Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.")

Aero-News has called upon the expertise of Thomas P. Turner, master CFI and all-around-good-guy, to bring our readers -- and us -- daily tips to improve our skills as aviators. Some of them, you may have heard before... but for each of us, there will also be something we might never have considered before, or something that didn't "stick" the way it should have the first time we memorized it for the practical test.

Look for our daily Aero-Tips segments, coming each day to you through the Aero-News Network.

Aero-Tips 09.04.06

A question came across my desktop:

I'm looking for data on Vyse as a function of gross vehicle weight. I frequently fly alone and am wondering if I'm carrying more speed than necessary on final approach to stay above blue line.

First, let's define our terms. VYSE is the indicated airspeed that results in the best rate of climb with one engine inoperative in a twin-engine airplane. VYSE is usually depicted by a blue-colored radial line on the airspeed indicator-hence "blue line" speed. "Best rate of climb" is something of a misnomer, too; in many cases VYSE is the speed that provides the least rate of descent with an engine out.

I wrote back:

VYSE is by definition an airspeed determined under worst-case conditions, which includes maximum takeoff weight. Like other angle-of-attack-related airspeeds, there are no published correction values for VYSE at lighter weights because by definition VYSE exists only at maximum weight.

However, the effect of VYSE does decrease with a reduction in aircraft weight. As a rough estimate in most light twins the indicated airspeed drops at the rate of approximately two knots for every 100 pounds below maximum takeoff weight.

Why don't you try an exercise? With a qualified multiengine instructor along to help keep you out of trouble and to record data as you fly, establish a safe altitude, put the left engine into zero thrust (or even shut it down and feather the propeller for maximum realism, doing so over an airport just in case practice turns into a real single-engine landing), and establish VYSE /blue line attitude. Note the rate of climb. Then increase pitch a degree or two to reduce airspeed slightly and see what steady-state climb rate results. Done safely this can be a fun and informative flight.

And lastly, once you're committed to landing you need to reduce airspeed below "blue line" to safely land. Flying in fast will cause you to use a lot of excess runway to flare and stop. Typical POH landing speed is 1.3 times the VMCA, the minimum controllable airspeed with the critical engine inoperative…and "effective VMCA" drops with a reduction in aircraft weight, too!

Aero-tip of the day: Understanding the certification basis of performance speed helps you design carefully controlled, safe experiments to determine the "best" technique for nonstandard conditions.

FMI: Aero-Tips