2008 Annual Report - NASA Airborne Science Program
2008 Annual Report - NASA Airborne Science Program
2008 Annual Report - NASA Airborne Science Program
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Figure 35<br />
Flight Envelope with contours encompassing<br />
90% of flight time at each flight condition<br />
<strong>NASA</strong> Dryden built a GIII engineering simulation<br />
for development and evaluation of the PPA. A<br />
Monte Carlo capability was also developed in<br />
parallel with the GIII simulation to examine the<br />
PPA performance in the presence of vehicle<br />
and atmospheric uncertainties. In early 2007,<br />
flight testing of the PPA began. Cycle 1 flights<br />
were designed to evaluate modeling of the GIII<br />
and associated systems including the navigation<br />
receiver, Flight Director, and factory GIII autopilot.<br />
Cycle 2 flights were designed to map out<br />
the flight envelope and determine the flight<br />
conditions where the requirements are met.<br />
Results<br />
The five meter radius tube requirement was<br />
met for the majority of flight conditions. Figure<br />
35 shows results from the Cycle 2 evaluation<br />
flights. The circles at each flight condition<br />
represent the five meter radius tube. Generally,<br />
there was adequate performance to keep<br />
the GIII inside (or within a meter) of the tube<br />
boundary over 90% of the time for each flight<br />
segment. It was also observed as a rule that<br />
tighter control, as reflected in more time spent<br />
closer to the tube center, was seen at higher<br />
Mach numbers.<br />
The Euler rates were all within the desired<br />
range during each flight segment for more<br />
than 90% of the time at each flight condition.<br />
Figure 36 shows the rates for representative<br />
altitudes ranges, low (25k to 31k ft.), mid<br />
(33k to 39k ft), and high (41k to 45k ft.), as<br />
a function of Mach number. As a general,<br />
rule roll rate was lower at higher dynamic<br />
pressures.<br />
Status<br />
The PPA completed flight testing in January<br />
<strong>2008</strong>. The precision autopilot demonstrated<br />
the capability to provide a stable platform<br />
that can repeatedly fly a predefined<br />
trajectory within the tolerances prescribed<br />
(five meter radius tube) over a 200 kilometer<br />
track. It is currently operating on the<br />
<strong>NASA</strong> GIII in UAVSAR flights throughout<br />
California. Future plans for the PPA involve<br />
deployment over Greenland to aid in ice<br />
sheet measurements and integration into<br />
the Stratospheric Observatory for Infrared<br />
Astronomy (SOFIA) program.<br />
Figure 36<br />
Ninety percentile Euler Rates vs. Mach for low<br />
(25k to 31k ft), mid (33k to 39k ft), and high<br />
(41k to 45k ft) altitude ranges.<br />
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