High, low, or in the middle — which is better and why (a not-so-serious look). When Otto Lilienthal started jumping off that mound of his near Berlin, you don’t suppose he tried surfing atop that glider, do you? It seems instinctive that it would be easier to dangle from a harness and get a running start, Fred Flintstone-style. Even birds seem to favor wings sprouting at shoulder height, rather than from their middle … although that probably has something to do with the physics of muscular anatomy. Regardless, why isn’t it always the same with airplanes?
Two Roads Diverged In A Wood
Just what factors influenced each airplane manufacturer to choose between either a high-wing or low-wing configuration after the Wright Flyer and the age of the biplane? Are there greater advantages of one design over another? This remains a never-ending source of debate. There often seems to be a fine line between objective engineering facts and opinion, and the respective advantages of each type can justifiably deserve selective weighting, depending on one’s needs or preferences. Even those who build them, not just those who buy them, can change (and have changed) their minds. Piper Aircraft itself used to build only high-winged airplanes, but starting in the late 1950’s it gave low-wings a try with the Comanche.
So, is it six of one, and half a dozen of the other? Let’s look and see…
The High Road:
- You don’t need to squat down to check fuel sumps, nor swallow your dignity and crawl around on all fours to do any semblance of a thorough check on the landing gear.
- You don’t have to go wing walking to enter your cockpit, nor have passengers clambering all over your upholstery, in order to reach their seats.
- Those ugly “NO STEP” signs on the wing — there aren’t any. Unless your preflight includes seven espressos per passenger it’s unlikely anyone will find the energy to step on the flaps by mistake.
- Loading cargo often involves less heave.
- You can enter and exit a high-wing airplane in the rain, without feeling like a drowned cat.
- There will be fewer solar cooking experiments conducted in the cockpit during summer months — either on you or trapped insects.
- You don’t need to lie down on your back, perambulating on a wheeled crawler, in order to thoroughly check or clean anything on the bottom of your wings.
- High-wing airplanes generally have larger center-of-gravity envelopes.
- A cantilevered low-wing is of necessity a heavier design than a strut-braced high-wing.
- There’s less trouble taxiing around obstacles, or the noses of nearby rows of parked aircraft, when taxiing in close quarters.
- The wings are less likely to be damaged by rocks or debris kicked up from prop blast.
- Passengers can see more scenery. In a low-wing airplane, if they wanted to see straight down, you’d have to be in one heck of a steep bank.
- A high-wing airplane has better visibility for any mission where viewing the ground is critical, such as search and rescue, aerial photography, pipeline patrol, or for that matter, simple pilotage.
- Checking for traffic beneath you isn’t too much of a challenge, either.
- Seeing where you’re going when you bank is not really not that much of a problem for a high-wing airplane, because where you’re headed is more like eleven or one o’clock, and it isn’t actually at your nine or three o’clock.
- You often don’t need fuel pumps; gravity usually does the work for you.
- A low wing requires much more dihedral for lateral stability, which does contribute toward some small “cosine loss” of vertical lift vector.
- Is the gear down? In a low-wing, you have only the lights to trust; in a high-wing, you can see the mains.
- A high-wing design has a fuselage that is naturally “under-slung“, which greatly assists with lateral stability, especially at low speeds.
- A high wing design has less interference drag, and needs little in the way of fairings between fuselage and wing (unlike the junction between the fuselage and upper wing in a low-winged aircraft).
- High-wing aircraft provide a better natural warning of airframe buffet caused by disturbed air from the wake of the wing impinging down upon the tail.
- It’s easier to land in a crosswind without worrying about which part of the airplane will touch down first — wing or wheel. There’s also less worrying about snowdrifts, fence posts, or bushes.
- A high wing has a lesser tendency to float and use up needed runway.
- There is better flap and aileron protection, when landing in unimproved fields.
- If you should ever transition from those who will to those who have, a gear-up landing is much less likely to rupture a fuel tank.
- If you have to get a pushback to the gate (i.e., your tie-down spot) and you don’t have a tow bar handy, a strut will do. With a low-wing, there isn’t much to push on without a tow bar, except — gulp — the prop. (And no, the leading edge of a wing is not meant to be shoved.)
- They’re just “way” easier to tie down.
- They’re great as seaplanes. (Not that there aren’t low-wing seaplanes, but when’s the last time you saw one?)
- Did you ever try to camp or sit under the shade beneath a low winged airplane?
The Low Road:
- You don’t need a ladder to check your fuel.
- Only the very shortest of low-wing pilots will ever sport a forehead tattoo from walking into a strut or trailing edge… or trip over a gear leg… or poke his eye out on a pitot tube.
- It’s easier to wash your airplane without taking a shower at the same time.
- A low-wing design is generally considered more aesthetically pleasing, and apprehensive passengers can better relate its design to that of the airliners (with which they’re probably more comfortable, anyway).
- Want a shortcut to a stiff neck? Try waxing and buffing the underside of a hundred-plus square feet of wing, positioned just at shoulder height.
- A low wing makes for a handy surface at a convenient height for, say, a picnic.
- It’s just easier to attach landing gear to the airplane. There’s no competition between the landing gear and the passengers for fuselage space.
- There’s a great place for those wheels to hide. You don’t need any complicated articulating contraption reminiscent of Rube Goldberg, and there’s no awkward intermediate position where onlookers gape in stunned fascination at your stork-like landing gear, evocative perhaps of some predatory insect, as they trail in the breeze.
- The wheels usually just hang straight down providing shorter legs with less drag in the air and a wider, more stable stance on the ground.
- No sticks jut out from the fuselage to the wing, so too no drag from said sticks.
- The pilot’s eyes are further from the wing in a low-wing airplane; thus, less percent field of the view is blocked.
- You have a good idea of who might be right above you.
- It’s a cinch to see your fuel caps are on and locked, and as far as icing goes (with the exception of tailplane icing), you’ll usually see it before you feel it.
- It’s generally easier to land a low-wing airplane, because ground effect is more pronounced, and again the wheels are usually further apart improving directional control.
- If you ever do forget to lower the gear, you will be spared the added indignity of having to squat down to exit afterwards, or scrape the ground with the cabin door. A low-wing pilot would exit sheepishly, but at least standing erect, from atop the wing.
- If you ever have to make a forced landing, there is a good deal more structure underneath the cabin to protect you.
- It’s easier for a crosswind to “get under” a high-wing design, and low-wing airplanes are less likely to get blown about by blustery winds.
- High wings may have better roll stability aloft because of that “under-slung” fuselage, but that works against them on the ground: their center of gravity is higher!
So, to answer my own question “why isn’t it always the same with planes?” Well, if one way were better, you can bet it would be.
One Man’s Preference
Personally, I kind of like the idea of being able to see that my fuel caps are still on, that there isn’t any ice on the top of my wings … and enjoy being able to see in the direction I’m turning. A low wing makes it a heck of a lot easier to clear my turns, like in the traffic pattern (Hel-lo!) not to mention avoiding those pirouettes to clear final when the run-up area doesn’t happen to be facing into the pattern. And have you ever fueled a high-wing airplane by yourself? Hah! What a production! Get ladder. Hoist hose up the ladder. Don’t fall. Try to aim for the right place. Brace your arm somehow to avoid fatigue. Hope you hear the increasing pitch as the fuel level nears to top. (Because unless you’re six feet tall or you’re perched near the tippy-top of that ladder, you sure as heck can’t see in there…) Watch sheet of fuel cascade down wing, because you missed hearing the pitch increase.
Then again, there’s always a mid-wing…