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These early pilots depended on a network of rotating beacon towers at four-mile intervals, like lighthouses in the sky. These facilities, operated by the federal government, used lamps powered by cylinders of acetylene. Simply by following the route from beacon to beacon, a pilot could arrive safely at the destination. Weather could be avoided because the planes flew at low altitudes, and illuminated diversion airfields were placed at frequent intervals. If the pilot felt things were deteriorating, he could be on the ground in less than 10 minutes.
Our February 2018 clinic (“Chicago’s 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.
You are an instrument-rated private pilot. Your friend is working on the rating and you have acted as her safety pilot while she practices under the hood. She’s doing great. Today ceilings are high but below final approach fix altitudes. You feel comfortable filing IFR as pilot in command while she flies, so you file and off you go in the club’s 172. No hood for your friend today. She does all the flying. Two approaches, with 12 minutes in actual instrument conditions. She did well.
Let’s 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 80’s, Bendix/King’s 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.
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—ATC’s radar doesn’t know that. It’ll 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 it’s an aircraft who was expected to hold for release.
Ever wonder how the FAA came up with §91.211 requiring oxygen use above 12,500 feet MSL for more than 30 minutes and any time over 14,000 feet MSL? The answer is geography, not physiology. When these rules were written, oxygen systems were expensive and heavy. General aviation wanted to fly anywhere in the U.S. without oxygen, and you can fly any mountain pass in the 48 contiguous U.S. states in less than 30 minutes between 12,500 feet and 14,000 feet MSL.