[ARC5] Bendix RA-1B receiver

[Roy Morgan]

On May 13, 2014, at 6:12 AM, Robert Eleazer <releazer at earthlink.net> wrote:

> With aircraft magneto switches, if you turn it to "Both" that means the switch is disconnected from both magnetos.  If you turn it to "1" the switch is then connected to Magneto #2, and vice versa for Magneto 1.  

To clarify a bit for those who may never have used an aircraft magneto switch:
 The switch SHORTS OUT the selected magneto.  So, if you put the switch in position 1, and the engine RPM falls more than the allowed amount, it means that magneto 2, or some of it’s spark plugs are not working well enough to reliably run the engine if the other one fails.  Aircraft engines have two spark plugs per cylinder for (at least) two reasons: to allow for continued operation if one magneto fails, and to ignite the fuel/air mixture under normal conditions in a better way.
 Putting the switch in the BOTH position should cut out the engine altogether. This is done VERY briefly to avoid blowing off the exhaust stacks from extra fuel.  I can’t remember related emergency procedures well but you might want to do this in a ditching landing where fire would be a further complication.  (Also, doing a full autorotation to landing in a radial-engined helicopter such as at the H-34 after loss of a tail rotor, you want no power from the engine, for sure.)

> Needless to say, no doubt a large percentage of magneto switches out there are wired backwards. "I hook it to Magneto #2 in order to use Magneto #1?  How can that be right?”

My guess is that there were very few magneto switches wired wrong.  It’s an essential and very basic part of the engine controls, and initial building of an aircraft and later maintenance would include enough specific tests to ensure it’s all correct.  To that end, I would be very surprised if the cables to the magnetos were able to be switched.  That would be a classic Murphy condition that aircraft design and maintenance people learned very early in aviation history.

There is a tale about one of our submarines that was lost a long time ago.  The story told that a change had been made to the torpedoes in use AND that a method of testing the torpedo internal systems was to use a jumper cable that was specific to the type and model of the torpedo.  The submarine went to the bottom and could not be recovered.  Investigation revealed that the cable for the older torpedoes applied enough voltage/current to the firing system of the newer model to detonate it.  The sub was sunk by its own torpedo.

> As for driving on the right versus left side of the road, there is considerable empirical evidence that driving on the right side of the road causes tornadoes.  In places where they drive on the left, tornadoes are relatively rare.

Oh good.  I’ll keep that in mind when I next visit England.  I remember focussing hard while driving there so as to not wander by habit into a crash!  I don’t remember any tornadoes at all.

Roy

Roy Morgan
RoyMorgan at alum.mit.edu
K1LKY Since 1958