the total distance or segment distance?
>
>For example: The starter is a total of 15' from the battery. But
>that total distance is made up of a 1' battery-to-master contactor,
>12' master contactor-to-starter contactor and 4' starter contactor-to-starter.
>
>So do we use a 30' round trip distance when sizing all the wires? Or
>do we size each segment based on its distance (i.e. 8' for the
>starter contactor to starter)?
Voltage drop calculations for the cranking
scenario are not particularly satisfying.
What size engine . . . are you considering a PM
starter? Do you anticipate cold weather operations?
Your words paint an image of a plastic, canard pusher
with battery in the nose. 95+ percent do just fine
with 2AWG wire which will have more than the 'idealized'
5% voltage drop for continuous duty ops of appliances
but acceptable for the few seconds it takes to get
an engine running.
Put starter contactor on firewall and use cranking
feeder to bring alternator b-lead forward.
Bob . . .
Message 10
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| Subject: | Re: COM radio/intercom wiring problem... |
Several of the gauges sold by Van's are susceptible to interference from
radio transmissions, particularly manifold pressure and amps. Probably
not worth the effort to determine how/why it happens...
Peter
On 28/07/2013 05:17, Michael Burbidge wrote:
>
> Yes, my ammeter is the Vans ammeter.
>
> My airplane is an RV-9A. My COM antenna is mounted on the bottom of the airplane,
approximately under where the left leg of the pilot is when sitting in the
airplane. The antenna is from Delta Pop Aviation. The coax cable is RG400 from
B&C.
>
> I have not checked the VSWR on the antenna. I see your book gives some instructions
on how to do that.
>
> The airplane is currently in my garage. Would that "focus" the RF energy more
than being out in the open?
>
> Thanks,
> Michael-
>
>
> On Jul 27, 2013, at 8:32 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>
>>
>> At 06:59 PM 7/27/2013, you wrote:
>>>
>>> I'm trying to chase down a problem with my Radio (Garmin SL-40) Intercom (Flightcom
403) wiring. One of the strange behaviors that I don't understand is
when I push the PTT to transmit on a common unicom frequency such as 122.7, the
ammeter pegs at -40 amps. When I transmit on one of the maintenance frequencies
such as 135.85, it only deflects negative 1-2 amps. But the radio is transmitting,
I can hear on my handheld.
>>>
>>> My ammeter is a shunt type ammeter and seems to work correctly in indicating
positive (discharge) loads for other equipment. What would make it indicate
in the negative directions. This is using just the battery. i.e. engine not running.
>>>
>>> The situation is that I'm trying to debug my initial wiring, so the setup has
never worked.
>>
>> You didn't say but I'm betting your ammeter is
>> the one Van's sells . . . minus 40 - zero - plus
>> 40?
>>
>> I have one of those things laying around here somewhere.
>> I think I reported to the List after I bought it that
>> the instrument was very vulnerable to strong RF
>> in the cockpit.
>>
>> What kind of airplane and where is your antenna
>> located? Have you checked VSWR on the antenna
>> over the vhf comm range?
>>
>>
>> Bob . . .
>>
>>
>>
>>
>
>
Message 11
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| Subject: | Re: COM radio/intercom wiring problem... |
I hadn't noticed it, but the manifold pressure gauge, is also deflecting a good
deal during radio transmission. I guess that's what I get for trying to be frugal
with my instrumentation. I was alarmed by the ammeter deflection. But everything
seems to be working otherwise, and there is no smoke or blown fuses, so
I'm going to assume that this explains the ammeter deflection.
Michael-
On Jul 28, 2013, at 11:56 AM, Peter Pengilly <peter@sportingaero.com> wrote:
>
> Several of the gauges sold by Van's are susceptible to interference from radio
transmissions, particularly manifold pressure and amps. Probably not worth the
effort to determine how/why it happens...
>
> Peter
>
> On 28/07/2013 05:17, Michael Burbidge wrote:
>>
>> Yes, my ammeter is the Vans ammeter.
>>
>> My airplane is an RV-9A. My COM antenna is mounted on the bottom of the airplane,
approximately under where the left leg of the pilot is when sitting in the
airplane. The antenna is from Delta Pop Aviation. The coax cable is RG400 from
B&C.
>>
>> I have not checked the VSWR on the antenna. I see your book gives some instructions
on how to do that.
>>
>> The airplane is currently in my garage. Would that "focus" the RF energy more
than being out in the open?
>>
>> Thanks,
>> Michael-
>>
>>
>> On Jul 27, 2013, at 8:32 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>>
>>>
>>> At 06:59 PM 7/27/2013, you wrote:
>>>>
>>>> I'm trying to chase down a problem with my Radio (Garmin SL-40) Intercom (Flightcom
403) wiring. One of the strange behaviors that I don't understand is
when I push the PTT to transmit on a common unicom frequency such as 122.7, the
ammeter pegs at -40 amps. When I transmit on one of the maintenance frequencies
such as 135.85, it only deflects negative 1-2 amps. But the radio is transmitting,
I can hear on my handheld.
>>>>
>>>> My ammeter is a shunt type ammeter and seems to work correctly in indicating
positive (discharge) loads for other equipment. What would make it indicate
in the negative directions. This is using just the battery. i.e. engine not
running.
>>>>
>>>> The situation is that I'm trying to debug my initial wiring, so the setup
has never worked.
>>>
>>> You didn't say but I'm betting your ammeter is
>>> the one Van's sells . . . minus 40 - zero - plus
>>> 40?
>>>
>>> I have one of those things laying around here somewhere.
>>> I think I reported to the List after I bought it that
>>> the instrument was very vulnerable to strong RF
>>> in the cockpit.
>>>
>>> What kind of airplane and where is your antenna
>>> located? Have you checked VSWR on the antenna
>>> over the vhf comm range?
>>>
>>>
>>> Bob . . .
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
Message 12
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| Subject: | Re: Low voltage indicator with dual alternators |
I installed the Intelligent Power Stabilizer IPS-12v-8a this past week
and did some testing. It appears to have solved my problems. Thanks to
all involved!
To recap:
Problem; Despite having a robust Z-14 power scheme installed in my RV10,
I found myself starting on 1 battery because if I started with both
batteries, my 3 GRT EFISs would re-boot. I This defeated one of the
advantages of the Z-14 dual alternator, dual battery, dual bus architecture.
Solution; I installed TCW's IPS-12v-8a unit and connected the 3 EFISs
and the GPS/NAV side of the G430. The EFISs each have 3 power inputs
and will draw from the input with most juice. So the EFISs remain
connected to one of the buses but the secondary inputs are connected to
the IPS unit. The G430/GPS/NAV is connected directly to the IPS only.
Test Results; I am now able to turn on the EFISs and the G430, use them
for flight planning and clearance work (say 10 minutes), then turn on
the other bus, interconnect the 2 buses and start the engine. The
engine turnover is clearly more robust and the EFISs continue to run
without a hiccup.
I also did some bus load rebalancing to better reflect the charging
capabilities of the main and secondary alternators.
Now I'll be flying with the Z-14 as it is designed. Fully
interconnected buses for start and disconnected into 2 separate buses
for flight operations. Interconnection is available if needed in
various failure scenarios.
Thanks Bob N and Thanks Bob N!
On 7/10/2013 2:11 PM, Tcwtech wrote:
> Our IBBS product line provides back-up power to devices like efis
> equipment as well as GPS and comm systems. One of the added benefits
> is that during engine cranking the auto transfer circuitry knows to
> keep the connected load from dropping out and resetting.
> Connecting our IBBS product to the GRT system is very straight forward
> and 1/2 the weight of adding another similar sized lead acid battery.
>
> Also, if you don't need the full feature of back-up power and just
> want to resolve the issues with system resets during engine cranking,
> our IPS systems provide consistent, stable voltage to the connected
> load(s) with a maintenance free solution.
>
> All the details are on our web site and can be seen at our booth at
> Oshkosh.
> Www.Tcwtech.com <http://Www.Tcwtech.com>
>
>
> On Jul 10, 2013, at 10:52 AM, Bill Watson <Mauledriver@nc.rr.com
> <mailto:Mauledriver@nc.rr.com>> wrote:
>
>> Wow! The TCW product seems perfect for the GRT issue. Was unaware
>> of it. Thanks.
>>
Message 13
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| Subject: | Re: Multi-hop wire sizing? |
Correct. Velocity with the battery (24v) in the nose and the starter contactor
on the firewall. Continental IO-550N with a factory starter. I can't find the
specs on the starter but I've been told that 200a is a conservative starting point.
So for instance, the length from the starter contactor to the starter is 4'. Based
on the chart in 43.13 (which requires some extrapolation for a 200a load),
theoretically, I could get by with 8AWG for that run. Whereas the master to starter
contactor would require 4AWG.
Which brings me back all the way back around to the question of: Is the wire size
based on the total distance or per segment distance?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=405515#405515
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| Subject: | Re: COM radio/intercom wiring problem... |
Are you using a shielded bundle to run the shunt sense wires? If so you could experiment
with where you terminate the shield, whether that's at a ground near
the shunt, or at a ground near the ammeter -- the idea would be to help get the
RF energy shorted back to the source (the radio) without forcing it to go through
the ammeter as it is now.
This particular model ammeter is passive, right? The shunt wires are the only two
wires coming out of it?
On Jul 28, 2013, at 2:41 PM, Michael Burbidge wrote:
>
> I hadn't noticed it, but the manifold pressure gauge, is also deflecting a good
deal during radio transmission. I guess that's what I get for trying to be
frugal with my instrumentation. I was alarmed by the ammeter deflection. But everything
seems to be working otherwise, and there is no smoke or blown fuses,
so I'm going to assume that this explains the ammeter deflection.
>
> Michael-
>
Message 15
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| Subject: | Re: Multi-hop wire sizing? |
I would add to Bob's response that in any circuit, you need to ensure
that the conductors involved, be they wire or bus metal, are adequately
sized to carry the required current from source, the battery, to the
load, the starter in your example, and back, as the current always has
to take that round trip.
Bill
On 29/07/2013 12:09 AM, donjohnston wrote:
>
> When sizing wires, do you use the total distance or segment distance?
>
> For example: The starter is a total of 15' from the battery. But that total distance
is made up of a 1' battery-to-master contactor, 12' master contactor-to-starter
contactor and 4' starter contactor-to-starter.
>
> So do we use a 30' round trip distance when sizing all the wires? Or do we size
each segment based on its distance (i.e. 8' for the starter contactor to starter)?
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=405493#405493
>
>
Message 16
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| Subject: | Re: COM radio/intercom wiring problem... |
At 05:14 PM 7/28/2013, you wrote:
>
>Are you using a shielded bundle to run the shunt sense wires? If so
>you could experiment with where you terminate the shield, whether
>that's at a ground near the shunt, or at a ground near the ammeter
>-- the idea would be to help get the RF energy shorted back to the
>source (the radio) without forcing it to go through the ammeter as it is now.
>
>This particular model ammeter is passive, right? The shunt wires are
>the only two wires coming out of it?
Unfortunately, no. See:
http://tinyurl.com/mpx8hze
This instrument is fitted with several 'radio
receivers' in the form of op-amps.
This design philosophy seems to be common to
the whole product line. It's a fundamental
design error which shielding of wires is
unlikely to rectify.
Bob . . .
Message 17
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| Subject: | Re: COM radio/intercom wiring problem... |
Zoiks.
Nice and cheap, but what are they gaining with all that circuitry? A
stiffer needle? That can't be it... A lower-ohm shunt?
"..unlikely to rectify."
haha nice
On Jul 28, 2013, at 6:18 PM, Robert L. Nuckolls, III wrote:
>>
>> This particular model ammeter is passive, right? The shunt wires are
the only two wires coming out of it?
>
> Unfortunately, no. See:
>
> http://tinyurl.com/mpx8hze
>
> This instrument is fitted with several 'radio
> receivers' in the form of op-amps.
>
> This design philosophy seems to be common to
> the whole product line. It's a fundamental
> design error which shielding of wires is
> unlikely to rectify.
>
>
> Bob . . .
>
>
>
>
Message 18
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| Subject: | Re: Multi-hop wire sizing? |
>>So do we use a 30' round trip distance when sizing all the wires?
>>Or do we size each segment based on its distance (i.e. 8' for the
>>starter contactor to starter)?
Neither. As I tried to articulate earlier, selection of wire
in the cranking circuit is not driven by current rating
of wire based on temperature rise and only loosely based
on voltage drop.
In the TC aircraft world, we concern ourselves with worst
case situations like battery nearing end of life, engine
and battery are cold-soaked at the lowest operating temperatures
recommended by engineering and marketing for operations
without ground assist (pre-heat or ground power cart).
There are lots of warm weather VariEz drivers who did their
long runs with 4AWG . . . and I've not heard of anyone finding it
useful to change out the wire . . . more than likely
they would go for a more robust battery first.
200A at 18 volts (worst case battery volts for starting)
is about half again more energy than the 300A at 9v
we use as a rule-of-thumb for 14 volt airplanes.
But I can tell you that nobody I've ever known picked
a cranking system wire size based on any predictive
performance based on analysis or calculation. I know
of some airplanes (a noteworthy Piper Cherokee) that
got a 'heavy duty' battery option added to its type
certificate due to poor cranking performance complaints
by some customers. These customers found it more attractive
to upsize to a 35 a.h. battery than to change out the
starter or make any other changes to reduce the stack-up
of conditions that degraded cranking.
If you're going to limit to warm weather flying and
plan to keep the battery well maintained, then perhaps
4AWG will be adequate to your intended use of the
airplane. 2AWG wire was common to all small SE aircraft
with remote mounted batteries. Once the batteries
moved forward to the firewall, I think the shift to
4AWG was axiomatic.
Selection of wire in this case was more a matter of
sticking a wet finger (or soggy battery) into a -20C
breeze than any carefully calculated design decision.
Bob . . .
Message 19
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| Subject: | Heathrow 787 lithium event |
As layers of the onion are being peeled back,
it seems that yes, the lithium battery within
the ELT was a source of the energy that started
this fire . . . but . . .
root cause may well have been a pinched wire
within the ELT. See:
http://tinyurl.com/mv7gohj
. . . watch this space.
Bob . . .
Message 20
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| Subject: | Re: Heathrow 787 lithium event |
The DreamLiner has had its share of glaring problems.- If a pinched wire
was the root cause of failure, then I attribute this to poor workmanship.
- This is a very bad attribute for a new, high tech airliner, possibly le
ading to other failures.- What else lurks inside that carcass?=0A=0ALast
thing I need is the stench of dilithium crystals boiling under my butt.=0A
=0A=0AHenador Titzoff=0A=0A=0A=0A=0A________________________________=0A Fro
m: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelec
tric-list@matronics.com =0ASent: Sunday, July 28, 2013 8:09 PM=0ASubject: A
eroElectric-List: Heathrow 787 lithium event=0A =0A=0A--> AeroElectric-List
message posted by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.co
m>=0A=0AAs layers of the onion are being peeled back,=0Ait seems that yes,
the lithium battery within=0Athe ELT was a source of the energy that starte
d=0Athis fire . . . but . . .=0A=0Aroot cause may well have been a pinched
wire=0Awithin the ELT. See:=0A=0Ahttp://tinyurl.com/mv7gohj=0A=0A. . . watc
=- - - - - - - - - - - - - - - -Matt Dralle
========
Message 21
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| Subject: | Re: COM radio/intercom wiring problem... |
At 06:35 PM 7/28/2013, you wrote:
>Zoiks.
>
>Nice and cheap, but what are they gaining with all that circuitry? A
>stiffer needle? That can't be it... A lower-ohm shunt?
>
>"..unlikely to rectify."
>
>haha nice
Actually, it was probably done to achieve a design
goal for an electronics assembly that would
work across a lot of products . . . by changing
scaling resistors and perhaps some jumpers you
could built a host of instruments with great
commonality of bill of materials.
I too like to operate under that banner.
If they're guilty of having fumbled the ball,
it was lack of understanding the environment
that their electro-whizzy was being asked to
function. I'll bet their major market is
automotive . . . vehicles without VHF
transmitters.
Bob . . .
Message 22
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| Subject: | Re: COM radio/intercom wiring problem... |
Wow I see from the link containing the pictures that the problems with this instrument
are well known.
Since my airplane is VFR and I also have a voltmeter, I'm probably going to stick
with my current setup at least until I'm flying. Perhaps I can find a drop-in
replacement that works with the same shunt.
Michael-
On Jul 28, 2013, at 5:52 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
wrote:
>
> At 06:35 PM 7/28/2013, you wrote:
>> Zoiks.
>>
>> Nice and cheap, but what are they gaining with all that circuitry? A stiffer
needle? That can't be it... A lower-ohm shunt?
>>
>> "..unlikely to rectify."
>>
>> haha nice
>
> Actually, it was probably done to achieve a design
> goal for an electronics assembly that would
> work across a lot of products . . . by changing
> scaling resistors and perhaps some jumpers you
> could built a host of instruments with great
> commonality of bill of materials.
>
> I too like to operate under that banner.
> If they're guilty of having fumbled the ball,
> it was lack of understanding the environment
> that their electro-whizzy was being asked to
> function. I'll bet their major market is
> automotive . . . vehicles without VHF
> transmitters.
>
>
>
> Bob . . .
>
>
>
>
Message 23
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| Subject: | Re: Heathrow 787 lithium event |
At 07:48 PM 7/28/2013, you wrote:
>The DreamLiner has had its share of glaring problems. If a pinched
>wire was the root cause of failure, then I attribute this to poor
>workmanship. This is a very bad attribute for a new, high tech
>airliner, possibly leading to other failures. What else lurks
>inside that carcass?
>
>Last thing I need is the stench of dilithium crystals boiling under my butt.
Yes but . . . it seems this 'pinched wire' is INSIDE the
ELT. The FAA issued an AD against the airframe
http://tinyurl.com/mekmrzd
stating . . .
"We are issuing this AD to prevent a fire in the aft crown of the
airplane, or to
detect and correct discrepancies within the ELT that could cause such
a fire."
. . .which I find a little odd. If the suspected
root cause is located inside a TSO'ed appliance
then I would have thought the AD would have been
written against that appliance.
There are approximately 6000 of this ELT in
service but the AD only investigates those installed
on the 787 and then in very unspecific terms except
to
"Inspect the Honeywell fixed ELT for discrepancies, and do all
applicable corrective actions
before further flight, using a method approved in accordance with the
procedures specified in
paragraph (h) of this AD."
Not sure I understand how this works . . .
perhaps every ELT installed on a 787
receives proper 'corrective action', gets
re-installed and all is right with the
universe? Seems there's a few thousands
yet to be inspected/corrected. . . oh,
perhaps another AD, this time against the
ELT.
In the mean time, how would you like to
be Honeywell looking at financing the fixing
of a smoked 787 and doing inspect/repair/replace
on a boatload of ELTs?
Aren't you glad you fly an OBAM aircraft?
Bob . . .
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