Defense Solutions Division
Aviation Electronics Europe - Munich 26th March 2015
Situational Awareness – latest and future challenges
Low Air Speed Data
Paul Hart
CTO Curtiss-wright Avionics & Electronics
1 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Situational Awareness – latest and future challenges
Back to Basics
Evolution of the Air Data Computer
NextGEN/SESAR Challenges and Possible Solutions
Helicopter situational awareness – an additional set of challenges
2 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Back to Basics – The Basic-T Instrument Panel
3 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
ADC – Air Data Computer & EFIS – Electronic Flight Information System
4 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
ADC – Air Data Computer & EFIS – Electronic Flight Information System
Symbol
Generator
IMA
Processor
Pitot
Probe
Static
Port Right
Static
Port Left
Total Air Temperature
(TAT) Probe
Angle of Attack Vane
Speed Tape
Indicated Airspeed IAS
knots/mach#
5 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Total Air
Temperature
Altitude
Tape ft
Instantaneous Vertical
Speed IVSI
Air Data Probes
Angle of Attack (AoA)
Sensors L&R
TAT Probe
Ice Detectors L&R
Air Data Modules
(inside fuselage)
Combined Pitot-Static Probes - Captain
First Officer & Standby
6 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Multiple Aircraft Systems use Air Data:
Flight Management System
EFIS
WPT/ETA calculation, Winds aloft, Range
Constant/Specific Range calculation
Primary Flight Information
Airspeed (knots, Mach), Altitude,
Vertical Speed, Corrected AoA
Flight Warning Computer
Flight Data Recorder
Stall Detection/Warning, Landing Gear,
Flap Extension
Mandatory FDR parameters
Passenger IFE
Airspeed, Altitude, Outside Air Temperature
HUD
Head Up Display
Symbology
Transponder Altitude Reporting
Modes 1-5, Mode S, ADS-B
EFB
Electronic Flight Bag
V1 VR V2 take off speed calculation
Control Surface Power Control Units
Autopilot/Autothrottle Computer
VNAV Modes, Throttle Lever Angle Clutch
7 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Rudder Ratio – gearing down actuator deflection with
increasing airspeed, “Q Feel”
Multiple Aircraft Systems use Air Data:
Flight Management System
EFIS
WPT/ETA calculation, Winds aloft, Range
Constant/Specific Range calculation
Primary Flight Information
Airspeed (knots, Mach), Altitude,
Vertical Speed, Corrected AoA
Flight Warning Computer
Flight Data Recorder
Stall Detection/Warning, Landing Gear,
Flap Extension
Mandatory FDR parameters
Passenger IFE
Airspeed, Altitude, Outside Air Temperature
HUD
Head Up Display
Symbology
Transponder Altitude Reporting
Modes 1-5, Mode S, ADS-B
EFB
Electronic Flight Bag
V1 VR V2 take off speed calculation
Control Surface Power Control Units
Autopilot/Autothrottle Computer
VNAV Modes, Throttle Lever Angle Clutch
8 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Rudder Ratio – gearing down actuator deflection with
increasing airspeed, “Q Feel”
Autothrottle
Pitot
TAT
ADC
Autothrottle
Computer
Static
9 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
NextGEN & SESAR objectives – getting closer together
Pre-1995
10 minutes
2,000ft
In-Trail Separation
Vertical Separation
Reduced Vertical Separation Minima (RVSM)
- above 29,000ft (=Flight Level 290 = FL290)
10 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
NextGEN & SESAR objectives – getting closer together
Pre-1995
10 minutes
Present day
5 minutes
1,000ft
2,000ft
In-Trail Separation
Vertical Separation
Reduced Vertical Separation Minima (RVSM)
- above 29,000ft (=Flight Level 290 = FL290)
11 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
NextGEN & SESAR objectives – getting closer together
Pre-1995
10 minutes
Present day
5 minutes
NextGEN & SESAR proposals: 2020+
105 seconds
500ft
1,000ft
2,000ft
In-Trail Separation
Vertical Separation
Reduced Vertical Separation Minima (RVSM)
- above 29,000ft (=Flight Level 290 = FL290)
12 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
NextGEN & SESAR objectives – getting closer together
Pre-1995
10 minutes
Present day
5 minutes
NextGEN & SESAR proposals: 2020+
105 seconds
500ft
1,000ft
Air Data Computers/Modules will require
minimum ±0.25 millibar accuracy to operate in
specific proposed NextGEN/SESAR airspace.
2,000ft
In-Trail Separation
Equates to ±18ft altitude & ±0.35 knots IAS
Vertical Separation
Reduced Vertical Separation Minima (RVSM)
- above 29,000ft (=Flight Level 290 = FL290)
13 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EUROCAE ED-140
EUROCAE Working Group 68
Improving Situational Awareness: High Accuracy Air Data
Vibrating Cylinder Technology:
Ultra high ±0.25mbar accuracy that exceeds RVSM and
meets future NextGen / SESAR requirements
Drift free and requires no calibration
Low cost of ownership: No routine maintenance other
than leak tests for pneumatic pipework connecting to ADC
Developed for Flight Critical Applications:
14 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
DO-178C Level A Software
DO-254 Level A Hardware
ARP4754 Safety Certified - Meets 1 in 10-10 Probability of
Hazardously Misleading Information
SIL3 Compliant Dual Core Processor (TMS570) with
duplicate application running in lock-step. Crosscomparison for each line of code execution
Extensive continuous built in test, loopback checking,
CRC checking, windowed watchdog
Vibrating Cylinder Technology Air Data Computer
Baro Correction:
ARINC 575 potentiometer or ARINC 429
±0.07% Measurement Accuracy (Baro Pot)
1083.5 to 745 mbar (equivalent to +1867 to -8266 feet)
TAT Inputs:
100 (BS.3G148)
130 (BS.2G148)
500 (ARINC 706-4)
Weight: 0.6kg /1.3lb max.
Dimensions: 170Lx110Wx430H mm
6.7”Lx4.4”Wx1.7”H
15 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
ADC parameter outputs:
ARINC 429: 12.5/100kbps
Flight Critical Ethernet: ARINC664P7 End-System
MIL-STD-1553B Remote Terminal
Static Pressure (Ps)
Pressure Altitude (H)
Vertical Speed (H')
Maximum Allowable Airspeed (Vmo)
Barometric Corrected Altitude (Hbc)
Barometric Correction
Differential Pressure (qc)
Total Pressure (Pt)
Indicated Airspeed (Vi)
Computed Airspeed (Vc)
Mach Number (M)
Total Outside Air Temperature (t)
Static Outside Air Temperature (s)
True Airspeed (Vt)
Indicated Angle of Attack
Corrected Angle of Attack
Improving Situational Awareness: Enhanced Fault Isolation
Static holes (x6) around the tube
circumference null out pressure
differentials at different angles of attack
Central port is piped to main Pitot
sensor for IAS/Mach measurement
“Delta P” ports above and below the
central port connect to a differential
pressure sensor in the ADC to provide
Angle of Attack
16 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Air Data – Source Selection
Standby Flight
Display System
Captain
Primary Flight Display Navigation Display
P
S
TAT
AoA
CAPT
F/O
ADC
ADAHRS
ADIRS
17 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EICAS
Engine Instrument &
Crew Alerting System
First Officer
Primary Flight Display Navigation Display
CAPT
F/O
ADC
ADAHRS
ADIRS
EFIS: Left/Right Disagreement
Standby Flight
Display System
CHECK IAS
Captain
Primary Flight Display Navigation Display
P
S
TAT
AoA
CAPT
F/O
ADC
ADAHRS
ADIRS
18 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EICAS
Engine Instrument &
Crew Alerting System
First Officer
Primary Flight Display Navigation Display
CAPT
F/O
ADC
ADAHRS
ADIRS
EFIS: Left/Right Disagreement
Standby Flight
Display System
CHECK IAS
Captain
Primary Flight Display Navigation Display
P
S
TAT
AoA
CAPT
F/O
ADC
ADAHRS
ADIRS
19 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EICAS
Engine Instrument &
Crew Alerting System
First Officer
Primary Flight Display Navigation Display
CAPT
F/O
ADC
ADAHRS
ADIRS
Improving Situational Awareness: Fault Tolerant Networked Sensors
Standby Flight
Display System
Captain
Primary Flight Display Navigation Display
P
S
TAT
AoA
CAPT
F/O
ADC
ADAHRS
ADIRS
20 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EICAS
Engine Instrument &
Crew Alerting System
First Officer
Primary Flight Display Navigation Display
CAPT
F/O
ADC
ADAHRS
ADIRS
Improving Situational Awareness: Fault Tolerant Networked Sensors
Standby Flight
Display System
CAPT
PITOT INOP
Captain
Primary Flight Display Navigation Display
P
S
TAT
AoA
CAPT
F/O
ADC
ADAHRS
ADIRS
21 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
EICAS
Engine Instrument &
Crew Alerting System
First Officer
Primary Flight Display Navigation Display
CAPT
F/O
ADC
ADAHRS
ADIRS
Which Airborne Network? (must be DAL A certified: Flight Critical)
ARINC 629
– Early 1990s technology. Only adopted on single aircraft type
MIL-STD-1553B
– Command/Response, more for military avionics, mission systems
ARINC 825 CAN Bus
–
CANbus (Controller Area Network) widespread and most established in automotive industry
TTE - Time Triggered Ethernet
– Time Triggered Protocol 4Mbps Ethernet
– Deterministic, time synchronised. Uses RS485 as physical layer
– Star topology, dual redundant
Flight Critical Ethernet - ARINC664Pt7
– 100Mbps. Copper and Fibre Implementations
22 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Helicopter Air Data Probe Locations
Agusta A109
Optimal location for Static Ports is slightly aft of the rotor
disc centreline with the least downwash effect
Sikorsky S-76
Pitot Probes are positioned forward as
practical to minimise source errors
Eurocopter EC155
Co-Pilot and Standby Pitot
Probes can be combined on
the same stalk to reduce the
fuselage attachment points
Sikorsky S-76
23 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
OAT probes, used to compute TAS are typically mounted on the
underside of the fuselage to avoid errors from direct sunlight
Helicopter Air Data Computers: Problems that need a Solution
Different set of problems to fixed wing aircraft:
1. Instantaneous downwash increase when pilot
applies collective shows as a negative Vertical
Speed when the helicopter is in fact climbing
2. Rotor blade modulation gives approx 4Hz air
pressure pulse/rev
3. Downwash from rotor blades at low airspeed make
measurement impossible at low airspeed (<30kt)
24 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Helicopter Air Data Computers: Problems that need a Solution
Different set of problems to fixed wing aircraft:
1. Instantaneous downwash increase when pilot
applies collective shows as a negative Vertical
Speed when the helicopter is in fact climbing
2. Rotor blade modulation gives approx 4Hz air
pressure pulse/rev
3. Downwash from rotor blades at low airspeed make
measurement impossible at low airspeed (<30kt)
25 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Helicopter Air Data Computers: Problems that need a Solution
Different set of problems to fixed wing aircraft:
1. Instantaneous downwash increase when pilot
applies collective shows as a negative Vertical
Speed when the helicopter is in fact climbing
2. Rotor blade modulation gives approx 4Hz air
pressure pulse/rev
3. Downwash from rotor blades at low airspeed make
measurement impossible at low airspeed (<30kt)
26 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Helicopter Air Data Computers: Problems that need a Solution
Different set of problems to fixed wing aircraft:
1. Instantaneous downwash increase when pilot
applies collective shows as a negative Vertical
Speed when the helicopter is in fact climbing
2. Rotor blade modulation gives approx 4Hz air
pressure pulse/rev
3. Downwash from rotor blades at low airspeed make
measurement impossible at low airspeed (<30kt)
27 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
LASP – Low AirSpeed Probe
LASP is installed on the tail rotor
tail fin or fenestron
High Accuracy Air Data Computer(s) connect to
existing pitot probes and static ports
28 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
LASP output connects to Air Data Computers
(single or dual installation) which merges the
sensor data to produce a high accuracy output to
EFIS & Flight Control (SAS/AFCS)
LASP: Low AirSpeed Probe – How it works
1
2
LASP operates by measuring the time of flight of an
ultrasonic sound pulse deflected off a top-plate, known as
the parabola. The reason for the 45 degree up and down
sound path is to remove any vertical airspeed component.
If there is a downwind component, the sound pulse will
arrive at the receiver faster than if the surrounding air was
static. Conversely, the pulse is slowed down if the airflow
is directly towards the transducer
Once the first pulse is detected, the time of flight is
calculated, the ultrasonic receiver is then re-configured as
a transmitter and a pulse is transmitted back the same
way. The reason is to remove any common mode errors,
such as humidity and temperature effects that would affect
the measurement of a single point-to-point transmission.
29 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Parabola
Ultrasonic Transducers
LASP: Low AirSpeed Probe – How it works
3
By having transmit/receive pairs positioned at 90 degrees,
it is possible to resolve the wind vectors and the x and y
axes and compute windspeed and direction. The
transmitters and receiver operate on a continuous
sequence, interleaving each of the 4 measuring paths
30 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
LASP: Low AirSpeed Probe – How it works
4
LASP measures the vector of
forward airspeed component
and windspeed & direction
An AHRS input is used for lever
arm correction (e.g. to remove
errors due to helicopter yaw)
and bank angles
31 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
“Forward” Speed
Indicated Air Speed
Helicopter Air Data System: ADC+LASP with Kalman Filter
Kalman filter (in ADC) uses weighting algorithm to provide highest accuracy airspeed across operating range
Auto cross-comparison between dual ADCs, single LASP and GPS (derived Groundspeed) used for error checking
LASP will also provide negative airspeed output in reverse flight
0
10kt
Accuracy
±3.0kt
Accuracy
±3.5kt
20kt
30kt
Accuracy
±4.0kt
40kt
Accuracy
±4.5kt
IAS measurement transitions to LASP at Low Airspeed
32 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
50kt
60kt
Accuracy
±2.5kt
70kt+
Accuracy
±1.9kt
ADC provides IAS above 35-50kt
Conventional EFIS Symbology does not depict IAS Vector
33 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Proposed Helicopter EFIS Symbology
332/21
16
34 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Proposed Helicopter EFIS Symbology
Wind Direction & Speed Vane
332/21
“Forward” Speed
Indicated Air Speed
16
Apparent Windspeed and Vector
35 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Helicopter Low Airspeed Probe – Dual ADC+LASP
Pitot Pneumatic Tubing
Static Pneumatic Tubing
ARINC 429
RS422
Analog
Combined Right
Pitot and SBY
Left
Pitot
Left
ADC
Right
ADC
Standby
Static Port
Cross-Compare Bus
Left Static
Port
Outside Air Temp probe
Mounted underneath fuselage
(out of direct sunlight)
Right OAT Probe
LASP - Low Airspeed Probe Mounted on Tail Rotor Fin
36 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Right
Static Port
Helicopter Low Airspeed Probe – Dual ADAHRS+LASP
Pitot Pneumatic Tubing
Static Pneumatic Tubing
ARINC 429
RS422
Analog
Combined Right
Pitot and SBY
Left
Pitot
Left
ADAHRS
Right
ADAHRS
Standby
Static Port
Cross-Compare Bus
Left Static
Port
Outside Air Temp probe
Mounted underneath fuselage
(out of direct sunlight)
Right OAT Probe
LASP - Low Airspeed Probe Mounted on Tail Rotor Fin
37 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright
Right
Static Port
Defense Solutions Division
Thank You !
Paul Hart
Q&A
CTO Curtiss-wright Avionics & Electronics
38 | April 1, 2015 | Proprietary | © 2015 Curtiss-Wright