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Proficient Pilot: In the company of eaglesProficient Pilot: In the company of eagles

Lessons learned from the birds

Once while in East Africa, I had the pleasure of flying with F.W. “Bill” Woodley, the chief game warden for Kenya’s mountain national parks. Woodley used a Piper PA–18 Super Cub to locate lost mountain climbers, spot poachers, direct firefighting countermeasures, and conduct law-enforcement activities.

He had a reputation for being a mountain pilot extraordinaire. It was said that he could coax high-altitude performance out of an airplane that exceeded even the optimistic claims of its manufacturer. This included operating the Cub from a short, unimproved strip at the 14,000-foot level of Mount Kenya and routinely nursing it to substantially above its service ceiling.

My stated purpose in accompanying Woodley on a simulated mountain rescue was to research a magazine article about him. My underlying reason, though, was to determine if his reputation was justified or just a fable.

Prior to climbing into the front seat of the Cub, Woodley removed his boots and socks. This, he said, helped him to better feel what the Cub was doing. My skepticism needle pegged. He also handed me an oxygen mask.

After departing Nanyuki, Woodley pointed the nose toward Mount Kenya, an extinct volcano that rises abruptly to 17,057 feet, the second tallest mountain in Africa, Kilimanjaro being the highest.

At 15,000 feet, the Cub’s climb rate had pooped out, and it appeared that the summit of Mount Kenya was beyond reach. Woodley fine-tuned the mixture once again and moved to within a wingspan of the mountain. He then spotted some eagles soaring over the edge of a bluff and moved the Cub toward them. The birds held their ground as Woodley joined their formation. We hugged the sunlit slope and began to gently rise, occasionally lifting a wing to avoid an outcrop of rocks. Moments later, we were skimming above the glacier defining the summit, and the Cub was still climbing.

After returning to Nanyuki, Woodley told me that the techniques he used to milk the last drop of performance from his airplane are not mysterious. “All I do,” he said, “is look for large birds. They are masters of soaring flight; they know how to avoid sinking air and locate rising air.”

This is not particularly new to sailplane pilots. Capitalizing on rising currents to remain aloft without power is a challenge they accept during every flight. But as Woodley demonstrated, the principles used to lift sailplanes and the outstretched wings of birds also can be used to enhance airplane performance. For example:

  • When flying along a valley (narrow or wide) with a crosswind, alter course to the downwind side. This places the aircraft in rising air and, by maintaining altitude, increases cruise airspeed. Those who fly on the upwind side of a valley lose performance even when winds are light.
  • When practical, conduct flights along the windward sides of other rising terrain and avoid the leeward sides.
  • When climb performance after takeoff is likely to be anemic (such as when heavily loaded at high density altitude), visualize how the local wind is influenced by the shape of terrain to determine where up and down currents are most likely to occur. Alter course to avoid sinking air and take advantage of rising air.
  • Rising air usually can be found beneath fair-weather cumulus, while sinking air often characterizes the air between them.
  • Expect the strongest thermals over dry, light-colored, sunlit areas; sinking air is typically found over terrain that appears moist and darkly colored.

Conventional wisdom suggests that VFR pilots should attempt to maintain altitude when flying through updrafts and downdrafts. Such wisdom, however, is counterproductive and prolongs flight time.

Maintaining altitude in a downdraft, for example, requires raising the nose, which results in reduced airspeed, and this prolongs time spent in the downdraft. Adding power at such a time—especially on warm summer days—can result in an overheated engine (in addition to increasing fuel consumption). As the soaring flight of birds teaches us, we should allow the downdraft to have its way and go with the flow. Birds dive out of downdrafts, so maintain or even increase airspeed, accept the altitude loss, and pass through the downdraft as quickly as possible to minimize its effects.

Lowering the nose to maintain altitude in an updraft make no sense. This increases airspeed—sometimes excessively—and rejects Mother Nature’s offer of free altitude, which later can be used to offset the altitude loss in the downdraft that inevitably follows. Instead, take advantage of the updraft and allow the airplane to climb for a longer period by not increasing airspeed.

We have so much to learn by observing the flight of eagles and other soaring birds.

Web: www.barryschiff.com

Barry Schiff

Barry Schiff

Barry Schiff has been an aviation media consultant and technical advisor for motion pictures for more than 40 years.

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