Visual Approach Guidance
James Albright (a former G450 driver)
Updated: 2014-01-17
Let's say you are about to fly a visual approach to an airport with no instrument guidance whatsoever but would still like something to help with lateral alignment and vertical glide path guidance. Well you are in luck, we've had that ability since the GIV and if you follow the same techniques your G450 Heads Up Display will give you even more help.
What follows are techniques to provide a course center line leading to the runway and a 3° glide path to the runway, using Kiritimati / Christmas Island as an example. Once you've followed these procedures to any airport, your FMS will provide course guidance and a glide path and you will have Heads Up Display guidance. The guidance isn't as good as an ILS, but it is better than an NDB or other non-precision approach that doesn't align with the runway. And it is certainly better than no guidance at all.
PLCH Example
Photo: Christmas Islands Airport
For our example, all we have is the destination airport and runway available in the FMS database.
Photo: DU map display on final flight segment.
With no other entries, the MCDU will contain a single line for the runway, the runway elevation in small numbers, and the course from the previous point.
Photo: MCDU Visual Approach, Flight Plan "Before"
Take note of the runway elevation, in this case it is 10 feet. Add 50 to that and enter it in the scratch pad with a leading slash, in this case: /60.
Photo: MCDU, Visual Approach, 50' height in scratch pad
Press the right line select key adjacent the runway line to enter the new threshold crossing height, in this case LSK 2R.
Photo: MCDU, Visual Approach, Threshold Crossing Height Entered
Press the left LSK next to the runway to insert the runway identifier and the runway's reciprocal heading into the scratch pad, in this case: "PLCH.RW08/260/". Notice the runway line still does not contain any vertical guidance.
Photo: MCDU, Visual Approach, Runway Data Line in Scratch pad
Add to the scratch pad your desired distance, a slash, and the correct altitude at that point. A three degree glide path comes to 318' per nautical mile.
More about this: 60 to 1.
For years we've preached 300 feet per nautical mile since we were "eye-balling" the glide path. But with all the electrons available to us now that would mean we were flying a 2.85° glide path and some locations prohibit that. But if you are flying to a runway with a 875' elevation do you want to do the math? (3 x 318 + 875 = 1829')
I tend to use 3 nautical miles and 1,000', because it is easy to remember, the math is simple, and keeps us above the 3° glide path. In the photo we've added "3/1060".
Photo: MCDU, Enter 1,000' Point
Press the left LSK one line above the runway to insert the 1,000' point just prior to the runway. You now have a 3° glide path starting at your chosen distance leading you down to the 50' point above the runway threshold. The course is aligned with the runway. Notice the MCDU indicates a 3.1° glide path because the 1,000' height is slightly higher than the mathematically pure equation of 318' per nautical mile.
Photo: MCDU, Insert New Waypoint
Set up this way, the FMS will give you a course line to intercept that aligns you with the runway and a glide path you can use with VNAV. The HUD will also provide a CDI with course center line. Setting up the reference flight path angle on the HUD, coupled with the VNAV, you should be able to fly a stable approach. Of course this will probably be at RNP 1.0 so it isn't good enough to shoot a low vis approach, but it is still pretty good.
Photo: Resulting Map Display
References:
Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013
Gulfstream G450 Maintenance Manual, Revision 18, Dec 12, 2013
Gulfstream G450 Operating Manual Supplement, G-450-OMS-02, Extended Operations (ETOPS) Guide, Revision 2, April 2, 2009
Gulfstream G450 Performance Handbook, GAC-AC-G450-OPS-0003, Revision 20, November 30, 2011
Gulfstream G450 Quick Reference Handbook, GAC-AC-G450-OPS-0003, Revision 34, 18 April 2013
Gulfstream G450 Weight and Balance Manual, Revision 3, March 2008