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Maximizing climb performanceMaximizing climb performance

The second type of airplane in which I had been checked out as a student pilot in 1954 was an 85-horsepower, 1946 Cessna 140 (N76283).

Barry SchiffThe second type of airplane in which I had been checked out as a student pilot in 1954 was an 85-horsepower, 1946 Cessna 140 (N76283). Compared to what I had been flying—a 65-horsepower Aeronca Champ—it had the performance of a rocket. It was technologically advanced, too. I mean, it even had a starter, a mixture control, and a landing light, which is why I used it for my night checkout.

A few weeks after that there appeared one of the most crystal-clear nights I can remember. It inspired me to see how high I could climb above Los Angeles. Oh, how magical that would be on such a night. As I recall, the speed for best climb rate (VY) was 70 mph.

It took forever to struggle above 10,000 feet, but the Christmas lights that December evening created a blanket of sparkling jewels that stretched to the horizon and made the effort worthwhile. Finally I got to a little more than 11,000 feet and began to wonder what might be wrong with the airplane. The service ceiling was supposed to be 15,500 feet, and I could get nowhere near that high even though I had judiciously adjusted the mixture control for maximum power.

The next day I complained about this lackluster performance to my instructor. He soon made me realize that I really hadn’t known how to properly climb an airplane. In subsequent years I discovered that I wasn’t the only one who didn’t know how to maximize climb performance (particularly at altitude where it can be most critical).

As most pilots realize, climbing at a speed other than VY results in reduced climb rate. In other words, VY always results in gaining maximum altitude in minimum time. The problem is that many pilots often don’t consider that VY varies with altitude and gross weight. Consider a Cessna 310R with a VY of 107 knots. This speed, however, is valid only at sea level and when the aircraft is loaded to its maximum-allowable gross weight. Elevate the aircraft to 20,000 feet and VY drops to 91 knots. Reduce gross weight by 800 pounds and VY drops further to 85 knots. This represents a substantial 22-knot difference between the “published” VY and the corrected one.

The same principle applies to all piston-powered airplanes. Climbing at the published sea-level climb speed when at altitude and light weight substantially reduces climb rate and might even make climbing impossible. This is what I didn’t know when making my “high flight” in the Cessna 140.

A chart showing how VY varies with altitude and gross weight usually is in the pilot’s operating handbook but frequently is not used, possibly because we forget that it is there or is inconveniently located. Recently I have begun suggesting that pilots prepare a small placard of VY versus altitude and weight that can be placed on the instrument panel as a ready reference during flight.

Although climbing at VY results in the most rapid climb to altitude, it might not be the most expeditious way to fly from one place to another. For this, you might want to use cruise-climb. One rule of thumb suggests using a climb speed that is as much faster than VY than VY is faster than VX (the best angle-of-climb speed). For example, if VX is 70 knots and VY is 100, use a cruise-climb speed of 130 knots. Such a climb speed can be reduced about 1 percent for each 1,000 feet of altitude. You can also reduce such a climb speed by about 1 knot for each 100 pounds below the maximum-allowable gross weight.

For those in a great hurry and without need to reach altitude quickly, climb at full power and at the shallowest climb rate consistent with safety (100 or 200 fpm, for example).

This raises an interesting point. In most airplanes, there really is no need to reduce power after takeoff (unless mandated by the POH or noise-abatement procedures). After all, power reduction occurs automatically with a gain in altitude (in nonturbocharged airplanes). This can have a dramatic effect on climb performance in the lower altitudes and reduce time en route. Do not expect improved fuel efficiency, however.

Upon reaching cruise altitude, be sure to maintain full or climb power until the airplane has accelerated to slightly beyond cruise speed. Reducing power prior to reaching cruise speed simply results in the airplane slowly mushing its way toward the target airspeed. In some cases, you might not ever get there.

A note of caution: Remember that climbing can reduce forward visibility. Be sure to occasionally execute shallow S-turns or dip the nose gently to see what might lie ahead. A midair collision seriously erodes climb performance.

Barry Schiff has been presented with the Gold Proficiency Award by the Aero Club of Switzerland.

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