The F-86, mig-15, Dassault Ouragan The b-1 and tu-160 Concorde, tu-144, 2707

The low wing and T tail with two engines at the back. (CRJ, dc9)

The 'standard' shape with the mid aircraft wings, and vertical and horizontal stabilizers at the back, used from the E170 to the a380.

And while many general aviation craft are low winged or differ from a high wing tricycle single engine design, most seem to stick with that formula as well.

For some of the odder shapes, the question is 'industrial espionage?' but in the greater context, is it simple convergent evolution in that there are only so many shapes which are functional and useful so most things take on that general shape?


It’s an interesting question. Aviation historian Bill Sweetman wrote about just that in an Air & Space article called How the 747 Got Its Hump. The answer to the question is quite long and specific to the aircraft type and use but the short and sweet answer is that airplanes are a great compromise between a number of factors, including mission profile, aerodynamics, structures, propulsion, avionics, manufacturability, realities and practicalities of product use, and on a few occasions customer insistence and industrial espionage. See illustration below.

enter image description here

It just works out that, when all the factors above are taken into account, the designs you describe tend to be the best all around solutions for particular aircraft sizes, costs, payloads, mission profiles, safety, etc. Like any other artifact made by humans, aircraft are but single answers to open ended design problems; a compromise between all of these competing requirements into a tangible product. No one answer is 'correct' per se, but these kinds of aircraft designs seem to be the most optimal and every single design team when confronted with the requirements and design constraints create much the same thing.

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    $\begingroup$ Thank you, so it does seem to be 'convergent evolution' based on responses to physics and current materials science, vs cost and (complicated formula involving all the above, plus what the person doing the end yes/no decision liked as a child) Military aircraft are mildly easier to understand edge cases with due to the lack of a lot of the (hair,??,profit!) equation. $\endgroup$ – Rose Thorne May 15 '18 at 8:49
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    $\begingroup$ Wow, that is a great Air & Space article. I read it in 'single page' mode, and about half-way thru to the end it got even better. A similar article on how smaller General Aviation got from the World War 1 era 2-wing designs to single wings would also make for a good read. High with a strut, then high with no strut. Low, with no wing bracing. T-tail! Tail draggers, then nose-wheel tricycle gear. Fixed gear, then retractables. Then Burt Rutan's composite planes, mid-wing pusher engine with front canards that sprouted into other almost tadpole shapes to carry more occupants. $\endgroup$ – CrossRoads May 15 '18 at 13:30

To put it simply, aircraft design is a war of compromises, and when characteristics and configurations of a design are combined in different ways, there emerges some combination that hits a sweet spot.

Like an airliner designed to cruise at high altitude (lots of area + high aspect ratio), near trans sonic speed (lots of sweep), needing 4 engines (best place to put them is on the wings for efficiency and centre of gravity reasons), with the engines on pylons forward (from the discovery by Boeing, during the B-47 program, that the aerolastic flexibility with the rear weight bias of a long skinny swept wing was a problem and the engines could be used as mass balances by putting them on pylons out front to move the wing's centre of mass forward). And presto! There's your near universal airliner configuration.

Or take the lowly Cessna 172. It's configuration satisfies a whole range of requirements, none perfectly, but all just good enough to make it the most practical arrangement, making it the light aircraft of the ages.

My favourite is the DC-3. A balance of compromises so perfect that over 85 YEARS after it was designed and almost 75 years after it was last built, it is still to this day a viable business tool that people buy, not for show, but to put to work.

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    $\begingroup$ The lowly Cessna 172 could be said to have hurt Cessna when they tried to improve the high wing line with the 177. Cantilevel wing with no struts!, better handling, more aerodynamic front window situated mre forward on the wing for a better view, wider cabin, wider Center of Gravity. Same 150 HP engine, so maybe underpowered a little. Ham fisted 172 pilots couldn't land the stabilator tail, or overfueled/overfilled the plane, so after one model year the wing was made more docile and slots were added to the stab, to make the plane tamer, 180HP used. Reputation hurt sales, limited its life. $\endgroup$ – CrossRoads May 15 '18 at 16:23
  • $\begingroup$ I owned a '68 and absolutely loved it. It was originally planned as the "all-new Skyhawk for '68!". But cautious heads prevailed and it was decided to keep the Skyhawk as is, except for adopting the O-320 engine, and redesignate the new airplane the 177. The wing was the cantilever wing from the '66 Centurion, scaled down about 20%. The stabilator gave it massive tail power and allowed a more forward CG limit. $\endgroup$ – John K May 15 '18 at 16:33
  • $\begingroup$ There were two handling issues. It had a NACA 63 series laminar airfoil which would develop huge sink rates if you got too slow, and had a sharp stall. The stabilator had a lot of authority, was geared a bit too fast, and had a lot of rotational inertia with the big mass balance in the fuselage. Pilots would be afraid of the low speed behaviour and approach too fast. The stabilator characteristics, especially the fast gearing and high interia, would promote PIOs and badoing badoing badoing down the runway. $\endgroup$ – John K May 15 '18 at 16:36
  • $\begingroup$ Glad that was all fixed in the 1969 model. I've flown a 1973 since 1996, we still like the plane. Just finished putting all new fairings on, replacing all the ABS plastic with fiberglass, plus some speed mods from Aircraft Speed mods. New avionics too to get caught with GPS moving map world and ADS-B. Going to be flying it for quite a while more! cardinalflyers.com for those that want to learn more. $\endgroup$ – CrossRoads May 15 '18 at 16:40
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    $\begingroup$ The stabilator slots were the result of the discovery that near full aft stick, possibly while in a sideslip with air curling over the dorsal fin and striking the inboard stabilator at a high AOA, the stabiliator could stall and cause the nose to pitch over right in the landing flare. The slots just add more AOA stall margin to the stabiliator. About half the fleet was modified with a field retrofit kit. $\endgroup$ – John K May 15 '18 at 16:40

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