Today's Message Index:
----------------------
1. 05:02 AM - Re: what is the truth about gps antennas? (Robert L. Nuckolls, III)
2. 05:05 AM - Re: what is the truth about gps antennas? (Robert L. Nuckolls, III)
3. 05:15 PM - Relay sticking (Sebastien)
4. 06:12 PM - Re: Relay sticking (Kelly McMullen)
5. 08:46 PM - Re: Relay sticking (Alec Myers)
6. 09:09 PM - Re: Relay sticking (Sebastien)
Message 1
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Subject: | Re: what is the truth about gps antennas? |
At 09:33 AM 12/23/2018, you wrote:
>
>
> >3dB is a doubling of whatever you measure.
> (Actually a factor of 10^0.3 = 1.995)
>
>I see this is actually true only for power
>quantities and power-like quantities. For field
>quantities and field-like quantities 3dB is a
>ratio of 10^0.15 = 1.41. So a signal ratio of
>40dB is ten thousand times the power and 100 times the voltage.
>
>That=99s what you get when you put the engineers
>in charge of defining units instead of the physicists.
The Bel (or its smaller descendant deciBel) was
derived from concepts in physics. . . as were
many other dimensionless numbers that described
RATIOS of many quantities that do have dimensions.
Look up dimensionless physical constants like
proton to electron mass ratio, Plank's constant,
Coulomb's constant, etc.
Then there are ratios near and dear to aviation
like Mach number, Reynolds number, strain,
and yes . . . even deciBels. The Bel is
always about energy ratios but is still
valid for discussion power. While power
is a rate function, it is proportional to energy
when the rates are defined over the same intervals
of time.
It is proper to discuss ratios of power (like
watts) and amplitudes (like voltage, amps) in
terms of dB if one compensates for the effects of
amplitude on power in the system. This is
accomplished with application of formula
that accounts for the square law effects
of amplitude on power. Hence the constant
for "deci" (10) has to be doubled to 20
when considering ratios of amplitude.
Emacs!
This was no shortcoming on the part of
engineers vs. physicists . . . they've
all been on the same page since day-one.
Bob . . .
Message 2
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Subject: | Re: what is the truth about gps antennas? |
At 10:13 AM 12/23/2018, you wrote:
>That=99s what you get when you put the engineers
>in charge of defining units instead of the physicists...
>
>
>I TOTALLY AGREE!=C2 =C2
>
>I=C2 have NEVER seen a more argumentative bunch than Engineers.
>They all went=C2 to collage.
>They all took the same courses.
>They all learned the SAME physics.=C2 <-- Well,they should have!
>They all learned the same electronics.
>Yet they disagree on more things than Congress.
I cannot speak for your personal experiences
except to observed that they are far removed
from my own. But in any case, this line
of thought does not advance the mission
of this forum.
Bob . . .
Message 3
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We had a strange event last week with our O-200 powered CH750. After
running the battery down during a fuel gauge calibration that lasted over
an hour, one of our pilots tried to start the engine to taxi back but with
the already depleted battery and a less than perfect start procedure they
gave up after a couple weak start attempts. I walked over to the aircraft
to brief them on a prop start and when I asked for the master on the
starter ran. Shut the master off, cycled the start button rapidly a dozen
times, master on again and the starter ran again. I could hear the starter
relay clicking loudly each time power was applied so it does not seem like
there was a physical failure of the relay but more some electrical short
activating the relay each time power was applied.
The build team inspected the relay and found a loose connection. Tightening
it took the problem from continuous to intermittent; in their words "it's
fixed but it did it again once".
We have removed the relay for replacement, I still think the switch is
suspect but they've decided the problem is the relay. Does the aeroelectric
list think there would be value in cutting open the relay and examining it?
Any suggestions on how best to do so?
Thank you,
Sebastien
Message 4
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Subject: | Re: Relay sticking |
I don't think you have a problem. I think that if the engine didn't
actually start, the starter might not reach enough speed to disengage.
Also, extended cranking at low voltage probably heated the solenoid a
lot, causing sticking in it. After the battery is fully recharged, give
it another try, without cranking more than 10-15 seconds on any try. It
is likely to start, and the starter will disengage normally. You can
test the relay on the bench, without a starter connected, just battery
cable on input side and switchable 12V on ignition terminal, just
activating long enough to see your multi-meter show voltage on the
output terminal.
On 12/24/2018 6:14 PM, Sebastien wrote:
> We had a strange event last week with our O-200 powered CH750. After
> running the battery down during a fuel gauge calibration that lasted
> over an hour, one of our pilots tried to start the engine to taxi back
> but with the already depleted battery and a less than perfect start
> procedure they gave up after a couple weak start attempts. I walked over
> to the aircraft to brief them on a prop start and when I asked for the
> master on the starter ran. Shut the master off, cycled the start button
> rapidly a dozen times, master on again and the starter ran again. I
> could hear the starter relay clicking loudly each time power was applied
> so it does not seem like there was a physical failure of the relay but
> more some electrical short activating the relay each time power was applied.
>
> The build team inspected the relay and found a loose connection.
> Tightening it took the problem from continuous to intermittent; in their
> words "it's fixed but it did it again once".
>
> We have removed the relay for replacement, I still think the switch is
> suspect but they've decided the problem is the relay. Does the
> aeroelectric list think there would be value in cutting open the relay
> and examining it? Any suggestions on how best to do so?
>
> Thank you,
>
> Sebastien
Message 5
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Subject: | Re: Relay sticking |
I say change the relay. (And have done, on two different aircraft, for identical
symptoms.) If the relay sticks on a good engine start it will take the starter
motor with it, unless you shut it down soon, and its hard to spot unless you
have a starter energized lamp. In my case I was lucky, the massive current drain
took the radio out before I took off, but I only worked out why when I heard
the weird grinding noise of the engine driving the locked up starter when
I took my headset off.
That was an O235 engine, similar starter configuration to yours.
Do you have a starter energized lamp?
On Dec 24, 2018, at 21:04, Kelly McMullen <kellym@aviating.com> wrote:
I don't think you have a problem. I think that if the engine didn't actually start,
the starter might not reach enough speed to disengage.
Also, extended cranking at low voltage probably heated the solenoid a lot, causing
sticking in it. After the battery is fully recharged, give it another try,
without cranking more than 10-15 seconds on any try. It is likely to start, and
the starter will disengage normally. You can test the relay on the bench, without
a starter connected, just battery cable on input side and switchable 12V
on ignition terminal, just activating long enough to see your multi-meter show
voltage on the output terminal.
> On 12/24/2018 6:14 PM, Sebastien wrote:
> We had a strange event last week with our O-200 powered CH750. After running
the battery down during a fuel gauge calibration that lasted over an hour, one
of our pilots tried to start the engine to taxi back but with the already depleted
battery and a less than perfect start procedure they gave up after a couple
weak start attempts. I walked over to the aircraft to brief them on a prop
start and when I asked for the master on the starter ran. Shut the master off,
cycled the start button rapidly a dozen times, master on again and the starter
ran again. I could hear the starter relay clicking loudly each time power was
applied so it does not seem like there was a physical failure of the relay
but more some electrical short activating the relay each time power was applied.
> The build team inspected the relay and found a loose connection. Tightening it
took the problem from continuous to intermittent; in their words "it's fixed
but it did it again once".
> We have removed the relay for replacement, I still think the switch is suspect
but they've decided the problem is the relay. Does the aeroelectric list think
there would be value in cutting open the relay and examining it? Any suggestions
on how best to do so?
> Thank you,
> Sebastien
Message 6
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Subject: | Re: Relay sticking |
We do not have a starter energized light but we do have a Dynon Skyview so
I'm thinking there must be a way of connecting it to a GP input to display
a warning. Have not checked the Dynon install manual yet.
On Mon, Dec 24, 2018, 20:50 Alec Myers <alec@alecmyers.com wrote:
>
> I say change the relay. (And have done, on two different aircraft, for
> identical symptoms.) If the relay sticks on a good engine start it will
> take the starter motor with it, unless you shut it down soon, and it
=99s hard
> to spot unless you have a =9Cstarter energized=9D lamp. In my
case I was lucky,
> the massive current drain took the radio out before I took off, but I onl
y
> worked out why when I heard the weird grinding noise of the engine drivin
g
> the locked up starter when I took my headset off.
>
> That was an O235 engine, similar starter configuration to yours.
>
> Do you have a =9Cstarter energized=9D lamp?
>
>
> On Dec 24, 2018, at 21:04, Kelly McMullen <kellym@aviating.com> wrote:
>
> kellym@aviating.com>
>
> I don't think you have a problem. I think that if the engine didn't
> actually start, the starter might not reach enough speed to disengage.
> Also, extended cranking at low voltage probably heated the solenoid a lot
,
> causing sticking in it. After the battery is fully recharged, give it
> another try, without cranking more than 10-15 seconds on any try. It is
> likely to start, and the starter will disengage normally. You can test th
e
> relay on the bench, without a starter connected, just battery cable on
> input side and switchable 12V on ignition terminal, just activating long
> enough to see your multi-meter show voltage on the output terminal.
>
> > On 12/24/2018 6:14 PM, Sebastien wrote:
> > We had a strange event last week with our O-200 powered CH750. After
> running the battery down during a fuel gauge calibration that lasted over
> an hour, one of our pilots tried to start the engine to taxi back but wit
h
> the already depleted battery and a less than perfect start procedure they
> gave up after a couple weak start attempts. I walked over to the aircraft
> to brief them on a prop start and when I asked for the master on the
> starter ran. Shut the master off, cycled the start button rapidly a dozen
> times, master on again and the starter ran again. I could hear the starte
r
> relay clicking loudly each time power was applied so it does not seem lik
e
> there was a physical failure of the relay but more some electrical short
> activating the relay each time power was applied.
> > The build team inspected the relay and found a loose connection.
> Tightening it took the problem from continuous to intermittent; in their
> words "it's fixed but it did it again once".
> > We have removed the relay for replacement, I still think the switch is
> suspect but they've decided the problem is the relay. Does the aeroelectr
ic
> list think there would be value in cutting open the relay and examining i
t?
> Any suggestions on how best to do so?
> > Thank you,
> > Sebastien
>
>
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