The plane was first tested for balance to determine the actual location of the center of gravity. This test was performed by first finding the balance point manually (by balancing on a finger), and then using that point as the spot to tie a string and hang the plane from it. The center of gravity was found to be within an inch of the aerodynamic center (AC) of the wing (between the AC and the tail), which is within the acceptable range according to Lennon’s Basics of R/C Model Aircraft Design. This was a test while plane was “empty”, meaning without cargo. The cargo bay is directly underneath the center of gravity, and only reinforced that location.
Before the group tried to start the engine, we decided we should take it apart and check its condition. It was the engine from two years ago, hadn’t been started in a while, and possibly needed to be rebuilt. Upon disassembling the engine, the group determined that all it needed was new gaskets, a new fuel filter, new fuel lines, and a thorough cleaning. The group assembled the engine, attached the propeller, filled it up with new fuel, mounted it in a vice, and started it up. After a few attempts, the engine started and ran without any problems or complications.
Next the group located the servos from the previous years to check if they were in good working condition. After charging the batteries for both the controller and the servos, the group determined that all 5 servos were in working order, and that purchasing new ones was not necessary.
After assembling the body of the plane, the group had to decide where and how to mount the servos. The group placed the aileron servos in each of the wings, with the linkage coming out of a hole underneath the wing. The servo motor for the flaps was placed in the middle of the top of the fuselage, as this location was between both flaps and also easily accessible. The other servos were placed in the body of the fuselage. The transmitter was position underneath the wing itself with the battery to ensure no change in the center of gravity.
After properly mounting the engine and confirming the functionality of the control surfaces by the remote, the group took the plane to a small, grass airstrip in Moonachie, NJ. With the aid of an experienced R/C model pilot, Sean Payne, the plane was tuned before attempting takeoff. The group then started up the engine successfully, and placed the plane on the runway (grass field). The first few attempts were unsuccessful, and it was found that the steering and front landing gear needed to be adjusted. After adjusting those as best as possible at the site, the group attempted to takeoff again. Steering proved to be a big problem, mainly because the grass was very bumpy and our tires had problems gaining traction for turning. On our final attempt, the plane reached speed and began to lift. The plane achieved takeoff, but stability was a problem. At about 6 feet off the ground, the plane rolled to the right and crashed, breaking the entire tailplane off of the fuselage.
There are a few possibilities for the lack of stability in the plane. Those reasons could include the play in the joining portion of the wings, an imbalance in the plane, a lack of enough tailplane, the shape of the tailplane, insufficient control surfaces, construction inexperience, and possibly the engine mounting. The majority of these shortcomings can be attributed to a general lack of experience in flying model aircraft; while calculations may have been correct, a lack of first hand knowledge (as opposed to textbook knowledge) was ultimately responsible for the disfunctionality of the plane. |
The unique experience of this project enabled the team to obtain many new skills. There was a great deal of knowledge and lessons learned involving the brainstorming process. After a semester of working as a team we discovered that brainstorming is needed to lead a strong and competitive design. Discussion techniques were often used when developing concepts for design and as a group we were capable in focusing our thoughts into one collective idea. The group had some issues getting along, mainly due to cultural differences and ideological discrepancies between group members. While we had problems working with each other at points, in the end the ultimate goal of getting the plane to fly united us.
The group has a few recommendations for future groups. The first would be to consult a local flight club very early in the design process. The lack of experience was the biggest setback for the group. Flight clubs have extensive experience and are usually more than willing to offer advice and share their knowledge. Some of the recommendations they gave were to utilize as large an aspect ratio as possible, to secure the wing so that very little vibration occurs, to be sure to balance the plane perfectly, to perfect the engine mount (slight variations dramatically affect performance), to lay the fuel tank horizontally to avoid head pressure issues, and to use proper axles for landing gear. Next, construct the plane very early; flight testing is very time consuming, and many adjustments will be necessary before liftoff can be achieved. Another recommendation would be to order materials very early, as many times there are delays involved with administrative issues, and backorder issues. Overall, the biggest advice is to manage time well, and to prepare very early. |
