Tuesday, October 6, 2020

The Wright Propeller: Reply by Author-Historian, Paul Jackson, to Comment on "Propelled to Absurd Heights"


. Barnstorming aviatrice Katherine Stinson was the fourth woman in the U.S. to earn a pilot's license, on July 24, 1912, in a Wright Model B. The massive propeller tips are obvious

Comment

August 11, 2020 at 3:08 PM

by Anonymous Reader of blog post titled Propelled to Absurd Heights --Paul Jackson, Author 


"Arm chair quarterbacking, as usual...

The Wrights had decided that they would only use information that they have verified themselves, so crap in a book that they may not have fully read or understood, and in which they don't didn't have the hindsight of knowing to be correct is unfair. Further, you slander them for the crime of successfully building and piloting and airplane while heaping praise on a fellow who only made a prop. What a load of crap.

Signed, Anonymous"

 

 Reply to Anonymous

 Dear Anonymous:


You censure me for being what is termed wise after the event. This I refute, having merely drawn attention to the fact that the Wrights were “unwise after the event” — the event in question being  Hollands’ design and public announcement of an efficient propeller nearly two decades before the Wright Flyer.

I must assume that the opprobrium directed towards me is because I recognized, and drew attention to the importance of Holland’s previous invention of the modern propeller, whereas the Wrights didn’t. That’s not arm chair quarterbacking; I prefer to call it painstaking research.

The statement that “they would only use information that they [had] verified themselves” reinforces a view of the Wrights as arrogant and negligent. I am not sure you wanted to say that. Good inventors survey their whole field, evaluating all that others have previously done, and putting the best of everything into their new invention. But, like others, the Wrights had a blind spot for Hollands’ work. The point I make is that if Wilbur and Orville were half as smart as they are made out to be, they would have (a) diligently read-up on, and tested Hollands’ previously published ideas and (b) realized that he had an excellent design. They failed to do so, even after Chanute gave them Hollands’ findings in great detail.

In actuality – as other entries in this blog make clear – the Wright patent filed in 1903 contains the most gargantuan error it is possible to make on the fundamental subject of how a wing creates lift. They could not conceivably have “verified themselves” that 100 percent of wing lift comes from the underside (and not 67% from above), or proved by experiment that the cambered leading edge is only there to stop it flipping over backwards. This is aerodynamic illiteracy—as demonstrated by Giovanni Battista Venturi  in 1797. Clearly, the Wrights aped others while not understanding the elementary science of what they were copying.

“In a book that they may not have fully read or understood.” Is it being suggested, here, that some Englishman, two decades previously, could write an aeronautical treatise on the superiority of pointed-tip propellers which the Wrights (a) could not be bothered to read or (b) did not have the intelligence to understand, even if they had read it? Remember: these were the “geniuses” who “invented the airplane.”

“You slander them for the crime of successfully building and piloting and airplane,” I am told. Firstly, the written word is not slander, it is libel. Secondly, building an airplane is not a crime. Thirdly, stating that someone has performed an entirely legal and morally upright act cannot be libelous. Although somewhat baffled by the accusations, I plead not guilty.

The bottom line is that, even today, most medium/small airplanes employ a propeller invented in London in 1885 and not a propeller invented in Dayton in 1902. It looks like by pointing that out, I have caused (what you refer to as) the “cr*p” to hit the (Hollands’) fan

Sincerely,

Paul Jackson 

Retired Senior Editor of Jane's All the World's Aircraft

-

 



Sunday, January 26, 2020

Propelled to Absurd Heights

A down-to-earth assessment of the Wright Brothers' competence in air-screw design

by Paul Jackson

Editor-in-Chief, Ret, Jane’s All the World’s Aircraft


Fig 1. William Shakespeare was “a man more sinned against than sinning” (King Lear Act 3, Scene 2). Over-hyped by fawning supporters he, sadly, has to be taken down a peg in the cold light of digitalized history

Wherever their skills permit it, traditional aviation historians employ Shakespeare-like prose to describe, with all the eloquence at their disposal, the inventions and achievements of the Wright Brothers. That is most apt, for the Bard of Avon was as fecund in the realm of the written word as were Orville and Wilbur in developing all aspects of the airplane.

Shakespeare has been credited with coining 3,200 words in the English tongue, plus at least 150 more expressions in daily use. Truly, he was a prolific and popular playwright.

Prolific and popular. Perhaps the shortest English sentence to be an enigmatic oxymoron. Why? Consider baffled Elizabethan audiences leaving The Globe theatre, grumbling that idiot Shakespeare had made it impossible for them to follow the plot because of all the invented words and phrases of obscure meaning littering the script. Why didn’t the fool write in English?

Of course, he did. What has happened is that modern researchers tasked with discovering the origin of any English word have traced it back through literature until they found it in Shakespeare — whereupon they declared that, because the man was genius, he must have invented it. Therefore, there is no need to look any further back.

The Internet has much to answer for in its debasement of scholarship, but it is highly efficient in exposing lazy scholars. The gradual digitalization of pre-Shakespeare literature in recent years has made it possible — in a search taking a few thousandths of a second — to pinpoint a given word in writings from before the Bard’s birth.

Thus, those 3,200 words credited to Shakespeare have shrunk, within the past few years, to 1,700, and the tally is diminishing with every passing month.

Similar exaggerations of the Wright Brothers’ prowess are also being exposed by freshly digitalized documents, but the process is being fiercely resisted by aviation historians who hope to emulate another significant figure in English history: King Canute, resister of the incoming tide.

Whereas it is not an offense to rob Shakespeare of the credit for a word it is now known he borrowed, the home of what purports to be the original Wright Flyer, the Smithsonian Institution in Washington, DC, has a serious legal problem with documents which prove the wrights did not do, or invent, something they claimed they did.

The covenant of November 1948 with the Wright family forbids the Smithsonian from publishing anything which disproves the Wright 1903 Flyer was, “The World's First Power-Driven Heavier-than-Air Machine in Which Man Made Free, Controlled, and Sustained Flight” and that, “By Original Scientific Research the Wright Brothers Discovered the Principles of Human Flight” and “Taught Man to Fly”.

Refusal to acknowledge the relevant pre-Wright documents was not the result of laziness, as was the case with Shakespeare’s writings, but of a legal imperative: Contradict any of these assertions and the Flyer gets removed from the building.

The Old Guard’s problem is that now, any literate child, working at a computer in their bedroom, can download, from the Internet, date-marked documents published by learned bodies which shatter claims of Wright primacy in more than one field.

A prop for the Wright legend of brilliance

The Hartzell company is based in the Wrights’ home state of Ohio and is one of the world’s leading manufacturers of propellers. Surely, it — of all authorities — can be relied upon to present an accurate, unbiased assessment of the chronology of airplane propeller development. Let’s see what its website (http://hartzellprop.com/wright-brothers-propellers) has to say on the matter:

“In the late 1800s, several flying machines emerged from early pioneers who based their propellers on screw-shaped design. But it was the Wright brothers who were the first to acknowledge that an aircraft propeller should be shaped more like a wing than a screw.

“The two brothers reasoned that propellers could act like rotating wings spinning through the air. The idea was that the rotating propeller blades would act as “airfoils” (wing shapes) that produce a pressure differential, displacing air backward to produce forward thrust.

“Using data from their wind tunnel experiments, the Wrights created an efficient propeller design modeled after one of their wing shapes. They then set out to invent a propulsion system that utilized a small engine and two large, slow-turning propellers.”

There; as plain as day: The Wright Brothers designed the world’s first efficient aerial propeller. They did so in their wind tunnel, which was put into service (according to the Smithsonian) in October 1901. The modern propeller was invented in Dayton, Ohio, in 1902 or 1903. The first such propeller was tested, at sub-scale, on a motorised rig at Dayton on December 15, 1902.

Don’t bother with Wikipedia’s history of the propeller; it is exactly the same: “...the Wright Brothers realized that a propeller is essentially the same as a wing, and were able to use data from their earlier wind tunnel experiments on wings, introducing a twist along the length of the blades.”

Surely, an impossible fact to miss

 

Fig 2. Sidney Hollands described the attributes of an efficient, modern propeller two decades before the Wrights’ failure to build such a device (via Royal Aeronautical Society)

But let’s use the wonders of modern digitalization of historic records to go back in time two decades before “the Wrights invented the propeller” in the wind tunnel at the rear of their cycle shop. Back to London, England, in June 1885, where the Aeronautical Society of Great Britain is holding an exhibition of the latest in aviation science in the Crystal Palace (which was originally built to house the 1851 Great Exhibition).

We know that a certain Englishman, Sidney Herbert Hollands, exhibited an airplane propeller of revolutionary design at that event. This was recorded in the Society’s archives by Baden Baden-Powell (sic), editor of the house magazine, Aeronautical Journal (and brother of Robert, later founder of the Boy Scouts) but, by an oversight, full details were not bound into the Society’s journal of proceedings.

But all is not lost, for a copy of the report crossed the Atlantic and landed on the desk of the doyen of US aviation pioneers, Octave Chanute. In February 1893, Part IX of Chanute’s book Progress in Flying Machines (downloadable at http://invention.psychology.msstate.edu/i/Chanute/library/Prog_Aero_Feb1893.html) had this to say:

Hollands however, made some experiments on the best form of lifting screw-blades, and 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° with the plane of motion at the tip and 30° at the root.

The form which he found most efficient was two-bladed; with the blades narrowest at the tips, slightly concave on the lifting side, the tip slightly drooping, each blade being approximately the shape of an elongated shallow spoon or scoop, and with a pitch equal to about two-thirds of the fan's diameter, giving a mean angle of blade of 22° 30' with the plane of motion.

These blades were of thin sheet steel, and their forms will be noted as confirming what has already been stated as to the advantages of the bird-like form of wing. M. Hollands said further:

I find another advantage accrues also from the use of these very thin, sharp edged hollow blades — viz, that there is no appreciable resistance to rotation that does not contribute to lifting effect.

Fig 3. A selection of typical, modern propellers, built for light aircraft by the Hercules company in the UK, home of its designer, Hollands

Let’s just recap. A cambered blade; wide at the hub and narrowing towards the tip; the angle of leading-edge incidence progressively reducing towards the tip. Doesn’t that describe a modern, efficient propeller? Chanute was a mentor to the Wrights and they were actively seeking out literature to assist their quest for flight. Does anyone, seriously, suggest that Hollands’ researches did not come to their attention, by active or passive means?

And Hollands’ ideas yet again crossed the Atlantic, but in first-hand form, when the Scientific American published his article, ‘Wind Motors, Ancient and Modern’ in its Supplement of September 1, 1894.

Wright Brothers: innocent bystanders

At this point, regular readers of this blog will be expecting so see a scathing denouncement of the Wrights for stealing Hollands’ ideas — in the manner they appropriated many others. Nothing could be farther from the writer’s mind. Together with the rest of the aeronautical experimenters, the Wrights foolishly ignored Hollands’ careful researches and pressed on with their own, inefficient designs.

No particular criticism can be made of the Wrights for not realising the significance of Hollands’ writings, because all the others failed to take them up, as well. But the Wrights have been elevated by their own boastfulness and the sycophancy of others into a category head and shoulders above “all the others.” Now it appears they were not as smart as they, or their biographers, made out.

To give him his due, Hollands kept trying. In another magazine, he co-authored with G Lacey Hillier a series of aviation articles, saying in Part III

“With further reference to aerial propellers, one of the present writers has found by comparative experiment that a very advantageous feature of design is to make the blades concave on the driving side (and, therefore, convex on the other side), which form really amounts to extending the lifting form of the aerocurve to propeller blades, which latter have been hitherto made flat.” [an ‘aerocurve’ being a lifting surface incorporating camber]

And then, in Part IV, referring to a series of comparative experiments with different propeller designs and numbers of blades:

“4. That it is very advantageous to make the blades with a certain degree of concavity on the driving side* (or ‘conchoidal’), and therefore convex on the other or advancing side.

5. That there is a distinct advantage in making the blades narrow at the tip, and broadest near the root, which form is quite contrary to previous aerial practice in aerial fans.”


[*The term “driving side” might be a little confusing to some. The reason Hollands and almost all others of his time refer to the concave back of the blades thus, is that they thought a cambered surface created lift (or thrust) by building up a pressure on the bottom, or concaved side. They were largely unaware of the dominance of a lower pressure on the convex side, sucking the aircraft forward. In spite of Phillips and Lilienthal publishing fairly correct explanations, the Wrights maintained their mistaken belief until well after they developed their airplanes.]

Part IV includes comparative diagrams of the Hollands pointed-tip propeller and the alternative design with its narrow root and wide tip. For two propellers, each of 10 feet in diameter, the Hollands has its centre of mass at 4 ft 2½ in diameter and centre of pressure at 4 ft 7½ in; for the wide-tipped propeller, the numbers are 6 ft 6½ in and 6 ft 4 in, respectively.

Comments Hollands:
“This reduction of the radius of the centre of mass not only reduces the centrifugal pull of the blades, but the centre of pressure being correspondingly reduced, the bending moment of the arms, and consequently the pull on the back stays becomes much less. Both these conditions conduce to lightness of construction.

“Because of the structural advantages, the reduction of radii of the two centres reduces the necessary torque, or turning effort. After all, it is only logical to make the blades narrow towards the region of the highest velocity, i.e., at the periphery, and, of course, a regularly increasing area towards the root where the velocity of rotation is least."


Fig 4. Hollands’ 1901 comparison (simplified and further annotated) of two blade shapes for a 10-foot propeller: his own (left) and the broad-tip variety employed (although in what was then the future) by the Wrights. On the left, the bending arm of the center of pressure (P) — which is trying to snap off the blade — is near to the prop’s axis. On the right, the leverage of P is enhanced and the blade is more highly stressed. And this was before the Wrights added even more mass to the tips of their later props, worsening the situation. Adjacent to P is M, the center of mass; the greater the distance of M from the rotational axis, the more horsepower is absorbed just in turning the weight of the prop. So, the narrow-tip prop scores on both counts
Apologies, good reader; you have not been provided with references for these two articles. They appeared in January and April 1903 in the UK quarterly magazine, Flying. The Wrights probably saw at least the January 1903 edition, as it also contained a four-page, second-part report of Wilbur’s talk to the Western Society of Engineers.

The articles were published as the Wrights were putting the finishing touches to their patent application (submitted March 23, 1903) and starting manufacture of the Flyer. So, as a further recap: cambered blades with narrowing at the tips and progressively reduced twist, outboard. Do the opposite, and more horsepower is needed to turn the prop; and the blades themselves are subjected to a greater force trying to snap them off backwards.

And, in the light of these vital and timely revelations, what did the wizard Wrights do? This:


Fig 5. The Flyer’s propellers at Kitty Hawk in December 1903. Twist, yes; camber, a little; narrowed tips, no way. An improvement on some others’ designs, granted; but a pitiful effort compared with what “aeronautical geniuses” should have been achieving at that time

America is not entirely without honors in the matter, though, for on February 10, 1901, Augustus Herring had written to Chanute reporting encouraging results of “experiments with curved surfaces and screw propellers with straight & with curved blades.” The following year, Chanute brought Herring to the Wrights’ gliding camp at Kitty Hawk, but it is unclear whether the latter had any influence on the Flyer’s prop.

Historians dazzled by the Wrights’ self-publicity feel obliged to give Herring a poor write-up and stress the later animosity between the two. But as Herring’s letter shows, he was closer to the optimum propeller formula in 1901 than were the Wrights at the time.

Fig 6. Herring tells Chanute he has been experimenting with both cambered and what, today, would be called ‘scimitar’ blades. The date was February 1901 — nine months before the Wrights even began experiments in their wind tunnel

And also was Hollands closer to the optimum propeller formula than he (or any others) realized. Nobody seemed to be taking into account another spin-off resulting from the propeller-is-a-wing-on-its-side concept. The ideal lift distribution across a wing from an induced drag standpoint is for lift to taper off near the tips — a concept which the Spitfire employs par excellence. This reduces the amount of swirling flow from the bottom of a wing around to the top, which destroys most of the lift at the tips; thus the proliferation of “winglets” on modern airliners.

The aerodynamic advantage of tapered tips is every bit as important as the mechanical bending moment advantage that Hollands did describe for that shape.

Cranks

Two basic shapes of Wright blade are discernible in the years after 1903. First came the rounded tip; then, from 1908 onward, the ‘cranked’, or bent tip. The waters are muddied slightly because the first disclosure of the Flyer, in France during August 1908, was with 1903-style propellers as a consequence of the others being damaged in transit. Further confusion arises from the fact that the props look bent only from certain angles. Whatever; there is an obvious kink in their trailing edges and they are appreciably wider at the tips.

The reader should also note that the later Wright propeller design was less close to Hollands’ ideal shape than its predecessor. It had even greater mass (and area), even farther from the hub, meaning it soaked-up even more horsepower for no good reason, and tried even harder to snap off its blades through increased backwards forces at the tip. Furthermore, the aerodynamic tip losses previously described — but not then understood, or taken into account — will have been multiplied (the wider the tip, the greater the loss.)

Yes, folks; the more the Wrights refined the design of their propeller, the more inefficient and dangerous it became.

Fig 7. The 1905 Flyer modified with two seats and ‘cranked’ blades during trials at Kitty Hawk in May 1908. Note that the aircraft still needs a downhill run to take off
Fig 8. Propellers of the Flyer which killed Lt Selfridge on September 17, 1908, when (according to the Wrights) one blade disintegrated in flight. Blade incidence to the direction of travel almost varies from 0° to 90°, and strain on the hub must have been immense
Fig 9. Wilbur flies sister, Katharine on February 15, 1909. The propeller tips seem to be of a compromise design

If it’s any good: steal it


Propellers are all about converting engine horsepower into forward thrust. Hartzell says the Wrights obtained over 66% efficiency (taking Orville’s written assertion as being true); some aviation historians report that this was later improved (with the cranked design of 1908) to 81½%. That may be compared with the near-ideal 90% of modern shapes.

How overloading the tip area and, consequently, increasing aerodynamic losses can make a propeller more efficient is a mystery which Wright-worshipers prefer not to explain. One conjectural explanation might be that the Brothers became vaguely aware of tip losses and thought the answer was to build a wider barrier to airflow overspill in that location. We now know the opposite to be the true state of affairs. In an analogy: faced with getting a Jeep across quicksand, the Wrights were loading it with concrete blocks to give the tires better grip.

And as Joe Bullmer highlights in The WRight Story, the Brothers’ airplane patent contains irrefutable, written evidence of a fundamental misconception in aerodynamics: their belief that 100% of lift (and of propeller thrust) generated by a cambered airfoil comes from the lower (propeller’s back) surface. In the real world, some 67% of lift (thrust) derives from suction on the top (prop’s front) surface — hence the tip losses because the top surface is trying to “steal” air from the underside.

In proceedings of the (UK) Society of Engineers in 1908, it was claimed that Hollands’ propeller achieved 26 lb of thrust per horsepower inputted, whereas the Wrights’ best figure was a mere 16 lb. The arguments can go back and forth ad infinitum, involving complex formulae and even more esoteric methods and calculation and comparison. (It helps greatly to be in ignorance of tip loss.) Let us, therefore, base our analysis on a simple human trait which infallibly gives a correct answer in such matters: pure greed.

If the Wright propeller had been the best available, it would have been widely copied. Had it been patented (and, interestingly, it was one of the few aeronautical things the Wrights didn’t attempt to protect), it would have been either built under license or, just pirated. Imitation is the sincerest form of flattery, yet nobody flattered the Wright propeller. This might have been because the rest of the world’s aspiring aviators were so staggered by the Brothers’ brilliance in propeller design that they felt unworthy of copying it; or because they investigated it and found it inadequate. Human nature suggests the latter is the right answer.

[*Let it be explained, here, that some propellers break Hollands’ rules by having constant-chord blades with square(ish) tips. Reasons for this did not concern the early aviators. It will be noted that such props are attached to high-power, or high-revving [eg, microlight] engines. Moreover, they are usually metal or composites in structure. Typical of the square-tipped type are those fitted to early versions of Lockheed Hercules — but each engine is rated at 4,200 hp, compared with the Flyer’s 12 hp. Current Hercules versions have abandoned the square tips for a more tapered design.]


In regular letters to the editor of Flight for most of 1909, Hollands was still stressing the superiority of his design and challenging Frederick Handley Page, and others, to better it. Had he but known, he was pushing at a door that was beginning to open — except in the US, where the Wright Flying School continued to employ the cranked-tipped monstrosity of a propeller that had (according to Orville*) shattered and killed Lt Selfridge, US Army, during the 1908 military trials. The Model B was no different, and even a decade after Kitty Hawk, Wright airplanes were still flying with broad, cranked-tip propellers.

[*The Wrights were their own air accident investigators for this crash and, if they are right, the unnecessarily large strain imposed on the prop, as predicted by Hollands, would be an obvious suspect for the cause of the disintegration. However — as it is planned to discuss in a future blog — later, less partisan analysis also points fingers at engine malfunction; overloading of the airplane; pilot’s unfamiliarity with the new propeller design; and structural failure, allowing the propeller to come into contact with a rigging wire.]

Around the same time, 1908, Hollands was working on a metal propeller, for which 85% efficiency was claimed. If confirmed in practice, this patented design scores only a few percent short of the figure for a typical propeller 100 years later. In fact, Hollands held several patents, including one for a reversible propeller with hydraulic actuation. This was applied for in 1898, some considerable time before Hamilton Standard of the US won the 1933 Collier Trophy for the world’s “first” hydraulic propeller.

Fig 10. Barnstorming aviatrice Katherine Stinson was the fourth woman in the U.S. to earn a pilot's license, on July 24, 1912, in a Wright Model B. The massive propeller tips are obvious
Fig 11. By 1917, Katherine had learned the error of her ways and switched to a Curtiss JN4 with a ‘Hollands’ propeller
Fig 12. In 1916, the Wright company, then on its last legs, finally discovered the (W)right stuff and fitted its otherwise unremarkable Type L with a cambered, scimitar-shape propeller, having pointed tips. If Hollands and Herring received letters of grateful thanks from Orville for their far-sighted observations of a decade-and-a-half earlier, they never mentioned them
Fig 13. Sopwith’s Camel — one of the more famous participants in the air battles of the First World War. If a camel is, “a horse designed by a committee,” then a Camel with a Wright propeller would have been, “an Allied fighter designed by the Kaiser,” and the Red Baron would have enjoyed a walkover

Postscript

To obviate any attempt to misinterpret the purpose of the above study, let it be understood that it is not the writer’s purpose to advance any claim that Hollands “invented the propeller.” There were other, relevant contributions from experimenters such as Lanchester, Drzweiki, and Prandtl. Hollands, perhaps, didn’t do it all by himself — but all the essential data are concentrated in his writings and the key fact is that they all pre-date, by a large margin, manufacture by the Wrights of a much inferior product.

Indeed, Orville’s account of propeller development, in How We Invented the Airplane, is bizarre. The Brothers borrowed books on ship propellers from the Dayton Public Library and found the data could not be applied to aerial propulsion — which is fair comment; air is compressible and water is not, thus an entirely different approach is essential. So, as a next step, they “began the study of the screw propeller from an entirely theoretical standpoint.” Entirely omitted is any expression of the faintest curiosity about what other aviation researchers were doing in the line of propulsion.

Yet, we know for certain the Wrights were cognizant of Hollands’ work because their authorized biographer, Fred C Kelly says, “they did not begin serious reading until 1899. Among the books they read was Octave Chanute’s Progress in Flying Machines...” which, of course, contained Hollands’ detailed formula for an efficient prop. Orville could have told Kelly that they found the air-propeller literature as unhelpful as that for water. They’d have been wrong, but at least admitted they had pursued a blatantly obvious avenue of research.

That said, the Wrights’ reputation for propeller prowess seems to have been thrust upon them by sycophantic historians, including those at Hartzell and Wikipedia. As far as is known, they (certainly Wilbur) never asserted that they invented the cambered, twisted propeller. True, they said things like, “we discovered” or “we reasoned” without claiming they were the first to do so; that was left to a later generation of unknowledgeable, lazy historians. The same false credit was awarded to them for wing-warping flight control. In truth, they came up with a poor propeller design; then modified it to be worse.

Those whose view of the Wrights’ aeronautical brilliance remain stubbornly undimmed, in spite of all the above, might wish to indulge themselves in the ultimate Wright experience. At Dayton-Wright Brothers Airport, Wright "B" Flyer Inc (www.wright-b-flyer.org) offers pleasure flights in a replica Model B, tail number N3786B. Nobody having persuaded any of the innumerable 1903 Flyer replicas to fly in anything remotely resembling a safe fashion, this is the nearest anyone will come to the original Wright stuff. Be assured, it’s perfectly safe; this one has narrow-tip Hollands propellers, built by Sensenich, instead of the over-stressed, super-wide originals. (Something approaching the latter can be seen on an accompanying Model B replica, N2283D, that managed 2½ hours of flight for a film before suffering an accident and permanent grounding. A third, new Model B, due to fly in 2020, appears to have pointed-tip, carbon fiber props. So: flyable Wright replicas without replica Wright propellers; there’s a message in there, somewhere.

Why the Wrights did not check-out Hollands’ more advanced thinking (and he receives several additional mentions in the Chanute volume on account of his parallel work with airplane engines) must remain a matter of conjecture, although one might suspect a certain degree of arrogance or pig-hardheadedness. Two lessons emerge:
  1. For all the remarkable capabilities ascribed to them, the Wrights failed to apply the basic mechanical knowledge demonstrated by Hollands two decades earlier.
  2. Not only did the Wrights not arrive at the same conclusion as Hollands, they did not have the wit to copy a good propeller design when it was handed to them on a plate.
And, in view of the earlier revelations of this blog, one question cries out for an answer: How might the Flyer have performed at Kitty Hawk in 1903 with a pair of decent, Hollands propellers?


---by Paul Jackson FRAeS, former Editor-in-Chief, Jane’s All the World’s Aircraft (1995-2019)






















Saturday, January 18, 2020

A Follow-On to Readers' Comments on Mensuration of the Fourth Flight by Paul Jackson

       PREAMBLE: Two readers (Anonymous' and "Unknown") kindly took the trouble to respond to the previous blog post,* authored by Joe Bullmer, in which the Wright Brothers' own photograph of the "852-foot, 59 second" fourth flight of December 17, 1903, is examined in detail and found to contain serious anomalies. The picture shows the launch rail and the airplane on the ground, the two separated by only some 277 feet  (as computed by trigonometry). The propellers have stopped, but  "Unknown" suggests this could be a photographic illusion - leaving open the possibility that the flight did, eventually, cover 852 feet.

        Yet, neither correspondent addresses, with anything stronger than a shrug, the fundamental point that this picture might well show, not the Mk I Flyer in  December, 1903, but the modified (two-seat) Mk III Flyer in May, 1908. Nor do they acknowledge contradictory testimony from the Wrights which compounds the uncertainty. Below, therefore, is a broader view of events, and a plea for traditional historians of the Wrights to "grasp the nettle" and declare their own view of what this picture really shows. If you have not already done so, we recommend you read Bullmer's analysis first.*

         COMMENT: Unknown----I offer a different opinion: It does not matter if the propellers are turning, or not. The apparently stopped prop was, merely, one of the factors alerting the observant expert  (Joe Bullmer) to the fact that several things do not seem right about this photo. 

       However, the propellers are a red herring. The airplane is pictured on the ground and going nowhere; it has finished flying (for ever!) and the elevator is broken off by a heavy landing. We have been told that at first-hand by Orville Wright; and seen a close-up picture of the crash site taken by Orville himself. The latter can be viewed on the Smithsonian Institute website at https://airandspace.si.edu/collection-objects/wright-brothers-1903-flyer-damaged-photograph

        In case anyone should think Orville is not to be believed, here is the proposition:

        The intention of the investigation described below is to determine the height of the aircraft above the local surface at the moment when the long-view photograph (analysed by Joe) was taken.

        As explained in a previous blog post, ‘Kitty Hawk – A New Perspective’ a line drawn between the eye (or camera lens) and the horizon bisects all objects it touches at the same height as is the eye/lens, providing the ground is level. (That, it was. Refer, for example, to Orville Wright in How We Invented the Airplane: “These flights started from a point about 100 feet to the west of our camp. The ground was perfectly level for a mile or two in every direction, excepting those towards the big and the smaller Kill Devil Hills.)

       As earlier demonstrated on this blog, the Wright camera tripod was of 4 foot height, and the distance from the camera base to the center of the lens was a further 3 inches or so.

   
Fig 1. Annotated photograph of the Flyer against the horizon  


       In the far distance of the photograph are sand dunes. Were they not to be there, the natural horizon would be slightly above the base of the dune, but below its crest. The natural horizon is marked X-X on the annotated photograph. Line X-X passes through all things 4 ft 3 ins above the surface of level ground, whether they be near or far.

       Turning now to the airplane, the Flyer exhibit in the Smithsonian has a gap between the wings of 6 ft 2 in. From this, it can be deduced that the line X-X passes about 9 inches below the propeller axis. Highly accurate drawings by Herb Kelley, available at https://silodrome.com/1903-wright-flyer-blueprints-free-download/ show that the vertical distance from the propeller axis to the underside of the landing skids is a fraction of an inch over 5 ft.



Fig 2. Part of Herb Kelley’s Flyer three-view drawing. The circled measurement is 5 ft 1/8 in

       As a further check, line X-X passes exactly equally between the two wing trailing edges, measured at the airplane’s centre-section. According to Kelley’s scale drawing, that line is fractionally under 9 inches below the propeller centers.
     Thus, 5 feet minus 9 inches equals 4 feet 3 inches: so the bottom of the Flyer’s skids are 4 feet 3 inches below line X-X and, furthermore, the ground is 4 ft 3 in (camera height) below line X-X as well. The skids are on the ground. The eagle has landed.


     In summary, therefore, the indicators determining that the Flyer is at rest are as follows:

               1.   Orville Wright wrote, by hand, on the back of the ‘fourth flight’ long-view photograph, currently held at Wright State University, that it showed, “the point where it landed in flight of 59 seconds.” He did not take the opportunity to write it was, “the point where it swooped close to the ground, but then recovered and flew for another 570 feet.” See archivist’s notes on attribution of the original picture caption at https://corescholar.libraries.wright.edu/special_ms1_photographs/1268/  

               2.   Perspective analysis, relying on the laws of physics, shows the skids and the ground surface  are in the same location (ie, the airplane is touching the ground).

               3.   If both props are turning, Joe’s analysis does not “fall apart” (as is claimed) at all. Even if both are whizzing round at full speed, the Flyer is stuck on the ground with a broken elevator and can’t take off to extend its flight because of the drag of the skids on the sandy surface; it needs a special launch rail before it can fly any farther. And Orville didn’t claim that the airplane got any farther than where it is shown in the picture; indeed, he took another picture to show why it couldn’t. 
      

          We are being deliberately sidetracked into a side-show debate on whether, or not, some ill-defined, mysterious, trick of the light has confused the camera shutter. What the aviation historians of the world — starting with those in the Smithsonian — need to be resolving right now is what airplane we are looking at, and in which (1903 or 1908) year.

          There is an alternative explanation for the apparent perspective of the airplane vis-à-vis the ground if the Wrights’ description of the event photographed (852 feet on 12-17-1903) is taken as Gospel. It would be most interesting if somebody would like to posit it.

        Paul Jackson FRAeS, former Editor-in-Chief, Jane’s All the World’s Aircraft (1995-2019)

    * The Wrights' Fourth Flight - Mensuration" - Joe Bullmer





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      Monday, November 4, 2019

      The Wrights' "Fourth Flight" - Mensuration



      Mensuration  of  the  “Fourth  Flight”
      by Joe Bullmer 

      ( Figure 1)  Photograph identified by Orville Wright as the end of the fourth flight Dec 17, 1903
      Measurements

                On December 17th, 1903,  the Wright brothers claimed they made four attempts at manned, powered flight near Kitty Hawk, North Carolina. Piloting was alternated between the brothers with Orville making the first attempt. The first three were basically out of control throughout, none exceeding 200 feet in distance. However, the fourth attempt, the second by Wilbur, was claimed to have gone 852 feet with its mid portion under fairly smooth control. 

               A photograph which Orville Wright asserted in writing was taken after the fourth attempt, shows the launch rail and the aircraft off at a distance. (See Figure 1 above.) Some have questioned whether the aircraft actually appears to be 852 feet, a sixth of a mile, beyond the end of the launch rail. Consequently, an analysis of the photo was done using magnification devices and common geometric and trigonometric mensuration techniques on large scale proportionally accurate prints of this and other relevant Wright photographic plates.

               One of the first things evident in this analysis, particularly on blowups of the photo in question, is that the propellers, and thus the engine of the aircraft, are stopped. Apparently this had not been noted prior to this examination. Also, the aircraft is on or very near the ground.  If indeed this is a photo of a flight, it was definitely taken after the end of it. (Figure 2)
            
      (Figure 2) "Fourth Flight" photo blown up, showing one of the stopped propellers highlighted.


           The first step in any mensuration analysis is to identify known dimensions. The launch rail appearing on the right of the photo was known to be 60 feet in length.  The airplane off in the distance had a wing span of 40 feet and four inches with a separation between the biplane wings of 74 inches.  (Due to the small size of the image and its rounded wing tips, for mensuration purposes the wing span used here was 40 feet, an approximation of less than 1%.)  Comparison of the ratios of wing tip separations to span showed the aircraft to be headed within a few degrees of directly away from the camera, its wings essentially crosswise to the camera. (parallel to the optical plane).

               Major unknowns in the subject photo are the focal length of the camera, the distance from the camera to the launch rail, the rail’s angle to the camera, and the size of and distance to the sawhorse appearing in the photo.  Focal length of a camera can often be used to calculate accurate distances to objects of known size. However the bellows type camera used by the Wrights has a variable focal length dependent upon the lens used, so since no record of it was found it was considered unknown for this analysis.  Also, since the camera’s tripod had adjustable legs, it’s height above the ground is not precisely known.

           In mensuration of this type, it is desirable, if possible, to perform independent analyses using horizontal and vertical dimensions for verification or refinement of results.

          Horizontal Mensuration 

               The camera was mounted on a tripod about four feet in height and obviously pointed somewhat downward as evidenced by the optical axis being below the far horizon in the uncropped version of the photograph appearing as Figure 3.

       
      (Figure 3)  Uncropped photograph that Orville Wright identified in writing as the end of the 852 feet fourth flight
         
               Subtended angles of objects in the photo as well as the angles between objects were measured from a reference point at the bottom center of a large proportional blowup of the image.These angles were then graphically referenced back ten feet to an assumed camera position.  The distance from the reference point at the bottom of the photo back to the camera position was estimated considering camera format, pointing angle, and footprint sizes appearing at the bottom of the photo.  It will be shown later that, due largely to compensating factors, the exact distance between the camera and reference point is not critical to calculation of the distance from the end of the launch rail to the aircraft. 
        
               Ignoring less than two degrees of parallax, the triangle described by the 60-foot rail and lines from its ends to the camera resulted very nearly in an isosceles triangle lying on the ground.  Bisecting the 26º vertex of this triangle yielded two right triangles 30 feet on their short sides with angles opposite those sides at the camera of 26º/2 = 13º.  (Figure 4)
      Figure 4

         Then 30/tan13º = 30/.231 = 130 feet for the distance from the camera to the center of the launch rail.  But the concern here was with the distance of the aircraft from the launch end of the rail, so that end was 130/cos13º = 130/.974 = 133 feet from the camera. The bisector of the 26º angle (the center of the rail) was 28º from a line through the optical axis.  
        
             Mensuration was carried out using these values, namely 40 foot wings separated by 74 inches and a 60 foot launch rail canted at 28º from the optical plane, the launch end of which was 133 feet on the ground from the camera.
      .
          In a large print of the fourth attempt photo, the launch rail measured 3.75 inches and the wing span .99.  Two thirds of the 60 foot rail equates to the aircraft’s 40 foot wingspan, so the rail measurement was reduced by two thirds to 2.5 inches to represent the aircraft’s wingspan.This measurement was rotated to be perpendicular to the optical axis of the camera (parallel to the optical plane and the aircraft's wings) by dividing it by the cosine28º which is .883.  Thus forty feet of the rail rotated to perpendicular to the optical axis became 2.5/.883 = 2.83 inches.  (Figure 5)
      Figure 5

           Objects twice as far look half as big, so the ratio of their measurement scales is proportional to their distances from the camera.  On the blowup the aircraft’s 40 foot wings measured .99 inches and 40 feet of the rail rotated crossways to the camera was  found to be 2.83 inches.  Their scale ratio is then 2.83/.99 = 2.86. The aircraft was thus 2.86 times farther from the camera than was the end of the rail, or 2.86x133 = 380 feet from the camera.

           Unfortunately since the rail end and the aircraft are not on a straight line from the camera their distances could not simply be subtracted to arrive at the distance of the aircraft from the rail.  Consequently a double triangulation had to be used. 
           The camera, rail launch end, and aircraft center formed a triangle whose angle at the camera was 32º with the distance from the camera to the rail's launch end having been found to be 133 feet.  (Figure 6)

      Figure 6

           A line was drawn from the rail end perpendicular to the line going from the camera to the aircraft. Thus two right triangles were formed, one with its acute angles at the camera and rail end, and an adjacent one with its acute angles at the rail end and the aircraft.  Both triangles shared the line from the rail end running perpendicular to the camera-to-aircraft line.The length of the shared line was sin32ºx133 = .53x133 = 70.5 feet.



           The length of the line from the camera to the perpendicular line was cos32ºx133 = .848x133 = 113 feet.  Subtracting this from the distance from the camera to the aircraft gave 380 – 113 = 267 feet from the perpendicular line to the aircraft.  Then the angle of the triangle at the aircraft equaled the arctan70.5/267 = 15⅓º.  The hypotenuse of this right triangle was 267/cos15⅓º = 267/.964 = 277 feet which is then the distance of the aircraft from the launch end of the rail.

            A possible uncertainty in this analysis was the distance of the point on the ground shown at the bottom center of the photo from the camera, so the entire analysis was repeated with the distance set at zero.  Since there are a number of offsetting factors in the procedure (primarily angles offsetting distances) the result for distance of the aircraft from the launch end of the rail in this case was 275 feet, a change of less than 1%.  Thus the calculated distance of the aircraft from the rail is essentially independent of the distance assumed from the camera to the reference point at the bottom center of the photo.   
          
      Vertical Mensuration

           There are two objects in the fourth flight photograph other than the airplane that show vertical dimensions, the launch rail and a sawhorse.  Unfortunately, the rail height is two orders of magnitude smaller than its length used in the horizontal analysis.  Analyses similar to the horizontal analysis just described but comparing rail heights to aircraft wing vertical separation revealed that an error of one one-hundredth of an inch in measuring the rail height on the blowup of the fourth attempt resulted in an error in calculating the distance from the rail to the aircraft of over 80 feet or about 30%.  The height of the rail near the launch end in the blowup varies from .04 to .06 inches depending upon exactly where it is measured.  Thus it was evident that rail height could not yield a solution comparable in accuracy to that obtained in the horizontal analysis.

         The other vertical dimension that might be compared to the aircraft’s wing separation is the height of the sawhorse.  But there are a number of problems associated with using the sawhorse.  First off, there were at least two sawhorses used by the Wrights at Kitty Hawk.  One appears in a photo from December 14th of 1903 and another in a photo from May 11th, 1908.  In both photos sawhorse heights could be scaled from the separation of adjacent aircraft wing tips.  The one from the 1903 photo measured about 21 inches high and the other 28 inches high.

            To calculate the distance from the camera to the sawhorse in the fourth attempt blowup the sawhorse width must be determined.  In both photos mentioned in the previous paragraph the sawhorses were at oblique angles to the optical axis of the photos, and the obliquity angles could not be determined with any accuracy.  Thus although their heights could be measured, the spread of the sawhorse legs could not accurately be determined from these photos.

           In the fourth attempt photo the sawhorse was almost in line with the optical axis and its leg spread is 0.825 of its height.  This ratio could be applied to the known heights of the sawhorses in the other photos to determine their widths, but this left another uncertainty, namely which sawhorse to use.

           A much greater uncertainty arose from the measurement of the subtended angle of the sawhorse legs from the camera in the fourth flight blowup.  Not only was the horizontal subtended angle small (from two to three degrees) but optical parallax becomes a factor.  The vertical parallax angle to the sawhorse would be nearly six degrees, a non-negligible amount.

           (The importance of parallax can be easily seen by looking down one of the acute angles of a 45º or 30º-60º triangle.  Looking straight down on the triangle the true angles are obvious.  But looking at an acute corner with the triangle nearly edge on to the line of sight it becomes evident that even small changes in viewing angles result in big changes in apparent angles of the corner.  In fact, at only small sight angles to the plane of the triangle its acute corners appear as obtuse angles.)

           Determination of the distance from the camera to the sawhorse was crucial in determining its scale factor relative to the scale factor of the aircraft, and thus the distance to the aircraft.  Multiple analyses revealed that an error in the subtended angle of the legs of the sawhorse of ½ degree resulted in an error in calculation of the aircraft distance from the end of the launch rail of over 70 feet.  Considering possible errors introduced from assuming:

            a.  that both sawhorse proportions are the same,
            b. that the subtended angle of the sawhorse legs from the reference point in the blowup can be determined much more accurately than ½ degree, and
            c.  that six degrees of parallax can be neglected,
      it was concluded that any aircraft distance derived from the sawhorse could not lend more accuracy to the result obtained from the horizontal analysis that used the launch rail length.

      Result
          
           To explore any possible source of significant error, the horizontal analysis was repeated assuming that the camera was positioned 60 feet farther back relative to the launch rail, i.e., 30 feet behind a line on the ground perpendicular to the rail at its starting end. In this case the distance of of the aircraft from the rail's launching end came out to be 298 feet, an increase of 7 1/2 percent.  Consequently, the horizontal analysis is considered accurate to within about 7%.  Both vertical analyses, although encompassing the horizontal result, showed uncertainties of nearly 30%.  So it was evident that vertical analyses could not improve confidence in the result.  Thus the most confident result of the mensuration was obtained from the horizontal mensuration alone.  Therefore the conclusion of this analysis is that

      The distance from the launch end of the rail to the aircraft was found to be 277 feet with a confidence of plus or minus 19 feet.

      This is less than one third of the 852 foot distance claimed for the fourth attempt at Kitty Hawk on December 17th, 1903.  Even the most distant results from the low confidence vertical analyses were well under half of the claimed distance.  In order for this analysis to yield the distance claimed, the rail would have to have been 200 feet long and 450 feet from the camera and this analysis would have to be in error by 210%.  Conversely, if it was 852 feet away from the end of the 60-foot rail, the aircraft's image would have to appear one-third of its present size.

      Implications

           The photo claimed to be of the fourth attempt on December 17th, 1903, at Kitty Hawk and examined here clearly shows that the propellers were stopped and the aircraft was on, or very near, the ground.  So, based on this analysis, either the aircraft did not go anywhere near 852 feet, or if it did, this is not a picture of it.

           In a November 2nd, 1906, letter* to Octave Chanute, Wilbur Wright stated their opinion that any flight of less than 100 meters, 328 feet, would just be a "jump" and would prove, using his word, “nothing.” Here he was discussing distances over the ground and considering the requirement to achieve sufficiently stable control to demonstrate the thrust necessary to maintain flying speed and generation of enough lift to sustain the vehicle in the air as opposed to merely making a semi-ballistic hop using the kinetic energy obtained from a ground run.  None of the other attempts earlier that day exceeded 200 feet.  Consequently, this analysis indicates that, if held to their own criterion for success, the Wrights' photography provides no evidence of a successful powered flight in 1903.

      Addendum

            To justify his first attempt on December 17th as being a success, Orville claimed that without the strong headwind he would have flown over 500 feet.  Some might find it tempting to use this rationale to legitimize their claim for distance on the fourth attempt.  However, to Orville an even more important and often repeated claim was that their aircraft took off using “its own power alone with no assistance from gravity or any other motive source whatever.”
      . 
           In fact the strong headwinds on the 17th supplied 80% of the lift required for his and their subsequent takeoffs.  Without those strong headwinds there would have been no flying at all by the Wrights in 1903.  Their aircraft was almost flying sitting still.  So either it flew a great deal farther through the air but could come nowhere near lifting off of the ground on its own, or the plane left the ground on its own but did not demonstrate sustained flight.  It can’t be claimed that the wind had nothing to do with its ability to achieve flight but everything to do with it demonstrating successful flight distances.  Historians can’t have it both ways, and neither could Orville Wright.

           The result of this analysis also calls into question the claimed 59 second duration of the fourth attempt.  Dividing 59 seconds into 277 feet yields an average ground speed of only 4.7 feet per second, or about three miles per hour.  The official government records of the sustained wind speeds at Kitty Hawk on December 17th as recounted by Orville Wright were 24 miles per hour at the time of their fourth trial and 27 miles per hour during the first attempt.  So the average airspeed for a 59-second, 277-foot fourth attempt would have been 27 miles per hour, the same as the minimum wind speed at the time of their first trial.  In other words, if on that day the wind was so strong that they needed 59 seconds on the fourth attempt to cover 277 feet, then with the stronger wind on their first attempt giving the same airspeed, their vehicle would have taken off on its first trial with no ground run at all and would have made no forward progress whatsoever. Obviously, a 59 second flight time is not compatible with the flight distance calculated herein.

           Assuming an average airspeed for their vehicle of 35 miles per hour on their fourth attempt, and a corresponding ground speed of 11 miles per hour (16 feet per second), it would have taken about 17 seconds to cover 277 feet. If the airspeed was 30 miles per hour, the flight time would have been 31.5 seconds. Headwind gusts would have increased these flight times slightly.


      (Figure 7)  Photograph clearly showing three objects on lower wing. Again, this is the photo claimed by Orville Wright and historians to document the fourth flight, December 17, 1903. (blown up and cropped) **

           This analysis can offer no further insight into the significant discrepancies between the times and distances claimed for the fourth flight attempt at Kitty Hawk on December 17th, 1903 and those calculated herein from the photograph claimed to show the end of the fourth attempt.  It also does not address the three dark objects on the lower wing of the aircraft. (Figure 7 above.)

       *  This article is a companion piece to the previous study in this blog by Joe Bullmer titled: Kitty Hawk - 1903 - What Happened?  
      Enjoy!

      Copyright 2019 - Joe Bullmer
       

      Aeronautical engineer, historian, and author, Joe Bullmer
      "The WRight Story" available at Amazon.com.

      **Note: Photos and their captions provided for the most part by the editor of "Truth in Aviation History."