Complex sentence: Careful shaping of the extensions is required when designing or else detrimental effects will occur, such as in early prototypes of the Su-27 it was discovered that the prototype would freeze at AOAs above 5 Degrees.
Split into simpler sentences: Careful shaping of the extensions is required when designing or else detrimental effects will occur, such as in early prototypes of the Su-27. It was discovered that the prototype would freeze at AOAs above 5 Degrees.