Pilots familiar with stalls on transport-sized aircraft say an extended flight envelope Bihrle Applied Sciences has developed for the Boeing 737-800 closely mirrors performance during a deep stall, marking progress in the FAA’s mandate to develop methods to improve stall training for pilots.

The agency plans to test the model independently this summer in advance of proposing new rules for enhanced simulators and training. Congress, as part of the 2010 Airline Safety Act, called on the FAA to begin providing ground and flight or simulator training to teach pilots to recover from stalls and upsets, a training deficiency noted in the 2009 Colgan Air Bombardier Q400 loss-of-control crash near Buffalo, N.Y.

Simulators typically use extrapolated data outside of normal operating regimes, including in the stall and post-stall regimes, leading to aircraft responses that are benign and unrealistic.

For that reason, simulators can only be used to train pilots how to recover the aircraft before a stall occurs. Accidents like Colgan’s, however, have revealed that pilots may not know how to recover an aircraft in the post-stall regime.

Jack Ralston, president of Bihrle Applied Research, says 737 pilots flying the company’s extended envelope in a Sim Industries-built 737-800 full-flight simulator in Miami say the model is representative of real life. The simulator can be switched between extrapolated data and the extended data to highlight the differences.

Birhle last year won a contract from the FAA to create a “representative” simulation model for a large transport aircraft to be used for stall training, but one that would not require flight test data in the stall and post-stall regime.

That information can be too costly to obtain from airframers, assuming that it exists and they would be willing to provide it.

The FAA contract took advantage of an effort Bihrle had already started with the U.S. Navy to create extended models for the P-8A, a highly modified version of the 737-800.

Bihrle created the stall and post-stall non-linear database using the aircraft’s 3D geometry, airfoil information and internal programs created during its 40-year history of collecting stall and wind tunnel test data, says Ralston.