Continuing Ed

Thankfully, the skies are not constrained by the tyranny of roads encumbered by speed limits, curves, stop signs, and traffic lights. Even a low-power trainer can easily beat ground-bound transportation over the same route.

Low power has its place, but those of us who fly mostly for transportation reasons feel a real need for speed. The point is not just getting there, but getting there as fast as possible.

What is fast? I consider the lower threshold of serious speed for a single to be about 130 knots true airspeed. That's 150 mph, or 2.5 miles per minute. At that speed, you can make a 500-mile trip in 3.3 hours (in no-wind conditions), which is about as long as most passengers can take in a light aircraft without a bathroom and a chance to stretch their legs. A Cessna 172 making 110 knots (about 126 mph) over the ground would take only another 40 or 45 minutes to make the same trip, but those extra minutes can seem like hours. Perception matters.

Speed helps to lessen the impact of ornery headwinds. At 130 knots true airspeed, you can fly into the teeth of a 25-knot headwind component and still be clocking 105 knots over the ground. Meanwhile, the 110-knot 172 is struggling along at a frustrating 85-knot groundspeed, giving the pilot plenty of time to determine whether or not he's going any faster than those tiny cars tracking narrow ribbons of highway below.

Enjoying the luxury and advantages of high speed in an airplane means learning and practicing specific go-fast skills. Most high-speed airplanes have retractable landing gear and constant-speed propellers-systems that require training in operating and emergency procedures, plus an instructor's endorsement. The requirements are spelled out in the federal aviation regulations.

You won't find any such regulations on another go-fast skill: thinking fast. Going faster calls for adjusting your mind to think further ahead of the airplane. When you graduate to 150 knots from 120 knots, you're flying 25 percent faster; so maybe you should be thinking 25 percent further ahead than before.

It's not quite that simple, however. Remember, perception matters, and on takeoff our perception of speed is affected by acceleration. Compare the takeoff performance of a 150-hp Cessna 172 with that of a 285-hp Bonanza F33A. When you shove the Cessna's throttle in to full power, the two-blade, fixed-pitch prop spools up to a few hundred rpm below redline on the engine tachometer. The airplane gradually gathers momentum until reaching liftoff speed of about 55 knots.

Shove the throttle in on the Bonanza and thanks to the constant-speed prop, the tachometer quickly climbs to 2,700 rpm-full power. If the Bonanza is loaded to its maximum gross weight (3,400 pounds), each one of those 285 horses has to pull 11.9 pounds of airplane. Each of those Cessna nags, on the other hand, is struggling under a 16-pound load. The Bonanza team obviously will get up to full gallop-71 knots, liftoff speed-much more quickly.

When you're accelerating faster on the runway there's less time to correct for off-centerline steering errors or to check instruments for the proper indications. If a problem suddenly pops up on the takeoff roll, you have to respond more quickly, especially if it's a short runway.

Speed also is a factor in climbout. Best rate is the speed to use in the initial climb (to at least pattern altitude), but from that point on until leveling off at cruise altitude you have choices to make-continue at best rate or lower the nose and accelerate to a cruise-climb speed for better forward speed, visibility, and engine cooling.

The climb-speed decision isn't much of a decision in a typical fixed-pitch single such as a Piper Warrior, because the difference between best-rate and cruise-climb speed is narrow, about eight knots.

Compare that to the Bonanza's 15-knot spread. That makes it possible to fine-tune the climb speed for the conditions. For example, in hot and bumpy conditions you'd like to climb as quickly as possible to smoother air, but not at the expense of overheating those six big cylinders and the engine oil. So, you might compromise at a speed halfway between best rate and cruise climb.

Speed-more of it-means more choices in cruise flight as well. Should it be a full-throttle go-fast cruise, maximum-range slow cruise, or something in-between? Just as with the climb phase, the choice is based on the objective. If saving time is the most important objective, you'll go for high cruise speed. If you have a long way to fly and can do it nonstop only by using maximum-range power, your decision is made.

The difference in speed and en-durance can be dramatic. At about 6,000 feet and 75-percent power, the F33A will cruise at 172 knots for 4.2 hours, according to the performance charts. At 45-percent power, speed drops to 135 knots but endurance zooms to 6.6 hours. Faster is the way most pilots usually like to fly, but speed comes at the price of fuel consumption, endurance, and range.

Faster, lower-drag airplanes, such as the Bonanza and the speedy and slick Mooney, operate with a smaller margin between normal indicated cruise speed and V_NO, the maximum structural cruising speed, which is the top of the green arc on the airspeed indicator. If you push the nose over to descend but don't reduce power, the airspeed needle will begin a rapid trek into the yellow arc.

At that point it's time for fast thinkers to make a transition to another frame of mind. It's time to think slow. Getting rid of speed when you're going fast can involve a lot more than simply yanking the throttle back to idle, which is almost never a good idea. Thinking slow is another valuable skill for high-performance flying, and a subject for another month.