Chapter 126: Testing Begins

Although always attentive to discussions with the Saudi side, Yang Hui now had to prepare immediately to begin the wind tunnel test. Model fabrication and theoretical analysis had already been completed rapidly, tasks that were routine for the seasoned veterans at Beihang University. Yang Hui stood to one side, observing the installation of the model.

For the new model’s installation, the back-support method was used—a term more vividly described as a back-hang configuration. Wind tunnel models could be installed in three primary ways: tail support, back support, or abdomen support. Any method was acceptable provided it met two essential conditions: the model must not extend beyond the test section’s working area, and the test section itself must remain within the core airflow.

Once the specialized tooling for the intended measurements was in place, testing could proceed. Each test project carried unique requirements in its finer details, necessitating purpose-built instruments to regulate the wind tunnel’s flow precisely. Wind tunnel testing was overseen by Yang Hui and Professor Zhu; in practice, however, professional operators handled the controls. The intricate manipulations demanded extensive expertise that ordinary aerodynamics researchers could not manage. During tests, instructions were relayed to shift to a specific flow interval, after which the control staff executed the adjustments.

“Everyone step back now. I’m about to start the wind tunnel. This one is no pushover.”

Irrelevant personnel withdrew to the safety zone. The wind tunnel activated with a powerful fan beginning to spin and accelerate steadily. Airflow velocity rose sharply until it reached its peak, after which the fan rotation stabilized and the turbulent flow came under control. At this juncture, observation could begin.

Precise airflow velocity was established, followed by introduction of particles suitable for visualizing the stream. Direct testing would render the flow patterns invisible. By incorporating specialized micro-uniform particles, the airflow behavior became observable. Actual data collection still required high-precision photography to capture the flow, which was later analyzed for the remaining test parameters.

In the 1980s, information technology was nascent. Wind tunnel testing had not yet merged with computing systems to streamline procedures, so substantial manual effort remained necessary. With the initial test data set complete, Professor Zhu nodded approvingly and signaled the adjacent measurement and control room staff to initiate the next phase.

Wind tunnel testing carried significant hazards, including both violent airflow and intense noise from the fans and rushing streams. While the facility was engineered for noise reduction, certain performance constraints left acoustic levels that could only be tolerated. On-site personnel therefore wore earplugs during actual runs. Prior coordination ensured that simple, effective hand gestures conveyed intentions clearly.

Understanding Professor Zhu’s directive, the operators inside resumed adjusting wind speed. The fan itself remained fixed; a dedicated wind-force adjustment mechanism handled fine-tuning. After a brief calculation, power was supplied to the stepper motor, which drove the throttle cone into position, achieving precise airflow control. Modifying airflow magnitude by directly altering fan speed proved nearly impossible, as the fan served as the primary generator of the tunnel’s massive airflow and could only be adjusted roughly.

As the throttle cone moved, airflow increased further. Once a reference point was reached, testing resumed. Wind tunnel experiments demanded meticulous, incremental progress; no margin existed for error or shortcuts. A single untested node might conceal a unique airflow phenomenon with profound implications for real flight, potentially triggering catastrophic failure on some future occasion.

Testing advanced step by step until the wind tunnel attained its maximum capability. Beyond that limit, more powerful facilities—such as a supersonic wind tunnel—would be required for continued trials.

Boundary layer testing followed the same rigorous incremental approach. Subsonic wind tunnels could not satisfy the demands, so other projects took precedence. Numerous untested items remained; the subsonic facility offered the greatest volume of tests, though these were also the most laborious.

According to the schedule, the intake duct trial came first. Following the boundary layer splitter plate, measurements addressed the duct’s lip geometry, cross-section, throat area, and variations in airflow through the converging section leading into the fuselage. Flow conditions during merger of the left and right intake streams within the body were also examined, among numerous other parameters. The extensive nature of these modifications underscored that alterations to the intake duct extended far beyond superficial changes.

Yang Hui continued his theoretical analysis alongside a group of graduate students. Although his formal education ended with a bachelor’s degree, subsequent studies at Beihang, combined with ongoing professional development and an opportunity for further postgraduate training, had equipped him well. These analytical tasks posed no challenge to him.

His group now performed preliminary analysis of the intake duct outlet—equivalent to the engine inlet—flow-rate testing. During the process, Yang Hui identified an inconsistency with the prevailing old aerodynamic test guidelines. In his view, the regulation seemed ill-suited to the case at hand.

The intake duct and engine constituted distinct units, requiring mutual agreement on a shared measurement interface. Both parties would rely on data derived from this common reference for calculations.

Examining the outdated test outline, Yang Hui pondered whether to raise these concerns. This represented the paramount issue: any beneficial modification would necessitate revisions to the test specifications, a substantial undertaking that redefined the standards all parties observed.

One change would ripple across too many areas, demanding considerable time and effort. For Yang Hui, such delays were intolerable. He decided to proceed provisionally with the existing guidelines. Although the older framework contained minor shortcomings, it remained usable.

Once the current project concluded, Yang Hui intended to compile and report to higher authorities any modifications from later implementations he had encountered, aiming for a comprehensive update. This approach was most effective, as compiling the full revised standards from later eras would require collaborative input from multiple experts rather than a single individual.

At the same time, he considered incorporating other design outlines, such as the engine specification guidelines.

Overthinking had clouded his focus, so he forced himself to set aside further reflection and adhere strictly to the old version. Gradually adapting to its provisions, he incorporated every refinement he could envision during analysis, striving for maximum completeness.

When the group’s results were compiled, disparities became evident. Insiders could immediately discern the relative value of each contribution.

Observing the aggregated data, Liu Jun—the individual most favored by Professor Zhu—studied Yang Hui’s analysis with evident surprise.

“Group Leader Yang, your analysis appears far more detailed than ours, especially the test precautions you noted strike me as particularly insightful.”

Liu Jun’s remark drew the attention of the others performing theoretical work. Pens were set aside as they gathered closely to examine the findings. It seemed the colleague from Base 0011 possessed notable expertise worth observing.

Yang Hui anticipated reactions to his results and offered no resistance to clarification.

“Oh? Where exactly do the differences lie? Please describe them, and I’ll explain.”