Today's RMI pointers: the ADF and RMI are becoming tools of a bygone era, but their descendant has a useful niche even in an all-glass cockpit.
I've learned that the oft-unused bearing pointers provide a great supplement to the standard G1000 display. Being old-school by training, I think of these pointers as modern analogs to the old RMIs used with ADF and VOR stations.
The head of the pointer points at the VOR or active waypoint and the tail shows what radial you're currently on. Bearing pointers home on VORs or active GPS waypoints, including airports or intersections. If you have an ADF installed, it also displays using a pointer.
You typically use bearing pointers for supporting information and cross-checks. But because they are displayed on the HSI, they are readily visible during the normal scan and, as such, provide an almost automatic situational awareness.
If you are navigating using a GPS flight plan, you'll rarely see the needle pointing aft. Exceptions are on vectors, outbound for a procedure turn, or in a hold. If you see the needle pointing anywhere except forward, cross-check your location. If you are navigating using VORs, the needle acts just like an NDB, swinging aft when you pass the VOR.
There are also specific occasions when the bearing pointers can be especially helpful and make up for some of the shortcomings of a modern glass cockpit.
A Departure Pointer
A typical northbound departure clearance from Santa Monica, Calif., is, "Fly heading 210 until reaching the LAX 315-degree radial, then turn right to 270 degrees for radar vectors ..." With no departure procedure in the database or waypoint where the departure path crosses the LAX 315 radial, this clearance doesn't lend itself easily to GPS navigation alone.
The easiest answer is to set a bearing pointer for the LAX VOR. I always leave the number one pointer selected for the next waypoint in my flight plan, so I'd use the number two pointer for this kind of supporting navigation.
The head of the needle points at the VOR, so the radial you're on is whatever value is under the needle's tail on the HSI. Fly the departure heading until the pointer's tail reaches 315 degrees, and then turn right to 270 degrees. That's it.
You could also use the MFD's Nearest VOR page, but the bearing shown is to the VOR, so you'd have to turn at the reciprocal of 135 degrees (315 - 180). Or, you could use the OBS feature to create the 315 degree radial from LAX and fly the departure heading until you reach the OBS defined intersection and then turn to 270 degrees. The problem with this approach is that it operates independently of the flight plan, and you'll want to make sure that the correct leg of the flight plan is active when you switch back to GPS guidance..
You could also create a User Waypoint for where the departure path crosses 315 radial, but that would take a bit of button-pushing or figuring. That might be worth it if you flew this departure all the time, but not when it comes up as a surprise with the engine running. The bearing pointer solution is quick, simple and effective.
Points for a Holds
As useful as GPS is, if you're asked to hold at a fix that isn't in a waypoint in the database, you have to find another way to identify it. If you're given a DME off a VOR, the process is simple. You could even use that information to create a User Waypoint for the holding fix.
But what do you do with this clearance: "Hold on Victor 107 at the Priest 60-degree radial"? Northbound, V107 is defined by the Avenal (AVE) 313-degree radial. The Priest VOR will be located to the south and west. This is old hat with two VORs and two CDIs, but the G1000 only has one HSI/CDI.
The simple answer is, again, bearing pointers. With either your GPS or VOR course set on the HSI, continue flying V107. Next, enter the Priest VOR frequency (110.0) into Nav 2 and display the pointer on the screen.
Track toward the fix using normal navigation. As the tail of the bearing pointer arrives on 60 degrees the holding fix has been reached so make whatever holding entry is appropriate. If it looks like you'll be there a while, you can always create a user waypoint at the holding waypoint as you cross the fix.
Even for your run-of-the-mill holds, a bearing pointer is great in a hold because it points at the holding fix so you always see clearly which way to turn in the hold.
If you're on vectors with a direct-to for the airport or the FAF, the pointer will point to that active waypoint. Having the bearing and distance to this waypoint right in your scan on the PFD is great for situational awareness when being vectored for a VFR arrival to an unfamiliar airport, or on the downwind for an instrument approach.
When you're doing your own navigation, the bearing pointer will line up under the CDI's course (magenta line) shown on the HSI whenever the aircraft is on course.
If the aircraft is left or right of course, the CDI will display ah off-course indication, and the bearing pointer will not underlie the GPS course. Typically, the bearing pointer will point to the same side of the HSI as the CDI's D-bar. Both of these tell you which way to turn to get back on course. In extreme-wind conditions, the bearing pointer might point toward the opposite side from the D-bar. You'd turn towards the D-bar as always, but this is a heads-up to you that you really blew the wind correction and/or that you're really close to the fix. Either way, it should be a wake-up call.
While flying a DME arc is a cakewalk with GPS, it's also simple with the inbound VOR on a VOR bearing pointer. Set the HSI pointer for the inbound course at the end of the arc and the bearing pointer to the reference VOR for the arc. Now keep the head of the bearing pointer aimed at your wingtip, adjusting for wind to keep the correct distance from the VOR. When the bearing is only five or so degrees from the HSI's inbound course, begin the turn inbound.
If the pointer is set to a GPS navigation source, such as the missed approach point or runway threshold, it will almost always point to where you can expect to see the runway when you break out. The pointer also helps keep orientation--and distance--clear when circling in low visibility or darkness.
If you go missed during a circling approach, the needle helps you keep track of where the next missed-approach waypoint is relative to you. What it shows is for situational awareness, so you still need to fly whatever turn takes you into a safe area to reconnect to the missed approach as published.
New Panel, Old School
If you want a real challenge, try flying the bearing pointers for an approach (preferably in VFR conditions). Essentially, you have the techniques you learned way back with ADFs, but the ADF needle is plopped directly on your HSI (which is essentially what the old RMIs did).
If you learn to use these ADF-like bearing pointers, you can add to your navigation and approach skills and will have something both new and old that is fun to practice and perfect.
Joe Shelton sometimes misses listening to hall games on his old ADF, but gets over it by surfing satellite radio.
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|Title Annotation:||IFR TECHNIQUE; radio magnetic indicator; automatic direction finder|
|Date:||Oct 1, 2009|
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