Piper Wing Lighting

zatatime wrote:
All three turned on at idle would exceed the
alternator output.
Doesn't that make your airplane "illegal" (technically speaking of
course).
I thought the total draw of an electrical system could not exceed 80%
of the output capacity of the alternator.
Am I incorrect, or is there more to this concept?

The way it was explained to me, once upon a time, was... Landing/Taxi
lights are considered "intermitant loads" and are not added in for the 80%
load calculation. Same goes for pitot heat. In fact, when you're adding
up your loads, you only add the receive power draw for your Com radios,
and not the transmit power draw.

--- Jay

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On 30 Oct 2004 21:18:02 GMT, (Jay Masino)
wrote:

The way it was explained to me, once upon a time, was... Landing/Taxi
lights are considered "intermitant loads" and are not added in for the 80%
load calculation. Same goes for pitot heat. In fact, when you're adding
up your loads, you only add the receive power draw for your Com radios,
and not the transmit power draw.


Thanks. Intermttent not being counted makes sense to me.

Thanks for the info.

z

Jay Masino wrote:
: The way it was explained to me, once upon a time, was... Landing/Taxi
: lights are considered "intermitant loads" and are not added in for the 80%
: load calculation. Same goes for pitot heat. In fact, when you're adding
: up your loads, you only add the receive power draw for your Com radios,
: and not the transmit power draw.

I just did the power budget on my Cherokee after installing a whole panel of
equipment. It's amazingly vague how one is supposed to calculate that stuff. I would
consider landing/taxi lights and landing gear operation (A friend has electric-gear'd
Comanche) "intermittent loads"... also probably the Tx on the COM (perhaps even
adjusted to the 20% duty cycle rated for the radios). I would *NOT* consider pitot
heat an intermittent load. I want that to be able to run whenever I need it.... even
if I shouldn't be in that situation to begin with. It'd rate it right up there with
carb heat for continuous operation.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:
adjusted to the 20% duty cycle rated for the radios). I would *NOT* consider pitot
heat an intermittent load. I want that to be able to run whenever I need it.... even
if I shouldn't be in that situation to begin with. It'd rate it right up there with
carb heat for continuous operation.

You can still operate it "whenever you need it" and it still be considered
"intermitant", because you don't operate it on every flight. The worse
thing that happens is that you pull the extra electical power out of the
battery for a little while. That said, it's alway nicer to have all the
alternator capacity you need in every situation.

--- Jay



--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

It's 80% of the max alternator output current. Mine just barely came under
the 80% when they were installed, but then I later added an autopilot which
brought it over the 80%. The avionics shop got around it by adding a placard
stating something to the effect that the autopilot may not be engaged with the
landing lights on.


Jay Masino wrote:

zatatime wrote:
All three turned on at idle would exceed the
alternator output.
Doesn't that make your airplane "illegal" (technically speaking of
course).
I thought the total draw of an electrical system could not exceed 80%
of the output capacity of the alternator.
Am I incorrect, or is there more to this concept?

The way it was explained to me, once upon a time, was... Landing/Taxi
lights are considered "intermitant loads" and are not added in for the 80%
load calculation. Same goes for pitot heat. In fact, when you're adding
up your loads, you only add the receive power draw for your Com radios,
and not the transmit power draw.

--- Jay

--
__!__
Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
http://www.oceancityairport.com
http://www.oc-adolfos.com

--
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President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

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