June 1, 2009
By Dan Namowitz
Where do you go—high or low—when picking an altitude for flight? The right altitude may seem obvious at first glance. But you may gather information and find yourself torn between factors that tell you to go high and others that say to fly lower.
Which imperatives will prevail today? How we are taught to resolve that issue helps determine whether we evolve into high fliers or low riders. Some general statements apply. If you’ve been flying for a few years but have not yet upgraded either your aircraft or your on-board equipment, I’d guess that you’re flying lower over the same routes than you did at the beginning of your piloting days.
New pilots—with those emergency landing drills still fresh in their minds—know academically that higher is safer, so they fly higher. Trouble-free experience tends to make more experienced pilots fret less about engine-out scenarios. Gradually they start working their way down to lower cruise levels, especially on oft-flown routes. Some carry this tendency too far; you can pick them out because they’re the ones who know where all the really low obstructions are. The mark of a true low rider is that when he gets where he’s going, he has to climb to enter the traffic pattern.
Other pilot traits help us isolate the DNA of high and low fliers as true subsets of the pilot population. VFR-only pilots enjoy freedom, and how better to express it than to fly along with the hills, hamlets, and homesteads not too far below? Pilots who fly frequently under instrument flight rules become accustomed to climbing many thousands of feet before leveling off, and they may return to their comfort zone even under VFR, still using minimum en route altitudes as a sturdy benchmark.
All this is why you can inspect the flight planning of two pilots flying similar aircraft (let’s say a rented single that is non-turbocharged, and produces its best power below 10,000 feet) on identical routes, and find yourself face to face with completely different plans of action. It all depends on how they evolved as pilots. One predictably flight-plans the highest altitude that seems reasonable under the prevailing conditions. The other pilot heads for the lowest altitude that will get him there in one piece. It’s not that one pilot’s right and the other is wrong. Intangibles from personality to navigational style to risk tolerance play a role in the decision making.
Nor would it be correct to assume that my use of the term risk tolerance is a swipe at the low flier. Sometimes as a flight instructor I have looked over the flight plan of a pilot who tends to select higher-than-average cruise altitudes, then posed the question, “How do you plan to get down from up there if that scattered cloud cover thickens up?” And by the way, you can also divide high and low fliers into subgroups consisting of those who add some altitude for a night flight, and those who don’t.
High or low, some pilots are extremely finicky about altitude selection. I was leveling off at 2,500 feet on a brief flight above the flatlands with the boss aboard long ago. He said, “Go on up to 2,650 feet, please.” Two-thousand, six-hundred, and fifty feet? I wondered what cruel test of my skills he was planning. All he said was, “Everyone flies at 2,500 feet.”
Point well taken. Certainly 2,500 feet was a favorite altitude for the low-powered single-engine fleet in our region. That altitude offered the convenient compromise of being lower than the usual IFR arrival altitude of 3,000 feet msl in our terminal area, but higher than the 1,500-foot-msl ceiling of choice used by our floatplane and taildragger fleet. Not many pilots even consider the collision factor when choosing an altitude.
Speaking of 3,000 feet and collision: Here in the lowlands, that nice round number seems to be the most popular altitude for pilots heading in any direction. Why? It’s high enough to provide a respectable glide if an engine seizes, but it’s low enough to spare pilots the imagined aggravations of working with the so-called hemispherical rule (odd or even thousands plus 500 feet depending on the direction of flight). Some pilots fly everywhere at 3,000 feet. They also come back from everywhere at 3,000 feet, which aptly illustrates the hazard.
Is there a favorite altitude that you gravitate toward, wind and weather permitting? There tend to be four general airspace blocks in which pilots of a like mind about altitude will be found. Because field elevations and the heights of terrain above sea level vary so widely across the country, let’s set aside specific msl values and instead think in terms of height above terrain. Working upward from the lowest to the highest available for VFR flight, we could regard them as hazard airspace, recreational airspace, travel airspace, and celestial airspace.
Of the four, the only block that is theoretically empty (except for takeoffs and landings) is hazard airspace. To be there at other times may be unsafe, a violation of minimum altitude restrictions, or both. Absent an airport nearby, the motives for flying in this block are usually suspect, except for pipeline patrollers, aerial surveyors, and crop sprayers. Enough—any thrills found at these levels derive their seductive powers from the dangers present, as accident summaries frequently confirm.
Lying directly above hazard airspace is a zone we can consider as the recreational airspace block. This can be a fabulous place to fly—but you’ve got to know the territory. This is still no place for guessing or relying on your ability to spot a tall obstruction ahead. Sightseeing flights for employment or pleasure are commonly flown at these levels. Some VFR cross-countries of modest length can be pleasantly flown here, given intimate knowledge of the route, and flat terrain. Classics and other slower aircraft do some of their best work here. A navigational sacrifice of this level, deterring some pilots from using it, is inability to see checkpoints more than a few miles ahead or to receive the straight-line signals from traditional navaids such as VORs. Communications and radar service are also curtailed; however, we can stipulate that pilots flying in this block keep their communications and interactions with ATC to a minimum.
Because of those constraints, cross-country routes flown in this airspace sometimes must zigzag around towered airports and special-use airspace. Typically, however, these pilots avoid such places altogether. Conflicting traffic remains a concern because you’ll encounter everything from ultralights, light sport aircraft, local traffic, and floatplanes hopping from pond to pond down here. Remember that if you’re having a great old time down here, so are others. What is the upper limit of this block? A good guess might be 2,000 feet agl. However, if we include flight training in the airspace’s uses, it may reach as high as 3,000 feet agl.
Moving higher, we come to that mainstream block of traveling airspace—going-places territory, the aeronautical analogy of an Interstate highway or a commuter railroad. It can be crowded, businesslike, usually orderly but occasionally subject to traffic snarls and roadblocks. Above 3,000 feet agl the traveling airplane derives its orderliness from the hemispherical rule, described above.
Traveling airspace may require VFR pilots to beg passage through Class B, C, or D airspace that lies along the route. But it avails pilots of plentiful radar flight following, as well as radio navigation. These are the levels where your flight instructor sent you on your student cross-countries. Pilots flying here have the luxury to be fickle in altitude selection. Flush with flexibility, they’re frequently fussy to find finer flight conditions. Bumpy down there? Let’s climb. Now we’re flying in smooth air, but we can’t see much in this haze. Pireps say we can top the haze if we climb another 2,000 feet—but up there groundspeed will drop off significantly. And so forth. How we pursue our preferences helps establish our identity as high or low fliers.
Next we have the tongue-in-cheek block I call celestial airspace in honor of the lofty ambitions of the pilots who climb up there. When I was asking myself who uses celestial airspace, it was easier to ask, “Who doesn’t?” One answer is me. On the rare occasions when I have flown in this airspace—not being the owner of a high-performance aircraft—it was to come home to Maine, northeastbound with a magnificent tailwind after an unexpectedly long interval on the ground in Maryland because of bad weather.
What are its boundaries? An obvious flexible upper limit might be either the onset of oxygen requirements, or the service ceiling of your aircraft. For a lower limit—and this may reflect an East Coast bias—I nominate 9,500 feet, so it is a narrow band of air. For many pilots the first venture into celestial airspace may be to take advantage of the tailwinds mentioned earlier. Some pilots end up at these levels in a continuing effort to escape turbulence or to climb atop a thick haze.
Up here, squawking altitude, you are able to overfly much of the surface-based controlled airspace that requires pilots down below to avoid or to seek permission to traverse. Opposing traffic up here tends to be faster, but often equipped with avoidance systems and receiving radar advisories. As mentioned, VFR flights here need to keep a careful eye on cloud layers below. Descent planning must be performed with care, allowing for a gradual descent that is kind to your engine. It is also humane; if you have passengers aboard, this would not be a good time to find out about someone’s ear block. Sea-level pilots may even notice some oxygen deprivation symptoms up here, especially visual effects at night. Getting some flight time up here is a good preparatory step to transitioning to a turbocharged aircraft or a light twin.
No matter what your default altitude preference, give sensible weight to selection factors that will make your next cross-country flight as safe and efficient as possible. If that means taking along another pilot for comfort, or a flight instructor to ease your transition to a new aircraft or airspace block (higher or lower), then do so. Abandoning old ways can be difficult, but they’re worth shedding if the result is acquiring more skill.
Dan Namowitz is a freelance writer and flight instructor living in Maine.
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