This also had to do with the fact that the speed of the plane I was flying (a Grumman) did not require a glidepath to be portrayed outside of the intermediate fix HOBMI at any point. I did this approach multiple times in July in 105° degree heat with no problems noted. Specifically, while flying the Dallas Executive Airport (RBD) RNAV Runway 35 approach, using an Avidyne IFD and its "advisory glideslope" functionality, the "advisory glideslope" allows us to comply with all of the crossing restrictions on the chart while simultaneously avoiding the "dive-and-drive" methodology often employed on non-precision approaches. I have not found an instance in 100+ hours of instrument instruction this past summer where the advisory glideslope takes an airplane below the minimum crossing altitude at the final approach fix, nor any intermediate fix. There is also no restriction on following an "advisory glideslope" outside of the FAF so long as the airplane is at or above the relevant minimum crossing altitude at the next fix. In areas where altimeter error is great enough to warrant a temperature correction, the FAA has established cold temperature operations procedures on those approaches. I'm not sure I agree with the premise of this post. ![]() Obviously I'm still struggling with how best to present them to instrument students. There's a glidepath that looks just like the LPV, but you can't intercept it prior to the FAF you can follow the glidepath if you want to, but you don't have to watch out for final stepdown fixes (that you can ignore on an LPV) you're flying a glidepath, but remember you can't go below DA like on an LPV, etc. An IR student is already pretty swamped by material, then you introduce all the weirdness of the +V. This is one reason why, while I understand the intent of the +V approaches, I do feel that they really complicate training. I agree, if there are stepdowns, then it would be silly to increase workload even more by approaching the glidepath from above, adjusting configuration to capture it, then adjusting again to level off prior to each fix (as you would have to do when its warm). The procedures that prompted this question do not have stepdowns in final so I was not considering that. Thanks to those who brought up stepdown fixes. ![]() LNAV/VNAV glidepaths, while designed for Baro-VNAV systems, are flown using WAAS in the Garmin GPSes so the same situation applies. So the glidepath itself is unaffected by temperature, however the location of the aircraft along the glideslope for any indicated altitude does vary by temperature. ![]() You have basically two choices - do you intercept it from above (which we usually specifically teach not to do with glideslopes), or ignore it?įor CFIs - how do you teach how to use the advisory glideslope on "+V" approaches? Then you reach the FAF and can start descending, however the advisory glideslope is now below you. However, in warm weather, inbound to the FAF, you will first pass through advisory-glideslope intercept, but can't start descending yet. Since these are still non-vertically-guided approaches, the FAF is still where we are to start descending, just like a VOR or LOC-only approach (or LNAV without the +V). No problem, on an ILS/LPV/LNAV-VNAV, you start down at glideslope intercept and follow glideslope.īut then we've got those oddballs, the LNAV+V and LP+V, where Jeppesen/Garmin publish an advisory glideslope that is not evaluated by the FAA. Especially during the summer, glideslope intercept can occur 1/4 to 1/2 mile before the charted FAF (in the winter, of course, it would be past the FAF). When flying an LPV, LNAV/VNAV, or ILS approach, you start on down at glideslope intercept - GS intercept is by definition the FAF for the approach, whether or not you have reached (or passed) the charted FAF.ĭue to altimeter errors caused by non-standard temperatures, the actual point of intercept can vary widely from the charted FAF. I've been teaching instruments a lot lately.
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