[Milsurplus] 400 cycle 3 phase and WW2

[Bruce Gentry]

WA5CAB at cs.com wrote:
> Which engine did you normally start first (the one with no alternator or 
> one of the other three)?
>
> In a message dated 1/12/2011 8:30:16 PM Central Standard Time, 
> smithab11 at comcast.net writes: 
>   
>> The earliest aircraft that I can remember  with 
>> main bus 400 cycle AC power was the KC-135(707), 
>> First manufactured in 1955?
>> I used to spend many moments  after starting 
>> engines trying to get all three alternators on 
>> line with those flashing lights blinking at 
>>     -       you had to get the timing just right.
>> Now come to think of it, why only three (3) ? 
>> Wonder why not 4 alternators ?   - -  one for each 
>> engine.
>> We had a lot of 400 cycle noise in everything.
>>
>> 73
>>
>> breck k4che
>>
>>     
>
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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>   
For reasons I don't know, it is traditional to start number 3  first on 
a 4 engine plane.  I will also guess that engine has only DC 
generator(s)   so it can start the others  and spare the onboard 
battery, battery cart, or ground power unit from  the strain.  Many of 
the onboard batteries overheat dangerously if they are used for more 
than one start without a lengthy cooling period, especially with 
turboprop engines. Another possibility is that number 3 on the 707/C-135 
motors the DC generator(s) to start, and it in turn provides compressed 
air to start the other 3 and ventilate the cabin while on the ground.  
There are many ways and combinations  to get the job done, these are 
only a few.
    When I was in high school and learning to fly, I was attracted to 
the flight engineer's station rather than pilot, and like most techie 
nerds, admired Mr. Scott more then Capt. Kirk. Unfortunately for me, 
most airliners coming into service in the late '60s had been designed to 
eliminate the engineer, so chances of perusing it as a career were 
fading very quickly.  I also think the engineer was somewhat of a radio 
operator and would make in-flight repairs within his knowledge and 
supplies of tools and parts.  Bruce Gentry,   KA2IVY