Operations take place daily in uncontrolled airspace. Paynesville, MN (KPEX) is a typical non-towered airport with the familiar vignette depicting Class E beginning at 700 feet AGL. Departing Paynesville, any time we spend in the clouds below the Class E floor is IFR in uncontrolled airspace. Of course, as you should recall, lacking that magenta vignette, the 700-foot limit becomes 1200 feet. Instrument approaches begin with an ATC clearance in controlled airspace, but often take us into uncontrolled Class G airspace. At Paynesville, the RNAV (GPS) RWY 11 approach LPV mins take us to 200 feet AGL, 500 feet into the surface Class G airspace.
Likely you either practice approaches to non-towered airports or fly into airfields with part-time control towers. Non-towered airports, hotbeds of GA activities, present our greatest risk of a midair collision; a risk mitigated by a disciplined adherence to procedures (proper entry into landing patterns, proper departure patterns) and proper use of the UNICOM frequency at uncontrolled airports. (FAA Aviation News, May/June 2001) Therefore, its important that instrument pilots play nice around the pattern. The updated AC 90-66 covering non-towered airports specifically identifies instrument pilots, maybe because of some past misbehavior.
For those unfamiliar, the Upper Peninsula of Michigan boasts generous lengths of shoreline off Lake Superior, scenic byways, and lots of trees. While it can be a winter wonderland during the off-season, its not unusual to have many days of dreary gray skies and fog that wears away the most sanguine spirit. Its the kind of weather that gets us burning through a whole morning figuring out how to get out, around and back without getting stuck who-knows-where. Welcome to the UP.
While stability and instability dont always cause weather, they leave a mark on even VFR forecasts in many subtle ways, and they influence everything from wind gusts to cloud layers. Even in forecast models, there are always complex equations that factor in stability. Stability is important enough that an entire chapter is dedicated to it in the FAAs Aviation Meteorology circular. For meteorologists, a chart known as the Skew-T diagram is used every day at forecast centers. Its literally a worksheet that helps forecasters visualize the days stability and make calculations on it.
Our February 2018 clinic (Chicagos Scenic Route) discussing a particular procedure at Chicago Midway International led to some reader mail about what should happen. The Midway Three departure for Runways 4L and 4R, if interpreted on its face, would have indeed involved extra maneuvering just after takeoff, as we discussed. It has since been noted that this DP calls for a more logical sequence of steps to make it work. So we went back to take another look at the Midway Three along with the other DPs published there. The charts have since been updated a little to clarify when, where, and how high to go.
What happens if you depart on the original IFR squawk? In a word: confusion. While, you are technically VFR-you voided your clearance by departing VFR-ATCs radar doesnt know that. Itll still detect that IFR squawk and tag you up on the scope as if you were on that IFR clearance. An unexpected IFR target popping up amidst their other IFR traffic is a real distraction to a controller, especially if its an aircraft who was expected to hold for release.
Lets connect some dots. In 1969, NARCO (now defunct) introduced the CLC-60 VORTAC Offset Control Panel that allowed navigation to a phantom fix defined as a distance and direction (rho-theta) from an existing VORTAC. It was touted as the first RNAV system. In the 80s, Bendix/Kings KNS-80 Integrated Navigation System might be considered the first practical RNAV navigator (it had VOR, LOC, DME, RNAV, and GS). Like the CLC-60, it could electronically move a VORTAC and was IFR certified.
IFR separation from other aircraft is well-understood in our community. Within the controller community there is something additional called terrain separation. A loss of terrain separation occurs when an aircraft enters a chunk of airspace at an altitude below the prescribed minimums. Minimum vectoring (or instrument) altitudes arent published, so initially theyre the controllers responsibility. Busting either is CFTT, but they are not the sole province of ATC. Pilots also cause CFTTs. Lets look in our own house first.
Depart Tri-Cities for Yakima from Runway 21R. You filed PSC V298 YKM and got a clearance with, Cleared to the Yakima airport via Tri-Cities 7 then as filed. Climb and maintain 6000. Use real-world weather so the winds are variable for this day. Or, if you must, dial up 800-foot ceilings and a wind out of the southwest. Set the radios, brief your route. Then fire up and taxi out. Assume Towers last words to you were, ...on departure, fly runway heading. Runway 21R, cleared for takeoff.
Some years ago, I was flying with a pilot in his Cessna. He was instrument rated, while I was working on mine. I watched him enjoying the two perfectly centered needles (old-style CDIs) accompanying the six-pack panel while flying to a VOR at 6000 feet. He remarked with a sigh of contentment, Now this is the way to fly. It sure was, especially for me, when I was building time in budget-friendly trainers where dual (working) CDIs was a luxury.
I could fly above the worst of that, but headed west wed need a fuel stop. Now, I trust the near-all-weather capability of my airplane, perhaps more than I should, but descending through freezing rain and snow, and then climbing back through it were activities Id rather avoid. A new route was needed.
Another good rule of thumb is Buys Bullots law: To locate where the bad weather is coming from, put your back to the wind and extend your left arm straight out. Thats where the low pressure bad WX is coming from. It works for me.