Page 26 - Volume 19 Number 10

Airspeed, AlphaBy LeRoy CookPrecision control of an aircraft be useful, or wasted, depending the popular lexicon) produces theon how well we apply it. If, on the other hand, we allow our aircraft to become deficient in energy, we’ll have to rebuild its energy status by pushing up the power or sacrificing some altitude.And so, much argument is made over how to control an airplane; do we manipulate speed by varying pitch attitude, or changing the power setting? For my part, the reply should be “Both, at the right times.” On the takeoff roll, for example, we are obviously attaining the desired speed by applying full takeoff thrust, with the aircraft in a level attitude. When it comes time to lift off, we change over to attitude control, rotating the nose up to a target pitch index, at which point the angle of attack (“alpha”, inin flight requires both pilotingskills and the tools to evaluate and perfect them. As pilots, we need to be capable of hand-flying the airplane, not just monitoring it. We can take satisfaction in knowing we can keep our aircraft under control, using our eyes, hands and feet. But, how do we know we’re being successful? We have to use instrumentation and visual cues to do this job, each of them providing some, but not all, of the feedback necessary.There are some basics under- pinning the art of airmanship that I believe are vital. One of them is “attitude, plus power, equals performance”, a formula behind every maneuver we perform with an aircraft. Apply the right pitch and roll attitudes, establishthe correct power setting,and the airplane will settleinto the performance stateyou desire. Get eitherinput wrong, and you’ll be chasing the needles to adjustthe results.Another fundamental precept is understanding how to assess the aircraft’s energy state. Primarily, we are interested in the total energy held, and capable of being generated, by the moving airplane. This includes kinetic energy represented by the aircraft’s motion, potential energy available from the stored altitude that we can tap, and further energy potential in the fuel that can be called upon to produce thrust. Excess energy can24 • TWIN & TURBINErequisite lift and the wheels leave the ground.Did the attitude provide climbout performance? Not by itself. Did the firewalled throttles cause the airplane to lift off? Not alone. The desired performance was achieved by combining the two fundamental elements of flying–Power, plus Attitude, equaled Performance. During the roll, the aircraft’s energy state was building toward a speed that would generate lift sufficient to support the loaded airplane’s weight against the pull of gravity, and a bit more to ascend the climb gradient.How do we determine the proper climb attitude? Traditionally, we refer to the airspeed indicator to see if it’s showing the desired number; V2,Vy or a cruise-climb speed or Mach. But, we don’t fly the airspeed indicator–we fly the airplane’s pitch attitude, either matching flight- director commands or using other familiar pitch targets that generate the right speed. If sufficiently over-powered, we may slip the throttles back to a climb-power setting, prolonging engine life and reducing noise and fuel burn. Again, our need is to fly pitch attitude, not the ASI; if visual, it’s probably easier to reference the glareshield against the natural horizon. And it’s safer, since the other airplanes representing a collision threat are coming from somewhere outside, rather than out of the instrument panel.Is an angle of attack indicator useful for thisOCTOBER 2015