Flight Planning on a Globe

** Retired airline pilot Bill Harrelson averaged
180 knots from Guam to Jacksonville,
Florida — nonstop.**

I was impressed when I read of the exploits of Bill ­Harrelson, the Virginia pilot who on March 1 flew his ­Lancair IV nonstop from Guam, in the western Pacific, to Jacksonville, Florida. The hop, if you can call it that, of about 8,000 statute miles took 38 and a half hours. If that weren't enough, his positioning trip to Guam included a 20-hour leg from Indiana to Hawaii, and he did the whole out-and-back journey in the course of a week. My parents, who spoke German around the house mainly to keep secrets from me, used the term Sitzfleisch — "sit flesh" — as a synonym for patience or, more precisely, the ability to sit still for a long time. Harrelson has it.

Naturally, I had to do the numbers to be sure this was not an elaborate hoax. Harrelson’s Lancair (if you’re new to aviation, the “c” in Lancair, in defiance of the conventions of English pronunciation, is soft) is the recip-engined, nonpressurized version, with extra tankage for long-distance flying. Unlike those of most Lancair IVs, Harrelson’s Continental 550 is unturbocharged and has 10:1 pistons, which improve its specific fuel consumption. According to FlightAware, on which I followed the slowly lengthening green lines indicating his progress, Harrelson planned 180 knots at 7,000 feet. A Lancair IV is a pretty clean airplane, so I figured he could probably manage 180 knots at 10 gallons an hour. Assuming some help from the prevailing westerly wind, he would have to carry about 400 gallons, plus a bit more for taxi, climb and luck.

It turned out that the airplane was better than I thought. Harrelson took off with 361 gallons and landed with six for an average fuel burn of 9.2 gph. His average true airspeed was 180 knots with an overall tailwind — important to the success of the flight — of 3 knots.

The Lancair IV’s landing gear retracts into the fuselage, so most of its 98-square-foot, 30½-foot-span wing could be wet. I doubt the wing could hold much more than 100 gallons, however — probably less — so at least 260 gallons had to be in the fuselage. That seemed like a lot, but actually it’s only 35 cubic feet, which is equivalent to a 39-inch cube and, in a properly shaped tank or collection of tanks, would obviously fit in a four-seat cabin next to, and behind, the pilot.

Setting human endurance aside — Dick Rutan and Jeana Yeager's nine-day Voyager flight in 1986 showed it to be almost limitless — the range of an airplane is a function of its aerodynamic cleanness, the efficiency of its power plant and the fraction of its takeoff weight that is fuel.

All aerodynamically clean airplanes are about equal regarding friction and pressure drag, so their flight efficiency is ruled not by their streamlining but by their induced drag. Induced drag is principally affected by wingspan. The two airplanes that have flown nonstop around the world — Voyager and Global Flyer — both had very large wingspans, with ­sailplane like lift-drag ratios above 30. They also had unprecedented fuel fractions. Nearly three-quarters of ­Voyager's takeoff weight was fuel; Global Flyer's was more than five-sixths.

The Lancair IV suffers, as a long-range airplane, from a shortage of wingspan. Its L/D ratio probably isn’t much higher than 15. What it lacks in that department it must make up in fuel fraction. To go 8,000 miles in a Lancair IV requires a fuel fraction of somewhere around 50 percent. With an empty weight of about 2,000 pounds and an allowance for the pilot and his survival gear and other life-support equipment like sandwiches, 2,200 pounds of fuel turns out to be about right.

Lest it seem that extremely modern and sophisticated equipment is needed for such a flight, let us not forget that way back in 1959 Max Conrad flew 7,668 sm from Casablanca to Los Angeles in a Comanche 250 — against the wind.

Two concerns arise when a great deal of extra fuel must be packed into an airplane: structural strength and takeoff distance. Voyager and Global Flyer distributed their fuel spanwise and in outboard booms to relieve wing bending stresses. When you load a lot of fuel into the fuselage of a conventionally configured airplane, you increase the wing bending stresses a great deal. For special-purpose flying, however, customary margins of safety are often ignored, and you keep your fingers crossed that you won't run into severe turbulence.

Takeoff distance was a great problem during the heyday of distance flying in the 1920s and ’30s, when long paved runways were scarce and power loadings were high. Today, it is not so difficult. With the Lancair’s 310 hp Continental, getting the 4,500-pound airplane up to rotation speed — somewhere north of 100 knots, depending how cautious the pilot is feeling — on an unobstructed sea-level runway should require a roll of less than 4,000 feet.

I did some longish flights — nothing like this, but one of them was from mainland Alaska to Japan, about 2,700 sm — in the 1970s in a homebuilt with a wing area of 92 square feet, a span of 23 feet, and a max L/D between 10 and 11. All of the fuel — 155 gallons — was carried outboard of midspan. Despite a takeoff weight of almost 2,900 pounds (and 500 x 5 tires), a 210 hp Continental readily got us airborne with a steady 500 fpm rate of climb. The most striking impression I remember is of the peculiar way the springiness of the wing, combined with the concentration of mass outboard at the start of the flights, caused the fuselage to bounce queasily up and down at the slightest disturbance.

On the other hand, things do sometimes go wrong on these overloaded takeoffs. Hans-Georg Schmid was an airline captain and distance-flying enthusiast who once flew around the world — not nonstop, of course — in his tanked-up Rutan Long-EZ, and then immediately turned around and repeated the trip in the opposite direction. Talk about Sitzfleisch! In 2007, he attempted a flight from Basel, Switzerland, to Oshkosh in a heavily modified Express 2000, a four-seat homebuilt broadly similar to the Lancair IV but with fixed gear. His takeoff weight was more than half a ton greater than ­Harrelson's. The airplane became airborne but failed to climb, and it hit a building a few miles from the runway, killing Schmid.

Schmid’s flight to Oshkosh was intended as a shakedown cruise for a more ambitious scheme he had in mind, namely that of flying around the world by way of the poles. This is one of those “last remaining challenges” that always pop up after the previous last remaining challenge has been disposed of, and it appears that Harrelson intends to be the one to finally meet it.

As you discover when you turn to your 12-inch globe — the preferred tool for long-distance flight planning — even an airplane with a rather modest range of 2,500 nm can get from, say, Hawaii to Cape Town by way of Alaska, Scandinavia, Europe and Africa.

It’s here that trouble begins. There are airstrips in Antarctica, but they don’t exactly invite transient light aircraft to stop by. In fact, the obstacles to refueling in Antarctica — cost, weather, political sensitivities and general weirdness — are so daunting that the ticket to a relatively hassle-free polar circumnavigation is to skip the place altogether. To do so, you need sufficient range for a nonstop flight from either Cape Town or ­Ushuaia, at the southernmost extremity of Argentina, to Australia or New ­Zealand. As it happens, the required range is about 7,000 nm — the same as the distance from Guam to Jacksonville.

If you Google “polar circumnavigation,” you will find that various teams claim to have done it already, but if you examine their routes you may balk at their claims. For my money, a true polar circumnavigation of the Earth ought not to deviate by more than a few thousand miles from a great circle. Of the two routes I regard as fulfilling this requirement, Hawaii-Cape Town has the advantage over Ushuaia-Perth of not requiring transit through China, Mongolia and Siberia. But, on the other hand, the Cape Town route involves a dogleg to New Zealand, whereas the Ushuaia route can be an almost perfect great circle.

For pilots satisfied to overfly just one pole, a flight from Barrow, Alaska, to the Norwegian island of Spitsbergen requires a range of only 1,900 nm and has a couple of other things to recommend it. For one, the great circle passes so close by the North Pole that almost no dogleg is required. For another, you take off from Alaska and you land in Europe — two places so distant from one another in imagination that you will feel you went much farther, or faster, than you really did.

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, "Technicalities" and "Aftermath," with FLYING readers.

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