“ZOOMIE SPIN” Sailplane Spin Recovery And Crosswind Testing

Captain Jeff DeJoannis, Flight Test Engineer, GPS Joint Program Office, Los Angeles AFB, USA
Major Landon Henderson, C-17 Test Pilot, Edwards AFB, USA

Abstract

In 2000, the United States Air Force Academy (USAFA) selected several new gliders to replace those in its aging fleet for cadet training. Prior to acceptance, a six-person multi-discipline ‘ZOOMIE SPIN’ team of USAF Test Pilot School students assembled three Czech-built Letecké Závody sailplane types at the Air Force Flight Test Center (AFFTC) in California. The team compared the spin recovery characteristics for flight manual procedures against the single traditional USAFA procedure, and also evaluated takeoffs and landings in elevated crosswinds.

The first objective was to determine if the single USAFA recovery procedure worked for all the glider types, thus simplifying training and increasing safety. The second objective was to expand the flight manual crosswind limits. Over 30,000 USAFA glider flights occur annually, but up to 40 percent of training days are lost due to high winds prevalent near the Rocky Mountains.

Spin recovery comparison was both quantitative and qualitative. The team designed flight instrumentation and a unique human factors rating scale to measure performance. Considering the USAFA population, a wide range of pilot experience, glider weight and center of gravity had to be addressed. However, safety concerns posed challenges to testing the complete envelopes. Results indicated that the USAFA recovery method was better than or equal to the flight manuals. An unexpected result was the discovery that the flight manual procedure did not recover one of the gliders in certain situations.

For crosswind investigation, the team developed quantitative performance criteria and also applied the Cooper-Harper rating scale. Safety was a critical factor for crosswind envelope expansion, and drove the creation of a dual-path buildup approach. The team set up a unique, mobile test operation that allowed for the desired wind conditions while providing safety measures in case of excessive wind. Results demonstrated greater crosswind capability than allowed in the flight manuals. A crosswind test mishap altered the project’s course midway through.

ZOOMIE SPIN results are of interest to the sailplane and wider aviation/test community. Issues raised included the scope of manufacturer testing for commercial air vehicles, adequacy for military application, and interactions between foreign flight communities. Teamwork overcame severe schedule, cost, and environmental limitations via a thorough planning process, clear success criteria, and innovative test techniques and operations. The importance of flight test safety was highlighted via reporting of universally applicable lessons learned.