How do you validate control systems in flight?

1 Simulation and testing

Before a control system can be flown, it has to be designed, developed, and tested on the ground. This involves using mathematical models, software tools, and hardware-in-the-loop simulations to emulate the flight dynamics, aerodynamics, and control inputs of the aircraft. These simulations allow the engineers to check the functionality, robustness, and performance of the control system under various scenarios and conditions. However, simulations cannot capture all the uncertainties, nonlinearities, and disturbances that may occur in real flight, so they have to be complemented by actual flight testing.

2 Flight test objectives

Flight testing is the ultimate validation of a control system, as it exposes it to the real physical and operational environment of the aircraft. The main objectives of flight testing are to verify that the control system meets the requirements and specifications, to identify and correct any errors or anomalies, and to evaluate and improve the handling qualities and performance of the aircraft. Flight testing also provides valuable data and feedback for refining the models and simulations used in the design process.

3 Flight test methods

Flight testing involves a series of carefully planned and executed maneuvers and experiments to assess the control system in regards to stability, response, sensitivity, bandwidth, gain, phase, margins, and frequency. Open-loop tests deactivate or bypass the control system, allowing the pilot or an external device to provide control inputs. This type of test is used to measure the natural characteristics and behavior of the aircraft. Closed-loop tests activate the control system with commands or disturbances from the pilot or an external device. This test measures the performance and robustness of the control system. Pilot-in-the-loop tests involve the pilot controlling the aircraft and evaluating its handling qualities, such as controllability, maneuverability, and comfort. These tests also assess the human-machine interface of cockpit displays, controls, and feedback.

4 Flight test challenges

Flight testing is an expensive and intricate activity that poses many technical and logistical challenges. Safety is of utmost importance, as it involves operating the aircraft in unproven or extreme conditions. Consequently, rigorous safety procedures, contingency plans, and emergency systems must be in place to prevent or mitigate any accidents or incidents. Additionally, flight testing requires a great deal of resources, such as time, money, personnel, equipment, and facilities. External factors such as weather, air traffic, and regulations may also limit or delay the availability and accessibility of the test conditions and locations. Finally, flight testing generates a large quantity of data that must be collected, transmitted, stored, processed, and analyzed. This necessitates sophisticated and reliable data acquisition, communication, and management systems, as well as specialized and experienced data analysts and engineers.

5 Future trends

Flight testing is constantly evolving and adapting to the advances and challenges of aerospace engineering, such as new technologies, designs, and applications. To keep up with the times, current and future trends in flight testing include virtual and augmented reality, autonomous and intelligent systems, as well as distributed and collaborative systems. Virtual and augmented reality create immersive simulations of the flight environment and aircraft systems to enhance training, testing, and evaluation. Autonomous and intelligent systems can perform some or all of the flight testing tasks without human intervention or supervision. Lastly, distributed and collaborative systems coordinate with multiple aircrafts, sensors, and platforms to increase efficiency, diversity, and scalability of flight testing operations.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?