Experiences and results so far and modifications made to date:
- Ground systems tests (load tests, engine adjustments, thrust measurements, pitot-static system check, avionics and navigation equipment check, fuel system check, rigging and levelling, weight and centre of gravity measurements, canopy emergency release check etc.) as well as all low and high speed taxi tests and low level flight tests were performed and completed. Based on these experiences a slight modification was made on the tail landing gear which has increased the strength of the construction, and improved the landing characteristics of the aircraft.
- The aircraft’s taxiing capabilities and braking efficiency are excellent even in case of a higher outside air temperature (T > 35 °C), view from the cockpit is appropriate and the airplane has an outstanding ground manoeuvring capability.
- During the test flights we checked the aircraft’s general handling characteristics, stability-control, and basic performance capabilities. It is reassuring that no major modifications are needed on the airplane.
- We have completed the calibration of the pitot-static system, which made it clear that it was worth modifying the design of the pitot tube, but the positions of the static ports on the fuselage were appropriate.
- We experienced excessive stick forces on the ailerons, but we managed to compensate this by adding aerodynamic spades under the wings. After this modification it turned out that the aircraft’s roll rate is excellent.
- Initial stall tests were also carried out showing good results. It has proved the preliminary design calculations to be right. The aircraft’s behaviour at stall speed – 57 kts IAS – meets the CS-23 requirements (stall speed must be below 61 kts), air flow separation on the wings starts at the points as expected and pre-calculated, and the ailerons are effective up to stall. So far we have not encountered any unexpected bad characteristics of the aircraft.
- The seat is comfortable due to the wide seat adjustment possibilities and the ergonomic design of the cabin has also proven to be appropriate.
- We have modified the canopy lock for the sake of safer operation.
- The electrical system is complete, there is no need for any further modification, it operates well and is trouble proof. Several additional electrical subsystems (such as position lights or navigation lights) will be developed which can be optional equipment.
- We have been working a lot on the engine cooling system, but we have finally found the proper configuration and built the final version.
- The throttle lever wasn’t comfortable so it had to be redesigned. Now it serves the proper operating range and ergonomy.
- We have also made the necessary modifications of the ventilation system to make it more efficient.
- We performed a crash test on the horizontal stabilizer and used the data acquired to reduce the weight of the components. Significant weight reduction has been achieved by producing a new horizontal stabilizer, elevator, vertical stabilizer and rudder.
Flight safety rules and the principle of step-by-step testing will be followed with maximal care due to the high load values. An important element in the next phases of flight tests will be the use of strain gauge system attached to the aircraft’s structure. Having evaluated the results of FEM finite element software, real stress values will be determined on each component. Precise strains will be measured at 12 points: 8 points on the frame, 1 point on the engine mount and 3 points on the composite structural parts.
Depending on weather conditions, tests flights continue with the aerobatic phase.