This document summarizes the development of a rotorcraft unmanned aerial vehicle (UAV) system by Boeing Phantom Works over less than one year. They selected the MD 530F helicopter due to its performance capabilities and military counterpart. The design integrated commercial off-the-shelf hardware and proprietary Boeing flight control software. Bench and flight testing were prioritized to rapidly expand the flight envelope from initial engagement of the electrical flight controls to autonomous takeoffs, landings and navigation. The manual override capability allowed high-risk prototype systems to be safely tested.

1. 1
Rapid Development of a Rotorcraft UAV System
D. Cerchie1
, G. Dockter1
, M. Hardesty1
& S. Kasprzyk2
1
The Boeing Company, Mesa, AZ
2
The Boeing Company, Seattle, WA
Abstract
This paper will highlight the Unmanned Little
Bird program, a Boeing Phantom Works
program that successfully developed a
helicopter Unmanned Aerial Vehicle (UAV) test
bed aircraft in less than one year. The design
represented the integration of Boeing research
programs and commercial-of-the-shelf (COTS)
hardware. The result of this effort was a UAV kit
that could be installed in most manned
helicopters with minimal integration.
UAV development has become a new frontier in
aviation. UAVs vary in size and shape from the
large endurance fixed-wing designs that require
equipment and personnel comparable to a
manned aircraft to the small micro UAVs that are
hand launched [Ref. 1]. The initial focus of the
UAV was to handle the dull, dirty and dangerous
missions. They would become the controllable
and tireless eyes-in-the-sky, the communication
and data links for air and ground personnel, and
the aircraft that could be sent to places where it
would be unsafe for a pilot or ground personnel.
However, their usage is still being developed as
their designs mature and sensor capabilities
increase. Most new ideas enhance a current
development plan, while other ideas, like this
one, can actually reshape our perception of
UAVs in the future.
Introduction
Boeing decided in late October 2003 to create a
helicopter UAV technology development and
demonstration aircraft with the size and
performance of current and planned helicopter
UAVs. The planned UAV would have attributes
that would differentiate it from all other UAVs by
providing a rapid development platform for UAV
airborne and ground systems. The platform
would have virtually no space, weight or
electrical power limitations typical of current

2. 2
rotary wing UAVs in development, allowing for
quick integration of prototype UAV subsystems.
It would also have the one critical attribute that
would allow for extremely rapid development, a
manual over-ride of the UAV by an on-board
safety pilot. This capability would allow high-
dollar or one-of-a-kind prototype systems to
operate on the UAV platform at the corners of
the flight envelope in civil airspace without most
of the safety and software concerns that limit the
pace of UAV development today.
The UAV Platform
The most important decision for this program
was the UAV platform. It had to be a high
performance rotorcraft with an operating
envelope that would provide high altitude, high
airspeed, and maneuverability. It also had to
have basic aircraft systems with no susceptibility
to the electromagnetic interference typical of
high powered data links and active airborne
sensors. It had to have a mechanical control
system for a safe reversion or failure mode, and
some military history to validate the generated
test data. The obvious choice was a MDHI 500
series aircraft. Table 1 below shows the
performance difference between the MD 500E
and MD 530F aircraft.
The MD 500E, with its Rolls Royce 250-C20B or
-C20R engine, can not hover out of ground
effect (HOGE) at 4k / 95°F at its maximum
internal gross weight of 3,000 pounds. Also, the
aircraft does not provide adequate hover
performance margin for testing based out of
Mesa, Arizona since the summertime mid-
morning temperatures can quickly reach 35°C
(ISA+23°C).
Table 1
MDHI 500 Series Aircraft Performance Comparison (source: Ref. 2)
Performance at Max Internal Weight 500E with C20B 500E with C20R 530F with C30
Max cruise speed SL
5k
Max range* SL
5k
Endurance*
Service ceiling ISA
HIGE ISA
ISA + 20°C
HOGE ISA
ISA + 20°C
Weight Max (internal)
Empty
Useful load
Max (external)
Useful load
Useable fuel*
Power Rated
Takeoff
Continuous
135 kt
133 kt
239 nm
264 nm
2.7 hr
13,900 ft
8,500 ft
6,000 ft
6,000 ft
3,100 ft
3,000 lb
1,481 lb
1,519 lb
3,550 lb
2,069 lb
403 lb
420 shp
375 shp
350 shp
135 kt
136 kt
233 nm
258 nm
2.5 hr
16,500 ft
11,300 ft
6,900 ft
8,700 ft
4,100 ft
3,000 lb
1,517 lb
1,483 lb
3,550 lb
2,033 lb
403 lb
450 shp
375 shp
350 shp
134 kt
135 kt
206 nm
232 nm
2.0 hr
18,700 ft
16,000 ft
14,300 ft
14,400 ft
11,600 ft
3,100 lb
1,591 lb
1,509 lb
3,750 lb
2,159 lb
403 lb
650 shp
425 shp
375 shp
(*) – Data represents performance for main fuel tank only. There are several FAA and military qualified
auxiliary fuel tanks that can increase the fuel carrying capability of the aircraft by a factor of 4.

3. 3
The MD 530F chosen as the UAV platform was
equipped with the more powerful 250-C30
engine which provided much more HOGE and
service ceiling capability but at the cost of higher
fuel consumption. The correlation between the
engine’s rated power and the performance of the
three aircraft designs is clear from the data in
Table 1. Given the payload capability of the
MD530F, existing commercial and military
auxiliary fuel tanks can be added to the aircraft
to easily increase its range and endurance to
values equal to or greater than existing
helicopter UAVs. Also, since the internal gross
weight applies to the landing gear
crashworthiness for the manned aircraft, the
UAV variant can operate to the performance
limited external gross weight value.
The MD 530F helicopter also has a current
military counterpart in the A/MH-6J aircraft.
Therefore, any kits or options that have been
qualified on the A/MH-6J in the past can easily
be installed on the UAV variant. This leveraging
of existing systems would also justify the direct
transfer of FAA or military qualified performance
data for this UAV. This may be the first
helicopter UAV design with military qualified
hover and level flight performance data. While
this is seen as positive point for this aircraft, it
does leave the design open to UAV performance
comparisons between actual versus projected
performance since most helicopter UAVs have
not actually flown to their quoted performance
envelopes.
The commonality in the 500 series control
design would allow for easy modification to the
MD 500E helicopter if low altitude, low payload
weight and cold day operations were desired.
The design could take advantage of the less
powerful, but more fuel efficient Rolls Royce
250-C20 class engine. The UAV kit design
approach also allows for easy modification to the
increased payload capability of the A/MH-6M
helicopter, with its 6-bladed rotor and the more
powerful Rolls Royce 250-C30/3M with a full
authority digital engine control (FADEC).
Design Approach
The aircraft design approach had only one
constraint, the internal research and
development (IR&D) funded program had to go
from a paper proposal to an autonomous aircraft
in less than one year. This one constraint quickly
led the design team to develop an achievable
plan in the program’s three critical areas:
hardware acquisition, software development and
testing approach.
The first time-critical objective of the design
team was to define the modified control system,
locate the COTS hardware and place orders for
these parts in the few weeks from the program’s
start to the end of the year. Even with the rapid
design approach, many of the critical COTS
control systems parts had lead times of nine
months. However, once the parts were on order
the program was able to concentrate on the
software development and acquiring a suitable
aircraft. The specific MD 530F helicopter
chosen was purchased from MD Helicopters,
Inc. in April of 2004. The aircraft had previously
been utilized for pilot training and had been in
service for over 400 hours.
The software development effort had two major
components, the aircraft software and the
ground station software. The aircraft software
was based on Boeing proprietary software
developed over the past two decades on various
AH-64 internal research and development
programs. The flight path command control laws
provided automated switching between four
flight modes: ground, hover, low speed and
cruise. Waypoint navigation algorithms were
added to the flight path command control laws to
provide the ability to upload navigation routes
from the ground station. In addition, all of the
user interface software for development and
troubleshooting as well as a majority of the I/O
handling software were already developed and
functional.
The aircraft software was loaded into the flight
control computer (FCC). Its design was based
on the COTS and open systems architecture
approach used on several AH-64 development
programs. The actual code could be compiled
and run on either a personal workstation, the
FCC itself installed on the development rack or
on the aircraft. This approach eliminated the
source of errors when different software tools
are used in moving the design from the analytic
phase to the actual aircraft. Figure 1 shows the
communication and growth capability built into
the FCC to support future development.

4. 4
Figure 1 – FCC Communication and I/O Capability
At the start of the program, the ground station
software was to be a simple proof-of-concept
code that would be replaced in the future with
the Open Mission Management (OMM) software
being developed internally by Boeing. The
program ground station goals were for the
system to allow waypoints to be uploaded to the
aircraft and also to be modified while the aircraft
was enroute. Initially, the program was going to
accomplish this goal by communicating with the
aircraft using UHF modem radios.
In April 2004, the program scope increased to
include the integration of an electro-optic /
infrared (EO/IR) sensor. The transmission of the
sensor video then required a more capable
communication approach. L3 Communications
was then asked to join the program with their
Tactical Common Data Link (TCDL) system, a
device common to the AH-64D airborne manned
/ unmanned system technology demonstration
(AMUST-D) program. While the ground station
portion of this system was owned by Boeing, the
aircraft portion of the TCDL was provided by L-3
Communications. The Unmanned Systems
group within Boeing had a MX-15 sensor, which
L-3 Communications Wescam provided it with
an autotracker and support of system specific
intercommunications.
Boeing’s Unmanned Systems group was then
asked to accelerate the OMM software
development to support the initial flight test
program. Since the aircraft testing approach had
a safety pilot and aircraft control laws to adjust,
they were not instantly placed on the critical
path. The ground system software structure is
shown in Figure 2.
The human-machine interface (HMI) chosen
was Tactical Display Framework (TDF), but this
can easily be switched to any other existing
interfaces. The power behind the OMM
approach is that it is based on the STANAG
4586 format [Ref. 3] and that all aircraft,
sensors, weapons and terrain models plug into
this basic core software structure.
Testing
What has differentiated this program from other
programs was the initial emphasis on the most
effective methods for both bench and flight
testing. Many design decisions were driven by
their potential impact on the cost and
effectiveness of lab and flight tests.
There are three major test fixtures for this
program: the actuator test computer; the FCC
integration bench; and the aircraft itself. The
actuator test computer was a standard desktop
computer that had been modified to drive and
characterize the flight control actuators. This test
device had been used to evaluate the flight
control actuators and compare the results to the
vendor data. Several discrepancies were found
FCC
½ ATR SHORT
Power PC Processor
4 of 5 VME64 card
slots used,
1 spare
Internally
Conduction Cooled
Discrete Inputs
Analog Inputs
EIA-232 Serial Ports
EIA-422/485 HDLC/
SDLC Serial Channels
USB 1.1 Interface
Discrete Outputs
Analog Outputs
Power Outputs
Ethernet Ports
Mil-Std-1553 Bus
(A & B)
80 Total, 31 Used
68 Total, 23 Used
6 Total, 2 Used
6 Total, 2 Used
1 Total, 0 Used
64 Total, 20 Used
16 Total, 6 Used
80 Total, 31 Used
1 Total, 0 Used
2 Total, 1 Used

5. 5
and corrected during this testing. The actuator
model used in analytic simulations was a result
of this testing.
The integration bench was built specifically to
test the FCC. It provided the capability to test all
of the analog and discrete inputs and outputs.
The bench also had the complete non-linear
helicopter simulation program, and provided
emulations of the sensors and navigation
system. This allowed for the FCC to be run in
closed loop testing prior to installation on the
aircraft.
Figure 2 – OMM Ground Station Software Structure
Throughout the developmental effort the aircraft
itself had been used as a hot bench to conduct
much of the integration prior to flight test
evaluation. As systems were installed on the
aircraft, polarity, continuity and aircraft interfaces
were verified. Systems were tested individually,
and finally all the systems were powered
simultaneously. The MIL-STD-1553 bus traffic
was monitored to verify proper functionality as
various systems were brought on line.
As scheduled nearly 8 months earlier, the first
flight of the aircraft was on September 8
th
,2004.
The flight was performed as a maintenance
activity due to the extent that the airframe had
been dismantled during the modification
program. During the maintenance activities,
which included tail rotor and main rotor head
balance, as well as main rotor track and balance
in flight, all mechanical and electrical systems
not originally a part of the basic aircraft were left
powered off. Once all maintenance related
activities were complete, electromagnetic
interference / electromagnetic compatibility
(EMI/EMC) evaluations were tested. EMI/EMC
testing revealed no safety critical issues, and
very few nuisance issues.
IP
TCDL
C
O
Translator
UDPTCP
I
N
F
A
P
P
Mission
Monitor
Mission
Planning
Performance
Check
Clobber
Check
Terrain
Modeling
Vehicle
Interface
H
M Tactical Display Framework (TDF)
Win 2000 System
Functions
SPREAD
Core OMM Objects
STANAG 4586
Messages
Sensor
Model
Flight / Navigation
Model
Weapon
Model
Vehicle Specific
Models

6. 6
Over the course of the next two weeks all the
added systems were turned on one-by-one and
operated during flight. Initially only the
instrumentation and data transmission was
available for real-time monitoring in the Fixed
Base Data Station. Within several days the L-3
Communications TCDL was turned on along
with the Wescam MX-15 electro-optical (EO)
video. The TCDL 10 megabit per second data
stream provided a redundant subset of the
instrumented TM data stream, along with color
video.
The most important element of the system
design philosophy was the choice of flight
control actuators. The primary actuators were
mounted in parallel with the standard aircraft
control system so that the flight controls move
as the system actuators command the aircraft.
Each electro-mechanical actuator has a belt
drive and an electrical clutch. In the event that
the pilot wished to disengage the system, a
cyclic mounted switch was depressed, which
immediately eliminated force from the actuators.
Should the pilot wish to temporarily over-ride the
system, control forces were light enough that the
pilot could easily back drive the actuators by
slipping the belt. This design philosophy
maximizes the safety of the system.
A large benefit of the design approach was
realized when the electrical flight control system
was engaged for the first time at 500 feet above
ground level and at 70 knots. This flight
condition provided the safest condition to test
due to the largest control and power margins
present at that flight condition for the MD 530F
helicopter. The flight envelope was expanded
from this point out to the maximum level flight
speed and back down to a 500-foot hover.
Actuator failure testing was then performed in
hover and forward flight to ensure that the pilot
would recognize and be able to correct for a
system failure before any significant aircraft
attitude upset would occur. The envelope was
then extended down to the ground for take-offs
and landings. This was the most critical part of
the flight envelope and where most UAV designs
begin envelope expansion.
A by-product of using the previously developed
manned aircraft control laws is that the aircraft
now has three different modes of operation. The
helicopter can be flown with the system totally
disconnected as the baseline mechanical control
aircraft. It can also be flown with the system
engaged, but controlled by the pilot, effectively
adding a four-axis autopilot to the aircraft. The
third mode is as an autonomous vehicle
controlled from the ground station. The system
is being expanded to provide a fourth mode,
where the pilot flies the aircraft from the cockpit
using the same navigational capability as the
ground control station, the digital map and
cursor commands.
It should be noted that this aircraft was designed
so that it could proceed from a flight idle
condition on the flight ramp and conduct a
mission in an autonomous manner without any
operator intervention. In other words, there is no
requirement for a ground systems operator to fly
the aircraft remotely using a joy stick type
control. Instead, uploaded mission waypoints
define each phase of flight and the system
responds appropriately.
Figure 3 shows the modified test cockpit on the
MD 530F aircraft. The screen in the upper right
corner of the instrument panel is the Digital
Interface Unit (DIU). This touch screen allowed
the flight crew to modify the control system gains
with the system disengaged. The crew could
then re-engage the system and evaluate the
flight characteristics with the new gain.
Throughout the entire flight envelope, all four
axes of the autopilot were tuned using this
method in very few flights. This approach
allowed the flight test team to rapidly modify any
software controlled parameter, like thresholds
and gains.
Figure 3 – MD530F Test Cockpit

7. 7
Table 2
UAV Envelope Expansion Update
As of Dec 2004
Tests
Total Flight Hours
Total Engaged Hours
Max Level Flight Speed
Max Altitude
Max Payload / Fuel
(in addition to EO/IR or TCDL wt)
57
88.0 hrs
44.0 hrs
126 KTAS
17,962 ft Hp
1205 lb
The screen on the co-pilot/observer’s (left) side
of the cockpit is an LCD touch screen provided
by Avalex, Inc. The screen provided the operator
the capability to select video from 5 different
sources - two VGA computer inputs and three
different RS-170A analog inputs. An on-board
hardened computer that interfaces to the MIL-
STD-1553 bus traffic drove a heads-down
display (HDD) program presented on this
monitor. The analog video output from the
Wescam EO/IR turret displayed on the monitor
using one of the RS-170A inputs.
The L-3 Communications Tactical Common
Data Link (TCDL) provided a 10 megabit per
second data stream. It included compressed
MPEG video at 30 frames per second, along
with a subset of the MIL-STD-1553 bus traffic.
The data link was bi-directional, which allowed
up-linked command and control. The Wescam
MX-15 EO/IR sensor video was also sent to the
ground station over the TCDL data link. Aircraft
position data, along with Wescam’s EO/IR
sensor target pointing data were plotted on a
moving map display on the ground station in the
flight monitoring room.
The EO/IR sensor video and the moving map
display provided the test monitoring team with a
level of situational awareness unlike any test
program before. Real-time comments from the
flight crew regarding system behavior were
immediately correlated to the video and aircraft
tracking data. This method of testing allowed the
flight test monitoring team to make highly
informed recommendations regarding system
gain or threshold changes.
An example of the sensor output is shown in
Figure 4. This JPEG picture was made from the
video tape copy of the transmitted picture. The
picture is of a lake in the local mountainous test
area. The quality of the picture over the TCDL
transmission was dependent upon the user
defined data rate. This is an example of the high
data rate setting that has a range in excess of
the entire Phoenix valley area. The lower data
rate compromises image quality and update
rate, however it provides for an even larger
range.
Figure 4 – MX-15 EO/IR Sensor Output

8. 8
Conclusions
The design approach that has produced this
UAV test bed has also lessened the separation
between manned and unmanned aircraft. The
design provides the ability for any aircraft to be
manned or unmanned during the course of a
single mission. The configuration flexibility and
versatility designed into manned aircraft will also
be required in UAVs since they fulfill similar
mission profiles.
The time and cost associated with this program
could cause future manned sized UAV programs
to rethink their development approach. The
trained test pilot is the ultimate sensor, and if
properly protected with safe failure modes, any
design can progress at a very rapid pace. Most
test pilots can in a single flight gain enough
knowledge to tell the design team more about
their aircraft than most want to hear.
This particular program has taken it one step
further in using an existing, high-performance
design as the starting point. The MD 530F
fuselage and controls represent less than 15%
of the total UAV related mission weight of the
aircraft. Therefore, the weight savings in making
it truly unmanned is negligible compared to the
benefits of a dual use aircraft. Also, there may
be a long-term benefit of providing the capability
for a maintenance pilot to conduct periodic
check flights to catch possible failures that the
onboard UAV health monitoring sensors may
miss.
The one unexpected benefit of this program was
the positive impact that the increased situational
awareness through the ground station tracking
and video output of the test aircraft brought to
the program. The ability to see the aircraft
motion and relative orientation to the ambient
wind direction provided the test team with
additional data that in the past is usually
misinterpreted when reviewing the plotted data
after the flight. This new capability, along with
the immediate visual feedback of software gain
or threshold changes made through the DIU
increased the efficiency of the costly flight test
development dramatically.
The other major cost savings idea used on this
program was the relocation of the UAV
hardware from the left pilot station to the aft
cabin area. The second pilot station was fully
functional and provided for a second crew
member to ensure safe operation of a new
design in FAA controlled airspace without the
use of a chase / observation aircraft. Pilot
workload was never critical due to the two-man
crew during the initial envelope expansion
testing. The test pilot was always able to focus
on the aircraft, treating the UAV control logic as
a new student pilot, capable of the most stupid
mistake at any time. The second crew member
was either the flight test engineer or a second
pilot, making observations of the flight and
handling some of the cockpit duties. Once the
design was stable, the second seat provided any
person willing to be taken on the best flight
available, a first hand view of a fully autonomous
aircraft.
References
1. Unmanned Aerial Vehicles Roadmap 2002-
2027. Office of the Secrtary of Defense; Dec
2002.
2. MDHI marketing data from aircraft procure
data located on www.mdhelciopters.com
3. NATO Standardisation Agreement (STANAG)
4586 Ed 2. Subject: Standard Interfaces of
UAV Control System (UCS) for NATO UAV
Interoperability