Test Flights of Your Model Plane Design
Lessons learned from the maiden flight of a new model aircraft design
One thing is certain when you design an RC model airplane. You will have to at some point take your new pride and joy up for a first test flight. Following are some discussion points and lessons learned from the Robin’s first flights.
As you advance the throttle forward of your latest model airplane you will quickly need to anticipate how the model flies.
Proven plane design
With a proven model airplane design you can be assured that the aircraft will perform as advertised. The aircraft’s weight, control set up and alignment has been verified by the original designer. You are more relaxed for this first test flight in that you know the aircraft will likely fly without too many surprises.
When the airplane is your own original design the test flight will be the first time the machine has ever left the ground. You can plan ahead with research on power, motor down thrust, and wing areas for optimum flight, as I did with the Fokker Spider.
No one knows for sure how an original model airplane design will behave on that opening takeoff. One method to address this concern is to ask a more experienced pilot to conduct the initial sortie of a new model airplane design. You can see some of these first flights at the E-Fest show.
You should follow a series of steps for any test flight. First, certify you have designed and built the model with adequate structural strength in the proper areas. Check that the wing center section is properly braced, the motor is securely mounted in the nose and control surfaces are hinged correctly.
Confirm the controls are not binding and they move in the proper direction. I cannot tell you how many RC models I have seen crash on their initial flight due to ailerons rigged backwards. Finally, ensure your model plane design balances at the correct center of gravity.
Test flight success
I am happy to report that the Robin’s test flights went exceptionally well. I had flown the Ultra Micro 4-Site biplane for a while and acquired a good understanding of the tiny geared electric motor’s power. The final weight of the Robin came out at two ounces.
With the generous wing area and control surface throw, I felt that the Robin’s power needs and controllability would not be a problem. If anything, I was more concerned with too much control authority from the large surface area of the ailerons, rudder and elevator. Double check for the correct center of gravity location.
For a new design, I first fly a few straight ahead hops to see if anything really strange has been built into the model plane design. These short test flights went without incident.
I verified that the Robin’s controls were about right for range of throw and that the engine had plenty of power. Do keep in mind that the Robin does not have a landing gear. When you touch down at the end of a flight, check the throttle is in the full off position and the propeller is stationary. This prevents stripping the motor gears.
The next event for the Robin’s test flights was at our local indoor flying facility. I had an assistant do the hand launch.
The Robin flew just fine. First order of business was a turn to avoid the rapidly approaching field house wall. I was concerned over the need to coordinate rudder and aileron for this first maneuver, but the Robin changed heading readily with just an aileron input. I was also pleasantly surprised with the Robin’s stability during all turns due to the generous surface of the profile fuselage.
Down and side thrust
The Robin’s down thrust combined with no side thrust for the motor seemed just about right. The zero-zero incidence arrangement for the wing and stabilizer felt very comfortable as well. I will incorporate these settings into the final version of the Robin’s construction plans.
In summary, the test flights of the Robin went exceptionally well. The plane was easy to handle and I was very relaxed flying in our indoor area. The engine mount was secure, and the Robin responded well to a variety of throttle inputs with no trim change required.
I did see the need to add some additional strengthening in the lower fuselage to assist with skid landings. As I discussed before, I will lengthen the nose a bit on the final version of the Robin to assist with the center of gravity balance. But overall, the Robin’s test flight produced zero surprises, and should make for an appealing and fun to fly RC model aircraft design.
Author: Gordon McKay