This paper will revisit an area of Short Take-Off and Landing (STOL) operations and powered-lift aircraft design that has been limited in scope, and at best, very specialized when it comes to research, aircraft built, and experimentation: The Upper Surface Blowing (or USB) aircraft configuration.
Five aircraft have been flown successfully using the Upper Surface Blowing powered-lift concept: The Boeing YC-14, the Ball-Bartoe Jetwing, the Antonov An-72, the NASA QSRA experimental aircraft, and the National Aerospace Laboratory (NAL) Aska or Quiet STOL Research aircraft. Only the Antonov An-72 (and its commercial follow-on, the An-74) reached any significant degree of production. This fact illustrates the uniqueness of the USB technology as applied to powered-lift.
A background of the technology will be given, what connects them as far as the USB configuration, discuss the main lessons learned, and briefly dwell on other configurations that are close relatives of aircraft using the USB as a source of powered-lift. An extensive review of the existing literature has been fundamental for the development of this paper since many years have passed since the last USB configured aircraft design has flown (the last new USB design to take to the air did so in 1985).
Although all the unclassified USB projects that have been constructed and flown will be mentioned in this paper (production and experimental), the main thrust of the paper will be the Boeing YC-14 prototypes and the Ball-Bartoe Jetwing. With respect to NASA’s QSRA demonstrator, the Antonov An-72 series, and the NAL Aska demonstrator, references will be listed for those readers wishing to review the technology and advances made by those aircraft. Their detailed review is beyond the scope of this paper; but the contributions of these aircraft to the state-of-the-art of USB powered-lift configuration is well established.