CHARTS & PLATES

Skew-T Revisited

The Skew-T log-p diagram, typically just called a Skew-T, is an amazing tool for understanding whats 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 cant underscore how valuable these diagrams are once you get to know them.

A Visual in IMC

Let's consider a situation. We are flying over the Florida Everglades in low IMC. Our alternator just died, which clearly counts as an emergency in IMC. So, we must land. Now! Wind is blowing from the west at 25 knots and we are close to Dade-Collier Transition and Training Airport (KTNT). Although it used to have three approaches to Runway 9-an ILS, an NDB and an RNAV-the only one now available is the RNAV (GPS) RWY 9 approach. With that wind, we certainly will not be landing on Runway 9, even though the runway is 10,500-feet long.

Good Plan Gone Awry

Time to check Off-Route Obstruction Clearance Altitudes. These start at 3400 to 4000 feet then quickly get up to 6000. The terrain continues to rise towards 8000 feet past Scottsbluff. Uh, were not in Minnesota anymore. OROCAs, as defined by the Instrument Procedures Handbook, are for situational awareness and emergency use. While OROCAs provide standard obstacle clearance margins (1000 feet in non-mountainous areas), you cant count on them. You decide its safest to file for 8000 feet.

Deadstick: The Movie

Get ready to star in this adventure by positioning your aircraft on Runway 24 at Muskegon County (KMKG) in Michigan. Pick whatever aircraft best resembles an aircraft you fly. If you have the option for retractable gear, you might want to use it as that adds a variable to this exercise and makes it more, um, fun. But the choice of the airplane is really up to you. If you fly a twin, slum it for this sim challenge and go back to the high-performance single you probably traded in for your first twin.

How the Wind Blows

The root cause of wind is the unequal heating of the earth. We usually take it for granted that tropical areas are hot while polar areas are cold. But whether youre in Greenland or Venezuela, the sunlight is the same. Its the angle at which the suns rays hit the ground that makes the difference. Near the equator, the summer sun is at very high angles. But, in Greenland the summer sun never gets higher than about 30-40 degrees above the horizon, spreading the energy over a larger area, reducing heating of the ground and air.

Reading the Fine Print

Recently, we heard from a reader with a question about an approach into Carlisle, Pennsylvania (N94). The RNAV (GPS)-A approach has a final approach course thats offset from the runway by around 12 degrees and a standard three-degree descent angle. Approaches are usually published with only circling minimums when the final approach course alignment relative to the runway exceeds 30 degrees (for most procedure types) or the descent angle is greater than 3.77 degrees (for Category C and below). Since neither of these reasons apply to this approach, why doesnt it have straight-in minimums?

Going Around Weather

We all have a different way to go about our flight planning, but most of it is along the lines of where to go, how high, how much fuel, weight and balance, etc. You factor it all into the plan, but at some point youll add that X for some bad weather and a re-route. Maybe the weather is fine where you are departing but not good where you are going, or vice versa. Depending on the mission, what are your options? It all comes down to a go/no-go on what youre comfortable doing and not doing. This is the typical process regardless of whether youre filing VFR or IFR.

Route Planning

This is a long flight, so you want to minimize distance and go as direct as possible. You scan the route from TAFOY to KFSM on the chart, and it doesnt pass through any special use airspace (SUA), so you could go direct. But, you want to comply with the AIM guidance (see below) and pick a fix or two in each centers airspace. You zoom in on the chart to see TAFOY clearly, then just scroll the chart to the east along your route, looking for fixes on your route that you could add.

Making Do

There are a few things in flying life we might take for granted. In fact, some of us are downright spoiled. For instance, flatlanders (like me) get 99.9 percent radar coverage in our mountain-free region, all taken for granted. Southerners take for granted their three seasons of comfortable flying. Those who fly to larger cities all the time definitely take for granted the big runways, ATC help, and all the information they need at their fingertips.

Summer Hazards

Without those tools its important to get on the ground or find a route out of the activity if buildups start growing around you, because air mass storms often grow as clusters and the open spaces will quickly close in. If you dont think air mass storms are a problem, check out our August 2018 issue that details two seemingly benign air mass storms: one that downed a Piper PA-23, and another that downed a Boeing 727.

Traffic Jam in Iowa

Among the caveats, though, is the fact that the guaranteed traffic separation works great with IFR aircraft, but not so much with VFR aircraft. On top of that, even those who always fly IFR must be in VFR mode at certain times, e.g. to depart and pick up a clearance, or to cancel IFR at or before the final landing phase. Even if you had those protections all the way in, though, you could be left to your own devices if VFR traffic conflicts occur. And they do.

Spring Break

Naturally, you want blue skies and full sun to get the most out of such a trip. Theres usually no issue with that, but the Gulf region and Florida Keys have their share of showers and thunderstorms. Hurricanes and tropical storms not withstanding, weather here is dynamic, so youre going to start familiarizing yourself with this new territory early. Little do you know that its the mapping, not the weather, that will catch you by surprise.