[Milsurplus] Can.military use of 14V/12V

[Peter Gottlieb]

An aircraft with engines off can actually glide quite far.  A large aircraft 
losing engines at cruise altitude can glide about 10 to 1 meaning that starting 
at say 39,000 feet could glide for 74 miles before landing.

12 vs. 14, 24 vs 28.  What do you say the line voltage is?  110? 115?  117? 
120?  And do you mean nominal or acceptable normal range?  A "12 volt" system 
might have a low cutoff voltage of 10.8 but be floating at 14.4 (or maybe even 
slightly higher) volts.

Peter



On 11/16/2012 6:25 PM, WA5CAB at cs.com wrote:
> As I've written (perhaps tongue in cheek) before, aircraft radios and other
> electrical equipment are typically marked (or called) 14V or 28V (the fine
> print on the dynamotors may actually give the performance at slightly
> reduced voltage but always above 12.6 or 25.2 volts).  Ground vehicular equipment
> at least into the late 40's was marked 6V, 12V or 24V.  This is because a
> truck or tank with its engine off will glide much further than an aircraft
> will.  :-)
>
> In a message dated 11/16/2012 15:19:15 PM Central Standard Time,
> ka2ivy at verizon.net writes:
>> On 11/16/12 10:05 AM, Ralph Cameron wrote:
>>> I am told by former Canadian military staff that 14V was often stated on
>>> RCAF equipment because a fully charged 12V battery is 13.8V and that was
>>> close enough to call it 14V. At some point in time it was renamed 12V as
>>> being a nominal value and to conform to other services.
>>>
>>> Ralph
>>> VE3BBM
>>>
>> Calling it 14 volts is a compromise. A fully and recently charged 12
>> volt lead acid battery will deliver about 12.7 to 12.8 volts under light
>> load. This will decrease to about 12.6 and remain fairly steady until
>> the charge nears depletion. Conversely, charging regulators adjust the
>> voltage for battery temperature to insure full charging. A battery at -5
>> degrees C. will need about 14.2 volts for a while. At about 5 degrees,
>> 13.8, dropping to about 13.2 at 30 degrees will assure a full charge.
>> Because aircraft batteries tend to be in cold locations, they usually
>> receive these higher voltages. Aircraft electrical systems were often
>> set for 14 volts, and if the battery life was shortened, it was just a
>> cost of operating the aircraft.  They tended to be at minimum size that
>> would start the engine for weight saving, and had to be as fully charged
>> as possible. It was a great source of batteries for me in high school, a
>> battery that would not start a Beechcraft Bonanza (or a DC-3!) on a cold
>> morning was still great for radios.
>>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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