Prescott Pusher (oz14320)

About this Plan

Prescott Pusher. Radio control scale model. Pusher layout. Wingspan 72 in, wing area 666 sq in. For .60 to .90 engines. Scale is 1/5.

Quote: "Tired of the ordinary? This unique aircraft will stand out in the crowd at your RC flying field. The Prescott Pusher, by Tom Prescott.

The Prescott Pusher began life in early 1980 as a marketing concept. How could I and countless others afford our very own aircraft? Certainly 'pay as you go' is an American way of life and why not 'pay as you build' your own aircraft? Thus, an aircraft purchase plan was outlined to allow a modest down payment and provide a method of monthly payments. Because a kit manufacturer, with the high cost of money, cannot become the banker, shipment of subsequent kits can only be made after receipt of payment.

The next task was to design an aircraft that could be tailored to this marketing concept. Some initial design goals included: sufficient payload capability to handle 95th percentile adults, a range of 1000 statute miles, lowest possible cost while maintaining a high quality of design, simplicity of construction tailored to the average hoinebuilder, development of the airframe with a proven powerplant and, finally, provide maximum performance with the power specified. That is quite a tall order, but attainable with careful planning and innovation.

One of the first steps in any aircraft design is to establish the basic configuration. It is safe to say that, as designers, we have squeezed almost the last ounce of efficiency from tractor configured aircraft. Therefore, many designers are realizing additional efficiency can be obtained by utilizing a pusher design concept. The Prescott Pusher posed some interesting design challenges that included weight control, structural configuration, and engine cooling.

Early in the design, I decided not to accept the challenges associated with a mid-engine aircraft and the six to eight foot drive shaft that the mid-engine dictates. This one decision narrowed the possibilities for the configuration and what resulted was the aircraft as presented here. It is interesting to note that the Prescott Pusher was originally conceived as a two-place aircraft. However, a look at the homebuilt market, revealed a very crowded arena. What was also apparent was the lack of a four-place transportation aircraft - so back to the drawing board. I stretched the fuselage to accommodate four, increased the horsepower, and enlarged the aircraft to accommodate the higher take-off weights.

In looking- back over my early notes, I discovered under the design philosophy Item 8 which read: model design and test. This philosophy has taken two roads. First, a one-fifth scale model was tested in the Wichita State University 7 x 10 foot low speed wind tunnel in November of 1983. This wind tunnel model was constructed using many R/C modeling techniques. Prescott Aeronautical realized significant savings by using this design approach. But the wind tunnel model is a story of its own, so back to the R/C model.

The 1/5 scale radio control model was flown in February of 1984. The model was scaled using Reynold's modeling techniques. The scale factors derived are shown on chart.

The 1/5 scale R/C model, as tested, weighed 17.5 lb without fuel; and, therefore, was over scaled gross with full fuel. It was powered by a Rossi 90. The control functions included ailerons, elevator, rudder, throttle, retracts and flaps. It should be noted that the normal cruise flap setting will be -10 degrees. Also, a unique data downlink system was developed to record airspeed, angle of attack, angle of sideslip, and all control positions. Again, the downlink system is a story all to itself.

Model Construction: Fuselage: The fuselage is designed to be constructed upside down on a flat building surface. Start construction with the rectangular center section. A centerline drawn on the building board will help with alignment. Also, four support blocks were nailed to the board to keep this section square. Install F-3, F-4 and the triangular stock. After the assembly has dried, install F-3a and F-4a.

Move rearward with the next section and install the firewall F-5. Note: The engine is installed with 1.50 downthrust and no sidethrust. As a matter of convenience, before installing F-5, locate and install the engine mount using blind nuts. Also, pre-drill holes for the fuel tubing, throttle cable, and rudder pushrod as noted on the plans.

Install F-5a with the engine and mount installed. Complete the aft section assembly and locate F-6. Now that the aft section is complete, turn the section right side up and reposition over centerline. Now install the forward section and F-2. When dry, install F-2a. To complete the forward section, F-1 is installed.

It should be noted that on the prototype model an additional bulkhead was added to mount the nose gear. Originally, a forward retracting nose gear was planned but has since changed to aft retracting for structural and CO. reasons. As with the engine, it is recommended that the nose gear be metalled on F-2 prior to its final installation. Next, install the nose gear floor made of 1/8 poplar plywood and the 1/4 in balsa triangle supports. The nose gear retract servo should be installed at this time and the linkage completed. Place the partially completed fuselage aside for now and begin construction of the vertical fin.

Vertical Fin: Make all the required parts for the vertical fin including VFJ-1 through VFJ-4. These vertical fin building jigs are layed out on the building board at their respective positions. Once these jigs are secured in position, the vertical fin is constructed in sequence from one side to the other. It should be noted that the elevator bellcranks are installed during this sequence. See plan details for construction method used on bellcranks. Start construction with the left skin properly located on building jigs.

Next install and glue to skin the main spars and ribs. Note: Do not forget the rib holes that allow the pushrod to be installed between bellcranks..."

Direct submission to Outerzone.

Scan by MarkD, cleanup by Circlip.

Supplementary file notes

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