IFR Navigation using RMI

[Flightbuff]

I love my DC-3 but ...
... can someone explain the use of the dual RMI.  For example flying the night mail run fron Newcastle (114.25) to Manchester via VOR POL (112.10) I want to approach POL on 196d from Newcastle.  After takeoff I turn right to a heading of 140d.  I can tune and activate the stations but hav`nt worked out the relationships between Mag. Compass, HI, and the moveable card and needles on the RMI to enable me to intercept and maintain 196d !

[garymbuska]

 Ok I admit it what is RMI  ??? not ever heard that term?
Are you talking abou ADF? I fly IFR alot and that term is new to me.

[Flightbuff]

I have it as Radio Magnetic Indicator but it may also be ADF

[RollerBall]

RMI stands for Radio Magnetic Indicator. Usually it has 2 needles - 1 for VOR (VOR2 usually in FS) and one for ADF.

Let's say for sake of argument that NAV1 and the VOR on your RMI are on the same frequency. They won't 'point' in the same direction since the arrow on the RMI always points directly to the VOR beacon, while the arrow on the HSI is aligned with the radial that is tuned in. The same goes for the ADF needle on the RMI, it points towards the NDB.

Dual RMIs are obviously useful for working out fixes between 2 VOR beacons which you had to do before all the conveniences of GPS and FMCs. If you wanted to fly from A to B using VOR's you rarely wanted to fly from VOR to VOR otherwise you would be zig zagging all over the place. Rather you wanted to fly from VOR intersection to intersection much as you do nowadays, although now it's all worked out for you.

In the days of the DC3 you had to get your chart, draw your track on it with your chinagraph pencil and work out your own waypoints using any navaids that were available. Because NDBs are of rather low range, you usually had to rely on VORs and your waypoints were therefore where radials of 2 VORs intersected. You had to work out the bearing to each VOR and use these bearings to fly your route.

You'd be flying by hand or maybe with a wing leveller. Unlike FS, you can trim most aircraft accurately enough to maintain an altitude pretty easily so you could fly without too much effort at the speeds of those days without too much effort without needing an autpilot.

Oh and if this all sounds a bit obscure compared to the 'jump in and go' approach nowa days, don't forget that these VOR radial intersections would in fact be 'secondary' checks on the accuracy of you flight planning. You would have taken an hour or more beforehand with full weather data for takeoff, en route and arrival plus winds aloft data which you used with your flight computer to accurately compute the headings, speeds and times of each leag of your flight plan and you took care to ensure that once you worked it out you flew it. If you didn't, you got lost.

I'm looking at my Airtour CRP-5 Computer right now which I used when I learnt to fly in the 70s - and used for all my flights at that time no matter how short. It's almost exactly the same as those good ole DC3 pilots would have used not to mention the guys in 1939-45.

[Brett_Henderson]

The RMI in the DC3 is a tricky beast. First (biggest) difference between it and it's modern cousin (like in the KinAir) is that the heading ring DOES NOT adjust automatically when you change headings. When you are established on a heading, you MUST adjust the RMI to the same (If you want the same, relative readings you're used to).

[iVIPER21]

the way you read the RMI is as follows:

if tuned to a VOR, the radial FROM the station is read under the tail of that arrow.

if tuned to an NDB, the bearing TO the station is read at the head of the arrow and the bearing FROM the station is read at the tail of the arrow.

just thought i'd point that out in case it wasn't clear enough in the other posts.

[Flightbuff]

Well done chaps normal service is (nearly) resumed !
With DC-3 on RWY 7 at Newcastle. Heading Indicator (HI) on 072. Bring up the Radio Stack Panel. Top left is VHF NAV-1 with default setting of 110.30. Click on right rim of large dial until vertical reads 114. Click once on left rim of small dial - horizontal now reads .25 (pointing to NAV-1 should show 114.25 MHz. You are now tuned in to Newcastle VOR. To activate click on the switch currently on ADF-1. This will toggle the switch to NAV-1 and green light will glow. Note that the red pointer on the Radio Magnetic Indicator (RMI) has moved. Hide the Radio Stack and rotate the RMI card until 196 is under the Marker (filled in white triangle). This is the direct bearing from Newcastle VOR to POL VOR and the one to track.
Takeoff and climb straight to 1500ft. Make a nice right turn until the Heading Indicator (HI) reads 240. This would meet 196 at a reasonable intercept angle of 45. Fly for a few seconds then bring up the map to check your approach to the plotted route. Continue an watch the red needle on the RMI creep up towards the Marker. You will need to judge when to make your left turn to bring you on track that is when the TAIL of the needle is ditectly under the Marker. Staying on track takes practice - try leaving your pointer on the HI which will give you an exact heading periodicaly.
Will add to this topic soon.

[Flightbuff]

So far so good -- on track for POL VOR and as per Flight Plan @ 6,000ft.
Unless I calculate by time and distance I will overfly POL and never know (no DME on the DC-3 !)
Time to tune and activate POL VOR (112.10) on VHF NAV-2. Note that the Green pointer is now overlaying the Red and is pointing towards 196 on the RMI card. The Red tells me that I am tracking FROM Newcastle on 196. The Green also tells me that I am heading TO the POL VOR but on the reciprical of 016 (196-180). I could have activated both at Newcastle. I now toggle NAV-1 to off and fly by NAV-2. When I overfly POL VOR the needle will reverse (very smartly if I am directly over the station).
I have decided to land on Rwy 24R at Manchester ...
Soon

[Flightbuff]

Ms Flight Plan for VOR to VOR Newcastle to Manchester gives a heading of 199 from POL to Manchester (113.55) which would be ok if ILS DME was available but I have only RMI. At night and with the possibility of poor visibility I will need a "straight in" approach. Jeppeson chart 11-3 for Rwy 24R gives an ILS DME approach and provides an option for a "straight in" when arriving direct from POL. This requires leaving POL VOR on R-180.
On arrival at POL @ 6,000ft things move quickly. As NAV-2 is still tuned in to POL I rotate the card to 180 and make a left turn of about 19 degrees to track 180 FROM the POL VOR. Chart 11-3 requires a descent from 6,000 30 3,000. With no DME I must improvise by being at 3,000 when I reach the "straight in" location.
After leaving POL I tune in and activate Manchester (113.55) and rotate the card to 236 (236 being the "straight in" bearing  for Rwy 24R). As the Red needle nears the Marker I make a right turn when I should be about 8.5 miles from the runway @ 3,000 on R-236 when the needle lines up with the Marker. I know 24R is long, allowing some margin if I get it wrong.
I made a good landing at night.
Final comments soon ...

[Nexus]

Well, I can't offer some major advice, since you seem very comfortable at "old school" navigation
But do you use a timer?
I though that was very important, so you can calculate distance from/to a VOR or NDB?

[Flightbuff]

My first post questioned the use of RMI in navigation. I now know how to find my way around but I have to admit that (apart from flying at night in fog) there has been no real weather challange. I also ruled the skies with no ATC and no traffic but at least I can navigate the DC-3. All that is to come.
Up to 1999 a DC-3 was chartered to carry mail from Newcastle to Manchester. I miss the familiar drone as she passed over my house some 20 miles from the airport at about 2300 hours. I regularly stay in Gunnerside (upper Swaledale) which is also under the flight path and it was great to hear her pass over at about 2320.
Happy flying and waggle your wings when you overfly my house but keep the noise down chaps !
Over and Out

[Flightbuff]

While connected just to enlarge on some points :-
1. Jeppeson Charts
I bought Europe only and it`s great if you intend to be even half serious about simming.  Departure procedure from Newcastle and arrivals at Manchester are included.  I simply scanned for an approach not requiring ILS or DME
2. Establishing on a given radial
ATC would expect you to do this in reasonable time.  Given the Newcastle scenario the quickest would be a tight right turn off 72 onto 108 bringing you parallel with the runway and a quick left turn off 108 onto 196 giving you an intercept angle of 88 (196-108).  You are allowed some leeway.
A 60 intercept would be better.  You could use a lot less but this would delay establishment.  I use 45 so for the above I would turn off 72 onto 150 (196-45=nearly).  As you approach the 196 make a 15 left and hold for a few seconds then another 15.  This will slow down the movement of the needle then do a slow left until the needle is plumb with the Marker.  Recovering from an overfly is a pain and uncessary
3. Staying on a radial
When established at the correct altitude you can use Auto-pilot AFTER you have practiced manual - these gadgets do fail !

[Flightbuff]

Hi Nexus82
MS Flight Plan gives distances between stations en-route.  ETAs can be worked from them
Otherwise I suppose tuning in to a station left or right of my track will tell me where I am on my radial and AERAD will give scaled distances.
As a last resort I could contact Radar Control with our call sign "We`re the Fegawi"

[Flightbuff]

Are you ready for this !
Its 1943 and you are a USAAF pilot flying Dakotas from your base on San Clemente Island.  Your mission is to fly the supply run from base to Los Angeles Int. carrying personnel and returning with personnel/supplies.
Set up a Flight Plan from San Clemente I (KNUC - Rwy 5) with destination Los Angeles Int. (KLAX).  Choose the options "IFR" and "VOR to VOR".  Edit to include waypoints VOR Santa Catalina SXC (111.40),  VOR Seal Beach SLI (115.70),  NDB Vinee (Burbank 253.00).  To avoid civil traffic you are routed via the "back door" to Los Angeles Rwy 24R which is reserved for the military.
Print the Flight Plan.  KNUC - SXC is Leg 1,  SXC - SLI is Leg 2,  SLI - UR is Leg 3.  For KLAX enter (113.60),  cross out Alt 126 and for Hdg 173 replace with 249.  On Leg 4 you will leave Hdg 313 onto 249 for an (almost) staight in to Rwy 24R (on extreme right) using charts/judgment for landing.
In IFR conditions you must adhere to the Flight Plan.  In VFR conditions you must land on Santa Catalina using best judgment.
TIP :- when nearing S. Catalina I (at about 3,000ft) save the file with name "Approaching Catalina".  Believe me you will run this a few times !
Chocks away

[nickle]

Airborne tune in Manchester VOR.

The present radial and distance is your position from Manchester.
You want to go to Manchester 194 degree radial at, say, 20 miles for an ILS approach.

Take a pencil and lay out a course tail end of the needle present position  to the 194 degree radial at the desired 20 mile distance on the RMI.  Say you are at 60 miles.  One third of the 194 degree radial is the point you want to navigate to.  Holding the pencil parallel 60 miles to 20 miles, move it to the center of the RMI and read the heading.  Fly that heading.  The distance is 60 miles present to 20 miles desired, 194 degree radial.  Measure the distance and estimate from the present radial 60 miles as reference.  You will then have both the heading and distance.  Divide distance by miles per minute and now have time.  Watch VOR needle radial change and remeasure from time to time.  VOR needle does not swing initially with changes in heading as does the ADF needle.  Needle movement is in response to change in position (radial and distance).  Think of the RMI/VOR as showing present location.  Inbound to the station on the 194 degree radial, the course will be 014 degrees.