Boeing XB-29 Superfortress serial 41-002 – first prototype
Transforming Flight Testing at Boeing: From Individual Expertise to Systematized Processes
In the late 1930s, Boeing’s flight test programs underwent a significant transformation, transitioning from a reliance on the individual skills of experienced test pilots to a more structured and systematized approach. This shift was driven by several factors, including the increasing complexity of aircraft designs, the growing demands of military contracts, and a series of tragic accidents that highlighted the need for more rigorous testing procedures.
Eddie Allen’s Impact: A New Era of Flight Testing
A pivotal figure in this transformation was Edmund T. “Eddie” Allen, a renowned test pilot who joined Boeing in April 1939. Allen’s arrival coincided with a period of financial instability for Boeing, as well as production delays and the tragic crash of the Model B-307 Stratoliner, which killed Boeing Chief Test Pilot Julius Barr.
Allen’s expertise and vision played a crucial role in revitalizing Boeing’s flight test programs. He recognized the need for a more scientific and analytical approach to testing, emphasizing:
- Data-Driven Analysis: Allen advocated for the use of meticulous data collection and analysis to understand aircraft behavior and identify potential issues. He championed the use of wind tunnel testing, flight research, and the development of detailed performance predictions to reduce technical risks and improve the accuracy of design projections.
- Systematic Flight Test Procedures: Allen established a more organized and structured approach to flight testing, outlining specific procedures and maneuvers to assess various aspects of aircraft performance and handling characteristics.
- Specialized Flight Test Teams: He recognized the need for dedicated teams with diverse skill sets to conduct thorough and comprehensive flight tests. This included expanding the flight test pilot team and recruiting co-pilots and flight engineers to support the program.
The B-29 Superfortress: Driving the Evolution of Flight Testing
The development of the B-29 Superfortress, a technologically advanced and complex aircraft, further propelled the evolution of Boeing’s flight test programs. The B-29’s unprecedented size, sophisticated systems, and demanding performance requirements necessitated an even greater emphasis on rigorous testing:
- Intensive Pre-Flight Testing: The B-29 program involved extensive pre-flight testing, including the use of wind tunnel models, scale model flight tests using a modified Fairchild PT-19A trainer, and specially configured B-17s to evaluate various components and systems. These pre-flight tests aimed to identify and mitigate potential issues before the first flight of the XB-29 prototype.
- The “Flying Guinea Pig” Approach: Boeing’s use of a Fairchild PT-19A trainer, modified with scaled-down B-29 wing and tail surfaces, as a “flying test-bed” exemplifies the commitment to gathering real-world flight data to inform the B-29’s design and development. This approach, which continued with the use of specially modified B-17s, allowed for the evaluation of aerodynamic characteristics and the testing of critical components in a controlled environment before incorporating them into the B-29.
- Managing Design Changes and Production Pressure: The B-29 program faced immense pressure to meet ambitious production goals set by the US Army Air Corps. This pressure often led to design changes being implemented concurrently with production, necessitating ongoing flight testing to assess the impact of these modifications on aircraft performance and safety. The use of a “production block system” helped to manage these changes by ensuring that all aircraft within a specific block were built to the same specifications, enabling more focused and efficient testing.
A Shift Towards Standardization
By the late 1930s, Boeing had moved away from relying solely on the intuition and experience of individual test pilots. Instead, flight testing became a more standardized and collaborative process, involving:
- Structured Procedures and Checklists: The development of standardized procedures and checklists helped to ensure that all aspects of aircraft performance and handling were thoroughly evaluated. This approach reduced the reliance on individual memory and judgment, promoting consistency and accuracy in data collection.
- Multiple Flight Test Groups: Boeing established separate flight test groups with distinct responsibilities, including production flight testing, customer flight acceptance, and engineering flight testing. This specialization allowed for focused expertise in each area, further contributing to the rigor and comprehensiveness of the testing process.
Tragedy and the Continued Evolution of Flight Testing
The tragic crash of the second XB-29 prototype in February 1943, which killed Eddie Allen and his crew, served as a stark reminder of the inherent risks associated with flight testing. This accident, attributed to an engine fire and structural failure, led to further scrutiny of the B-29’s design and a renewed emphasis on safety and reliability testing:
- Enhanced Engine Testing: The investigation into Allen’s crash revealed issues with the Wright R-3350 engines, leading to a more intensive focus on engine testing and development to improve reliability and address the persistent problems of overheating, oil leaks, and fires.
- Refinement of Test Procedures: The accident prompted a reevaluation of flight test procedures, further emphasizing the importance of meticulous pre-flight inspections, comprehensive emergency procedures, and thorough data analysis to identify potential hazards early in the testing process.
Conclusion: A Legacy of Rigor and Innovation
The changes in Boeing’s flight test programs in the late 1930s laid the foundation for the rigorous and innovative testing practices that would characterize the company’s approach to aircraft development in the decades to come. The emphasis on data-driven analysis, standardized procedures, specialized teams, and a commitment to continuous improvement transformed flight testing from a largely intuitive art into a more scientific and disciplined process, ultimately contributing to the development of safer, more reliable, and higher-performing aircraft.