The Skew-T log-p diagram, typically just called a “Skew-T,” is an amazing tool for understanding what’s happening in the atmosphere at a given station. They are essential for understanding a precipitation regime or differentiating icing layers. Even after nearly three decades in meteorology I would find it almost impossible to understand an icing situation without this tool, and I often visualize the makeup of an environment with a sort of mental Skew-T image. I can’t underscore how valuable these diagrams are once you get to know them.
It’s certainly legal to fly through the AIRMET. These are advisories covering large areas. But it behooves you to determine that your flight plan won’t enter “known or forecast light or moderate icing conditions” as prohibited in §91.527. Here goes. There’s a stationary front just west of the route, bringing in cloud layers and scattered showers. Freezing levels will hit between 7000 and 12,000 feet. So, at 8000 feet, you do risk picking up ice. One lone pilot report from a single-engine turbine over Iowa shows negative ice in climb from 3000 to the tops at 11,000. This isn’t all that useful since you’re flying lower and slower, but you are willing to climb as high as 12,000 feet to be on top. Your Plan B, while not at all mission-friendly, is to turn back to warmer air and land in Iowa, or even return to Bowling Green if that’s best.
Dark clouds are looming on the horizon of our otherwise exciting GPS future. With increasing frequency, the military is jamming or spoofing GPS over huge swaths of airspace. A typical GPS NOTAM for Albuquerque center covers a radius of 237 NM at 10,000 feet, 207 NM at 400 feet and 165 NM at 50 feet daily for most of a week. Pilots in the Southwest have become accustomed to these NOTAMs, but they’re becoming more frequent and expanding to other areas of the country.
Just to make sure you understand what’s up, let’s review. In the U.S., we’ve got excellent radar coverage, so all those radar sites have been modified to understand your aircraft’s ADS-B out transmissions. In those areas where radar sites don’t quite have adequate coverage, the FAA has added ground stations specifically to receive your ADS-B Out. The bottom line is that the FAA has sufficient ground-based coverage to know where you are almost all the time, using your ADS-B Out.
TCAS II is the most comprehensive form of TCAS, but its range depends on what it is asked to do. Overall pulse detection range is 30 NM for Mode S transponders and 14 NM for Mode A/C units. Surveillance must be reliable within 14 NM, but TCAS II will only assess threats within 12 NM as possible RAs. TCAS II guarantees system reliability within at least 4.5 NM. Two TCAS II systems can coordinate RAs to maximize vertical separation, typically 300-700 feet. There is even a reverse RA if one aircraft fails to respond correctly in the latest version 7.1 software.
It should be obvious that we never say the words, “Declare,” “Emergency,” “Mayday,” or “Pan-Pan” unless we indeed have a dire situation. These words have the potential to flip a controller’s airspace upside down faster than a Vmc roll, so they should be used with discretion. Even saying “Declare” by itself could lead us to believe that assistance is needed, as well as “Pan-Pan” (Urgent condition). Because Pan-Pan is considered an urgent condition (maybe not a full-blown emergency), it has the potential to turn into “Mayday” (Distress) so we mostly treat it as such.