Tuesday, September 24, 2013
Beware The Fickle Winds
Winds almost never play fair
In those days, the most challenging leg on the Pacific route to Japan, Korea, the Philippines, Australia or New Zealand was the first one, West Coast to Hawaii. If you have to, you can depart from Oakland in Northern California and flight plan for Hilo, flying 2,035 nm. After that, both the prevailing trade winds and the leg distances become more favorable.
(Unfortunately, that's no longer the case. Mobil was the primary supplier of avgas on the Pacific islands in those days. Since they stopped refining 100LL, there's no longer any avgas available in Majuro, Marshall Islands, only 1,980 miles southwest of Honolulu. Now, you must fly 2,260 nm straight south from Honolulu to Pago Pago, American Samoa, to buy avgas from BP. At least, the winds are usually on the tail.)
Finally, in early January, the low-level wind backed off to a forecast -4 component with nothing worse than the usual scattered cu over the ocean, and I launched from Santa Barbara for Honolulu, 2,160 nm.
Flying the first leg on the Pacific to Hawaii often requires a certain leap of faith. If you calculate your how-goes-it too early, you'll wind up turning around and heading back to California, as the numbers will suggest you won't make it.
The wind pattern is nearly always the same. You start the trip on a Southwesterly heading, and the wind is usually on the nose at 10-20 knots. Then, the wind begins to shift clockwise to the north as you pass 800 miles out. By 1,100 miles, roughly the halfway point, the wind will have continued to rotate to a slight tailwind, and at about 1,700 nm from Santa Barbara, you'll start to see as much as a 20- to 30-knot push when the trade winds take effect.
For that reason, we nearly always file for an initial 6,000 feet, the lowest IFR altitude, to stay out of the worst initial headwinds, then climb to take advantage of the trade influence. In a normally aspirated single, I'll often climb to 10,000-12,000 feet as a final altitude, starting uphill at 1,500 nm out.
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