Variable Stability Learjet
In-Flight Simulator
Capabilities
Paul Schifferle
Flight Test & Aircraft Operations
•
Wind Tunnel Testing
•
Vehicle Crash Testing & Investigations
Variable Stability Aircraft and In-Flight Simulators
• Variable Stability Aircraft
– Permit in-flight variation of aircraft flying
qualities
– Allow pilots to determine the suitability of
these characteristics
• In-Flight Simulator (IFS)
– Extension of variable stability aircraft to
fully represent another aircraft
– Extension of ground-based simulators to
real flight environment
• Real world spatial environment
• Fully representative motion cues
© Calspan Corporation 2014
Variable Stability In-Flight Simulator Learjets
• Programmable interface to full-authority Fly-by-Wire (FBW)
flight control system
• 4 degree-of-freedom In-Flight Simulation (IFS) capability
– Pitch
– Roll
– Yaw
– Throttles
• Safety Features
– Automatic Safety Trip System
– Experienced Safety Pilots
– Accelerated Maintenance Program
© Calspan Corporation 2014
Calspan Fleet of IFS Learjets
• Lear 1 (N101VS)
– Model 24D
– 1st Flight 1981
• Lear 2 (N102VS)
– Model 25B
– 1st Flight 1991
• Lear 3 (N203VS)
– Model 25D
– 1st Flight 2007
• Lear 4 (N515TC)
– Model 25D
– 1st Flight 2014
© Calspan Corporation 2014
Uses of Learjet In-Flight Simulators
• Original Design Missions
– Test Pilot Training
– Handling Qualities Research
– Development of New Piloted Aircraft
• Upset Recovery Training
• Unmanned Air Vehicle (UAV) Surrogacy
– Autonomous Aerial Refueling (AAR)
– Sense and Avoid (SAA)
– Remotely Piloted Aircraft (RPA)
© Calspan Corporation 2014
UAV Surrogacy
© Calspan Corporation 2014
Progression to Autonomous Control of Air Vehicles
Learjet with
Reversible FCS
Calspan
Programmable
FBW FCS
© Calspan Corporation 2014
7
Highly Augmented
Learjet for Manned Ops
Progression to Autonomous Control of Air Vehicles (cont’d)
Evaluation Pilot
Sensors
Highly Augmented
Learjet
Calspan UAV Surrogate
© Calspan Corporation 2014
8
Benefits of Learjet IFS UAV Surrogate
• Replicate flight dynamics of UAV being simulated
• Aircraft modified with actual UAV sensors and associated
equipment
• Full-authority programmable FBW flight control system
• Can safely and efficiently conduct RDT&E early in
development
– Calspan safety pilots onboard to take control as required
© Calspan Corporation 2014
Aircraft State Data
© Calspan Corporation 2014
Symbol
p dot
q dot
r dot
p
q
r
phi
theta
psi
psi m
sin phi
cos phi
sin theta
cos theta
sin psi
cos psi
sin psi m
cos psi m
nx
ny
nz
nxp
nyp
nzp
Vt
alpha vc
beta vc
Vt cf
alpha cf
beta cf
Vt dot i
alpha dot i
beta dot i
Vt dot cf
alpha dot cf
beta dot cf
Vt gust
alpha gust
beta gust
sin alpha cf
Description
Roll Acceleration
Pitch Acceleration
Yaw Acceleration
Roll Rate
Pitch Rate
Yaw Rate
Roll Attitude
Pitch Attitude
True Heading
Magnetic Heading
Sine of Roll Attitude
Cosine of Roll Attitude
Sine of Pitch Attitude
Cosine of Pitch Attitude
Sine of True Heading
Cosine of True Heading
Sine of Magnetic Heading
Cosine of Magnetic Heading
Longitudinal Load Factor
Lateral Load Factor
Normal Load Factor
Longitudinal Load Factor at Pilot Station
Lateral Load Factor at Pilot Station
Normal Load Factor at Pilot Station
True Airspeed from Air Data System
Vane Corrected Angle of Attack
Vane Corrected Angle of Sideslip
Complimentary Filtered True Airspeed
Complimentary Filtered Angle of Attack
Complimentary Filtered Angle of Sideslip
Inertial True Airspeed Rate
Inertial Angle of Attack Rate
Inertial Sideslip Rate
Complimentary Filtered True Airspeed Rate
Complimentary Filtered Angle of Attack Rate
Complimentary Filtered Sideslip Rate
True Airspeed Gust Component
Angle of Attack Gust Component
Angle of Sideslip Gust Component
Sine of Complimentary Filtered Angle of Attack
© Calspan Corporation 2014
Units
deg/s/s
deg/s/s
deg/s/s
deg/s
deg/s
deg/s
deg
deg
deg
deg
g
g
g
g
g
g
ft/s
deg
deg
ft/s
deg
deg
ft/s/s
deg/s
deg/s
ft/s/s
deg/s
deg/s
ft/s
deg
deg
-
Symbol
cos alpha cf
sin beta cf
cos beta cf
u
v
w
Ax
Ay
Az
qc
Vc
qbar
Ve
Mach
T0
Ta
rho
p0
a
ps
hp
hp cf
h cf
qnh
h radar
h ddot i
h gust
h dot
gamma
l1
l2
l3
m1
m2
m3
n1
n2
n3
phi dot
theta dot
Description
Cosine of Complimentary Filtered Angle of Attack
Sine of Complimentary Filtered Angle of Sideslip
Cosine of Complimentary Filtered Angle of Sideslip
Longitudinal Body Axis Airspeed
Lateral Body Axis Airspeed
Normal Body Axis Airspeed
Longitudinal Body Axis Acceleration
Lateral Body Axis Acceleration
Normal Body Axis Acceleration
Impact Pressure
Calibrated Airspeed
Dynamic Pressure
Equivalent Airspeed
Mach Number
Total Air Temperature
Ambient Air Temperature
Air Density
Total Air Pressure
Speed of Sound
Static Air Pressure
Pressure Altitude
Complimentary Filtered Pressure Altitude
Complimentary Filtered Altitude
Altimeter Setting
Radar Altitude
Inertial Vertical Acceleration
Altitude Gust Component
Climb/Sink Rate
Flight Path Angle
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Direction Cosine
Roll Attiude Rate
Pitch Attitude Rate
Units
ft/s
ft/s
ft/s
ft/s/s
ft/s/s
ft/s/s
psf
knots
psf
knots
K
K
slug/cuft
psf
ft/s
psf
ft
ft
ft MSL
in Hg
ft AGL
ft/s/s
ft
ft/s
deg
deg/s
deg/s
Symbol
psi dot
de
da
dr
dthl
dthr
dfcl
dfcr
dxl
dxr
ds
flap
gear
spoiler
WOW
delta pe
delta pa
delta pr
de err
da err
dr err
dthl err
dthr err
total fuel
fuse fuel
m
W
Ixx
Iyy
Izz
Ixy
Ixz
Iyz
x cg
y cg
z cg
x cg mac
nav valid
nav fresh
lat
Description
Turn Rate
Elevator Positon
Aileron Position
Rudder Position
Left Throttle Servo Position
Right Throttle Servo Position
Left Fuel Control Lever
Right Fuel Control Lever
Left Engine Thrust
Right Engine Thrust
Stabilizer Position
Flap Position
Landing Gear Status
Spoiler Status
Weight On Wheels
Elevator Delta Pressure
Aileron Delta Pressure
Rudder Delta Pressure
Elevator Servo Error
Aileron Servo Error
Rudder Servo Error
Left Throttle Servo Error
Right Throttle Servo Error
Total Fuel Weight
Weight of Fuel in Fuselage Tank
Aircraft Mass
Aircraft Weight
Roll Moment of Inertia
Pitch Moment of Inertia
Yaw Moment of Inertia
Roll-Pitch Product of Inertia
Roll-Yaw Product of Inertia
Pitch-Yaw Product of Inertia
Fuesalge Station CG Location
Butt Line CG Location
Water Line CG Location
CG Location as Percent of Mean Aerodynamic Chord
Navigation Valid
Navigation Fresh
Latitude
© Calspan Corporation 2014
Units
deg/s
deg
deg
deg
deg
deg
deg
deg
lb
lb
deg
deg
0 or 1
0 or 1
0 or 1
psi
psi
psi
deg
deg
deg
V
V
lb
lb
slug
lb
slug-sqft
slug-sqft
slug-sqft
slug-sqft
slug-sqft
slug-sqft
in
in
in
%
0 or 1
0 or 1
deg
Symbol
lon
nav h
Vn
Ve
Vu
mag var
track
Vg
nav time
diff corr
num sat
stear valid
bearing
range
dtk
xte
dtk next
w speed
w dir
w dir m
loc dev
gs dev
Description
Longitude
GPS Altitude
Velocity North
Velocity East
Velocity Up
Magnetic Variance (East)
True Ground Track
Groundspeed
Navigation Time
Differential Correction
Number of Satellites
Steering Valid
Waypoint True Bearing
Waypoint Range
Desired True Track
Cross Track Error (Left)
Next Desired True Track
Windspeed
True Wind Direction
Magnetic Wind Direction
Localizer Deviation
Glideslope Deviation
Units
deg
ft
ft/s
ft/s
ft/s
deg
deg
ft/s
sec
0 or 1
0 or 1
deg
nm
deg
nm
deg
knots
deg
deg
dots
dots
Safety Trip System
© Calspan Corporation 2014
Learjet Modes of Operation
• Basic Aircraft
– Manual control by left seat Calspan safety pilot
– Retains production Learjet reversible controls
– Safety pilot flies the aircraft when the VSS is disengaged
• Variable Stability System (VSS)
– Aircraft controlled by VSS driving surface actuators
– Control by right seat evaluation pilot, inputs from onboard
sensors or data link
– Safety trip system enabled
• Emergency Fly-By-Wire
– Enables evaluation pilot to fly Learjet home if safety pilot
incapacitated
– Reduced VSS mode using fixed gains with basic Learjet
characteristics optimized for landing
– Safety trip system disabled
© Calspan Corporation 2014
Safety Trip System
• Automatic safety trips
– Preset threshold level and persistence
– Keeps aircraft dynamic response well within actual airframe
limitations
– Surface hardover protection
– System failures
• Manual safety trips initiated by either pilot
• Trip results in VSS disengagement
– Control surface and feel actuators are disengaged by
removing hydraulic pressure
– Control of aircraft immediately reverts to safety pilot
– Accompanied by aural and visual cues in the cockpit
© Calspan Corporation 2014
List of Automatic Safety Trips
•
•
•
Protection on Servos
– Surface servo errors
– Surface servo differential pressure
– Throttle servo errors
– Throttle differential
– Feel system servo errors
Protection on Flight Condition
– Lateral load factor (ny)
– Normal load factor (nz)
– Angle of attack
– Top tail rolling moment
System Monitoring
– Flight control computer heartbeat
– Flight control computer safety trips
– Low hydraulic fluid level
– Attitude gyro flag
– Autopilot/yaw damper engaged
© Calspan Corporation 2014
±2° (δe) ±6° (δa, δr), 10 ms
±850 psi, 10 ms
± 1.7°, 100 ms
25.3°, 100 ms
±0.5 in (stick) ±0.25 in (pedals), 20 ms
±0.3g, 20 ms
+0.25g to +2.8g, 20 ms
-5° to +12°, 20 ms
±7900 ft-lb, 20 ms (sideslip, rudder, airspeed)
discrete, 120 ms
discrete, 0 ms
discrete, 0 ms
discrete, 40 ms
discrete, 0 ms
Manual VSS Disengage Buttons in Cockpit
© Calspan Corporation 2014
Backup FBW Mode
• In the unusual circumstance that the safety pilot is
incapacitated or a control cable breaks, the aircraft can be
flown by the evaluation pilot by engaging the backup FBW
mode
• The feel and control surface system gains are fixed and
optimized for landing configuration
• The handling characteristics are basic Learjet with yaw
damper ON
– No aircraft state feedback is used (except for yaw
damping)
• Safety trip system is disabled (automatic and manual)
© Calspan Corporation 2014