Why no RMI?

[jbs007]

Of the large and random assortment of GA aircraft I have flown, I don't think I've ever seen an RMI in one of them. Being a military pilot, I was taught to use one in flight school and every military aircraft I've been in has one. The truth is, it is probably the best instrument I have ever used. Nothing builds SA better than an RMI (for me at least).  Why do so few GA aircraft use them? Are they expensive to buy/maintain? I'm buying a Mooney and I think an RMI is the first thing I'm going to do to it. 

[Vref]

Quote: jbs007

Of the large and random assortment of GA aircraft I have flown, I don't think I've ever seen an RMI in one of them. Being a military pilot, I was taught to use one in flight school and every military aircraft I've been in has one. The truth is, it is probably the best instrument I have ever used. Nothing builds SA better than an RMI (for me at least).  Why do so few GA aircraft use them? Are they expensive to buy/maintain? I'm buying a Mooney and I think an RMI is the first thing I'm going to do to it. 

[xftrplt]

An Aspen Pro provides a RMI display with source-selectable needles on a slaved compass card.  I'm not familiar with Garmin and other brands, but I should think they offer similar displays.

[jbs007]

Hm, I guess I never considered the EFIS RMI's.  I'm kind of partial to old fashion.  Sounds like to have an RMI requires a few other gadgets as well.  I'm looking forward to getting my plane and figuring it out from there.  Thanks for the help!

[jlunseth]

An RMI assumes ground based navigation systems.  There appears to have been some excitement about them some years ago.  But the trend is towards GPS and away from ground based nodes.  Nothing gives a pilot better SA than a picture of where the aircraft is and where the airport is.  iPad, EFB's, MFD's are the trend.  So to give you an example, I have ADF, two Nav. Receivers, and a GPS?  If I were considering a further investment in Nav. Equipment, why would I choose on that relies on ground nodes that are going away, rather than better GPS and map display technology?g

[Vref]

Quote: jlunseth

An RMI assumes ground based navigation systems.  There appears to have been some excitement about them some years ago.  But the trend is towards GPS and away from ground based nodes.  Nothing gives a pilot better SA than a picture of where the aircraft is and where the airport is.  iPad, EFB's, MFD's are the trend.  So to give you an example, I have ADF, two Nav. Receivers, and a GPS?  If I were considering a further investment in Nav. Equipment, why would I choose on that relies on ground nodes that are going away, rather than better GPS and map display technology?g

[KSMooniac]

Quote: jlunseth

An RMI assumes ground based navigation systems.  There appears to have been some excitement about them some years ago.  But the trend is towards GPS and away from ground based nodes.  Nothing gives a pilot better SA than a picture of where the aircraft is and where the airport is.  iPad, EFB's, MFD's are the trend.  So to give you an example, I have ADF, two Nav. Receivers, and a GPS?  If I were considering a further investment in Nav. Equipment, why would I choose on that relies on ground nodes that are going away, rather than better GPS and map display technology?g

[Parker_Woodruff]

The RMI displays are useful in identifying intersections where you need to know that you're crossing a radial, such as on an IAP, STAR, or DP.  However, I would only bear that expense if it came with the purchase of a G500 or Aspen display.

Having a display like that assumes you have GPS, in which there are very few cases when it actually makes sense to use the RMI for primary identification of a fix.

[jbs007]

Well, sounds like the answer for no RMI's would be the GPS.  I can understand that.  The aircraft has a VFR moving map GPS (Garmin 250XL) connected to a STEC-30 with alt hold/GPSS, 1 VOR (on a CDI/GS) and an inop ADF.  I am not comfortable with ONE IFR instrument so I will do some upgrading.  I will probably get an IFR GPS (I was thinking 430W or maybe the new GTN-650). I also wanted the RMI because that is what I'm used to.  When it comes time to do some upgrading there will be plenty more research and yet another "Hey look at me! I'm upgrading my panel!" thread in the Vintage Mooney forum.

Thanks guys

[jlunseth]

If you have a GPS connected to a good AP you get a very capable IFR setup.  The 430W is an excellent unit, the only flaw is that it does not load Victor airways automatically, but I have never found that to be a problem.  If you fly on one of the coasts where Victor airways are assigned alot, you might feel differently.  A couple of thoughts.  One is that the new Voiceflight system is gaining a great reputation.  It allows you to orally dictate waypoints into a 430/530, and it does Victor airways which would elminate that problem. 

Typically, a GPSS is needed to hook a 430 directly to an AP, I noticed in your post that your AP appears to have one, which is good.  The 430W, with a GPSS and good AP, will fly entire approaches hands off, including procedure turns.  Some pilots don't like that idea, but I have found that having the AP control the aircraft gives you much more time to check and double check what is going on and where you are on the approach.  Really makes it safer.  You do have to make yourself fly some approaches hands on to stay in practice though.

The display on the 430W is quite small.  If you are a young guy with great eyesight that is probably no big deal, but a larger moving map, or event the combined GPS/moving map units such as the 530W or 750 are a great combination.  Of course, they want more money for them also.

I have to say, having a good AP, GPSS, WAAS GPS and a moving map, especially one with XM weather, takes an awful lot of worry out of instrument flying.  I just get them all going, then switch on the XM radio and put on the Love channel. 

[OR75]

All about situational awareness ...

With GPS moving map, there is no need for RMI or HSI

[Parker_Woodruff]

Quote: OR75

All about situational awareness ...

With GPS moving map, there is no need for RMI or HSI

[OR75]

Inside the IAF,  you only need one needle (+ a timer or a DME or a marker).   

[Vref]

For those flying international ADF is a must and an RMI a nice feature...everything depends on your mission.....World wiide there are still 6700 NDB's in use go figure....

[PTK]

Quote: OR75

Inside the IAF,  you only need one needle (+ a timer or a DME or a marker).   

[jlunseth]

The big problem with ADF's is that they are being treated as irrelevant.  So NDB's get decommissioned, or just turned off, but they still show up on the charts and most of the time you will not see a Notam either.  They are charted all over the place in the upper Midwest, but it seems like half the charted NDB's are not in service when you want them.

[danb35]

Quote: OR75

Inside the IAF,  you only need one needle (+ a timer or a DME or a marker).   

[BorealOne]

Quote: OR75

Inside the IAF,  you only need one needle (+ a timer or a DME or a marker).   

[Parker_Woodruff]

Quote: OR75

Inside the IAF,  you only need one needle (+ a timer or a DME or a marker).   

[kris_adams]

RM What??? Just kidding.  I've never actually seen one.  Only studied when I was getting my IR.

[jbs007]

Quote: Parker_Woodruff

I just find the HSI to be better for situational awareness than a moving map that requires a departure from the scan of the 6 pack, especially inside the FAF where there is no course change. 

[M016576]

A moving map/gps and a HSI are complementary... And I wouldn't want to fly any ifr without at least one ground based receiver (tacan/vor).  Two independent votes on your position are far better than one.  I find moving maps to be good for long range nav, but if I want precision in an approach, or close to a field, I rely on my HSI for course guidance.  As far as a vor/tacan point to point is concerned: it's quickly becoming a lost art, as most "new students" don't want to be bothered learning them, they'd rather just twist in the waypoint and follow the magenta line.  Once you think on a RMI card, though, and can "see" the correct point to point heading, I believe you have an advantage over those that rely solely on a gps.  I have an RMI display on my sandel sn3500: I use it quite a bit (the vor needle is displayed as well as the gps needle on the RMI card).  It's a nice display, similar to the aspen pro, but without the ADI portion.

[Jerry 5TJ]

Yes, an RMI is fine to have.  The G500 uses an RMI indication for your ADF receiver, if you have one.

Flying an NDB approach with the RMI on the G500 is easy...especially with synthetic vision, a moving map, a wind vector display, ground track and speed, well, it sure isn't like chasing the needle on my old KR86.