[ARC5] Interesting documents

[Michael Bittner]

In our SNJ training aircraft in 1955, the ARC-5 transmitter was mounted against the right side-wall, by the front cockpit pilot's right elbow, the MD-7 modulator was located between the front and rear cockpits, above the rear cockpit pilot's knees, and I don't know where the ARC-5 receiver was installed  - never saw it.  Nothing was tunable by either pilot.  If a VHF transceiver was installed (I don't remember the nomenclature), it was located in the baggage compartment behind the rear cockpit.  If not installed, a sand bag was strapped to the floor of the baggage compartment in its place (weight & balance).  
  ----- Original Message ----- 
  From: Michael Hanz 
  To: Chris Bowne 
  Cc: arc5 at mailman.qth.net 
  Sent: Monday, November 21, 2016 4:55 PM
  Subject: Re: [ARC5] Interesting documents


  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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