Barry Schiff has been flying and instructing for nearly 50 years. He is a retired airline captain for TWA.
When I first checked out in the Boeing 767 in 1984, I was amazed at how much less data had to be memorized than when I checked out in earlier aircraft such as the Boeing 707 and 747. This was because so much of the needed information is presented on the glass-cockpit's display panels. No longer did we have to memorize so many numbers and respond monkey-like to questions asked during an oral examination. After all, there's no point in memorizing data that is available at a glance. This made checking out in Boeing's wide-body twin somewhat easier than other jet airliners. (I prefer not to discuss the difficulty we had in adapting to the computerized flight-management systems.)
This made me wonder why more performance information isn't as readily available to general aviation pilots. For example, why do we have to memorize speeds for best climb rate, best climb angle, best glide, and so forth? Why isn't maneuvering speed and other such information presented where it would do the most good, on the airspeed indicator?
Some months ago while administering a flight review to the pilot of a Cessna 414A Chancellor, I asked what the best glide speed was for his cabin twin. His response was indignant. "Glide speed? You've got to be kidding. I don't need to know the glidespeed for this airplane. Idling these turbocharged engines would ruin them."
I then asked what speed he would use to glide following a double engine failure caused by an unknown fuel leak and subsequent fuel exhaustion. He got the idea, dismounted his high horse, stroked his chin, and guessed at 90 knots. (At gross weight, clean, and with the propellers feathered, the 414A glides best at 120 kt.)
Although many pilots who fly the same airplane day in and day out might have all of the pertinent performance figures committed to memory, those who fly infrequently or who fly a variety of aircraft probably do not. (And getting older doesn't help when it comes to remembering a plethora of unrelated numbers.)
Wouldn't it be nice if thin radial lines were etched on airspeed indicators and marked appropriately? This would make it easier to fly airplanes more efficiently, especially during an emergency or other stressful situations. (Beechcraft, for example, lends a helping hand by placing a small white triangle at the 154-kt point on the airspeed indicator of its B36TC Bonanza to indicate the maximum speed at which 15 degrees of flaps and the landing gear may be extended. It's a handy marking.)
I did this on some photocopies of an airspeed indicator and was delighted to discover that this did not clutter the dial and to find how easy it was pick out various performance speeds. (To prevent clutter, I used single-letter designators such as G for glide, Y for best rate of climb, and so forth.)
I don't think for a minute that such a suggestion will ever be adopted, but there is an alternate solution that is equally effective, one that I use in my American Champion Explorer. I simply had a small placard engraved and installed near the airspeed indicator. Although I don't have trouble remembering the important V-speeds for such a simple airplane, the placard is there for others who might fly it. I included V X, V Y, V A, and V GLIDE. I also added V LO (maximum speed for landing gear operation) as a joke, but so far no one seems to have noticed.
Knowing or having access to these various speeds, however, is only a starting point. Pilots also need to know how some speeds vary with changing conditions. For example, V SO (the lower limit of the white arc) and V S (the lower limit of the green arc) usually are values for maximum-allowable gross weight, power off, and 1 G at the forward center-of-gravity limit of the airplane. (Depending on the model and year of manufacture, stall speeds shown for many older aircraft are shown for the aft CG limit.) Pilots should know that stall speed decreases as CG moves aft, decreases as gross weight declines, and increases as G load increases.
Similarly, to fly the typical lightplane proficiently, we should remember: V X increases with density altitude and decreases as the aircraft gets lighter; V Y decreases as density altitude climbs and decreases as the aircraft gets lighter (V X and V Y converge so that they are identical at an airplane's absolute ceiling); V A decreases with gross weight and is unaffected by changes in density altitude; and V GLIDE decreases at lighter weights and is unaffected by changes in density altitude. (Although V GLIDE changes with aircraft gross weight, the resultant glide ratio is unaffected.)
This leads to one of my pet peeves, which is when an FAA inspector or designated examiner holds an applicant for a rating or certificate responsible for memorizing something that is published on the instrument panel. Who cares, for example, what V NE is when the redline is clearly displayed on the airspeed indicator? Questions involving numbers should be confined to those that a pilot must commit to memory because they are not available by glancing at the instrument panel.
This reminds me of how one grizzled TWA captain replied during an oral exam for a type rating when the FAA inspector asked him for the wingspan of the Boeing 707. "Wingspan? I'll let you know when I get ready to build a box for it."
Visit the author's Web site ( www.barryschiff.com).
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