INTRODUCTION

Aeronautics is defined as “the science that treats of the operation of aircraft; also, the ^art or science of operating aircraft.” Basically, with aeronautics, one is concerned with predicting and controlling the forces and moments on an aircraft that is traveling through the atmosphere.

A BRIEF HISTORY

Thursday, December 17, 1903

“When we got up a wind of between 20 and 25 miles was blowing from the north. We got the machine out early and put out the signal for the men at the station. Before we were quite ready, John T. Daniels, W. S. Dough, A. D. Etheridge, W. C. Brinkly of Manteo, and Johnny Moore of Nags Head arrived. After running the engine and propellers a few minutes to get them in working order, I got on the machine at 10:35 for the first trial. The wind, according to our anemometers at this time, was blowing a little over 20 miles (corrected) 27 miles according to the government anemometer at Kitty Hawk. On slipping the rope the machine started off increasing in speed to probably 7 or 8 miles. The machine lifted [гот*Щр truck just as it was entering the fourth rail. Mr. Daniels took a picture just as it left the tracks. I found the control of the front rudder quite difficult on account of its being balanced too near the center and thus had a tendency to turn itself when started so that the rudder was turned too far on one side and then too far on the other. As a result the machine would rise suddenly to about 10ft. and then as suddenly, on turning the rudder, dart for the ground. A sudden dart when out about 100 feet from the end of the tracks ended the flight. Time about 12 seconds (not known exactly as watch was not promptly stopped). The level for throwing off the engine was broken, and the skid under the rudder cracked. After repairs, at 20 min. after 11 o’clock Will made the second trial.”

The above, taken from Orville Wright’s diary, as reported in Reference

1.1, describes mankind’s first sustained, controlled, powered flight in a

Figure 1.1 The first flight, December 17, 1903. (Courtesy of the National Air and Space Museum, Smithsonian Institution.)

heavier-than-air machine. The photograph, mentioned by Orville Wright, is shown here as Figure 1.1. Three more flights were made that morning. The last one, by Wilbur Wright, began just at 12 o’clock and covered 260 m in 59 s. Shortly after fhis flight, a strong gust of wind struck the airplane, turning it over and over. Although the machine was severely damaged and never flew again, the Wright Brothers achieved their goal, begun approximately 4yr earlier.

Their success was no stroke of luck. The Wright Brothers were painstak­ing in their research and confident of their own results. They built their own wind tunnel and tested, in a methodical manner, hundreds of different airfoil and wing planform shapes. They were anything but a “couple of bicycle mechanics.” Their letters to Octave Chanute, a respected civil engineer and aviation enthusiast of the day, reveal the Wright Brothers to have been learned men well versed in basic concepts such as work, energy, statics, and dynamics. A three-view drawing of their first airplane is presented in Figure 1.2.

On September 18, 1901, Wilbur Wright was invited to deliver a lecture before the Western Society of Engineers at a meeting in Chicago, Illinois. Among the conclusions reached by him in that paper were:

Figure 1.2 Three views of the Wright Brothers’ flyer.

1. “That the ratio of drift to lift in well-shaped surfaces is less at angles of incidence of five degrees to 12 degrees than at an angle of three degrees. ” (“Drift” is what we now call “drag.”)

2. “That in arched surfaces the center of pressure at 90 degrees is near the center of the surface, but moves slowly forward as the angle becomes less, till a critical angle varying with the shape and depth of the curve is reached, after which it moves rapidly toward the rear till the angle of no lift is found.”

3. “That a pair of superposed, or tandem surfaces, has less lift in proportion to drift than either surface separately, even after making allowance for weight and head resistance of the connections. ”

These statements and other remarks (see Ref. 1.1) show that the Wright Brothers had a good understanding of wing and airfoil behavior well beyond that of other experimenters of the time.

Following their first successful flights at Kitty Hawk, North Carolina, in 1903, the Wright Brothers returned to their home in Dayton, Ohio. Two years later they were making flights there, almost routinely, in excess of 30 km and 30 min while others were still trying to get off the ground.

Most of the success of the Wright Brothers must be attributed to their own research, which utilized their wind tunnel and numerous experiments with controlled kites and gliders. However, their work was built, to some degree, on the gliding experiments of Otto Lilienthal and Octave Chanute. Beginning in 1891, Lilienthal, working near Berlin, Germany, made ap­proximately 2000 gliding flights over a 5-yr period. Based on measurements obtained from these experiments, he published tables of lift and drag measurements on which the Wright Brothers based their early designs. Unfortunately, Lilienthal had no means of providing direct aerodynamic control to his gliders and relied instead on kinesthetic control, whereby he shifted his weight fore and aft and side to side. On August 9, 18%, as the result of a gust, Otto Lilienthal lost control and crashed from an altitude of approximately 15 m. He died the next day. During 1896 and 1897, Octave Chanute, inspired by Lilienthal’s work, designed and built several gliders that were flown by others near Miller, Indiana. Chanute recognized Lilienthal’s control problems and was attempting to achieve an “automatic” stability in his designs. Chanute’s principal contribution was the addition of both vertical and horizontal stabilizing tail surfaces. In addition, he went to the “box,” or biplane, configuration for added strength. Unfortunately, he also relied on kinesthetic control.

When the Wright Brothers began their gliding experiments in the fall of 1900, they realized that adequate control about all three axes was one of the major prerequisites to successful flight. To provide pitch control (i. e., nose up or down), they resorted to an all-movable horizontal tail mounted in front of

the wing. Yaw control (i. e., turning to the left or right) was accomplished by means of an all-movable vertical tail mounted behind the wing. Their method of roll control (i. e., lowering one side of the wing and raising the other) was not as obvious from photographs as the controls about the other two axes. Here, the Wright Brothers devised a means of warping their “box” wing so that the angle of incidence was increased on one side and decreased on the other. The vertical tail, or rudder, was connected to the wing-warping wires so as to produce what pilots refer to today as a coordinated turn.

The Wright Brothers were well ahead of all other aviation enthusiasts of their era. In fact, it was not until 3 yr after their first flight that a similar capability was demonstrated, this by Charles and Gabriel Voisin in Paris, France (Ref. 1.2). On March 30, 1907, Charles Voisin made a controlled flight of approximately 100 m in an airplane similar in appearance to the Wright flyer. A second machine built by the Voisin Brothers for Henri Farman, a bicycle and automobile racer, was flown by Farman later that year on flights that exceeded 2000 m. By the end of that year at least five others succeeded in following the Wright Brothers’ lead, and aviation was on its way.

Today we are able to explain the results of the early experimenters in a very rational way by applying well-established aerodynamic principles that have evolved over the years from both analysis and experimentation. These developments have their beginnings with Sir Isaac Newton, who has been called the first real fluid mechanician (Ref. 1.3). In 1687 Newton, who is probably best known for his work in solid mechanics, reasoned that the resistance of a body moving through a fluid is proportional to the fluid density, the velocity squared, and the area of the body.

Newton also postulated the shear force in a viscous fluid to be propor­tional to the velocity gradient. Today, any fluid obeying this relationship is referred to as a Newtonian fluid.

In 1738, Daniel Bernoulli, a Swiss mathematician, published his treatise, “Hydrodynamics,” which was follov^l in 1743 by a similar work produced by his father, John Bernoulli. The Bemoullis made important contributions to understanding the behavior of fluids. In particular, John introduced the concept of internal pressure, and he was probably the first to apply momen – ( turn principles to infinitesimal fluid elements.

I Leonhard Euler, another Swiss mathematician, first put the science of hydrodynamics on a firm mathematical base. Around 1755, Euler properly ^ formulated the equations of motion based on Newtonian mechanics and the f works of John and Daniel Bernoulli. It was he who first derived along a } streamline the relationship that we refer to today as “Bernoulli’s equation.”

The aerodynamic theories of the 1800s and early 1900s developed from f’, the early works of these mathematicians. In 1894 the English engineer, Frederick William Lanchester, developed a theory to predict the aerodynamic I; behavior of wings. Unfortunately, this work was not made generally known

Table 1.1 (continued) Designer or Manufacturer a. Model Number b. Model Name First Flight Date Span, ft Length, ft Wtng Area, о2 Gross Weight, 10001b Empty Weight, 10001b Useful Load, 1000 lb Power Plant, no. x hp/eng. Kalinin a. K-7 8/33 173.9 91.9 4,887 83.78 53.79 29.99 7 x 750 hp Tupolev a. ANT-20 b. Maxim Gorki 5/34 206.7 106.5 5,233 116.84 92.58 24.26 8 x 875 hp Douglas a. XB-19 6/41 212 132.3 4,285 162 75 65 4 x 2,000 hp Lockheed a. 89 b. Constitution 11/46 189.1 156.1 3,610 184 114 70 4 x 3,000 hp Hughes a. H-4(HK-1) 11/47 320.5 218.5 11,450 400 248 152 8 x 3,000 hp Convair a. XC-99 11/47 230 182.5 4,772 265 140 125 6 x 3,000 hp Bristol a. 167 b. Brabazon 1 9/49 230 177 5,317 290 145 145 8 x 2,500 hp

Power, Wing lb/ft2 lb/hp or lb Number*1 Flown Passenger Capacity Range, ST. M. Comment 17.14 15.96 1 620 Bomber; projected 120- passenger transport version not built. 22.33 16.69 2e 64е 1,240 Equipped with printing press and propaganda aerial loudspeaker system. 32.67 17.50 1 7,700 Bomber. 50.97 15.33 2 168 4,700 Full double-deck accommoda­tions. 34.93 16.67 ik 700 5,900 Flying boat; all wood. 55.53 14.72 400 6 wing-buried engines with pusher propellers; full double-deck accommoda­tions. 54.54 14.50 1 100 5,500 8 wing-buried engines coupled in pairs to 4 tractor propellers.

Designer or Manufacturer a. Model Number b. Model Name	First Flight Date	Span, ft	Length, ft	Wing Area, ft2	Gross Weight, 10001b	Empty Weight, 1000 lb	Useful Load, 1000 lb	Power Plant, no. x hp/eng.
Wright b. Flyer	12/03	40.3	21.1	510	0.75	0.6	0.15*	1 X 12 hp
Sikorsky/RBVZ b. Ilya Mourometz	4/ІЗ	113	67.2	1,615	10.58	7.28	3.3	4 x 100 hp
Zeppelin-Staaken a. VGO. l	4/15	138.5	78.7	3,572	20.99	14.38	6.61	3 x 240 hp
Handley Page	4/18	126	64	3,000	30	15	15	4×275 hp

a. H. P. 15(V/1500)

Caproni a. Ca 60 b. Transaero	1921c	98.4	76.9	7,696	55.12	30.86	24.26	8 x 400 hp
Junkers	11/29	144.3	76.1	3,229	44.09	28.66	15.33	2 x 400 hp
a. G-38								2 x 800 hp
Dornier a. DoX	7/29	157.5	131.4	4,736	105.8	72.2	33.6	12 x 500 hp

Power, Wing Ib/hp Number0 Passenger Range, lb/ft2 or lb Flown Capacity ST. M. Comment
0
Canard biplane and single engines driving two pusher propellers. 300 Biplane with tractor engines on lower wing; used effectively as a bomber in W. W.I. Biplane with one nose mounted engine and two wing-mounted pushers. 1,300 Built to bomb Berlin in W. W.I; biplane with 2×2 tractor/ pusher arrangement. 410 Flyingboat: triple triplane.
1.47 62.50 1
6.55 26.45 80	16
5.9 29.2 44
10.00 27.27 10	40
7.16 19.69 0C	100
746 Engines wing – buried; DLH line service from 1932 to 1944. 850 Flying boat.
13.63 18.33 8′	30
22.34 17.63 3
100′

Table 1.1 (continued)

Loadings Designer or Manufacturer a. Model Number b. Model Name First Flight Date Span, ft Length, ft Wing Area, ft2 Gross Weight, 1000 lb Empty Weight. 10001b Useful Load, 10001b Power Plant, no. x hp/eng. Wing lb/ft2 Power, Ib/hp or lb Number43 Flown Passenger Capacity Range, ST. M. Comment Boeing a. YB-52 b. Stratofortress 4/52 185 153 4,000 390 166 224 8 x 10,0001b 97.50 3.00t 1 744 7,000 Bomber. Boeing a. B-52G b. Stratofortress 3/61 185 157.6 4,000 488 8 x 13,7501b 122.00 2.854 10,000 Bomber. Antonov a. An-22 b. Antheus 2/65 211.3 189.6 3,713 551.2 251.4 299.8 4 x 15,000 hp 148.45 9.19 SP* 6,800 High-wing, tail­loading cargo transport; contra-rotating propellers. Lockheed a. C-5A b. Galaxy 6/68 222.7 247.7 6,200 764.5 320 444.5 4×41,000 lb 123.31 4.n< SP* 1,000′ 7,500 High-wing, nose and tail-loading cargo transport; T-tail.

Power, Wing Ib/hp Number0 Passenger Range, lb/ft2 or lb Flown Capacity ST. M. Comment
0
Canard biplane and single engines driving two pusher propellers. 300 Biplane with tractor engines on lower wing; used effectively as a bomber in W. W.I. Biplane with one nose mounted engine and two wing-mounted pushers. 1,300 Built to bomb Berlin in W. W.I; biplane with 2×2 tractor/ pusher arrangement. 410 Flyingboat: triple triplane.
1.47 62.50 1
6.55 26.45 80	16
5.9 29.2 44
10.00 27.27 10	40
7.16 19.69 0C	100
746 Engines wing – buried; DLH line service from 1932 to 1944. 850 Flying boat.
13.63 18.33 8′	30
22.34 17.63 3
100′

Source. From F. A. Cleveland, “Size Effects in Conventional Aircraft,” J. of Aircraft, 7(6), November-December 1970 (33rd Wright Brothers Lecture). Reproduced with permission.

“ Counting original(s), subsequent series production, and derivatives—if any. k Counting pilot (Orville Wright) and 5 lb of fuel. c Destroyed in taxi-test which resulted in unintended liftoff. d Set world record 21 Oct. 1929 with 169 onboard.

‘ One ANT-20 is built with six 1100-hp engines.

1 Turbine energy expressed in terms of gas-hp with 0.8 efficiency.

* SP = in series production.

k Used mainly as freighter: 724-seat stretched version projected.

1 Triple deck version.

’ Two in Germany; six in Japan.

* Flew only once on high-speed taxi test.

until 1907 in a book published by Lanchester. By then the Wright Brothers had been flying for 3 yr. Much of the knowledge that they had laboriously deduced from experiment could have been reasoned from Lanchester’s theory. In 1894, Lanchester completed an analysis of airplane stability that could also have been of value to the Wrights. Again, this work was not published until 1908.

Lanchester’s wing theory was somewhat intuitive in its development. In 1918 Ludwig Prandtl, a German professor of mechanics, presented a mathe­matical formulation of three-dimensional wing theory; today both men are credited with this accomplishment. Prandtl also made another important contribution to the science with his formalized boundary layer concept.

Around 1917 Nikolai Ergorovich Joukowski (the spelling has been angli­cized), a Russian professor of rational mechanics and aerodynamics in Moscow, published a series of lectures on hydrodynamics in which the behavior of a family of airfoils was investigated analytically.

The work of these early hydro – and aerodynamicists contributed little, if any, to the progress and ultimate success of those struggling to fly. However, it was the analytical base laid by Euler and those who followed him on which the rapid progress in aviation was built.

After 1908, the list of aviators, engineers, and scientists contributing to the development of aviation grew rapidly. Quantum improvements were accomplished with the use of flaps, retractable gear, the cantilevered wing, all-metal construction, and the turbojet engine. This impressive growth is documented in Table 1.1. Note that in less than 10 yr from the Wright Brothers’ first flight, the useful load increased from 667 N (150 lb) to more than 13,300 N (3000 lb). In the next 10 yr, the useful load increased by a factor of 10 and today is more than 1.78 x 106 N (400,000 lb) for the Lockheed C-5A.

Our state of knowledge is now such that one can predict with some certainty the performance of an airplane before it is ever flown. Where analytical or numerical techniques are insufficient, sophisticated experimental facilities are utilized to investigate areas such as high-lift devices, complicated three-dimensional flows in turbomachinery, and aerothermodynamics.