Plot Summary and Description for "Aerobatics Flight Data"

Aerobatic maneuvers of an instrumented R/C aircraft demonstrate stick inputs and dynamic response during agile flight. The R/C Flash 3D EPP aircraft is equipped with instrumentation to measure accelerations, angular rates, pitot-static pressure, GPS, and servo motion at 100Hz. The data is recorded to on-board flash memory and is animated and synchronized to the external video in post-processing. DataNinja is used to measure and record the analog signals generated by the IMU, NinjaSense.

Several representations of flight data are shown in the lower portion of the video.

Figure 1: Lateral and Vertical G-Load (Acceleration), Left plot

Lateral versus vertical accelerations (G-load) are presented in the left cross-plot (Figure 1) and show the combined loads on the aircraft during the maneuvers. The level flight case of 0G lateral and 1G vertical is indicated by a black cross. Positive lateral Gs express acceleration toward the right wing and positive vertical Gs are upward accelerations. The current acceleration is shown as a color-coded point on the plot, where the color indicates the magnitude of the total acceleration. Zero G is shown as a blue dot, whereas 3+Gs are shown as a red dot. Intermediate loadings are shown as green, yellow, and orange. A temporal trail is added to show a 1-second time history of the accelerations. The color saturation of the points on the trail decrease with time, such that the current time is fully saturated, and 1-second-old data is fully desaturated.
Figure 1 shows the acceleration transitioning from (+1.5G,+2G) through (0G,+2.8G) to (-1G,-1G). The line starts as faded red and becomes yellow then brighter green. The change in color is due to the decrease in acceleration, while the change in saturation is due to the decreased acceleration magnitude.

Figure 1: Roll, Pitch, and Yaw Angular Rates (Rotations), Center plot

Angular rates are shown versus time in the wide center scrolling plot (Figure 2), where the current time is approximated by the points on the center black dashed line. Roll, pitch, and yaw rates are shown as blue, green, and red lines, respectively. All data to the left of the black line are in the past and all data to the right are in the future. The plot is scaled to +/- 700 degrees per second, although the roll magnitude exceeds this in one instance. The angular rates in Figure 2 show the response of the aircraft in the second part of a three-sequence spin. Various control combinations are used to generate the disparate spin modes. The corresponding acceleration trail in Figure 1 is the result of the spin-mode transition between t=227 and t=228. The sign convention for the angular rate data is roll right positive, pitch up positive, and yaw right positive.

Figure 3: Aileron, Elevator, and Rudder Stick Positions, Right plot

A representation of the stick position is shown on the right plot from the measured servo positions. The standard R/C convention is used (Mode 2), where aileron and elevator share a stick and are actuated by horizontal and vertical motions, respectively. Rudder is shown on the lower stick and is actuated by horizontal motion.

Figure 4: Small Radius Loop

Figure 4 shows flight data during a small radius loop with the aircraft nearing the bottom of the loop after having completed a pitch rotation. The high pitch rate (green line in center plot) remains positive (+125 deg/s) indicating that the aircraft is, and has been, pitching up through the loop. The roll and yaw rates are mostly zero, which correspond to the stick positions (right plot) showing 30% back elevator stick with no aileron or rudder input. The accelerations (left plot) show a transition from +1G at the top of the loop while inverted, and +3G near the base of the loop while pulling against gravity.

Figure 5: Point Rolls

Figure 5 shows the second of four point rolls, where the aircraft is rolling from left knife edge to inverted. The blue roll rate pulses in the center plot correspond to the left aileron stick inputs shown in the right plot. A small amount of right rudder remains from the period between t=200s and t=201s, where the aircraft is in knife edge and requires top rudder to maintain level flight. The acceleration (left plot) transitions from (-1G,0G) toward (0G,-1G) of inverted flight. The large negative vertical acceleration is due to the forward elevator input in anticipation of inverted flight.

Figure 6: Inverted Spin

Figure 6 shows the aircraft stabilized in an inverted spin, with the control inputs fixed at the maximum left aileron, down elevator, and left rudder positions. Note from the lack of temporal trail that the acceleration is stabilized at (+1.5,-1G). The angular rates are stabilized at large negative roll and pitch rates and nearly zero yaw rate. Curiously, the yaw rate is very small despite the full authority rudder input.