[Milsurplus] indicator id

[J. Forster]

Gregory W. Moore wrote:

> GE, all,
> Just a quick question re this indicator.... is the dial a slaved compass
> card?

No. The card is just a 0 to 360 dial, settable by a knob in the lower RH corner of the indicator. What I don't know is why the pointers are red
and green.

> F'r instance to be used with either a remote fluxgate (usual) or
> as a gyro repeater?

Not AFAIK.

> Is there an adjustment knob for the aforementioned
> compass card (if there is one)..

Yes. See above.

> 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.

AFAIK, there is no magnetic heading on the unit. I suppose a fluxgate compass COULD have been adapted to indicate on one of the needles (both
readout via a selsyn), but it was not done AFAIK.

> 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.

>From the brochure I have, it's two ADFs reading out on one dial. Period.

> 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),,

The flyer is on it's way to the UK to be scanned for RoyalSignals. With luck it'll get there by mid Sept.

> I actually would, at first glance, from the description, probably call
> the indicator an RMHI,

It's a dual ADF. Basically two MN-62s on one indicator. This was 1946. The indicator just repeated the loop azimuth via a simple selsyn. The loop
was motor driven to null the received signal. It required 115 VAC 400 Hz at 0.85 A plus some DC. The ONLY servo loop is to turn the loops, one
per loop & rx set. The card is not on a servo. Period.

> 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

No. No motor tachs or loops. This is essentially an MN-31 (ADF version of a MN-26)

> 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..

No. Selsyns.

> 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
> >>