NASA - National Aeronautics and Space Administration

Project Summary

A Gulfstream III business jet has been modified and instrumented at NASA's Dryden Flight Research Center to serve as a multi-role cooperative research platform for a variety of flight research experiments. The twin-turbofan aircraft provides long-term capability for efficient testing of subsonic flight experiments for NASA, the U.S. Air Force, other government agencies, academia, and private industry. NASA obtained the aircraft, which carried the military designation of C-20A, from the U.S. Air Force in 2003.


Image right: Gulfstream III in flight over the NASA Dryden Flight Research Center on April 8, 2003. (NASA photo)

NASA Dryden's Gulfstream III, informally known as the G-III, is equipped with a self-contained onboard Data Collection and Processing System, or DCAPS. This embedded instrumentation system allows for automated configuration setups to reduce required engineering support for each mission. It includes primary and backup systems to assure mission reliability, with the backup system available for use concurrently as a parallel system when needed. The DCAPS is designed to allow easy upgrades and addition of add-on systems for expansion, and to operate in both autonomous and manual modes.

The custom DCAPS was developed to enable processing, distribution, display and archiving of aircraft flight data and customers’ experimental data in real time. In addition, it features a video collection and distribution system, cabin Ethernet capability, a satellite phone, and an upgraded 120-amp AC electrical power system. Satellite communication capabilities include a Global Positioning System, Iridium, Inmarsat and a Tracking and Data Relay Satellite System.

Representative Projects and Experiments

The Gulfstream III advanced instrumentation capabilities have been used in several experiments, among them:

UAVSAR

The Unmanned Air Vehicle Synthetic Aperture Radar project, or UAVSAR, is an Earth Science Capabilities Demonstration project jointly supported by the Jet Propulsion Laboratory and NASA Dryden in which a synthetic aperture radar is flown on the G-III in an underbelly pod. The pod is designed to be interoperable with unmanned aircraft in the future. The G-III provides a platform not only for test and evaluation of the new radar, but it also can be used to gather scientific data for geological studies on earthquake prediction, ice studies supporting climate change, and biological studies supporting ecology and carbon cycle science. In order to support installation of the UAVSAR pod, the G-III airframe was structurally modified to accommodate addition of an MAU-12 ejector rack beneath the fuselage. This unique modification, which has electrical and data connectivity with the aircraft cabin, can accommodate several different external pods for carrying instruments.

Access 5

Acting as an intruder aircraft, the G-III flew an experiment for the Access 5 program in September 2005 with Scaled Composites' Proteus aircraft. The Proteus, which served as a surrogate unmanned air vehicle, was flown remotely by a ground-station pilot. The G-III carried collision-avoidance systems and flew a flight-test matrix to analyze sense-and-avoid displays and UAV pilot reaction times.

Aircraft Description

The Gulfstream III was built by Gulfstream Aerospace Corp. In commercial versions, the G-III’s basic role is that of an executive business aircraft capable of carrying up to 12 passengers. The C-20B version currently flown by the Air Force serves in a similar capacity for high-level government and military officials.


Image right: Gulfstream III on NASA Dryden Ramp on October 3, 2002. (NASA photo)

The G-III's maximum takeoff weight with full fuel and passengers/cargo is 69,700 lbs. Empty, the unmodified airplane weighs about 38,000 lbs. It has a wingspan of more than 77 feet, is about 83 feet long and just over 24 feet high. Average cruising speed for the aircraft is 495 mph (430 knots) and its top speed is 581 mph (505 knots/Mach 0.85) at 28,000 feet. Maximum operating altitude is 45,000 feet. Fully loaded, the Gulfstream III has a range of about 4,000 nautical miles (4,600 statute miles).

The aircraft features a precision autopilot designed by NASA Dryden engineers. The Platform Precision Autopilot guides the aircraft using both a kinematic differential Global Positioning System, developed by the JPL, and the aircraft's inertial navigation system to replicate a flight path within an accuracy of 15 feet. With the precision autopilot engaged, the synthetic aperture radar is capable of acquiring repeat-pass data that can measure changes within millimeters.

Two Rolls-Royce Spey Mark 511-8 turbofan engines power the aircraft. Each engine produces 11,400 pounds (5,170 kg) of thrust.