NASA's LoFLYTE Program Flown
Flights Demonstrate Airworthiness of "Waverider" Shape
During the week of June 23, 1997, LoFLYTE made three
successful flights at Edwards Air Force Base under the direction of
445th Flight Test Squadron. In the next stage of the program, a
neural network flight control system will be installed and
The LoFLYTE (Low Observable Flight Test Experiment)
program is a joint NASA Langley Research Center/U.S. Air Force
Research Laboratory ground and flight test program that has
resulted in a demonstration aircraft. LoFLYTE passed an
important milestone in 1997 with a series of successful flights.
This was the first flight of a true waverider aircraft
configuration. The LoFLYTE prototype, a 100-inch-long
jet-powered remotely-piloted vehicle (RPV), has demonstrated the
subsonic airworthiness of the "waverider" shaped aircraft.
The LoFLYTE program is designed to provide a technology
testbed for many emerging aerospace technologies with initial
emphasis on neural network controls. The LoFLYTE jet
completed its first flight on December 16, 1996, at Mojave Airport
after completing design, airworthiness, and flight safety reviews
required by NASA and the U.S. Air Force. LoFLYTE is flown at
Edwards Air Force Base in California. Flight testing using neural
network controls will begin in late 1997. This small jet-powered
aircraft will demonstrate neural network control and sensing
technology. The LoFLYTE concept was first tested at NASA
Langley Research Center as a wind tunnel article with 191 runs in
both the 12-Foot Low Speed Tunnel and 30 x 60 foot wind tunnels.
The present LoFLYTE shape is the same size as the wind tunnel
article. In addition, the Naval Postgraduate School in Monterey,
California, did water tunnel flow visualization tests and tested a
72-inch-long drop model.
LoFlyte banks after take-off
Accurate Automation Corporation, of Chattanooga, Tennessee, was
selected as the contractor for LoFLYTE under the NASA and
U.S. Air Force Small Business Innovation Research (SBIR) Programs.
The LoFLYTE RPV will eventually become an unmanned autonomous
vehicle (UAV). The shape of LoFLYTE is based upon a high
lift/drag Mach 5 configuration. The actual shape takes advantage of
engine/body integration and was derived from a Mach 5 conical
flowfield. The LoFLYTE vehicle demonstrates clearly how rapid
prototyping can build flight-quality hardware inexpensively. It
also features onboard subsystems, including an advanced real-time
airborne data acquisition and control system with 16 channels of
analog sensor input as well as 14 channels of control telemetry,
GPS for position, retractable landing gear, video and spread
spectrum communications to the ground.
The LoFLYTE Mobile Ground Control Station provides the
test team with all of the facilities needed to conduct flight
including all aircraft maintenance and safety equipment,
for telemetry and data recording, and a weather station.
LoFLYTE will eventually fly the Accurate Automation Neural
Network Processor and Neural Air Data Subsystem. This 72 pound
aircraft is powered by a 38 pound thrust jet engine built by SWB
Turbines. An advanced engine controller will be tested for future
use with this miniature JP-8 fueled engine.
Some of the technologies that will be tested with the
LoFLYTE aircraft include:
- Rapid Aircraft Prototyping and Design Concepts
- Aircraft Instrumentation
- Fault Diagnosis and IsolationTechniques
- Real-time Airborne Data Acquisition, Control System and
- Miniature Spread Spectrum Telemetry
- Antenna Placement
- EMI Minimization
- Neural Network Flight Controls
- Interface for the Neurocontrol With Flight and Propulsion
- Neural Air Data Subsystem for Determining Angle of Attack,
Sideslip, and Velocity
- Advanced Nozzle Concepts
- Various TitaniumAlloy Parts With Subsequent Non-destructive
- Adaptive Compensation for "Pilot-induced Oscillations"
- Trajectory Control
- Advanced Landing Concepts
Neural Network Flight Controls
The LoFLYTE Neural Network Flight Control System is an
important advance in aerospace technology because of the adaptive
nature of the control system. The controller is designed to learn
as it flies, so the control system, not the pilot, determines the
most effective commands to give the plane for a particular
During normal flight, the neural controller will use the data it
receives from the telemetry system to compute the most efficient
flight characteristics and adjust the control surfaces accordingly.
However, where the neural control system has an enormous advantage
over traditional control systems is during abnormal and unexpected
flight conditions. For example, if the control system determines
that the rudder is not responding, it will adjust quickly to
control the aircraft using the remaining flight surfaces. Neural
network control is necessary in hypersonic vehicles where the
center of gravity of the vehicle can change significantly
throughout the flight. The neural network can adjust to changing
flight conditions faster than a human pilot, greatly enhancing the
safety of the aircraft.
Accurate Automation's Neural Network Processor.
The neural network control system, designed and manufactured by
Accurate Automation Corporation, is based on the companyճ
successful Neural Network Processor (NNP®), also funded under
the SBIR program. The NNP® is a multiple instruction/multiple
data (MIMD) system that can be used in personal computers as well
LoFLYTE flying over the pilot's position on the flight of
June 23, 1997.
The LoFLYTE fiber-optic "Fly-by-Light" communications
offer lighter weight, increased transmission capability and safety
from electrical system short circuits and EMI problems.
The LoFLYTE telemetry captures the data from the
instrumentation in real-time and displays it for operational
decisions during flight and transmission to remote sites.
Future Versions of LoFLYTE
Once testing of the 100-inch version of LoFLYTE is
concluded, a larger transonic version may be developed to explore
supersonic flight characteristics of the waverider shape. This
larger version will include a unique hypersonic flowpath
configuration. Other hypersonic aerodynamic shapes will be tested
using the LoFLYTE subsystems.
An advanced engine controller is being developed for ramjets
under NASA Lewis Research Center's SBIR program. This controller
will be tested on the LoFLYTE vehicle with the current
An advanced autolanding system is being developed for NASA Ames
Research Center, under SBIR, that may be tested with
Small Business Innovation Research
The objective of NASA's Small Business Innovation Research
Program is to stimulate technological innovation in the United
States by using small business, including minority and
disadvantaged firms, to help meet Federal research and development
This is the 15th year of the NASA SBIR program, which allocates
2.5 percent of NASA's research and development budget to support
NASA Langley Research Center, the U.S. Air Force and
LoFLYTE were awarded the Small Business Administration's
National Tibbetts Award in 1996.
One of 191 wind tunnel tests conducted at NASA Langley Research
Center to test the airworthiness of the LoFLYTE waverider
Glossary of Terms
conical flowfield. The cone-shaped shockwave generated by
a supersonic or hypersonic vehicle.
hypersonic. Operation at Mach numbers exceeding 4.
neural network. A class of computational methods that
loosely imitate the function of the brain. Among the benefits of
neural networks are that they learn from experience, can generalize
from their data set, are fault tolerant, and can exploit parallel
systems for rapid processing.
pilot-induced oscillations. A condition of aircraft
uncontrollability caused when pilot's intent and the control system
get out of sequence, forcing the plane to swing back and forth,
often with disastrous results.
supersonic. Operation between Mach 1 and Mach 4.
waverider. A type of supersonic or hypersonic aircraft
where the vehicle takes advantage of the shockwave flowfield,
instead of cutting through it, increasing lift and reducing
For more information contact:
Accurate Automation Corporation
7001 Shallowford Road
Chattanooga, TN 37421
NASA Langley Research Center
Office of Public Affairs
Mail Stop 115
Hampton, VA 23681