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nuckolls.bob(at)aeroelect
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 Posted: Thu Jan 13, 2011 6:30 am Post subject: Request review of Electrical Load Analysis - using Z13/8 a |
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At 06:48 AM 1/13/2011, you wrote:
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Jeff,
Thanks I'll add those items. I'm going to go without the cooling
fan initially and see how the avionics fare. I might have to add later.
For those planning IFR w/ similar equipment....it looks like the
LC-60 amp alternator is a must due to the high current consumption
of the pitot heat, navigation, strobe, and landing lights.
For anyone who has not yet purchased equipment you'll want to buy
LED style, and maybe the Gretz Aero pitot heat system to keep the amps down.
I'm going to switch to the B&C LC-60 amp alternator and plan for a
max continuous electrical load of 80-85% or 48 to 51 amps.
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Really that high? Do you run all those things all the time
for any flight condition? Here's an exemplar load-analysis
form I've used for many years.
http://www.aeroelectric.com/PPS/Load_Analysis/Blank_Form.pdf
It set's up a series of flight conditions that comport with
suggestions offered by FAR23.1351(a)(1)(i) that says:i)
"For normal, utility, and acrobatic category airplanes, by an electrical
load analysis or by electrical measurements that account for the electrical
loads applied to the electrical system in probable combinations and for
probable durations"
The operative words are "combinations" and "duration".
Not all things are turned on at any time. The last
detail load analysis I did on a small airplane some
years ago showed a max CONTINUOUS demand of 27 amps
for the worst case flight condition (IFR, pitot heat
ON).
This left 10A plus for battery maintenance with
only a 40A alternator.
The rule of thumb for alternator sizing is to
reserve 25% of total capacity for battery charging
so if you're planning a 60A alternator, you want
to establish operating conditions that do not
demand more than 45A continuous.
Bob . . .
Bob . . .
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plevyakh
Joined: 10 Jan 2011
Posts: 39
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| Posted: Fri Jan 14, 2011 4:49 am Post subject: Re: Request review of Electrical Load Analysis - using Z13 |
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| Quote: | "nuckolls.bob(at)aeroelect"]At 06:48 AM 1/13/2011, you wrote:
Really that high? ...... The last detail load analysis I did on a small airplane some years ago showed a max CONTINUOUS demand of 27 amps for the worst case flight condition (IFR, pitot heat ON).... |
Bob,
You have me thinking my scenario estimates are wrong. In my sheet I estimate Pitot heat (8amps), Strobe (7amps), and Navigation / Position lights (8amps) totaling 23amps just for that alone.
I've checked with a few other builders that have similar equipment and they all told me they had to upgrade to a 60amp alternator....and that 40amp wouldn't do it.
I did talk with Whelen engineering yesterday and I can get my Nav/Position lights down to 1.0 amps by switching to an LED setup. But I'm stuck with high loads for the pitot heat and strobes.
I need some help with a paradigm shift on how I'm estimating these loads.
I'm looking at your form and for IFR cruise I would still think I'd need to assume Pitot heat, Strobe, and Nav/Position lights as continuous loads if I were flying in the soup on a cold wet day. I'd appreciate a reality check from the list on this assumption.
I'll try to rework my numbers using the flight condition approach and see how I fit using the 25% reserve factor. Thx.
Howard
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_________________
Howard Plevyak
GlaStar / Cincinnati, Ohio |
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Tundra10
Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario
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| Posted: Fri Jan 14, 2011 9:25 am Post subject: Re: Request review of Electrical Load Analysis - using Z13 |
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With glass panels, IFR and HID wig-wag headlamps (I fly with them on all the time to increase visibility and perhaps reduce bird strikes), even with LED position and collision lights, I still add up to 34A continuous in cruise.
Jeff Page
Dream Aircraft Tundra #10
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