Real-world RMI usage?

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Martymccasland

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M.McCasland
I notice nearly any commercial jet has a RMI in the panel -- usually a separate gauge from the EFIS -- like a backup AI. However, few GA planes have a RMI.

Why?

How do you truly use one in the real-world? Not a textbook answer, but how you really use it?

I've have 2 in my Aspen. However, it dawned on me I rarely use them -- and wanted to reach-out for great little tips that aren't obvious / unlock something I've been overlooking.

The extent of my usage to date as been in instrument missed approaches. e.g. if the missed approach is something like "turn right direct ABC VOR, climb and maintain..", I dial-up the ABC VOR on NAV2 and turn on the RMI. On the miss, I just turn and make the RMI needle point straight ahead -- no twisting, turning, tuning, etc...

I did a little Googling and didn't find anything other than textbook regurgitation of what a RMI is.. 'Did find a few posts of ex-Military pilots talking of putting RMIs in their planes to feel comfortable, to have good SA, mention "it'll be the first thing I install"...

How do you really use an RMI in a way that truly makes it an indispensable instrument?
 
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An RMI is not indispensable unless you have no other device for determining what radial/bearing you're on. It's just another tool in the toolbox. However, if you have an Aspen, and the GPS satellites go on the fritz (or the military is playing GPS jamming games, as they are in Florida this week), the RMI function is very useful for determining when you cross a fix defined by a VOR/ADF crossbearing (assuming you have a VOR/ADF).
 
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When flying ADF approaches it make it much easier. Also it is possible to go direct to an intersection with a RMI but it's been so long since I've done it I can remember how. They are good for situational awareness.
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Here the panel of what I fly at work and while the HSI is displaying the FMS course the RMI is tuned to a local VOR. If the FMS stops working I know where I am without much guess work.
 
Martymccasland said:
I notice nearly any commercial jet has a RMI in the panel -- usually a separate gauge from the EFIS -- like a backup AI. However, few GA planes have an RMI.

Why?

How do you truly use one in the real-world? Not a textbook answer, but how you really use it?

I've have 2 in my Aspen. However, it dawned on me I rarely use them -- and wanted to reach-out for great little tips that aren't obvious / unlock something I've been overlooking.

The extent of my usage to date as been in instrument missed approaches. e.g. if the missed approach is something like "turn right direct ABC VOR, climb and maintain..", I dial-up the ABC VOR on NAV2 and turn on the RMI. On the miss, I just turn and make the RMI needle point straight ahead -- no twisting, turning, tuning, etc...

I did a little Googling and didn't find anything other than textbook regurgitation of what an RMI is.. Did find a few posts of ex-Military pilots talking of putting RMIs in their planes to feel comfortable, to have good SA, mention "it'll be the first thing I install"...

How do you really use an RMI in a way that truly makes it an indispensable instrument?
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RMI's are starting to disappear. The new Airbuses being delivered have deleted the Stand alone RMI's on the center panel (next to the last analog gauge in the airplane).

Newer technology is replacing them. With that said, I used RMI's for years and found them as a useful tool.
 
RotorAndWing said:
RMI's are starting to disappear. The new Airbuses being delivered have deleted the Stand alone RMI's on the center panel (next to the last analog gauge in the airplane).

Newer technology is replacing them.
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Except Aspens, Avidynes, and G1000's have them incorporated in their HSI displays -- and they are very useful in certain circumstances.
 
Ron Levy said:
Except Aspens, Avidynes, and G1000's have them incorporated in their HSI displays -- and they are very useful in certain circumstances.
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If you have the time, I'd appreciate some elaboration of the "certain circumstances".

Other than tuning them to a local VOR, NDB, or GPS fix and cross-checking every once in a while for SA -- or -- maybe direct-to navigation, I can't figure out many ways to use the ones in my Aspen.

Many thanks in advance for the education.
 
Ron Levy said:
Except Aspens, Avidynes, and G1000's have them incorporated in their HSI displays -- and they are very useful in certain circumstances.
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Used the RMI in G-1000 every time I flew...used the GPS as primary and used the RMI to see VOR's...

Also can use the RMI and DME to do a perfect DME arc...usually within .1 of a mile....
 
Martymccasland said:
If you have the time, I'd appreciate some elaboration of the "certain circumstances".

Other than tuning them to a local VOR, NDB, or GPS fix and cross-checking every once in a while for SA -- or -- maybe direct-to navigation, I can't figure out many ways to use the ones in my Aspen.

Many thanks in advance for the education.
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Sometimes on arrival or departure center will request to notify them we are crossing a certain radial. Without configuring the FMS I can just look at the ND and see the needles, makes it easy.

(I operate in a lot of non radar environment)
 
Kelvin said:
Used the RMI in G-1000 every time I flew...used the GPS as primary and used the RMI to see VOR's...

Also can use the RMI and DME to do a perfect DME arc...usually within .1 of a mile....
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Same. The RMI needles on the display track VOR (or ADF if selected) so it's a good cross check and SA tool.
 
Martymccasland said:
I've have 2 in my Aspen. However, it dawned on me I rarely use them -- and wanted to reach-out for great little tips that aren't obvious / unlock something I've been overlooking.
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I sometimes use them to dial in upcoming VORs that I'll be close by and watch them slide by. :D

I was going to write something about how you could use them if ATC queried you on what radial of XYZ VOR you are on; but if you have a 430, it's probably easier to go to nearest VOR and get the info there.
 
I have the Aspen 2000 setup. The RMIs are nice for crossing information when it is required, but it is rare that I use it on the PFD. Where I find it beneficial is to setup the MFD with the RMI for the localizer as a secondary confirmation of at least being on final course.
 
Martymccasland said:
If you have the time, I'd appreciate some elaboration of the "certain circumstances".
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When the GPS is out, say, because of satellite outages or military GPS jamming games (like those going on in North Carolina about 10 days ago or Florida this week) and you are trying to identify an intersection. This is especially true in those planes with no second CDI (like many Diamond and Cirrus aircraft), and most especially when you're flying a VOR or LOC approach with a step-down on final (where you have to keep the course tuned in and can't switch back and forth).
 
To the OP:

Since 2000 every VOR approach I've shot I've coupled the ap to the GPS overlay. To make the approach legal the VOR has to be displayed and an RMI fits the bill. So, how do I use an RMI? To make a VOR or NDB approach legal. Plane flies a nice smooth GPS approach and I monitor the ground station with the needles.
 
Captain said:
To the OP:

Since 2000 every VOR approach I've shot I've coupled the ap to the GPS overlay. To make the approach legal the VOR has to be displayed and an RMI fits the bill. So, how do I use an RMI? To make a VOR or NDB approach legal. Plane flies a nice smooth GPS approach and I monitor the ground station with the needles.
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Actually GPS overlays are uncommon now (very few "or GPS" remain). I think maybe what you are saying is that your GPS has the VOR approach in its database and will allow you to navigate using GPS even though you're not supposed to be using the GPS for primary navigation here so you use the RMI while leaving the HSI or whatever your primary course indication is to GPS.
 
flyingron said:
Actually GPS overlays are uncommon now (very few "or GPS" remain). I think maybe what you are saying is that your GPS has the VOR approach in its database and will allow you to navigate using GPS even though you're not supposed to be using the GPS for primary navigation here so you use the RMI while leaving the HSI or whatever your primary course indication is to GPS.
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Sort of. If I shoot the VOR 6 at ABC airport ill load the VOR 6 in the FMS. The plane flies the procedure using GPS with terminal sensitivity. But it's not a GPS, it's a VOR, right? That's why the needles come up. They show the course too, and more importantly show the station is active. If the VOR dies in the middle of the approach then that's controlling and a missed is executed. Interestingly, in that case I'd have to either fly the published missed using GPS alone (VOR is dead, right?) or get radar vectors.

So yes, VOR is controlling as it alone drives whether or not we can do it. But location and control of the airplane are GPS driven. Works great as this way the plane doesn't seek over the VOR when the needles get wobbly. Makes for a smooth ride throughout the approach...at least until the AP comes off :)
 
They don't always point to NDB/VOR. Some are selectable up to give RMI to the waypoint.
 
We use them all the time for:

- Visual approaches (D-> airport and OBS to arrival runway, bearing pointer will show BRG to the airport while the HSI needle will point in the direction of the approximate final)

- To fly a VOR approach with no overlay, couple to autopilot to the FMS but keep the pointer displayed to have legal raw data presented.

They make DME arcs way easy, but we never do those outside of training.
 
Many airports in Russia have dual NDB approaches. A dual needle RMI is a must for these approaches. The NDBs are line up with the runway so you need to keep the needles line up with each other to be on the approach path. Works pretty well.

José
 

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Piloto said:
Many airports in Russia have dual NDB approaches. A dual needle RMI is a must for these approaches. The NDBs are line up with the runway so you need to keep the needles line up with each other to be on the approach path. Works pretty well.

José
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Fascinating. Have never, ever heard of a dual NDB approach before.

'Could see it working well -- or really mixing up your mind if one was not totally in front of what was going on...
 
DME arc. That's about it. RMI functionality is embedded into (E)HSI displays these days. Stand alone RMI presentation is a waste of panel. Hell, so are standalone CDIs.
 
Piloto said:
Many airports in Russia have dual NDB approaches. A dual needle RMI is a must for these approaches. The NDBs are line up with the runway so you need to keep the needles line up with each other to be on the approach path. Works pretty well.

José
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I love these; stupid simple, gives sure-thing runway alignment and other necessary information, using ground stations which are cheap to erect, cheap to maintain. Depiction simple as simple can be - needles make a straight line? You're lined up.
 
Martymccasland said:
The extent of my usage to date as been in instrument missed approaches. e.g. if the missed approach is something like "turn right direct ABC VOR, climb and maintain..", I dial-up the ABC VOR on NAV2 and turn on the RMI. On the miss, I just turn and make the RMI needle point straight ahead -- no twisting, turning, tuning, etc...
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If you just make the needle point straight ahead, any crosswind component will result in a curved path to the station.

On the Aspen (or G1000, and presumably most other glass) the better technique for this situation would be to put the head of the relevant RMI needle right on the little diamond that represents your ground track. That'll give you a straight path to the station.

I have RMI's in the planes I fly most now - Argus display in the Mooney, Aspen in the 182RG, and G1000 in the DA40. I still don't use them a whole lot.
 
My Sandel has two "bearing pointers", essentially RMI needles that can be configured to point to either the next GPS waypoint or a VOR. I thought I'd use them a lot as I really liked the RMI when I flew a plane without a MFD or a moving map GPS. But except on XCs where I use them as a backup for SA, I rarely use the BPs at all. For primary SA, the MFD is much more intuitive. Heck, for that matter, so is the iPad. :)

Now I'll probably feel differently the first DME arc approach I fly. But there aren't any nearby.
 
RMI really are nice for arcs.

Here's something funny. People mention using them for SA. Okay I get that. But ProLine 21 has auto tune feature. It's tuns the Nav 1 and Nav 2 radios to get DME/DME info to fix the plane and augment the GPS. It tries to select a VOR off the nose and one off the wing tip to maximize accuracy of the fix.

The funny thing is I see guys throwing up the bearing pointers on their PFD citing SA. Really? You have no idea what VOR it's pointing at! How is that SA? That's clutter in my book.
 
So far, except for the double NDB approachs which do not exist in the US, no one has answered the OP's question. It wasn't in what situation does one use an RMI but how does one physically interpret it in these situations.
 
Captain said:
The funny thing is I see guys throwing up the bearing pointers on their PFD citing SA. Really? You have no idea what VOR it's pointing at! How is that SA? That's clutter in my book.
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It's not clutter if you ID the VOR first...
 
azure said:
It's not clutter if you ID the VOR first...
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The system auto IDs. But in AUTO it doesn't display to the pilot. It only displays to the pilot when VOR is selected taking it out of AUTO. Plus, it constantly tunes and re-tunes without warning to the pilot. Trust me, it's clutter.
 
Captain said:
To the OP:

Since 2000 every VOR approach I've shot I've coupled the ap to the GPS overlay. To make the approach legal the VOR has to be displayed and an RMI fits the bill. So, how do I use an RMI? To make a VOR or NDB approach legal. Plane flies a nice smooth GPS approach and I monitor the ground station with the needles.
Click to expand...

Henning said:
So far, except for the double NDB approachs which do not exist in the US, no one has answered the OP's question. It wasn't in what situation does one use an RMI but how does one physically interpret it in these situations.
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My first post on this thread answered his question directly. He asked how I use an RMI real world and I told him.
 
The last airplane I flew professionally was a twin turboprop, with dual VOR/DME, ADF, and no autopilot/GPS.

We had EFIS tubes that showed us data from the above in a bunch of different ways. My favorites were arc (the top of an HSI - better precision) and a crude moving map that let you visualize the selected radial, a preselected radial, and stations.

However, bearing pointers could be imposed on the HSI view or ARC, and they were really useful in a number of ways. Ones I can think of right off:
- DME arcs (along with groundspeed.. you could do them perfectly)
- Situational awareness in getting set up to intercept a final approach course, provided there was a locator for a marker, or a VOR on the field. When you fly that segment at 160kias it was really, really easy to blow through or come in too shallow and then just not have enough time prior to FAF
- For any flying that took you over a station. you could get really nice clean station passage by taking note of the needle behavior before entering the cone of confusion, versus passing off to the side a mile

And no, this was not just training environment type stuff. Holding, full procedure approaches, and the like were done to most stations we flew to.

Rarely did I use a bearing pointer over the HSI (in other words, the true RMI) by itself. It was the additional data to whatever I was doing above that was really useful.

Finally, the beauty of the RMI was that there was no difference in VOR vs ADF work. The dreaded NDB approach was no big deal, at least in terms of instrument interpretation.
 
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Captain said:
The system auto IDs. But in AUTO it doesn't display to the pilot. It only displays to the pilot when VOR is selected taking it out of AUTO. Plus, it constantly tunes and re-tunes without warning to the pilot. Trust me, it's clutter.
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Hmm, learn something every day! :)

Actually, I missed that you were talking about PFDs and thought you were including aftermarket pseudo-glass like my eHSI. It doesn't do auto ID, though both the 480 and the SL-30 do.
 
Martymccasland said:
If you have the time, I'd appreciate some elaboration of the "certain circumstances".

Other than tuning them to a local VOR, NDB, or GPS fix and cross-checking every once in a while for SA -- or -- maybe direct-to navigation, I can't figure out many ways to use the ones in my Aspen.

Many thanks in advance for the education.
Click to expand...

RMI on a DME arc makes them brain dead easy.
 
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