How to fly a GPS Approach using an Autopilot + GA News

Aviation News Talk podcast

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: Faulty gauges, Plugged fuel vents, Gas cap comes off in flight, Blocked fuel filter, Ice in fuel lines, Vapor lock, Failed fuel pump, or Failure to lean, which uses more fuel.

Some pilots like to run a tank dry in flight. I don’t, as sometimes the aircraft won’t start immediately after you switch tanks. Therefore, if you do plan to run a tank dry, switch it at altitude; don’t wait to switch until your low in the pattern, where if the tank runs dry you might not have time to restart the engine. Cessna started installing “LOW FUEL” annunciator lights in their C172s, 182s, and 206s beginning in 1997. The annunciator turns on whenever there is less than 5 gallons in a tank in a C172. At one point Cessna claimed that they have had no fuel incidents since these fuel annunciator were added.

In older Cirrus, the fuel annunciator sensors in the tanks are connected in series. For example, in older SR20s, the sensor doesn’t come on until the fuel quantity in both tanks drops below approximately 8.5 gallons (17 gallons total with tanks balanced in level flight). Since both tanks must be below 8.5 gallons to illuminate the light, it might not illuminate until there is as little as 8.5 gallons total on board, if one tank was allowed to run dry.

General Aviation News

1. NATCA, the National Air Traffic Controllers Association honored controllers at the 13th Annual Archie League Medal of Safety Awards banquet in Las Vegas. The awards are named for Archie League, who was the first air traffic controller. We play the ATC audio from an accident involving a Piper Aztec. According to an NTSB report, on March 27, 2016, the aircraft departed Charlestown, SC for Baltimore. The pilot stated that the flight departed with 5 hours of fuel onboard for the estimated two and a half hour flight. After about one hour the pilot reported to air traffic control that he had lost his directional gyro and attitude indicator. While diverting to Roanoke-Blacksburg Regional Airport (ROA), Roanoke, Virginia, the right engine abruptly lost power. After switching fuel tanks, power was briefly restored to the right engine, followed by an abrupt loss of power in both engines. Our next story comes from the Wichita Eagle with the headline “FAA forecasts decline of 17,500 piston airplanes” “The FAA’s 20-year forecast expects the general aviation fleet to increase from 209,905 airplanes and helicopters in 2016 to 213,420 in 2037, a weak 0.1 percent annual increase. During that period, turbine aircraft – business jets and turboprops – are expected to grow at an annual clip of nearly 2 percent a year. Offsetting turbine growth (and helicopters’ annual growth rate of 1.6 percent) are piston airplanes. The piston airplane fleet is expected to shrink 0.8 percent annually, the FAA forecast said, or by 17,500 aircraft over the next two decades. The FAA uses input for its forecast from sources including its 2014 General Aviation and Part 135 Activity Survey, as well as discussions with industry experts.
2. Earlier this month, investigators were confused by the crash of a Cessna in the woods earlier this month just before midnight near Manitouwadge, Canada, which is just north of Lake Superior. At the crash site, they found the Cockpit was empty and there were no footprints in snow around the wreckage. Earlier in the day, the Cessna 172 had been rented by a 27-year old experienced pilot who was also a PhD candidate at the University of Michigan. He was from, China, studied artificial intelligence at the university's School of Information, and hoped to one day work in aviation safety. Please believe he committed suicide by jumping from the plan in mid-flight.
3. In an ironic twist, officials at Hartsfield-Jackson Atlanta International Airport are now using drones to inspect runways and document pavement issues for future maintenance. Traditionally, the FAA works hard to keep drones away from airports. The FAA granted a waiver to the airport and a surveying contractor to allow drones to be flown in the restricted airspace of the airport. The aircraft will be used to make accurate surveys of areas of the airport that are slated for changes in the $6 billion ATLNext construction project,
4. AvWeb reports “Boom Technology Raises Additional Capital To Support Supersonic Demonstrator” Boom Technology, which is developing a supersonic airliner has raised an additional $33 million to fund development of its one-third-scale demonstration aircraft. Boom CEO and founder Blake Scholl says “our mission is to make supersonic flight a reality,” and expects to see the XB-1 fly in 2018. If successful, Boom says the XB-1 will be the first independently developed and privately funded supersonic jet. The company indicates the final production aircraft will be capable of carrying passengers at costs comparable to business-class on modern wide-body jets.
5. EAA Announces VMC Club First there were IMC Clubs, now EAA introduces VMC Clubs for non-instrument rated pilots who want to improve their proficiency. The VMC Club is modeled after the popular IMC Club concept, which provides organized “hangar flying” focused on building proficiency in instrument flying. The VMC Club will do the same, but for pilots who are not instrument rated and fly primarily under visual flight rules and under VMC. The VMC Club offers monthly meetings in which pilots can network and share knowledge and experience.
6. Earlier in the year, Harrison Ford mistakenly landed on a taxiway at John Wayne Airport, after being cleared to land on a runway. TMZ released the audio from his phone call to the tower immediately afterwards. He starts off by saying “I’m the Schmuck who just landed on a taxiway.” We disagree. Everyone makes mistakes, and he owned up to his. A Schmuck would have said, “it wasn’t my fault, and nobody got hurt so what’s the big deal?” Hopefully, all pilots, including Harrison Ford, learn from their mistakes and avoid making any of the fatal ones!