[ARC5] Interesting documents

[Michael Hanz]

On 11/21/2016 6:39 PM, Chris Bowne wrote:
> Re the SCR-274 modulator (containing the dynamotor) and the SCR-522 
> dynamotor located forward of the cockpit and the radios aft, perhaps 
> that was to minimize voltage drop on the high current dynamotor 28 VDC 
> supply cables by keeping them close to the generator on the engine?

A resounding NO!  It has _always_ been about the magic words "weights 
and balance".  I have a weights and balance analysis for the Enola Gay, 
and it is perhaps surprising to the uninitiated how much detail is put 
into this issue.  There was a formal document produced for every 
aircraft in WWII, and a great deal of effort was expended in getting the 
weights and balance right on the mark.  (It is often just a ditto copy 
for aircraft which do not regularly receive special equipment.)  It 
wasn't easy to keep them all up to date considering the rapid rate of 
equipment additions throughout the war, but no document was considered 
more important to the proper operational readiness of the aircraft 
involved.  If you put something new in the tail, you had to offset it 
with a weight forward of the center of balance - which is normally in 
the wing area.  A little thought will reveal why that is so critical - 
you can overpower bad balance with brute engine power (as happens with 
loading today's commercial aircraft), but what happens when things go 
south?  Lose an engine, and where are you?  It is even more critical 
with smaller, lighter aircraft.  Anyone who has flown in a light 
aircraft can almost feel if it is tail heavy or front heavy.

The current required by a BC-456 modulator is a tiny fraction of the 
total aircraft load, and it has an acceptable range of 24-28vdc. That 
doesn't require a large copper cross section to deliver from one end of 
the aircraft to the other.

73,
Mike  KC4TOS

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