The WRight Perspective: by Joe Bullmer. Article One of Four

The WRight Perspective    

by Joe Bullmer

     Since its publication by the Smithsonian in 1987, the 107 page booklet The Wright Flyer, An Engineering Perspective (above), hereinafter referred to as the Perspective, has been considered by many to be the most technically thorough and accurate assessment of the development and characteristics of the earliest Wright aircraft.  It has an impressively technical appearance, is a compilation of papers written by impressively credentialed authors, and carries the authority of the American Institute of Aeronautics and Astronautics (AIAA) and the Smithsonian.  It can be seen online at the wright flyer, an engineering perspective – internet archive 

    Unfortunately, close examination of the Perspective reveals numerous judgments and opinions which, while popular with both prominent and amateur aviation historians, contradict Wright statements and records.  A number of statements appearing in different sections of the compilation actually contradict each other.  Also, most of the technical material presented gives very limited added insight into the design and performance of these vehicles.       

     The author of this article, a retired aeronautical design engineer, has written a book titled The WRight Story. 

 

Its purpose is to correct the historical record of the Wrights’ work using their own words and records.  In that book, the Perspective was referred to as “perhaps the best example of excellent detailed research and reporting” on technical aspects of the design and performance of early Wright aircraft.  Research for The WRight Story did reveal information differing from statements appearing in the Perspective, but this was mostly on non-technical points and no worse than in most other previous publications about the Wrights.  

     However, since publication of The WRight Story numerous differences between information in it and material appearing in the Perspective have been pointed out by concerned readers.   This is the first of four articles by the author of The WRight Story presenting his positions on these differences.  These positions are presented in further detail, with many hundreds of references to specific sources, in The WRight Story.

     Not counting the brief half page Forward, the first section of the Perspective is titled, The Wright Brothers, The First True Aeronautical Engineers.  On page 10 appears the statement “wing warping, was another one of the major ingredients of the Wrights’ success”.  Although the Wrights did indeed need some form of roll control, others had used warping previously; and better ways to control aircraft roll, such as ailerons or separate winglets, already existed.  Unintended effects of warping turned out to be a source of trouble for the Wrights throughout flight testing; and it was eventually rejected by aircraft builders and buyers world wide.  The Wrights finally abandoned it for ailerons in 1915 after challenges to their patent, largely based on opposable warping, were rendered moot by the federal government.

        

The 1901 Wright glider at Kill Devil Hills, North Carolina.

     Page 11 contains the statement that the Wrights’ 1901 glider “embodied the best aerodynamic state of the art”.  Actually, with a terrible aspect ratio, poor camber, and extreme instability caused by the canard elevator and inappropriate center of gravity location, the 1901 vehicle could barely be made to fly.  However, a number of aircraft and unmanned models developed by the Wrights’ predecessors did not have these deficiencies and flew quite well.

     Appearing on the same page is the popular quote of Wilbur’s 1901 statement as “nobody will fly for a thousand years.”  According to Smithsonian historians his actual and more reasonable statement was that man wouldn’t fly for 50 years.

    One of the most common beliefs about the Wright aircraft appears on page 13.  There it is stated that control over all three axes of the aircraft allowed the 1902 glider to “make smooth banked turns.”  Actually the Wrights added the vertical aft rudders to enable that vehicle to continue to fly straight when correcting an inadvertent roll. That’s why their first rudder was a fixed installation.  Soon they found that didn’t work, and that the rudder had to be moveable and connected with wing warping to keep the vehicle on course.  The similarly configured 1903 Flyer had the same control scheme for exactly the same purpose.

  

The Wright 1902 glider in flight. The famous Wright 1906 patent was based on this glider and not for a powered machine.

     The Wrights’ patent, based on the 1902 vehicle, makes it unmistakably clear that the three axis control of that vehicle was to allow it to maintain heading while correcting inadvertent roll, not to facilitate a turn.  Another obvious proof of the lack of turning ability of the 1902 and 1903 vehicles is that the whole purpose of their subsequent extensive flight testing and development throughout the next two years, including numerous serious crashes, was to develop the capability to initiate and complete turns with their aircraft.  This was only accomplished by totally abandoning the patented interconnected rudder and warping control scheme of the 1902 glider and 1903 aircraft.

     Page 13 also contains the statement that the Wrights decided that the empirical techniques used by designers of maritime propellers “were useless [for an] aeronautical application”.   Actually the main reason maritime designs were and are largely irrelevant is that air is compressible and water is not.  Consequently the propellers must function differently in the totally different mediums.  But the Wrights did not understand how cambered wing sections develop lift, so they did not appreciate this basic problem.  However they did object to the maritime “empirical” design techniques and wanted a positive theoretical approach.  

     Having actually designed a propeller in 1960, this author can attest to the fact that, at least over a half century after the Wrights, propeller design was still not a unified mathematical theory.  It is not what mathematicians would call a “closed” problem but rather an “under-constrained” problem.  There are over twice as many unknowns as there are known factors.  Usually one starts with a known number and type of engines and maximum prop diameters dictated by the proximity of engines to each other or to the fuselage or ground.  Although there may also be speed objectives, unknowns to be determined include number of blades, blade rpm, cross section shapes, angles of attack or twist, blade width and taper, and resultant thrust from the prop(s) which actually determines speed of the props (and the vehicle) through the air.  One must also account for the acceleration of air as it approaches the propeller at various flight speeds, what the Wrights called “throwdown.”

Editor's note: These are attempts at creating close reproductions of the Wright propellers as they evolved, using the fragments of broken propellers, what few original notes that are in existance, and photographs.

     Although some equations used by the Wrights to get a handle on the problem survive, the complete design procedure they used does not. This is no doubt because their procedure also employed some “empirical” techniques such as simply picking some parameters, calculating the other factors, constructing tables of data, and iterating based on data trends.  Either they were not satisfied with the appearance of that procedure, or they wanted to preserve their design secrets.  Remember, contrary to usual practice they never published the aerodynamic data derived from their wind tunnel either.

     While on the subject of propellers it would be well to address another incorrect statement appearing on page 13, namely that Wilbur Wright “was the first to recognize that a propeller is nothing more than a twisted wing”.  It is fairly well known that Sidney Hollands presented a paper to the Aeronautical Society of Great Britain in 1885 on exactly that subject.  As recounted in Chanute’s Progress in Flying Machines, a document that the Wrights had originally studied, Hollands “stated that he had found it advantageous to make the fan blade concave on the driving or lifting side, and that the angle of maximum efficiency was 15 degrees with the plane of motion at the tip and 30 degrees at the root.”  (Here it must be remembered that Hollands, like most others including the Wrights, erroneously thought cambered sections developed their push or lift by pressure on the bottom or concave side.)  Hollands also pointed out that the blades should be tapered toward their tips, something the Wrights didn’t appreciate.

     What’s more, as pointed out in the next section of the Perspective, three designers of maritime propellers, Lanchester, Drzweicki, and Prandtl, had developed design theories for air propellers that considered them as cambered twisted airfoils well before the Wrights addressed the problem.

     Page 16 quotes Orville’s claim to have taken off on the first flight of December 17^th with the airplane having “raised by its own power alone” into the air.  This statement should not be allowed to stand since the headwind of 25 to 27 mph recorded by the Wrights supplied 90% of the airspeed and 80% of the lift required for takeoff.  The aircraft was almost flying sitting still.  In fact, later that day the vehicle was raised by the wind and rolled over while stationary and unattended.

     Finally, on page 16 the author presents his opinion that “Wilbur and Orville Wright were indeed the first true aeronautical engineers” and lists six reasons to support this claim.  They are:

1.       “They were the first to recognize the importance of    control around all three axes of the airplane.”  Actually they did not originally “recognize” the importance of three-axis control but rather were eventually driven to it in order to be able to maintain straight and level flight.  Others before the Wrights did “recognize” the importance of three axis control of aircraft.  These include John Montgomery, Francis Wenham, Pierre Mouillard, and go all the way back to Jean-Marie LeBris in 1857.

2.   "They were the first to modify and improve their flight controls by means of a systematic servies of successful glider flights in 1902." In fact, Otto Lilienthal and Augustus Herring were testing and improving their flight control through glider tests in the mid 1890s as was John Montgomery in the 1880s.

Otto Lillienthat in one of his many successful glider flights

3.            Here the statement is made that they were “the first to use wind tunnel results to correct some defective data existing in the literature.”  Actually the Wrights admitted to Chanute that their wind tunnel showed that “the [Lilienthal lift coefficient] table is probably as near correct as is possible,” and in a November 24th, 1901 letter to him they admitted that their previous lift inadequacies were their own fault for misusing Lilienthal's data.  And it was flight test data that convinced them to adopt Langley’s value of Smeaton’s coefficient months before they built the tunnels.  Their tunnel did not “correct” any of Lilienthal’s data.

4.    Although the Wrights did develop the most complete technique yet to design efficient propellers, their “understanding of the true aerodynamic function of a propeller” was preceded by others.  As previously discussed, the others include Hollands, Lanchester, Drzweicki, and Prandtl.  And technically, since they believed that cambered wings produced lift by pressure on their bottom surfaces, they also did not really understand how propellers produced thrust.

5.          The Wrights’ creation of a functioning engine, along with the help of Charlie Taylor, was indeed an impressive accomplishment. 

Charlie Taylor, the mechanic who built the Wrights' early engines.

     However, with no fuel, oil, or water pumps, and no carburetor, their engine was definitely not “beyond the state-of-the-art” as claimed here.  It was also behind the state-of-the-art in smoothness, reliability, and in weight per horsepower.

6.     The final reason given is that "the Wrights were the first to treat a flying machine as an integrated system involving aerodynamics, propulsion, structures, and flight dynamics." Although there were machines before December 17th, 1903, that had structure, engines, and aerodynamic features, it is arguable how integrated these features may have been. But the author mentions flight dynamics, which is the study of how a vehicle moves through the air, both linearly and angularly, with or without flight control inputs. In this regard, it appears that by October of 1905, the Wrights were well ahead of any of their predecessors or contemporaries. *

     The next article in this series will discuss the second paper in the Perspective compilation titled Aerodynamics, Stability, and Control of the 1903 Wright Flyer.

* Editor's note: We  respect Joe Bullmer's conclusion in number 6 and can see the validity of his reasoning. However, we are not yet certain that the jury is fully out, as new discoveries are being made in the research of some of the Wrights' contemporaries and predecessors. The standing of the Wrights in 1905 could possibly change in comparison.

 All of the pictures and most of the links in this essay were selected and added by the founding editor of "Truth in Aviation History."

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Joe Bullmer, above, has a Master's degree plus advanced studies in Aeronautical Engineering. His first contribution to the"Truth in Aviation History"series of articles is "Joe Bullmer Rebuttal to Tom Crouch in the"Huffington Post."