Pulsing Ammeter?
RASI
systems of some aircraft and not others with the same system. For
example, we have numerous Cessna and Citabria aircraft on our rental line,
some have show current pulses indicated on the ammeter that oscillate at
about 4 cycles per second. Any fixes ? One aircraft had the alternator,
battery and voltage regulator replaced and it sill did it!
Help!
Eric
Ron Natalie
: Does any one know why there are current fluctuations in the electrical
Turn off the rotating beacon?
-Ron
Mike Mladejovsky
It's probably the Pulsating Beacon in the tail. The lamp in the beacon
pulls about 10A, and the Flasher wired in series with it just pulses it
on/off. The ammeter shows the current pulsations going to the beacon.
Its harmless unless a sloppy job was done installing the avionics, in
which case the current fluctuations can be heard through the radios or
intercom as a "clicking", or it can modulate the alternator "whine".
Newer Cessna 182s have a big wire-wound resistor mounted in the tail
which serves as a dummy load for the solid-state flasher module. The
flasher alternately switches current from the beacon lamp to the load
resistor, keeping the current drain through the ammeter constant.
---------------------------------------------------------------------------
Michael Mladejovsky, Phd PPsel
University of Utah, Center for Engineering Design, Salt Lake City, Utah
Ham Radio: WA7ARK Civil Air Patrol: Uncle Mike 41 Skylane N3453R
Opinions mine, not CED's
Jeff Oslick
>From: ra...@aol.com (RASI)
>Subject: Pulsing Ammeter?
>Date: 22 Jan 1995 12:30:05 -0500
The ammeter on the C-150 I rent pulses in response to current draw from the
red tail beacon.
__________________________
Jeff Oslick New Bedford, MA (EWB)
Dept. of Geological Sciences
Brown University
Providence, RI
Jim Agnew
>Does any one know why there are current fluctuations in the electrical
>systems of some aircraft and not others with the same system.
Do the aircraft that pulse have strobes?? If so the strobes draw a lot of
charging current in pulses so this could be the problem.
Jim
/**********************************************
Jim Agnew, Tampa, FL
/**********************************************
Curtis Wheeler
I would check to see that these aircraft actually have the same systems. Of
course strobes and flashing beacons are the big cause of a moving ammeter but
not likely at 4 Hz - but then again, unsychronized dual flash strobes might do
it. Have you tried turning systems and accessories on one at a time to see if
there is any changes? Oscillations of a small amplitude (+/- <.5 amp) might
just indicate noise getting to a tired meter - are ammeters filtered in
airplanes?
Curtis Wheeler San Ramon, CA (cg...@chevron.com)
KD6ELA / GROL PG10-25691 / Pvt. Pilot ASEL
Bluejay Adametz
You'll normally see ammeter variations in response to large current load
changes, such as switching on landing lights or other high-current items.
There's a certain amount of lag in the response of the voltage regulator/
alternator, and the battery fills in the gap.
If the variations are excessive or become noticable in the overall system
voltage (such as seeing your panel lights flicker or dim), there is
probably something wrong. Common problems include insufficient alternator
output (may have one or more bad diodes), malfunctioning voltage regulator,
or poor ground connections. Less common causes include a weak battery and
a failing battery solenoid.
It couls also be the case that some electrical device is malfunctioning and
intermittently drawing more current than it should. Switching things off one
at a time and noting what happens should narrow that down.
The thing to do is get a good DMM on there and see exactly what is happening
on the system bus.
---
Bluejay Adametz, CFII, A&P feathr::blu...@ampakz.enet.dec.com
AMP-Akzo Co. blu...@ampakzo.UUCP
Greenville, SC, USA +1 803 675 7425
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carved into it. It was the first concrete example.
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Michael Bywater
Natalie) wrote:
Indeed... a few years back, when I had my Cougar done up, they replaced
the old beacon (a rotating mirror going around a steady lamp) with a new
strobing one. The pulsing ammeter really gave me the willies for a while
until (a) the strobe unit blew up, as they do, and (b) the pulsing
stopped.
Problem solved.
New problem appeared: finding $$$ for a new strobe :-(
--
Michael Bywater <m...@bywater.demon.co.uk>
London WC1N 3LE, U.K.
RASI
The current fluctuations are not related to the beacon. All the aircraft
in question have the dummy loads.
Also one C152 1978 model used to be solid but now is pulsing, even has a
new alternator wich made the problem worse.
Eric
RASI
the same, strobes beacons, etc. The pulsing does not seem to change with
load of any kind. Even my T210 does it somewhat. Could this be a ground
loop type problem?
Marc Rodstein
scott_...@arthor.cais.com says...
>
>To: Michael Bywater
>Subject: Pulsing Ammeter?
>
>In Reply-To: m...@bywater.demon.co.uk (Michael Bywater)
My Lake Bucanner does the same thing, with stobes on or off.
The pulsing frequency changes with changed electrical load. I
think it is from the voltage regulator.
--
Marc Rodstein
Boca Raton, Florida
Randy Stockberger
: In article <PCPN073...@arthor.cais.com>,
--
It may be the voltage regulator, but more likely is is corrosion in the
electrical system. Have your A/P remove, clean and reconnect all the
high amperage connections, i.e. the battery, voltage contactor,
alternator, etc. It could also mean a bad cell in the battery, but you
would probably notice starting problems first.
--
Randy Stockberger The people are not *given* freedom by the government.
ran...@cv.hp.com The people *take* freedom from the government.
Corvallis, OR
503-715-3589
--
