Quest for Performance: The Evolution of Modern Aircraft
Chapter 3:The Lean Years, 1918-26
Transport Developments in Europe
[68] In contrast to the slow development of airline aviation in the United States, European air transport began almost immediately after the cessation of hostilities in 1918. The major capitals of Europe were soon connected by primitive passenger-carrying airlines. The aircraft types utilized for carrying passengers were at first hastily converted [69] military bomber and observation types. Later, new aircraft were constructed for the infant airlines; however, these aircraft usually followed the standard biplane formula developed during World War I. Typical of these transport aircraft is the Handley Page trimotor shown in figure 3.2. The aircraft was a multibay biplane, similar in configuration to the bomber types of the war, but employed an enclosed cabin capable of carrying 10 passengers. The two pilots were accommodated in an open cockpit just forward of the leading edge of the upper wing, as can be seen in figure 3.2. Note the four-blade propellers and the multiple wheels of the landing gear. The use of the four-wheel gear was no doubt a concession to the relatively soft sod or mud landing fields of the period. A glance at the characteristics of the aircraft given in table II indicates a relatively heavy machine of 13 000-pound gross weight, but with only 840 horsepower as the combined output of the three engines. The wing loading was a very low 8.9 pounds per square foot in order that the aircraft could operate out of the small fields that existed at the time. The cruising speed was a modest 85 miles per hour; the drag coefficient at zero lift was 0.0549, which was larger than that of the DH-4. Although the use of multiple engines is usually thought to increase safety and reliability, that was not the case with the Handley....

trimotor transport
[70] Figure 3.2 - Handley Page model W8F 12-passenger trimotor transport; 1924. [Flt. Intl.]
.... Page trimotor. The aircraft could not maintain level flight following the loss of one engine according to the information given in reference 75. The Handley Page trimotor was Put into operation by the British Imperial Airways and the Belgium Sabena Airways Systems in about 1924 and continued in operation, at least to some limited extent, until about 1931. In fact, very large multiengine biplanes were utilized on some European airlines right up to the beginning of World War II.
Aircraft employing the monoplane configuration had been built since the early days of aviation. The first nonstop flight across the English Channel was made in 1909 by Bleriot flying a wire-braced monoplane, and many early World War I fighters were also monoplanes (chapter 2). Most early monoplanes employed a multitude of wires and struts in order to provide strength and rigidity to the wings. As a consequence, the drag characteristics of these aircraft showed little if any improvement compared with contemporary biplane drag characteristics. Furthermore, there seemed to be a lack of confidence in the structural integrity of the monoplane configuration. There were also experiments with internally braced, cantilever monoplanes. As indicated in chapter 2, the German designer Junkers built cantilever monoplanes constructed of metal. The materials and design methods available during World War 1, however, did not lend themselves to the construction of light, all-metal cantilever designs. Another early proponent of the cantilever [71] monoplane was the Dutch designer Anthony H. G. Fokker. Fokker designed and built fighter aircraft for the German Air Force during World War I. His first cantilever monoplane fighter was the model D-VIII, which featured an internally braced wing mounted on struts above the fuselage. (See figure 2.16.)
In 1920 and 1921, Fokker developed a single-engine transport employing an internally braced wing similar in concept to that of the DVIII fighter. This aircraft, known as the Fokker F-2, is depicted in figure 3.3. The aircraft seated three or four passengers in an enclosed cabin, and a single pilot was located in an open cockpit Just under the leading edge of the wing. The absence of external struts and wires to support the wing is obvious from the photograph. The relative aerodynamic cleanliness of the design would be expected to produce a correspondingly low value of the zero-lift drag coefficient. The data in table II, however, suggest that the value Of CD,O is not much better for the Fokker than for the DH-4. The open cockpit together with a poor engine installation and consequent high cooling drag suggest themselves as possible reasons for the relatively high zero-lift drag coefficient. The wooden cantilever wing and steel-tube, fabric-covered fuselage formed the basis for a long line of Fokker aircraft built right up to World War II. An improved and larger version of the Fokker F-2, known as the T-2, was the first aircraft to fly nonstop across the United...

ground view of a Fokker f-2
[72] Figure 3.3 - Fokker F-2 four-passenger transport; 1920. [Flt. Intl.]

.....States. This flight was made by the U.S. Army Air Service in 1923 (ref. 38). The famous Fokker trimotor was very similar in configuration to the F-2 but employed three modern engines, had a fully enclosed cabin and cockpit, and was much larger than the F-2. The first of the Fokker trimotors was employed by Richard E. Byrd and Floyd Bennett in their historic first flight over the North Pole in 1926.