For those of you flying in the IFR world, you know how often ATC will grant a visual approach when circumstances permit. This can be a real time saver, both for you as the pilot, and for a swamped controller, working busy airspace.
Conducting such a procedure in a small piston plane is simplicity in of itself--you just land the plane like you would in VFR conditions. But for those planes with an FMS, it can be done with a bit more finesse, allowing the autopilot to remain on until short final. This prevents you from making a sloppy lineup with the runway centerline and (in the real world) following a 3 degree glidepath down to the runway threshold.
The ISG Smith's FMS (and probably the other one too) allows you to create these approaches "on the fly", either when you create your initial flightplan, or later, in the air as you approach your destination.
Here is an example of a flight I took from KLVK (Livermore) to KAPC (Napa Valley) in the Bay area on a VFR day:
I've created a very simple flightplan here--just two waypoints between these two airports which are close by each other anyway.
Now, I know conditions at Napa are VFR so I want to create a Visual Approach and I know because of the wind, I'll be using runway 36.
Looking on the airport diagram for KAPC, we find that the runway has an actual heading alingment of 006 degrees. Taking the reciprocal of that, we get 186. I want to create a waypoint about seven miles away from the airport so in the scratchpad, I type KAPC186/7 (see pic above).
Note that if you don't have the airport diagram, you can simply take the reciprocal of the runway number, in this case 180, to make it easier.
Go to the LEGS page, and enter what you've typed in the scratchpad for the new waypoint. Think of this point as the FAF on an ILS. In the plane I'm flying, I'd want to be at about 124 knots and 2500 feet at that point, so I'll enter 124/2500 in the scratchpad and enter it on R3:
Now you're ready to fly!
Here's what the presentation looks like, prior to the waypoint I created for the visual (the FMS labels the waypoint KAP01):
And as VNAV and LNAV descend the plane to the runway, here is how things look prior to landing;
Note the green boottom of the descent arc on the MFD. You want to watch this at all time to make sure the plane will be at the desired altitude at the right place. This can be adjusted by controlling your vertical speed as needed, in case the VNAV function fails or is inadequate for what you're doing. Note that the FMS always selects at least a 100 feet as the altitude for the airport which will leave you rather a high on short final. You can either change the altitude to zero (in the case of a sea level airport) or click off the AP at that point.
A few notes about this:
1. Like their real world counterparts, pre-programmed visual approaches won't necessarily line you up perfectly with the runway. This is due to three factors, but suffice to say that it needs to be understood that this is a visual procedure, as an aid to the pilot to get him in a position for a normal landing without making any radical manuevers. In addition, one must keep in mind that these do not guarantee terrain seperation.
2. The angle you have between your route and the last leg to the runway may cause the plane to start its turn late or early, which will affect how closely aligned you are with the runway centerline. This can be alleviated by slowing down prior to the turn or even creating an additional waypoint, two miles prior to the Visual waypoint.
3. I still find the VNAV function to be iffy at best, so be prepared to click the VNAV button off and descend using VS or manually.
Enjoy!
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