GA News,fuel exhaustion tips & listener question on autopilot use for GPS approach to LP minimums. How do you fly a GPS Approach with an advisory glide path, such as an LNAV+V or a LP+V using an autopilot? APR, or Approach mode works great with an LPV approach, but it won't level off the aircraft when flying a non-precision approach. After the news, we answer a listener question about a WAAS GPS instrument approach with LP approach minimums. He was flying the RNAV (GPS) X Runway 31 approach into Hailey, Idaho. He said, “on final, I hit APR on my S-TEC 2100 and yes, it captured ‘the glide slope,’ I put GS in parenthesis because it’s a non-precision approach, so technically there is no GS, but yes, the S-Tec capture it. Ok, here is the rub: I’m descending down and sure enough, the autopilot takes me BELOW 6180’ MSL, the MDA for this approach. And yes, it’s snowing and full disclosure, I can’t see the runway environment but it does pop into view at about 6000’MSL (roughly 750’ AGL). My bad. My fault. “So here is the mistake I think I made: 1. I should NOT have hit the APR button on the S-TEC 2100. It captured the GPS GS, when in truth, there is none on an LP approach. And it lulled me into thinking I was safely on a GS. Is this correct? 2. In other words, I turned a non-precision approach into a precision approach when it does not exist. I should have NOT hit the APR button. 3. Having hit the APR button, I noticed on the S-TEC, that any ALTITUDE numbers were erased. Second question: could I have hit the ALT button when I noticed I had slightly descended below the MDA of 6180? Would that have stopped my decent? “Lastly, when I got home I researched LP approaches AND looked at both the JEPP chart of the RNV (GPS) X 31 and the Government Charts. Interestingly, the JEPP charts shows a dotted line of the what I will call, “GS guidance,” and it shows a dotted line BELOW the MDA. The Government chart does not. I’m not looking for excuses, but it seems to me the JEPP chart in this case, almost encourages you to get on the GS, rather than ‘dive and drive.’ ” My response, in part, to his question includes: You fell into one of the WAAS traps that I’ve discussed with others, but I haven’t seen documented anywhere. The issue is that the APR key of most autopilots will couple to any glide slope (ILS) that’s present, or any glide path (for GPS) that the GPS manufacturer has included in their database for a particular approach. This works great for ILS and LPV, where you have a DA and can descend below minimums while making your decision to land or go around. It works poorly for any LNAV+V, or in your case, LP+V advisory glide path. With the advisory +V glide paths, autopilots don’t know to level off at the MDA for these approach types, and they continue through minimums as if these approaches have DAs, which they don’t. So you should monitor the approach and plan to push the autopilot’s autopilot just before you reach the MDA, so that you don’t descend below the approach minimums. For this and more about GPS approaches, I recommend my Max Trescott’s GPS & WAAS Instrument Flying Handbook. General Aviation Flying Tips We share some thoughts about how to avoid fuel exhaustion (running out of gas) and fuel starvation (gas not making it to the engine) type accidents. It’s important to know before you depart how much fuel you have using more than one source of information. For example, you should ALWAYS visually inspect the fuel in the tanks. In addition, you could look at fuel gauges, see how many gallons were added if you’re present during refueling, or if it’s a rental aircraft, see how long plane was flown on previous flight. If you use a fuel stick, may sure you put it straight down into the tank, and not at an angle. For some planes like the Cessna 210, the fueler has to put the last few gallons in slowly, otherwise the tanks won’t be completely filled. Some things that could happen in the air which might lead to fuel starvation include: Fault