A series of important evaluations are completed.
Work to evaluate the aerodynamic characteristics and the cavity acoustic environment of the SOFIA (Stratospheric Observatory for Infrared Astronomy) airplane has been completed. The airplane has been evaluated in its closed-door configuration, as well as several open-door configurations (see figure). Work performed included: acoustic analysis tool development, cavity acoustic evaluation, stability and control parameter estimation, air data calibration, and external flow evaluation.
747SP SOFIA Airplane undergoing tests in an open-door configuration." class="caption" align="right">Cavity acoustics were evaluated
using measured pressure
data. Of primary interest were
sound pressure levels and
frequency response curves.
Analysis tools were primarily
written for MATLAB. Several
tools were developed to allow
rapid analysis of acoustic data,
giving engineers the ability to
calculate and examine results
from acoustic sensors in and
around the telescope cavity. A
batch analysis capability was
created so that analysts could
process data from an entire
flight with one command.
Significant effort was put into completing the evaluation of the aerodynamic characteristics of the modified 747SP airplane in closed-door and open-door configurations. Parameter identification maneuvers were designed and then performed during closed and open door flight tests. Parameter estimation data analysis techniques were used in conjunction with existing aerodynamic models to create aerodynamic models for various airplane configurations. Any differences between configurations were examined.
Air data calibration maneuvers were also flown and calibrations were developed for the various air data systems, including the airplane pitot static system and a Flush Air Data Sensing (FADS) system. Results were compared for different door configurations, to determine if door position affected air data measurements.
Qualitative airflow data were obtained during the closed- and open-door flights using tufts on the aft portion of the fuselage. Video was taken from a chase plane. This video was analyzed for various flight conditions, and general flow descriptions of the aft fuselage of the 747SP were developed for the different closed and open door configurations.