I’ll admit that I fib to controllers. Not about my altitude, or airspeed or course, but about approach procedures. I secretly track GPS/RNAV approaches without telling.
The good news is that the FAA has proudly announced that it has published 3,052 LPV (localizer performance with vertical guidance) procedures as of mid January. An LPV is the approach that mimics and replaces an ILS in terms of precision and reliability.
The FAA has also published thousands more, 6000 in all, I believe, GPS/RNAV approaches. Those procedures all have lateral guidance with excellent accuracy, and many also have glideslope style vertical guidance. Those are called LNAV with V procedures.
I congratulate the FAA for moving more quickly than I ever thought possible to take advantage of GPS accuracy and availability. And to accommodate airplane owners who have installed GPS navigators in droves.
But I fib to controllers because all of this wonderful progress in creating GPS/RNAV approaches hasn’t made it to the radar control room. Most controllers I deal with continue to believe that an RNAV approach is a different animal than say an ILS, or VOR procedure and must be flown differently.
Invariably if I ask to fly the GPS/RNAV approach instead of the conventional procedure being advertised as active I am cleared to some distant fix far out on the approach. If I were to fly the ILS the controller would simply vector me toward the localizer center line of the approach at some distance outside the final fix. There would be no need to go to an initial or intermediate approach fix. But ask to fly the LPV to the same runway and the controller sends me to an initial fix instead of vectoring me to the “localizer.”
There is absolutely no reason to treat the GPS approach any differently than a conventional approach. The centerline of the procedure is the same for the LPV and the ILS it overlays. A GPS approach on top of a VOR procedure is the same path over the ground. In our cockpits we can see the centerline right there on the moving map. Many flat glass displays have a dotted flight path prediction line so you can see where you will intercept the centerline of the approach based on your present heading.
My solution to this complication is to accept the clearance to fly the ILS while really having the LPV dialed in. The controllers see me intercept the LPV centerline exactly as I would the localizer of the ILS. And they see me start down at LPV glidepath interception just as I would when capturing the glideslope of the ILS. Everybody is happy.
And I don’t think my fibs are breaking any rules. I dial the second navigator to the ILS frequency. I glance at the “green needle” of the raw data ILS and confirm that it matches the LPV exactly. So I get the rock steady signal of the LPV while monitoring the less stable ILS signal. Am I really flying the ILS as I was cleared to? Yes. I am. I am flying exactly down the center line of the ILS even though the LPV is what I look at most for guidance.
Of course, the minimums can be different for a GPS approach versus a conventional procedure so you need to compare and be sure you know which decision height or visibility requirement to observe. For example, at my home airport at Muskegon, Michigan, the LPV minimums are the same 200 and one-half as the ILS to Runway 24. But on Runway 32 the LPV decision height is 300 feet compared to 200 feet for the ILS, but the visibility minimum is the same one-half mile for both procedures.
The FAA says it is totally committed to a world of WAAS aided GPS navigation. The entire Nextgen air traffic system is based on WAAS and GPS. And the procedures are established. All I want to do is fly those wonderful procedures without the hassle of flying extra distances to get out to some initial approach fix.
The FAA has even helped me in my innocent fibs by using the same names for final approach fixes on both ILS and LPV approaches in most cases. When GPS procedures were first overlaid on existing approaches the GPS procedure typically had different names for fixes, even though the outer marker or final approach fix was the same point on the ground. I used to compare the ILS and GPS approach charts to see if the fixes were in the same spot and to report the name of the ILS, not the GPS fix. But that’s not a problem anymore.
What I really think is happening is that many controllers do not understand that GPS, especially the LPV approach, is a total replacement for ILS. No procedural changes are needed for either pilots or controllers.
And I think there is also the issue of radar presentation. Controllers may not have, or may not be sure, of the exact path of the GPS approach course on their radar screens. For that reason they clear us to an initial fix so that we fly between fixes instead of intercepting a centerline that isn’t depicted on their scope.
I plan to keep telling the little white lies and fly the LPV or GPS approach. And I’ll dial up the conventional signal, too, until ATC catches up.