By Curtis Farnham
WICHITA, KS -- Let's face it. The world economy is in a slump. Retailers report slow sales. The aviation industry has slowed or stopped production. Aerial applicators struggle to stay out of the red. Just about every industry is feeling the pinch. Is a solution in sight?
Kenneth Razak, president of Razak Engineering, Inc, prefers not to think about it that way. Speaking of his 30-year experience teaching engineering, he writes, "Ordinarily we think of 'problems' and seek 'solutions". What we should do is say that there are 'situations' and we seek 'options'. Razak has put his premise to work. He has analyzed the aerial application situation and has tabulated options for action. It started in the late 1950s. Razak was then a consultant to Cessna Aircraft Company and was commissioned in September 1958 to study the aerial application industry. He was to report to Cessna on the economic potential of developing and building an ag-plane.
His first step was to analyze all phases of aerial application in agriculture. The goal was to find basic factors and parameters that affected agricultural use of aerial application. Among his findings, three items stood out.
(1) Aerial application was limited to crops that had a field value (in 1960) of at least $100 per acre.
(2) The maximum rate of ejection of material from airplanes in use at that time was about 20 pounds per second.
(3) Ag airplanes were inefficient high-drag machines.
The first factor formed a lower limit to crops that could justify aerial application. The second factor eliminated crops that required high rates of fertilizer or liquid application. The third factor limited profits of aerial applicators.
Razak studied the effects of these and other factors by using an operations analysis approach. He wrote a complex computer program that "flew" airplanes through every step of an aerial application mission. He found that by increasing the possible rate of material ejection and by increasing aerodynamic efficiency, the profit making potential was substantially increased. This defined the situation. Options were to design a new type of wing and make ag airplanes more efficient.
Razak approached the University of California at Davis where professors Norman Akesson and Wesley Yates had long worked on ag aviation topics. He proposed an approach to a new wing design. They considered it had enough potential to justify initial tests on a semi-span wing. These tests proved his theory and Razak outlined an airplane that included these features. This was the Distributor Wing Airplane (DWA).
Razak submitted his report to Cessna and described four options.
(1) Do nothing. Let ag operators use current production airplanes of 170s, 172s and 180s and hang distributing equipment on them.
(2) Equip current airplanes with features that would make it easier to hang distributing equipment on existing airplanes.
(3) Design an "on purpose" airplane using existing manufacturing procedures to produce a 'new' airplane that could be called an ag airplane.
(4) Design and build a prototype of the DWA.
Cessna chose the third option and built the AgWagon 230 and the AgTruck 300. These airplanes were in production for several years. They were useful machines but neither of them addressed the basic factors that Razak had defined in his analysis.
Cessna released the Distributor Wing principle to Razak and he arranged to conduct further tests at the University of California. A full scale semi-span wing was built and tested. These tests expanded and corroborated initial tests and provided airplane design data. In January 1964, Razak and company negotiated a contract with International Minerals and Chemical Company (IMC) to build N361DW, the first prototype DWA. Its first flight was in January 1965 and was followed by a successful round of flight testing. These flights further verified the principles and showed that the Distributor Wing approach was practical.
The unique feature of the DWA is a fan that continuously blows air out of a slot ahead of the flap. The air passes over the flaps and gives the plane distinct performance advantages. For aerial applicator planes there is a further advantage. The blowing system functions as a built-in spreader. The air transports material from the hopper through the wings and discharges it from the slot.
Sadly, the fertilizer industry collapsed the same year. The sale price of fertilizer dropped by 50%. IMC was encountering very high costs to develop a new potash mine and was forced to cancel its financial backing for many projects. One of these was the DWA. The project was set aside late in 1965.
The Distributor Wing Airplane is based on a fundamental aircraft design concept. Airplanes must be designed for the missions they are to fly. Existing airplanes were adapted for the purpose of aerial application; they weren't designed for the mission. From the very first, spreaders and sprayers were hung outside the airplane. The Stearman is the classic example. This was a high drag, low-power airplane to start with. Adding spreaders and spray booms, plus increasing the payload, made it necessary to use bigger engines. Bigger engines were also required to attain higher ejection rates and wider swaths. But bigger engines cost more money, they are more expensive to overhaul, and they have higher maintenance and fuel costs.
This power race was necessary at first, because the aerial application industry was not big enough for a manufacturer to justify development of a completely new airplane. However, when specialized aerial application planes became available, the legacy continued. Spreaders and sprayers continued to be hung on airplanes, the airplanes still were high drag machines, and bigger and still bigger engines were required. The DWA breaks this cycle. By incorporating a blowing system and using the wing as a built-in spreader, there is no need for externally hung equipment. Profitability increases because the plane has substantially less drag and therefore needs less power.
In 1999, Razak renewed his activities in airplane design. He laid out low-drag configuration with the built-in spreader of the Distributor Wing. He also incorporated new technology. The result is the CDWA Mark X". To verify its performance, Razak has rewritten his operations analysis program and is offering it to the aerial application industry. More details will be forthcoming in a future editon of AgAir Update. Operators are invited to submit data on (1) their current airplanes, (2) missions they are now flying and (3) missions they would like to fly. These data will be used to compute the earning power of existing airplanes and compare with his new DWA.
Razak's next move will depend on the results of the operations analysis. If the results show a clear improvement in earning power and the ability to open new markets, Razak says that he will be in touch with major fertilizer and ag chemical companies to determine their interest in assisting with the development of the new model of the Distributor Wing Airplane.
Curtis Farnham is a senior in aerospace engineering at Wichita State University. He has been a Cooperative Education student at NASA Houston for three semesters and now works part-time for Razak Engineering while planning his future career.