1. Presented at the American Helicopter Society International Technical Specialists Meeting on Unmanned Rotorcraft Systems,
Scottsdale, Arizona, January 20 – 22, 2009. Copyright © 2009 by the American Helicopter Society, Inc. All rights reserved.
Unmanned Little Bird Testing Approach
Mark Hardesty1
, David Guthrie2
, Dino Cerchie3
Abstract
The Unmanned Little Bird (ULB) program was initiated in the Fall of 2003. Program
discriminators are its flight-test friendly design as well as the unique approach for developing
VTOL UAVs. First flight occurred on September 8th
, 2004, with a fully autonomous multiple
waypoint demonstration flight from takeoff through landing achieved six weeks later.
The ULB team succeeded in creating a powerful UAV technology development and
demonstration aircraft, assisting in the rapid development and understanding of the operational
concepts and requirements. The platform’s autonomous characteristics continue to be
expanded through low risk testing in support of UAV subsystems development.
The Unmanned Little Bird’s design size and proven performance make it highly competitive in
the evolving multi-mission VTOL UAV market. The design approach and integrated test
capability that the ULB provides supports rapid development and cost avoidance in the growing
VTOL UAV market. As with the fixed-wing UAVs that vary from hand-helds to over 100-foot
wing spans, it is envisioned that there will be more than one VTOL UAV design world-wide once
a design is demonstrated in the field highlighting the benefits provided by VTOL aircraft.
Introduction
The Unmanned Little Bird (ULB) program
represents a true paradigm shift in the high-
risk development of larger VTOL UAV
systems. While the norm has been to
develop UAV understanding on lower cost
scale models, or even step directly to the
full size aircraft and the risk associated with
that approach, the ULB team decided to
create a full size UAV aircraft without
incurring the risk associated with traditional
UAV development programs.
___________________
1
Flight Test Director, Unmanned Little Bird Program, The Boeing Company, Mesa
2
Project Test Pilot, Unmanned Little Bird Program, The Boeing Company, Mesa
3
Program Manager, Unmanned Little Bird Program, The Boeing Company, Mesa

2. 2
This approach has created the “optionally
manned” UAV test aircraft. The design
allows a program to safely develop the sub-
systems that will lead to its initial fielding,
but also support the continuing development
that all aircraft experience once they are
found useful.
The figure below explains the ULB design
concept.
Figure 1. ULB Design Concept
A new UAV program, when developed from
the concept stage, requires investing a
significant part of the development cost into
the platform. In reality, autonomous payload
placement is the objective unless unique
attributes of the platform itself contribute
significantly to the mission objective. Also,
once the baseline platform is complete the
aircraft still needs to qualify all of the
capabilities that the customer requires.
A significant cost saving has been realized
in the ULB program design approach. The
platform is complete with an unmodified
external shell, providing internal mounting
volume for the many capabilities already
designed and qualified for the aircraft.
The key attributes of the ULB program are:
 leverage existing technology
 treat the UAV as a mission capable
aircraft and provide mission planning as
the basis of operations
 reduce the ground station workload
 make the ground station compact and
mobile
 make the platform autonomous so that
the aircraft takes care of itself and the
GCS operator can concentrate on the
payload products.
Boeing Mesa has excelled in rotorcraft
development over the years. The ULB
program was the integration of several
helicopter specific internally-funded
programs in the area of control laws,
avionics architecture, and human-machine
interface. This allowed the program in 2004
to go from initiation to a flying prototype in 9
months, to fully expand its envelope to
18,000 feet in 4 months after first flight, and
to accumulate more flight hours that any
other VTOL UAV platform with payload
capabilities greater than 100 pounds.
The ULB program name covers two aircraft
designs, the unmanned version of the 3100-
pound commercial MD 530FF helicopter
that first flew in the autonomous mode in
2004, and its more capable unmanned
variant; the A/MH-6M manned aircraft, more
commonly known as the MELB, Mission
Enhancement Little Bird, that first flew in the
autonomous mode in 2006.
Figure 2. ULB program test assets
Boeing currently has one ULB aircraft
(N7032C) and two UMELB aircraft (N106HX
& N206HX). All three aircraft are designed
to be “optionally manned” aircraft. This
design feature allows these aircraft to be
flown as single or dual pilot in the
contiguous US in day and night VFR
conditions. They are licensed by the FAA as
Airframe UAV Payload Qual
New UAV Program Cost
UAV
Leverage existing
airframe Leverage existing
payloads

3. 3
experimental aircraft for the purpose of
“Research & Development/Market Survey”.
All three aircraft can also be operated as
UAVs, controlled from a ground control
station, with or without a pilot aboard. When
flown as a UAV without a pilot, the aircraft
must comply with the standard UAV rules of
flight within FAA designated airspace or
within restricted airspace.
The ULB aircraft has logged 576 hours of
flight testing since September 2004. The
UMELB design has logged 219 hours of
testing since its first flight in December
2006.
Fixed Wing UAVs Success Relative to
Rotorcraft UAVs
The tremendous contributions that fixed
wing UAVs of all sizes have made over the
last several years in both civil and combat
environments are well documented. The
lack of any operational VTOL UAVs for
either civil or military applications is equally
noteworthy. The general complexity of
VTOL designs and the operational
considerations for VTOL UAVs in terminal
area operations continues to delay the
fielding of any VTOL design.
Figure 3. Sensor performance for
brownout landings
A UAV is simply an aircraft equipped with; a
programmable all-axis autopilot for up and
away flight; a command/control data link
with remote control and monitoring station,
and a method for either automated or
manually controlled takeoffs and landings.
The absence of an operational VTOL UAV
in either a civilian or military application may
highlight the difference in maturity of
manned fixed wing autopilot control relative
to manned helicopters. While cruise flight is
relatively straight forward and leverages
fixed-wing autopilot methodology, the zero-
zero landing capable helicopter autopilot
represents a tougher challenge.
Only a handful of programs in the history of
helicopter aviation have attempted a full
authority automated flight control system.
Much of the ULB’s flight test related
success is due to the lessons learned
during helicopter specific control law
programs over the years such as the fly-by-
wire AH-64 program that was flight tested in
the late 1980s.
Figure 4. Landing to 16’x16’ platform
In addition to the challenge of VTOL
autonomous takeoffs and landings,
operation in General Airspace requires the
UAV to have be able to “see and avoid” air
traffic and obstacles.
Large fixed wing UAVs such as Predator
operate in a similar manner to manned IFR
flight operations, and generally at altitudes
where airspace clutter is limited and positive
control is maintained to provide separation
for competing aircraft. Just like their
manned counterparts, VTOL UAVs are
more suited for lower altitude operations
where aircraft separation may not be
provided by air traffic controllers.

4. 4
Transponder based electronic collision
avoidance systems (TCAS) are certified and
commonly found on commercial or higher
end private aircraft. However, a barrier to
UAV operation in the national airspace is
the detection and avoidance of what can be
called “non-compliant” aircraft which are not
equipped with TCAS.
Emerging technologies that exploit IR, EO,
and various radar devices as inputs to
sense and avoid capability are still in
prototype form and not yet ready for
certification. However, the ULB program is
furthering their maturity by supporting their
development with safe flight testing in
congested airspace. It is expected that
these devices will be certified to provide an
“equivalent level of safety” to a human
piloted aircraft for traffic sensing. The
“avoid” piece of the equation represents an
additional challenge, as the response must
be tied to the sensors effective field of
regard.
Figure 5. Enhanced Synthetic Vision
System test configuration
ULB Program Philosophy – Lower The
Risk, Raise The Yield
Many aircraft designs are defined and
presented as the final design even before
they attempt first flight. Flight test
qualification is viewed by these programs as
an inconvenient step towards fielding.
Therefore, many designs, and especially
UAVs, do not appreciate the unique
qualification tests necessary to define a safe
operational flight envelope.
By 2006 the program had accumulated
several hundred hours of development and
the tests were considered low risk, even for
a proof-of-concept demonstrator aircraft.
However, to some observers the program
had not answered the fundamental UAV
question – could it fly without a safety pilot.
The ULB program proved it could operate
completely unmanned in 2006 when the
aircraft flew a 20 mile mission sortie with
over 700 pounds of payload for this first
unmanned flight. Absolutely no operational
differences existed between this flight and
the preceeding prepatory sorties.
Figure 6. Purely autonomous (no safety
pilot on board) demonstration flight at
Yuma Proving Ground, June 2006
Development testing is characterized by
changes to either the flight envelope or the
aircraft capabilities. Additional unmanned
flights during developmental testing adds
risk as well as substantial time and cost
associated with software/system validation.
The ULB program philosophy is that
anything more than proving the unmanned
flight capability is a reliability issue. All
VTOL UAV programs are seeking to
achieve platform reliability on the order of
10 or less accidents per 100,000 flight hours
(similar to manned platforms). Therefore,
MPG06-93788-017.ppt

5. 5
reliability is better addressed through
analysis.
The ULB program’s “safety pilot” approach
brings two notable strengths to the program.
First is the ability to rapidly develop and
integrate any system in a low risk
environment. When the risk of losing an
aircraft or sensor package is removed, the
ability of the team to develop system
capability is greatly enhanced. Second, it
brings test pilots into the UAV program as
key members of the design staff. This is true
for manned programs, but rarely true for
UAVs. The cockpit perspective, even when
the flight data may indicate that the test was
acceptable, proves invaluable when
developing an optimized aviation system.
Additionally, conducting developmental
flight test with a pilot onboard allows the
aircraft to be operated amongst the general
aviation community which avoids the costs
associated with relocating the aircraft,
equipment, and support personnel to
locations with restricted airspace. Even
inside restricted airspace, approval must be
obtained from the owning agency prior to
operations. The avoidance of travel
expenses combined with the elimination of
the delays and expense of approvals to fly
UAVs in restricted airspace has allowed the
ULB program to reap enormous financial
benefits. Developmental flight operations
conducted with the safety pilot on board
better serve the industry and the customer
base by more rapidly advancing the
technology and developing concepts of
operations, while simultaneously minimizing
the timelines and associated costs.
The “lessons learned” by operating at a high
operational tempo with multiple flight
experiments flown in a single day are simply
not available to programs that only fly
occasionally. On one technology integration
and demonstration program, the ULB flew
an average just over 8 hours per day for 3
consecutive days in support of both day and
night mission related testing back in 2005.
The safety pilot also provides immediate
feedback regarding the “machine like” or
“human pilot like” flight capabilities of the
VTOL UAV. The advantage of a smooth
ride should result in longer sensor
component life due to the reduced vibration
present in steady state and maneuvering
flight. This will be significant factor in the
total operational budget when the sensor
cost may approach or even exceed the cost
of the baseline aircraft.
In short, the presence of a safety pilot
accelerated the VTOL UAV development
process. If errant autonomous mode
behavior was presented during the
development phase of the aircraft, the
safety pilot was able to quickly take manual
control of the aircraft and debrief the test
team. In contrast, a program working
without a safety pilot may have spent
additional time and budget determining the
cause of an incident as well as how to avoid
future occurrences. It was not uncommon
during the first autonomous mode flights to
find an issue during the morning flight,
debrief, make a software change, and
validate the software change during the
afternoon flight.
Figure 7. Safety pilot allows different
mission concepts to be explored

6. 6
Design Concept
The rapid prototyping philosophy of the ULB
team dictated that off-the-shelf actuators
would be exploited to develop the UAV
concept. Additional actuators were added
to manage throttle and collective control
inputs, and a patented method of combining
the load relieving low bandwidth control
force trim actuators along with the high
bandwidth autopilot actuators has resulted
in a design that flies in a manner virtually
identical to a skilled human pilot.
The UAV actuators are installed in parallel
to the mechanical control system. When the
aircraft is in the autonomous mode, the
safety pilot can disengage the system or
mechanically over-ride the UAV system,
taking full flight control authority. The pilot’s
treat the UAV system as a student pilot,
always alert to the possibility of an improper
control input at any time.
Figure 8 depicts the cockpit of the original
ULB test aircraft. The red button on the
cyclic stick is what instantly transforms the
UAV to a pure mechanical aircraft. The
display mounted in the console in front of
the pilot allows the crew to disengage the
system, modify gains in the control laws,
and then re-engage the system. The system
optimization is measured in days rather than
months. In the early days of development,
the flight computer would launch with two
distinct software loads to test in one sortie.
It was also not unusual to fly one software
load in the morning and the fix in the
afternoon. These were flights that were
expanding the flight envelope or adding a
new aircraft capability. The software tools
are mature enough that a change would be
made, tested in ground simulations and
loaded into the aircraft in a span of time less
than two hours.
Figure 8. Original ULB Cockpit
The 8.4” diagonal touch screen on the left
side of the cockpit is driven by a hardened
PC, streamlining integration issues for PC
based payloads and test hardware. Due to
this design strategy nothing added to the
aircraft is flight critical. This opens the door
for flight testing prototype, non-flight
qualified hardware to help finalize its design
and performance prior to the expensive
qualification process.
Technological Development &
Demonstration Capability
The strength of the ULB design is that it can
safely investigate a new capability in a very
short period of time and bring that new
capability within the aircraft’s already proven
capabilities for the unmanned design. There
is no question that the operational design
will be offered in a purely unmanned
configuration. The ULB has just provided
what appears to be a more efficient, cost-
effective solution on how to get to the end
point and develop new capabilities without
losing program assets or precious prototype
payloads along the way. Many of the
payloads tested are nearly the cost of the
aircraft itself. Therefore, knowing that the
payload will be tested and returned safely is
a key feature of the ULB design.
The safety pilot approach also allows the
ULB to test anywhere in the U.S. Unlike
other UAV programs that must reside within
restricted airspace or defined COAs, the

7. 7
ULB can go to where the test is rather than
forcing the test to come to a UAV. This
becomes very powerful when participating
in large scale exercises where the UAV may
not be the most important element. Figure
9 illustrates this point, showing the ULB
aircraft conducting testing with other
manned aircraft in the local airspace at
Boeing Mesa. Figures 3 and 5 show the
testing of an Enhanced Synthetic Vision
System for brown-out landing conditions,
conducted at a low cost test area in rural
Arizona.
Figure 9. Manned / unmanned testing.
Figure 10 documents the test configuration
for a ground based hostile fire flash
detection system as a prototype for an
aviation installation. Again, this test was
conducted in local airspace adjacent to a
civilian weapons firing range. The results
from this testing provided the design data to
yield a smaller optimized aviation unit with
the required performance.
Figure 10. Testing a prototype hostile fire
flash detection system.
Figure 11 shows a developmental test that
was conducted using the ULB to host a
high-bandwidth UAV communication
system. The antenna mounted to the bottom
side of the aircraft was a phased-array
antenna previously mounted to a fire station
tower in the mountains of California. The
un-altered assembly was installed on the
ULB aircraft and flown in a demonstration at
Ft Campbell, Kentucky.

8. 8
Figure 11. High bandwidth comm relay
configuration
The autonomous and programmable
capability of the ULB makes it a good test
platform for aircraft that may not even be
designed to fly on Earth. The test aircraft
has supported Lunar and Mars lander
navigation and landing zone identification
technology[1]
. Figures 12 and 13 depict 2 of
the 6 experiments flown during this test
program. The ULB demonstrated that it
could emulate the final approach and
landing phase of extra-terrestrial flight
trajectories, providing a safe and
inexpensive method for developing and
validating a variety of technologies.
Figure 12. Crater navigation sensor
suite for development of lunar lander
capabilities.
Take it to the Customer
Decision makers in the customer base are
located all over the world and have very
limited time to travel to manufacturer’s
locations. The safety pilot on board concept
guarantees that the ULB can be operated at
the customer location. The availability of an
observers seat in the cockpit insures that
the customer can experience first hand the
unique flight capabilities of the aircraft and
system, as well as to witness that the safety
pilot is not intervening in the operation of the
aircraft. The ability to develop and upload
missions using a simple laptop computer or
via TCDL simplifies the cost and time of
demonstrations.
Figure 13. Prototype flash LADAR for
rough terrain landing zone assessment
On several occasions the ULB has been
flown through civil airspace to customer
locations in order to provide on-board
demonstration flights to high level decision
makers. Figure 14 is from an autonomous
flight demonstration provided to various
individuals at Redstone Arsenal in
Hunstville, Alabama.
The safety pilot approach also insures that
UAV related testing can be supported
anywhere in the United States. Precision
delivery using VTOL aircraft is a growing
requirement and its military application may
require operation to and from higher ground
elevations. The ULB can safely and
immediately conduct testing in any
MPG06-93788-006.ppt

9. 9
environment to validate operational
requirements in any terrain (Figure 15).
Figure 14. ULB performs autonomous
demonstration flights at Redstone
Arsenal in Huntsville, Alabama
Figure 15. Aerial resupply CONOPS
Logistics Footprint
The ULB test team is very compact and
efficient. In a typical test scenario, the
aircraft flies through national airspace as a
manned aircraft to the test location with the
test truck and crew in chase. The truck
holds a ground power cart for extended
ground test operations, the TCDL antenna
tower, and a connex of spare parts and
tools to support the aircraft during the
testing (Figure 16).
Figure 16. ULB support hardware
Platform Selection
The MD530FF is a platform with a rich
heritage. Initially conceived as the OH-6 for
service in Vietnam, the airframe has
enjoyed a long evolution and still shows
much growth capability. The Mission
Enhanced Little Bird operated by the 160th
Special Operations Aviation Regiment
based at Fort Campbell, Kentucky is the
latest generation military variant of the
MD530FF. The MELB helicopter has a
military pedigree complete with a -10
operators manual, maintenance manuals
and procedures, parts supply chain, and a
wealth of experienced pilots, maintainers,
and mission planners. A large variety of
sensor, weapons, communications, and
extended range fuel systems are qualified
and available for the airframe. There are
hard points all over the aircraft for mounting
equipment and the pre- and post- flight
inspections are quick, easy, and well
documented. The electrical system is
capable of 400 amps of 28 vdc electrical
power output. Transportability by truck or
military airlifter is customary and well
understood.

10. 10
Figure 17. MELB at a NASCAR event
The A/MH-6M growth variant is one of the
few aircraft that can carry its own empty
weight in fuel and payload, in fact 30% more
than its empty weight (Figure 17). The still
maturing aircraft has enjoyed a few decades
of refinements and improvements driven by
military customers over the world to help
develop one of the lowest operational cost
aircraft in its payload category. It also has
many existing military qualified capabilities
that can easily be made automated for the
unmanned application.
Airframe Performance Growth Potential
In its current form the aircraft has
documented performance for 4700 pounds,
demonstrating a mission equipment and fuel
capacity of 2400 lbs. Future changes to the
aircraft will be driven by both the manned
and unmanned customers.
The Rolls Royce 250-C30R/3M engine on
the aircraft provides the existing design with
high altitude HOGE capability. This is unlike
many designs that are optimized for sea
level operations and suffer tremendous
weight and performance penalties when
operating from higher ground elevations.
Even with its current performance,
additional engine power and drive train
growth programs are taking shape.
New main and tail rotors will also be
incorporated in the coming years. The
aircraft already has crashworthy and
ballistic tolerant fuel tanks for the UAV
application as an added safety feature for
the ground crew. Even though the design
has demonstrated sloped landings greater
than 7 degrees in all axes, the design team
is looking to expand the landing envelope
further, both in slope and contact velocity for
maritime applications.
A UAV specific design enhancement would
be the integration of an engine recouperator
to increase the efficiency of the overall
thermal cycle of the installation.
Consequently the aircraft performance
envelope would improve in terms of
increased flight duration or increased
mission equipment package payload
capability due to the reduction in fuel burn.
Forward Thinking – What’s Next?
Time and funding appears wasted on true
UAV programs during the development
stage in safety reviews and extensive
regression testing due to the risk associated
with the loss of an aircraft. The ULB
program has eliminated that loss possibility
and can develop and understand critical
flight and design capabilities quickly and
safely.
Selection of an airframe already in the
inventory, with all the certifications and a
myriad of qualified weapons, sensors, and
communications systems greatly reduces
the cost of UAV development. Perhaps
more importantly, this choice allows
precious funding to be applied to developing
UAV capabilities, rather than being spent on
the basic development and certification of
the airframe and fundamental systems.
With only the UAV capable autopilot and
command/control data link to develop and
integrate, a VTOL UAV with powerful
capabilities can be fielded much more
quickly and for a fraction of the cost of
traditional UAV programs.
The ability to operate as an optionally
manned platform is a huge advantage. With
shrinking budgets and growing
requirements for both VTOL UAV and

11. 11
manned VTOL platforms, military and civil
customers can enjoy all the advantages of
both types of platforms. As the ULB UAV
concept can be deployed in a kitted form,
airframe operators have the option of a
growth path from manned to optionally
manned airframes as CONOPS,
requirements, and the regulatory
environment mature.
The maritime environment presents special
challenges for terminal operations and
dynamic mission replanning. To that end,
the ULB program has collaborated with
NovAtel [2]
to develop and test a moving
baseline Differential GPS based navigation
system. Initial testing of this low cost
JPALS approach has provided very
promising results. Formation landing
approaches have been completed to a
moving automobile (Figure 18) and a
helipad has been installed on a tractor-
trailer rig (Figure 4) for autonomous takeoff
and landing development testing at speeds
up to 50 knots. Work is ongoing to examine
at-sea terminal operations demonstration for
2009.
Figure 18. Moving baseline navigation
system development
Conclusion
The technical success of the ULB program
can be attributed to several factors. Most
importantly are the people; team members
that are willing to think outside the box and
develop an entirely new approach to an
existing problem. The ability of the aircraft to
be pushed to the envelope limits, to test
new payload capabilities, and to investigate
new autonomous capabilities safely and
rapidly is the key. High operational tempo
operations promote excitement and high
team morale.
The ULB concept appears to be the
standard that all new designs must improve
upon. Many design concepts falter upon
reaching flight test and only after significant
investments are made.
The Little Bird is not a stagnant design;
rather it continues to evolve. In the
unmanned mode, the excess payload
capability and additional fuel capacity,
extend the range of the UAV design to
values that far exceed the current manned
aircraft. Recently, a new test cockpit was
installed in the ULB to allow data fusion
testing, where the data can be validated at
the aircraft level prior to being sent down to
a ground station (Figure 19).
Figure 19. Second generation cockpit
design

12. 12
In summary, ULB is the most cost and
calendar time efficient VTOL UAV
development platform available for rapid
prototyping. The design continues to evolve
and mature along with the complimentary
technology. ULB allows safe and effective
exploration of CONOPS so that regulatory
and operational requirements documents
can be developed. The ultimate objective is
to provide the customer the most capable,
effective, and flexible platform possible,
while allowing for continued growth as ideas
continue to mature.
[1] M. Bayer, S. Berg, M. Hardesty,
“Helicopter Flight Demonstration of Lunar
and Planetary Lander Technologies”,
Proceedings of the American Institute of
Aeronautics and Astronautics Space 2008,
San Diego, CA, September 9-11, 2008,
AIAA-2008-7803
[2] T. Ford, M. Hardesty, M. Bobye:
“Helicopter Ship Board Landing System” ,
Proceedings of the Institute of Navigation
Global Navigation Satellite Systems, Long
Beach, California, September 15th, 2006.