Von sends me this Mark Vanhoenacker essay from the New York Times, full of fascinating titbits on planeflying:
“Boston has etched a particularly rich constellation onto the heavens above New England. There is PLGRM, of course; CHWDH, LBSTA and CLAWW; GLOWB and HRALD for the city’s newspapers; while SSOXS, FENWY, BAWLL and OUTTT trace the fortunes of the city’s baseball team in long arcs across the stars. There’s a NIMOY waypoint; Leonard was born in Boston.In a letter written in 1869, Mark Twain wrote that “the grand problem of aerial navigation” is “a subject that is bound to stir the pulses of any man.” Twain, the pilot of riverboats who died seven years after the first flight at Kitty Hawk, never flew. But he might be pleased by the thought of 747s, and of TWAIN, the waypoint over Hannibal, his childhood home on the Mississippi.”
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“These rigorous calibrations to the local air were a surprise to me when I was first taught about them. But even more surprising is the fact that at the higher points of flight, we abandon them. At high altitudes we are far from any obstacles below. But we face a new problem: Our local altimeter setting would soon become inaccurate — both to the changing air around us, and to the settings of other aircraft that departed from other cities. So, to ensure our safe separation from other high-flying aircraft, we all set standard. We switch the reference point for our altimeters to a common pressure setting that’s derived from a universal, standard model of the Earth’s air.To ignore local air pressure, of course, is to ignore our true altitude. Indeed, planes following altitudes referenced to the standard atmosphere collectively and continuously adjust their degree of wrongness — gently climbing or descending in a collective, school-of-fish-like movement as the true air pressure below changes with time and location.”
Best of the Transparent Hummingbird