[Milsurplus] indicator id

[Gregory W. Moore]

GE, all,
Just a quick question re this indicator.... is the dial a slaved compass 
card? F'r instance to be used with either a remote fluxgate (usual) or 
as a gyro repeater?  Is there an adjustment knob for the aforementioned 
compass card (if there is one)..  The reason why I am asking is, since I 
am an 'ol Aerospace engineering type, as well as a comml pilot (no 
medical, groundpounder now) I am more than familiar with
the good ol RMHI (Radio Magnetic Heading Indicator) which, if  someone 
on the list is not familiar with same, is an instrument with a slaved 
compass card, and two indicator needles, one wide and double, and one 
single. 

The configuration can ( and was) myriad, one needle ADF and one showing 
course "TO" the selected VOR, or both to ADF or both to VOR "TO".  I 
have seen all three variants.... The compass card could be switched to 
"slaved" or "fixed" allowing one to show magnetic bearing, or, relative 
bearing, and many of them allowed magnetic variation to be dialed in 
without the slave feature trying to compensate.

They also were great as a backup compass, since, for all practical 
purposes, they mirrored the fluxgate, and could be checked against the 
good ole whiskey compass anytime,.

If you have a pix of this, I would surely like to see it, for this one 
is a new animal as far as I'm concerned, as I am not familiar with the 
NA-1 Bendix Nav system ( wouldn't mind seeing a pix of that either),,

I actually would, at first glance, from the description, probably call 
the indicator an RMHI, because that's what I am familiar with,
and what I am used to working on.   If you want to get it operational, 
the requirements ( this is a SWAG on my part, because I am
going by all the other RMHI's on which I have worked) would be 400Hz 1~ 
excitation for the rotors of each synchro rcvr ( they could well be 
transmitters as well, as synchro xmtrs and rcvrs are inherently 
interchangable) the same for the rcvr of the compass card ( there is 
possibly a servo loop here, depending on the manufacturer, so there may 
be a torque motor/tachometer driving a gear train, and a CT (control 
transformer) reading the compass card position.  This is due to the fact 
that in a lot of cases, these were in multiplace aircraft
with multiple installations of this instrument, and one servo amp fed 
several units, as well as fed into the autopilot for "course hold"...

There is a possibility that one, or both of the pointers are also servo 
loop driven as well, but I have rarely seen this..

At any rate, 400Hz 1~ for the rotor excitation of the pointers and the 
compass card synchros, and adjustable DC for the dial lamps ( I will 
leave the volts up to you, since that can change with the end user... 
you are good to go..

Just connect the stator windings of whatever synchro xmtr you wish to 
use to the appropriate pointer rcvrs, the same with a synchro
xmtr for the compass card, excite the rotors with the same 400Hz 1~ that 
you used for the indicator, and it should work fine.

At any rate, since I never have seen this particular navigation system, 
I really would appreciate a pix.. I always wanted to put an RMHI
in the A/C I briefly owned, but never could afford one... ( actually I 
never could find a complete system that I could put in a box and walk 
away with ==hi==)....Calll me crazy, but I used to actually enjoy flying 
NDB approaches, it is too bad that the FAA just arbitrarily decided to 
do away with so many of them, they were really handy..

I don't mean to lecture on the use of this if you already know all of 
the above, but if you aren't familiar with instrumentation, maybe this 
will help for starters ;-)

73 de Greg "GW" Moore WA3IVX/NNN0BVN

J. Forster wrote:

>It's a dual azimuth indicator used with the NA-1 Navigational System by Bendix.
>It's a dual ADF using two MN-62 Rxs and two loops. It gives you two independent
>bearings to two Txs at the same time. The R and G likely stand for the pointer
>colors (red and green)
>
>The data sheet (C 1946) will appear on RoyalSignals in a couple of months, with
>luck.
>
>-John
>
>
>jedifox wrote:
>
>  
>
>>hi group,
>>          does anybody know what a MN-42 dual indicator made by bendix
>>goes with ? it has 2 indicating needles one marked 'R' and one marked
>>'G' .  thanks in advance for any assistance.
>>
>>highest regards
>>leigh
>>    
>>
--


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