The Birth of the Seaplane!

The possibility of combining the ability to fly and the capacity of a marine vessel had been around even before the Wright Brothers flew their Flyer aircraft at Kitty Hawk, N.C. Serious experimentation on this concept began around 1897, but it was not until 1898 that the first attempt to fly a boat was made. Wilhelm Kress, an Austrian, began construction in 1898 on what would eventually be considered to be the first flying boat craft. It was a simple design. A tandem tri-plane frame fitted with two massive floats. Its power plant was a single Daimler 30hp engine, driving two broad propellers. The craft was first tested in October 1901 on a reservoir near Tullnerbach, Austria; it did not make it to the air. Problems with the floats and the aerodynamics of the fuselage doomed the aircraft. Undaunted, Kress pressed on with his ideas, and in 1903, was ready to make another attempt, but by this time the lack of interest on the project and his financial situation forced him to abandon the idea.

Experimentation with flying boats gained a renew interest with the news of the first ever powered controlled flight by the Wright Brothers in Kitty Hawk, NC. On the other side of the Atlantic, the Vosin Brothers, Charles and Gabriel; after receiving the news; promptly commenced work on their own flying boat design. Their hard work finally payoff when on June 6, 1905; Gabriel became the first man to take-off and land a plane on a body of water. Although the aircraft was used as a glider, which required an external power source to propel it into the air, the craft did prove the feasibility of the concept. The next aircraft design by the Vosin Brothers was destined to be a groundbreaker. Named the Bleriot III after the individual who requested the craft’s design and production; this new concept was made out of two wing structures in an ellipse form placed on tandems. The complete airframe floated on water by function of skids surrounded by sealed tubes. On a clear morning in May 1906, the Bleriot III was ready for the first of a series of tests intended to prove the aircraft’s airworthiness. In each test, the aircraft performed badly, leading the Brothers to suspend further collaboration with Bleriot on this particular project. Bleriot, unmoved by the Brother’s decision, tried himself to build a workable seaplane. In late 1906 he was ready for another set of trials, and again, the results were less than promising.

Fabre-Voisin Connection (photo, via author)
(photo, via author)

In the other side of the Atlantic, the United States military was quickly to recognize the potential of a sea-based plane. During the month of November 1908, an American aviation pioneer by the name of Glenn H. Curtiss performed an airframe modification to his already successful airplane, the June Bug. He removed the wheel undercarriage and replaced with a tandem of wooden floats covered by canvas. The new plane, named Loon, was first tested in late November 1908. Initial test results were somewhat promising. The Loon was able to lift itself from the water but with a relatively slow speed of 25mph; the Loon was not able to accelerate enough to gain air stability. The hydrodynamic drag caused by the massive floats was too much for the engine to propel the aircraft above that speed. Nevertheless, encourage by the test results on the Loon, Curtiss expanded his research. He followed the Loon with the modification of the Curtiss Model D for water duties. In this configuration, the Model D was fitted with a single canoe decked over with canvas. This configuration presented Curtiss with the same problems as before: hydrodynamic drag. But as with the Loon, the results were promising enough to encourage Curtiss to invest more resources on the project.

What history had in store next for Curtiss was truly groundbreaking. In early 1910, the U.S. Navy, after being refused by the Wright Brothers, asked the newly formed Curtiss Company to build an aircraft capable of taking-off from a platform installed on a warship. On November 14th, 1910, Eugene Ely, a Curtiss Company test pilot; successfully took-off from a provisional platform installed on the USS Birmingham near Hampton Roads, Virginia. A series of take-off flights followed, culminated with a successful landing of a Curtiss built plane on a provisional platform installed on the USS Pennsylvania in January 1911. However impressive these tests had been, the Navy’s top brass was not overly impressed. They focussed their attention on the development of an aircraft that could be launched and recovered by a battleship in times of conflict.

For the next phase of story of the development of the seaplane as a realistic alternative, one needs to look at a young French engineer. Henri Fabre, was born in Marseille in 1882 and since his early teen years he devoted his time in the study of aerodynamic forces. He experimented with kites and aircraft models to look at how aerodynamic characteristics of airframes and wings are affected by wind flow. He also studied the effects of hydrodynamic forces on a structure. Thus giving him an inside look at the forces that affect air travel. His first attempt at building a seaplane was a simple design. A conventional monoplane was modified to carry two floats mounted under the wing structure in a catamaran-type configuration. A small float was added to the tail section of the fuselage. The aircraft was powered by three Anzani engines capable of generating a 12hp each. They drove a single tractor propeller. The first series of test occurred in July 1908 and achieve little, if any, positive results. Reasons for the failure were never properly explained, but most aviation historians place the blame on the weight of the floats.

For his next design, Fabre chose a canard layout. On this configuration, the main wing structure was placed at the rear of the fuselage, with two small canard wings near the front. The idea behind the concept is simple. The canards, Fabre thought, would give the aircraft a long sought longitudinal stability. His first test of this new concept was performed on Christmas eve, 1909. The aircraft, powered by a single Anzani engine, took-off for a brief time, but ultimate fell hard to the water due to its underpowered characteristics. The relative short flight did show that the canard configuration could provide air control to the aircraft once airborne. Realizing that the aerodynamics was sound, Fabre promptly went out to find a more powerful engine to propel his new design. After searching hard for a power plant, a friend recommended to Fabre the Gnome’s Omega 7 cylinder rotary engine. The Omega was capable of generating 50 hp and its weight was a respectable 165 lb. With the engine now in hand, Fabre began the development of a new seaplane. As was in the case before, the new plane was centered on the canard wing configuration. What varied from previous designs was the massive wing area, now composing 258 sq ft. The Omega engine was installed at the end of the aft in the main frame. It was located in this area because Fabre calculated that a pusher-type system would better achieve the necessary lift-power ratio needed to propel the aircraft into a stable and controlled flight.

Testing on this new concept commenced in early March 1910. Immediately, taxing testing showed the aircraft’s sound aerodynamic characteristics. On the morning of March 11th, 1910 the Hydravion, the new name for the aircraft, was ready to take to the air for the first time. It was towed to the middle of the Etang de Berre. With nothing more that calm water surrounding the test site, the Omega engine was brought to life. Immediately, the aircraft responded to the Omega and the Hydravion achieved substantial speed in the water. After more taxi testing, the Hydroavion took to the air on that same day. In series of relative short flights, the Hydroavion once again demonstrated its ability to achieve flight status. Fabre continued his experiments into the spring of 1910. All successful flights, but on May 18th, 1910, with Fabre himself at the controls, the Hydroavion lost control and fell into the water from an altitude of approximately 130 ft. The crash did little to alter the course of the programme, the Hydroavion was recovered and repaired, but it did affect Fabre deeply, it is said that he never flew another aircraft after the incident.

(photo, via author)
(photo, via author)

Back in America, Glenn Curtiss was observing with interest the progress made by Fabre. He even took time to visit Fabre in late 1910. By this time, Curtiss had moved his winter flying operations to North Island in San Diego, CA. There, the weather was more conduits for sea-flight experimentation. After many months of research, Curtiss, now with the assistance of Lieutenant Ellyson, a brilliant U.S. Navy engineer that specialized in physics and mechanics; determined that the main obstacle to achieving flight status on a seaplane was the shape of the floats. They researched many forms of floats, eventually settling on a configuration first suggested by Fabre: the use of a flat bottom with a positive trim angle. On January 26th, 1911, after years of extensive research and development, Curtiss saw his dream come true when his new seaplane design, a bigger canoe configuration airframe fitted with the new floats; took to the air. The test result was more than promising; they inspired Curtiss to redouble his efforts. They did extensive modifications on the canoe frame as well as in the float configuration to make them flight operational.

Curtiss, now embolden by the test results, decided to call his old friend, Captain Charles F. Pond of the USS Pennsylvania. The same ship platform that Curtiss used for his ground breaking experiments; and asked him if he would mind that Curtiss made a ship call on the Pennsylvania, now anchored off San Diego Bay. Pond, who was at the time one of the few true advocates of naval aviation, was ecstatic about the possibility and gave Curtiss the go ahead order. On February 1911, Curtiss took-off from his base at North Island and proceeded to land at the side of the Pennsylvania. After arriving, the ship used its boat crane to lift up the aircraft to the deck, the same concept was used to put the plane back in the water. This amazing exercise performed by Curtiss was the first step in the operational development of the seaplane by the U.S. Navy. After the demonstration, Curtiss went on to develop several series of flying boats in 1912, some of them served in the Great War two years later. In France, Fabre recognized Curtiss’s achievements and promptly proclaimed him as the father of the operational seaplane. Fabre, sensing that there was not much new ground to break at that time, decided to abandon major experimentation with seaplanes. That did not mean that Fabre stopped completely his association with flying boats. He supplied floats pieces to many countries during the years up to the Great War, and during the conflict, he was placed in charge of the vaunted Saint Raphael Naval Aviation Depot.

The colorful story of the birth of the seaplane is actually the story of two dedicated and visionary men, Glenn Curtiss and Henri Fabre. The seaplane was born out of their collective dedication and vision. Their need to prove a new and untested concept improved our understanding of how aerodynamic forces affect a sea-based flying platform. We are indeed grateful for their compliments and contributions to the development of the airplane in an era dominated by skeptics and doubters. They truly gave birth to the seaplane.

– Raul Colon

 

More information:
The Pioneers: Henri Fabre (1882-1984)
Wikipedia: Glenn Curtiss
Glenn Curtiss, Father of Naval Aviation

A Brief Look at the Future Flying Wing Airliner

The Flying Wing aircraft configuration has been around since the early days of aviation. The flying wing is a fixed wing airframe capable of sustaining a controllable flight profile without the need of lifting systems such as canards or tail mechanism. Experimentation with flying wing designs began early in the 1920s. The configuration was championed by those who thought that it was the logical evolution of an airframe. As technology caught up with design, the flying wing concept would become the standard aircraft fuselage design, they thought. Many individuals experimented with flying wing configurations, most notable, the Horten Brothers in Germany and, who was to be called the father of the flying wing in the United States: Jack Northrop. Both the Horten brothers and Jack Northrop eventually managed by build an actual flying wing platform. The Horten’s effort was to be curtail by the cloud of war in Europe. The same cloud that gave birth to the first true expression of the flying wing concept: the YB-49.

Northrop YB-49 (photo, US Air Force)
Northrop YB-49 (photo, US Air Force)
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An aircraft based on a flying wing airframe has always been believed to posses an increase in operational range, better speed to power ration, and more weight-lift capability compare to a conventional airframe design. These advantages were the reason the military was behind every major attempt to field a flying wing aircraft in modern times. There were many attempts to field a serviceable flying wing aircraft, and also many failures. That was until the YB-49 first took to the air. The YB-49 was the first truly serviceable winged aircraft. It posses the entire trait marks that engineers were looking for. Range, speed, power ratio and an enormous payload capacity. But what the YB-49 lacked, and would lead to the eventual cancellation of the project; was stability. The YB-49 lacked the ability to make sharp turns. It was also deficient in projecting a stable operational line for bombing runs. Deficiencies that with today’s computer power could be easy overcome. But in the 1950s, these facts made the aircraft impractical for military operations, thus the Air Force was forced to terminate the project. After the Air Force’s initial order for termination of the program, Jack Northrop and his top engineers tried to sell the YB-49, with its massive payload capabilities, to the civilian aviation community. He envisioned a fleet of commercial flying wing carriers traveling the country. He even made an Ad commercial relating the advantages of the commercial flying wing. It was to no avail. If the wing was not stable enough for experience Air Force pilots, it certainly could not perform at a civilian standard. This realization, for all practical matters, ended the brief life of the YB-49. It would be more than thirty years before another flying wing configuration would take to the air. But when it did, it was a spectacular sight, such as was the first time the YB-49 flew. The B-2 Stealth Bomber is the realization of years of experimentation, couple with unprecedented advances in technology, airframe design and avionics. These advances lead to the production of the finest expression of a flying wing configuration design. Could there be a commercial-type version of the B-2?

Boeing C-Wing concept (photo, Boeing)
Boeing C-Wing concept (photo, Boeing)
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In the mid 1970s a quiet research program was commenced by the Boeing Corporation with the objective of adapting a flying wing configuration design and develop it into a passenger-carry airframe. After an extensive period research and design experimentation; Boeing engineers came out with two main flying wing concepts for a passenger airliner. They unveiled them in January 1998. The first concept was the C-wing configuration. The C-wing concept is centered around a fuselage structure of tubular shape fitted with small horizontal winglets to be placed at the end of the vertical ones. The wings on the C-concept were designed to be swept at an angle of 35 degree, the same goes for the horizontal winglets. This fuselage configuration was adopted by the design team for its ability to reduce drag on the wings. The C-wing was design from its conception to disperse payload evenly throughout the airframe in order to reduce high amounts of lift. The airframe in a C-wing concept would be equip with a canard system to be utilized as a control mechanism in cruise flight conditions. The aircraft was conceived to be propelled by two forward and two aft turbojet engines. But, as it was the case with the first generation of flying wing platforms, the fuel consumption-to-performance ratio was in the negative. This fact alone will probably lead to the shut-down of the whole program. Sensing this problem, Boeing engineers also studied a modification to the original C-wing platform. In this alternative, the aircraft will be powered to the air by only three engines. Early design experimentation with this concept had indicated that the design would achieve a better aerodynamic profile than the one mounted with four engines. Still, this concept is not as promising as the newest Boeing pre-design mock-up.

Besides the C-wing concept, in 1998, Boeing unveiled the most far reaching flying wing platform concept in the history of civilian aviation: the Blended Wing Body Platform. The blended wing concept is the pinnacle of civilian aviation design and engineering prowess. The blended wing airframe is very similar in shape and control systems orientation to the amazing B-2 bomber. The concept is simple enough. The wing fuselage will also serve as an engine mounting platform, and again, like the B-2, the engine’s inlets will be absorbed by the wing’s frame. There considerations for a two engine configuration of the blended wing. Research has also demonstrated that a four engine version can perform equally successful. Control mechanisms for directional stability, such as flaps, will be house on small winglets at the end of each wing tip. The complete aircraft will be fly-by-wire, thus enhancing its flying stability and optimizing its avionics package. The operational profile for this amazing aircraft is ambitious. It is design to carry a load of eight hundred passengers and crew members to a distance of over 7,100 nautical miles. It will be fitted with all the comforts of the modern era. The aircraft will have state of the art galleries, lavatories, and a sound and video system. An improved row sitting system that will enable the passenger to roam around the “wing” on flight is on the design board. But maybe the most unique cabin feature of this concept, is the proposed forward view windows mounted along the curve of the wing. A concept first developed by Jack Northrop in the late 1950s. This feature will give the passenger the ability to see through the window at the “world below”. A view normally only experienced by the aircraft’s crew.

Boeing X-48B demonstrator (photo, Boeing)
Boeing X-48B demonstrator (photo, Boeing)

Could Boeing or any other company find operating a flying wing concept aircraft profitable? Research and development data has shown that the time of the commercial flying wing has arrive. Technology, unlike before, is now on our side. The question is not so much as “if” and more as “when”. We don’t know when the time will come. But we certainly know that is far approaching. Approaching the visions of so many giants of aviation, approaching history. We are close, very close.

– Raul Colon

 

More information:
Northrop’s flying-wing airliner
Blended Wing Body – New Concept in Passenger Aircraft
NASA: Advanced Configurations for Very Large Subsonic Transport Airplanes
British help Boeing with Blended Wing

Willard Custer Ideas, Ready for the Aviation World?

Engineers at the Georgia Institute of Technology Research Institute in Atlanta, U.S.; are quietly researching the possibility of applying a Channel Wing Configuration technology to the designs of future aircrafts platforms. The Channel Wing Configuration, when implemented on the wing design, would give the aircraft the ability to generate a high volume of lift, which could open the path to many design possibilities. The idea of configurating the wing design to be able to generate more lift has been around since the birth of aviation early in the 1900s. Preliminary studies by aviation engineers on the subject in the mid-to-late 1910s resulted in experimentation with various form of wing configurations and settings. Eventually, advances on airframe deign and a premium on engine performance took center stage, thus neglecting the concept of wing modification to achieve greater lift. For years, research into a greater lift-generating wing design was shaped by traditionalist aviation engineers and designers. Thus, radical new ideas were never fully pursued, that was until a brilliant Maryland inventor came forward with a new concept in 1935.

Willard Custer was one of the first true champions of the lift principal called aero physics. He stated that the amount of lift generated by any aircraft is determined by the speed on which the air flows over the wing, not solely on the speed of the wing moving thru the air as articulated by many. If a wing configuration were to be designed with deep channels, dropping like a couple of “smiles” under the propellers; then the aircraft would generate more lift with it than a conventional wing configuration. For Custer, the idea was simple enough. An aircraft can generate lift with zero forward speed utilizing the engines to provide the necessary airflow to sustain the plane in the air, thus achieving an impressive amount of Short Take-Off and Landing (STOL) capability. Additionally, with the channel wing shape, the engine thrust is propelled downward, providing the aircraft with the ability to perform short take-offs, and, as an added bonus; maintaining air control at relative slow speeds. The idea that an aircraft can achieve virtually vertical take-off and landing capabilities by re-designing its wing configuration a was radical concept in the late 1930s.

Custer CCW-1 (photo, via author)
Custer CCW-1 (photo, via author)

The aviation community did not think much of Cluster’s Channel Wing Concept. That’s the risk someone takes when propelling radical new ideas. Nevertheless, Custer marched on. In the summer of 1943, his first aircraft design with channel wings was demonstrated to the United States Army Air Forces in Maryland. Immediately, the CCW-1, as the plane was designated, was a media darling. Stories of this strange-looking aircraft, nearly hovering over the ground, fascinated many in the country. Unfortunately, the US Army was not one of them. They branded the CCW-1 impractical because of the extreme nose-up attitude requirement for landing. There were also issues about the survival of the CCW-1 in combat. Test flights showed that if one of the engines were to be lost, the pilot could not maintain effective control over the aircraft.

Despite the setback, Custer persevered, and in the fall of 1959; he presented his new aircraft, the CCW-5 to the Marine Corps. Again he was turned down. Mainly, for the reasons stated in 1943; the concept seemed to hit the wall. No major research was invested on the channel wing concept until 1995, when the idea was resurrected by Dennis Bushnell, Chief Researcher at NASA’s Langley Research Center in Virginia. For years Bushnell mulled over how to fit an aircraft in tight locations off the ground. He researched the accepted principals of direct thrust and rotary wings, but they were not able to produce the desired results, as recent experimentation had shown. But Bushnell had an ace. For years he had known and studied the work of Custer on the Channel Wing; and he wondered if a combination of control circulation, a method from which lift is generated utilizing jet of air to improve the aerodynamic characteristics of the wing, and the channel wing, could be the answer. Either of these systems, by themselves, could not provide the aircraft with the necessary characteristic he desired, but combining the two was seen by Bushnell as the way forward.

Custer CCW-5 (photo, via author)
Custer CCW-5 (photo, via author)

A new research program commenced in 1999 and lasted until 2004. The research focused on the Coanda Effect, named after its founder; Romania researcher Henri Coanda, who in August 1910 discovered that hot gases exiting a jet followed the contour of the plates installed to deflect it. Circulation Control follows a different path. Simply put it, circulation control works when compressed air is directed over a curve or leading edge to generate greater lift capacity. Researches believed that circulation control, could in the future rend obsolete moving surfaces on aircrafts. The next step in the developmental process for Circulation Control is the replacement of mechanical lift augmenters with air hoses to make the aircrafts lighter, quieter and maintenance friendly. For all of this to take effect, surface system needed to be introduced, and here is where the Channel Wing Concept comes into play.

Current computing systems used to measure fluid dynamics of aircrafts’ surfaces had established the feasibility that a Channel Wing configuration with enhance Circulation Control, could produce a serviceable and stable super-STOL platform. Wind tunnel testing and computer animations had confirmed the Channel Wing design payoffs in ways that Custer could not have done in his time. Custer clearly understood the airflow needed to generate lift could come from two different sources: the engine or the airframe forward motion. What he lacked was an understanding of what happened to the air stream once it hit the channel. The end result is turbulence. This is why both the CCW-1 and 5 failed to achieve major air-control properties. At low speeds, the flow of air is detached form the traveled surface; leading to the aircraft to lose differential pressure that is the cause of lift. At Custer’s time, there was no method accurate enough to calculate when this effect comes to play or how to design an aircraft that used this effect in its advantage. The solution: Circulation Control. One of the most challenging arenas for the CCWs models were the high angle of attack that the aircraft needed to be flown, a dangerous proposition because the pilot will temporarily loss the ability to see over the plane’s nose. Another problem was the lost of an engine. If the aircraft were to loss the use of one of its engines, the aircraft will be subject to high stall degrees and rolls, without the necessary energy to compensate for them. Circulation Control can solve this problem.

At present, Bushnell and his team had been pressing for sometime to design and aircraft that incorporates both concepts, but like Custer before, without much success. Skeptics’ rapidity pointed out that all the research data done during the past five decades had failed to produce a serviceable aircraft design, thus leading them to the conclusion that the concepts are incompatibles. The Channel Wing concept may need to wait until advances in technology can undisputable show that an airworthy aircraft can be achieve; but the Circulation Control concept is already been use by various countries in the design on unmanned air vehicles. Even a naval application was found for the concept. Submarines could use jets instead of conventional dive planes and rudders to change aspect ratios.

Custer’s idea was years ahead of his time, and seems today, that is still ahead of us. Further research and data collection maybe needed, but with the current military situation, a premium is been place on the ability of aircraft to perform short take-off and landing s procedures, its only a matter of time before the next great engineering breakthrough comes along and Custer’s idea will probably be at the center of it.

– Raul Colon

 

More information:
Custer Channelwing Website
The Official Custer Channel Wing Website
Les avions de Willard Custer
Mid-Atlantic Air Museum: CC-W-5
That Extra Little Lift

China’s Plan to Introduce Reduced Vertical
Separation Minimums Radius on its Airspace

Only one year before the 2008 Olympic Games Inauguration Ceremonies, Chinese aviation authorities are planning to introduce the Reduced Vertical Separation Minimums’ system on a nationwide basis to cope with the expected air-traffic congestion associated with the games. In the past, Chinese officials have requested technical assistance from Europe and the United States in order to handle the implementation of new systems for China’s aging ATC system. The US Federal Aviation Agency has been providing technical advisors to China on this matter since July 2005. Chinese officials see the incorporation of RVSM as an integral part of the modernization of China’s civil aviation sector. China already uses the RVSM system on one of its ocean going flight pattern region and has plans to add up nine more regions to the system, all in the mainland. Even with this first step, China lags far behind other nations. A global transition to RVSM has been underway since the heavily used North Atlantic Airspace Region switched from 2,000ft to 1,000ft altitudes intervals in the fall of 1997. Australia was the first major commercial market to implement RVSM in 2001, Europe followed a year later, and United States incorporated the system in 2005.

However, one aspect of the proposed Chinese RVSM system that must be considered by the commercial aviation industry is the fact that China is the first nation to implement a RVSM system in meters, instead of the traditional feet scale. This could trigger errors in flight operations due to the different altitude measurements. The Chinese air control system would assign a pilot an RVSM altitude in meters, then the pilot, using a Chinese supply conversion table; will translate this figure into a feet scale. Today, many Boeing and Airbus commercial carriers posses altimeters that can be set on meters, but this feature will not apply to China-bound flight routes. Here then lies the potential problem with China’s RVSM system. If an aircraft is assigned by RVSM an altitude of 9,800 meters, which equals 32,150ft, using the RVSM conversion table, the pilot would round this figure to the closest 100ft mark and then set the airplane on a 32,100ft altitude. Back on the ground, the air traffic controller will see the metric conversion, and the ATC display will show the plane’s current altitude at 9,780 meters, not the assigned altitude of 9,800 meters. This would lead to confusion regarding the planned altitude patterns of all flights. Added to this potential problem is that most of China’s neighbors still use several types of altitude cruising level systems, including the conventional 2,000ft separation. This will require the pilot to adjust the plane’s altitude as its travel from a national air-space to another.

Ideally, China will implement a RVSM system based on a feet scale, as most of the world already does, but the Chinese Air Force have all their air equipment pre-programmed in meters and a conversion to a feet scale would probably disrupt the current military state of their Air Force. Thus China would go on to use the meter scale for the foreseeable future. Eventually, the world community should design and implement an RVSM system of uniformity for all nations to use, but this is a long term vision today; China needs to make the necessary arrangements, perform the necessary experimentation and trials with its RVSM system in order to minimize confusion or even incidents when the entire country converts to RVSM.

– Raul Colon

 

More information:
FAA Website: Reduced Vertical Separation Minimum
Pilot Journal: What’s RVSM?