Process control?

▪ Measurement and control engineering controls dynamic

systems by adjusting a process based on
“James, fly me home!”
measurements.
▪ Without measurement, there is steering.
▪ With measurement, there is control.
History and Basic Principles
▪ The measurement is compared to the desired value and
of Automatic Flight
adjusted to produce a particular desired result.

▪ Example: temperature control in a room/oven.

January 2023 – Paul HOPFF

3

Process Control What is a “process”?

Plan Noise

▪ A process can refer to a period in which something develops.

CONTROLLER PROCESS
▪ A process can occur in many areas. Natural processes are
Commands
about developments that occur in nature.
▪ Industrial processes are found in chemistry, power plants,
Feedback (measurements) production industries, etc…

4 2
 The early years... A Flight is a Controlled Process

▪ No systems, except the engine

Flightplan Noise
▪ Almost no instruments
▪ Flight controls
▪ Feedback through pilot visual
(and aural?) observations PILOT FLIGHT
+ DYNAMICS
SYSTEMS Steering

Flight Parameters (Pilot observations + Instruments)

▪ Anthony Fokker (1910)

7 5

Elmer Sperry Lawrence Sperry Evolution 1900-Today

(1860-1930)

▪ The Sperry Corporation developed

Lawrence Sperry
(1892-1923) the original gyroscopic autopilot in
1912. The device was called a
“gyroscopic stabilizer apparatus,”
and its purpose was to improve
stability and control of aircraft.
▪ Lawrence Sperry demonstrated it
with startling success in France in
1914.
▪ Sperry is also credited with
developing the artificial horizon still
used on most aircraft

Sperry Corporation - Wikipedia 8

Manual Flight Automatic Flight 6
 James “Jimmy” Doolittle Lawrence Sperry
▪ In 1929, he became the first pilot to take off, fly and land an airplane
using instruments alone, without a view outside the cockpit. ▪ The Sperry Corporation developed
Lawrence Sperry
(1892-1923) the original gyroscopic autopilot in
▪ He helped develop, and was then the first to test, the now 1912. The device was called a
“gyroscopic stabilizer apparatus,”
universally used artificial horizon and directional gyroscope.
and its purpose was to improve
▪ He attracted wide newspaper attention with this feat of "blind" flying stability and control of aircraft.
and later received the Harmon Trophy for conducting the ▪ Lawrence Sperry demonstrated it
experiments. with startling success in France in
1914.
▪ Sperry is also credited with
developing the artificial horizon still
used on most aircraft

(1896-1993) 11 9

James “Jimmy” Doolittle Elmer Sperry Lawrence Sperry

(1860-1930)

Lawrence Sperry ▪ The Hewitt-Sperry Automatic

(1892-1923) Airplane was a project
undertaken during World War I
to develop a flying bomb, or
pilotless aircraft capable of
carrying explosives to its
target.
▪ First flight: September 1917
▪ It is considered by some to be
a precursor of the cruise
missile.

12 10
 Wiley Post’s solo flight around the world Wiley Post’s solo flight around the world
(1933) (1933)

Wiley Post
(1898-1935)

Lockheed Vega “Winnie Mae”

(National Air & Space Museum – Washington)
15 13

War times... Wiley Post’s solo flight around the world

(1933)
▪ The Honeywell C-1 Autopilot was an
electronic-mechanical system used to Wiley Post
lessen pilot fatigue by automatically (1898-1935)
flying an airplane in straight and level
flight.
▪ It could also be used to fly the aircraft
through gentle maneuvers.
▪ When combined with the Norden
bombsight, it created the stability
necessary to bomb targets accurately
from high altitude.

Lockheed Vega “Winnie Mae”

Installed on the Boeing B-17, B-29 and Consolidated B-24 Liberator (National Air & Space Museum – Washington)
16 14
 Evolution... in the cockpit War times...

▪ This autopilot essentially consisted of two spinning

gyroscopes located in cases attached to the airplane.
▪ One gyroscope, called the Flight Gyro, was located near
the aircraft's center of gravity (10) and detected changes in
roll and pitch.
▪ The Directional Gyro, located in the bombsight stabilizer
(1), detected changes in yaw.
▪ Using a series of electrical signals, the
C-1 Autopilot controlled the aircraft with servos connected
to the control surfaces (15, 18, 19).

19 17

Automation for... All phases of flight! War times...

▪ Initially attitude stabilization.

▪ Evolution towards automatization of almost all phases of flight.
▪ Most challenging: the landing phase...
▪

▪ https://youtu.be/5SWIUrT08XQ (Movie made by Disney!)

▪ WWII Operation of C-1 Autopilot - 250152-01 | Footage Farm Ltd

▪ https://youtu.be/Ofp49oBt60Q (Movie made by Disney!)

▪ A simulated flight on the B-17G

▪ Using the C-1 Autopilot - FSX A2A B17G Flying Fortress -

Fokker Y1C-14B. - U.S. Air Force The Havilland Trident 1 - BEA YouTube
August 23rd, 1937 June 10th, 1965 20 18
 Finally: automatization of the take-off! The first completely automatic landing of
an airplane.
▪ 23 August 1937: The first completely automatic
landing of an airplane took place at Patterson Field,
near Dayton, Ohio. With Captain George Vernon
Holloman in the cockpit, and Captain Carl Joseph
Crane and Mr. Raymond K. Stout in the cabin, a
Fokker Y1C-14B, Army serial number 31-381,
departed Wright Field then automatically intercepted a
series of four radio beacons, initiated a descent, and
landed at nearby Patterson Field and braked to a stop,
all without any input from the pilot.
▪ The automatic landing system used a barometric
altimeter, a radio compass and Sperry Autopilot.

Airbus has achieved autonomous taxiing, take-off and landing (ATTOL) of a commercial aircraft through fully 23 21
automatic vision-based flight tests using on-board image recognition technology (January 2020)

Why automatic flight? 1965 – The first ‘commercial’ Autoland

▪ Need for crew workload reduction

▪ Crew comfort.
▪ Need for optimization
▪ “A well-designed process controller offers advantages
over a human controller.”
▪ New navigation requirements
▪ Impossible to comply with in manual flight.
1965 – Hawker Siddeley Trident

24 22
 Optimization? Crew Workload Reduction

▪ 1950: 5-person cockpit (DC-6)

▪ 1960: 4-person cockpit (B707)

▪ 1970: 3-person cockpit (B747)

▪ 1980: 2-person cockpit (A310)

▪ ....

▪ 20XX: 1-person cockpit?

Boeing E-3 Sentry, commonly

known as AWACS, at FL300
27 1935: Boeing 314: 5-person crew... 25

New requirements? Optimization?

Airbus A330 - CAT 3 landing at Brussels Airport...

Manually flown

Automatically flown

ANT

28 26
 Internal versus External Conditions Auto Flight Control Systems (AFCS)

▪ Internal conditions are those derived from sensors ▪ AFCS is generally understood to mean any flight control
within the AFCS, and relate to pitch, roll and yaw augmentation that assists the pilot in flying an aircraft.
attitudes, and their associated rates and ▪ Overcome a stability and control deficiency.
accelerations. ➔ INNER LOOP control ▪ Dutch Roll
▪ Improve the handling or ride qualities.
▪ External conditions relate to airspeed, altitude, track
▪ Holding altitude or heading.
and other navigational information derived from
▪ Turn to and capture of a new track.
sensors external to, but integrated with the AFCS.
▪ Carry out a manoeuvre that the pilot is unable to perform.
➔ OUTER LOOP control
▪ ILS-coupled approach in low visibility.
▪ Autopilots are typically outer loop devices.
31 29

A Flight is a Controlled Process Types of AFCS

▪ Rate Damping Systems / Control

Flightplan Noise
Augmenting Systems
▪ Stop unwanted rates of motion from
developing.
PILOT ▪ Make rates commanded by the pilot more
FLIGHT
+ predictable.
DYNAMICS
Automatic Pilot Steering
Commands ▪ Autopilots
▪ Hold the aircraft to an external condition.

▪ Operational Autopilots
Flight Instruments ▪ Perform a manoeuvre or series of
Navigation Systems manoeuvres, such as an automatic ILS
Observations of the pilot
approach, flare and landing.
32 30
 Components of an AFCS Closed Loop Handling
Information Transfer
Information Transfer

Cockpit Control Stability/Control Aircraft

Pilot Cockpit Control Stability/Control Aircraft
Controls Surfaces Characteristics Reaction Pilot
Controls Surfaces Characteristics Reaction
MAN-MACHINE LOOP
MAN-MACHINE LOOP

Inner Loop

Outer Loop

Output Input
Computers
Devices Sensors
35 33

Input Sensors (Examples) Closed Loop Handling

▪ Inner Loop: Information Transfer

▪ Pitch & Roll attitude Vertical ref. Gyro - IRS

▪ Pitch, Roll, Yaw rates Rate Gyroscopes - IRS
Cockpit Control Stability/Control Aircraft
Pilot
Controls Surfaces Characteristics Reaction
▪ Outer Loop:
MAN-MACHINE LOOP
▪ Heading Compass, INS/IRS
▪ Airspeed, Altitude Air Data System
▪ Groundspeed INS/IRS - GPS Inner Loop

▪ Navigation Data Radio Nav - INS/IRS - GPS

Outer Loop
IRS – Inertial Reference System
INS – Inertial Navigation System
AFCS LOOP
36 34
 Primary Flight Controls - Schematic Computer (controller) Functions

▪ Amplification
▪ Integration
▪ Differentiation
▪ Limiting
▪ Shaping (non-linear amplification)

(Power Control Unit - PCU) ▪ PROGRAMMING

39 37

Components of an AFCS Output devices: Servomechanisms

▪ What?
▪ A closed-loop control system in which a small power
input controls a much larger power output in strictly
proportionate manner.
▪ Functions?
▪ Detect the difference between an input and an output.
▪ Amplify the error signal.
▪ Control the closing of the servo loop by providing the
feedback.
Generic S-TEC System 55X

40 38
 System Architecture Classification of Systems
MCP/FCU

▪ The number of control loops, or channels, is dependent on the

I number of axes about which control is to be exercised.
N
P G
U U ▪ Single-axis: Roll axis only.
FCC
T I
Pitch Servo
D
S Roll Servo A ▪ Two-axis: Roll & Pitch axes.
Y Yaw Servo N
S C
T E
▪ Three-axis: Roll, Pitch & Yaw axes.
E
M
S

ARINC 429 ANALOG SIGNALS

43 41

System Architecture System Protection

MCP/FCU
▪ Comparators
▪ Outputs from the sensors and actuators are monitored
FCC1 and compared.
I Pitch Servo
N Roll Servo
P
Yaw Servo G ▪ Rate trigger systems
U U
FCC2
T I ▪ Thresholds are introduced that will trip off the system if
Pitch Servo
D the rate exceeds a predetermined value.
S Roll Servo A
Y Yaw Servo N
S FCC3 C ▪ System redundancy
T Pitch Servo E
E Roll Servo ▪ Duplex system
M
S Yaw Servo
▪ Cross-coupled feedback
▪ Triplex system
ARINC 429 ANALOG SIGNALS
(Legacy architecture)
44 42
 Autopilot Modes - Inner Loop Flight Control Computer (FCC)

CPU 1 CPU2
Pitch Axis Roll Axis
A/D
▪ Pitch Hold ▪ Bank Hold Analog Sensors CONVERTERS
(e.g. Synchro information)

D/A
CONVERTERS
Analog Outputs
(e.g. Servos)

DISCRETE
Discrete Inputs INPUTS
(e.g. Engage/Disengage)

DISCRETE
OUTPUTS
Discrete Outputs
(e.g. Interlocks)

429 Other Avionics

TRANSMITTERS ARINC 429
(e.g. EFIS)

Input Data sources 429

ARINC 429
(e.g. IRS, DADC, MCP) RECEIVERS

FLIGHT CONTROL COMPUTER

47 45

Autopilot select - Manual demand Inner Loop Stabilisation

Aerodynamics

CWS
Control Wheel Steering Manually operated
flight controls

Inner loop

Attitude Error Signal Servo

sensing sensing processing actuators
Feedback Control surfaces

Autopilot select
and manual INNER LOOP STABILISATION
demand inputs
Belgian Defence – Lockheed C-130H
48 46
 Autopilot Modes - Outer Loop Inner Loop Control
Aerodynamics
Pitch Axis Roll Axis
▪ Altitude Select and Hold ▪ Heading Select and Hold
Inner loop

▪ Vertical Speed ▪ Radio Navigation (VOR) Attitude Error Signal

sensing sensing processing
▪ Airspeed Select and Hold Feedback

▪ Vertical Navigation (VNAV-FMS) ▪ Lateral Navigation (LNAV-FMS) Autopilot select

Interlock Servomotors
and manual
Controls (actuators)
▪ Glide Slope demand inputs
▪ Localizer Control surfaces

▪ Approach

▪ Flare (autoland) ▪ RWY Align (autoland)

▪ Roll out (autoland) INNER LOOP STABILISATION

51 49

Autopilot Mode Selection Inner + Outer Loop Control

Aerodynamics

Boeing
Mode Control Panel (MCP) Inner loop

Attitude Error Signal

sensing sensing processing
Feedback

Autopilot select
Interlock Servomotors
and manual
Airbus Controls (actuators)
demand inputs
Flight Control Unit (FCU) Control surfaces

Manometric,
radio nav. and Signal
other signal processing
sensing
Outer loop

INNER LOOP STABILISATION

AND OUTER LOOP CONTROL
52 50
 The 737 MAX disaster... Interlock Controls
Aerodynamics

▪ Design deficiency
Inner loop
▪ Single AoA-sensor
Attitude Error Signal
sensing sensing processing
▪ Knowledge deficiency Feedback

▪ No awareness of MCAS-function Autopilot select

Interlock Servomotors
and manual
Controls (actuators)
demand inputs
▪ Training deficiency Control surfaces

▪ How to handle a trim runaway? Manometric,

radio nav. and Signal
other signal processing
sensing
Outer loop

INNER LOOP STABILISATION

AoA: Angle of Attack AND OUTER LOOP CONTROL
55 53
MCAS: Maneuvering Characteristics Augmentation System

How to “disengage” the autopilot? Purpose of Interlock Controls

▪ Ensure that the system is in a condition whereby it may safely take

▪ DISENGAGEMENT of the autopilot: a VITAL action! control of the aircraft.
▪ Several methods: ▪ Check that all involved systems are correctly supplied.
▪ Disengage button on stick/yoke ▪ Check that the required data for the intended operation are available and
▪ Manual override of the controls valid.
▪ Autopilot main switch to “OFF” ▪ Check that the aircraft is in a state compatible with the intended
operation.
▪ Pull the autopilot/servo circuit breaker(s)
▪ Is it safe to engage the autopilot in the intended mode?
▪ Aural and/or visual warning at disengagement!
▪ Is it safe to continue to fly in the selected mode?

56 54
 Autopilot / Flight Director Autopilot / Flight Director
Aerodynamics

Inner loop

Attitude Error Signal

sensing sensing processing
Feedback

Autopilot select
Interlock Servomotors
and manual
Controls (actuators)
demand inputs
Control surfaces

Manometric,
radio nav. and Signal
other signal processing
sensing
Outer loop

INNER LOOP STABILISATION

AND OUTER LOOP CONTROL Airbus: Flight Control Unit Boeing: Mode Control Panel
59 57

Flight Director (FD) - Principles Autopilot / Flight Director

Aerodynamics

▪ The FD is a command instrument which instructs the pilot Inner loop

how to steer a particular manoeuvre (e.g. interception of a Attitude Error Signal

VOR radial). sensing sensing processing
Feedback

▪ Commands are displayed by moving magenta bars on the

Autopilot select
(E)ADI: Interlock Servomotors
and manual
Controls (actuators)
demand inputs
▪ Roll commands: Vertical bar Control surfaces

▪ Pitch commands: Horizontal bar Manometric,

radio nav. and Signal
other signal processing
sensing
Outer loop

EADI: Electronic Attitude Director Indicator INNER LOOP STABILISATION

AND OUTER LOOP CONTROL
60 58
 Automatic Landing (AUTOLAND) Flight Director (FD) - Principles

▪ Approach and landing are the most demanding phases of flight!

▪ Control of the aircraft is needed about all three axes
simultaneously, as well as control of airspeed through engine power
changes.
▪ System Reliability: 10 -6 to 10-7.
▪ The substitution of the pilot’s direct vision with an automatic
ground guidance system, having an integrity and reliability of the
same high order as that demanded of the ‘on-board’ system.

▪ Provision of adequate monitoring information on the progress of

the approach and landing manoeuvre.

63 61

RVR – Runway Visual Range Automatic Landing (AUTOLAND)

Airbus: Flight Control Unit Boeing: Mode Control Panel

64 62
DH – Decision Height RVR – Runway Visual Range

Ceilometer

67 65

DH – Decision Height RVR – Runway Visual Range

68 66
Flight Control System Requirements - ICAO AH – Alert Height

71 69

Fail-Passive Autoland System AH – Alert Height

72 70
 Category 3 RVR minima - ICAO Fail-Operational Autoland System

75 73

Weather minima Example “fail operational” architecture

MCP/FCU

Cat. 1
200
FCC1
I Pitch Servo
N Roll Servo
Cat. 2 P G
Yaw Servo
U U
100 FCC2

Decision Height (ft)

T I
Pitch Servo
D
A B C S Roll Servo A
50 Y Yaw Servo N
S FCC3 C
Cat. 3 T Pitch Servo E
0 E Roll Servo
M
1000 800 600 400 200 50 0 S Yaw Servo
550 300 175
Runway Visual Range (RVR - meters)
Amendment ICAO Annex 6 – 19/11/2009
ARINC 429 ANALOG SIGNALS
76 74
 Synergy AFCS – A/T Autoland Sequence
Detailed 4D FPLN FCU / NCP
CONTROL PANEL

FMC
CONTROL SURFACE
FPLN SERVOS

THROTTLES
AUTOTHROTTLE
FCC FADEC
SERVOS

Commands to
A/T
fly the 4D FPLN
FMC: Flight Management Computer
FCC: Flight Control Computer (autopilot)
(Legacy architecture) A/T: Auto-Throttle computer
79 77

Autoland Sequence Autothrottle System (A/T)

▪ System to control the thrust of an aircraft’s engines

with specific engine design parameters.
▪ The throttle position of each engine is controlled to
maintain a specific value of thrust or a target
airspeed, over the full flight regime from take-off to
touchdown.
▪ The A/T is designed to operate in conjunction with an
AFCS to maintain an aircraft’s speed and vertical
path.

80 78
ICAO Problem Statement related to ‘5G’ LRRA – Radio Altimeter – Operating principle

Most radar altimeters use a triangular modulated frequency technique on the

transmitted energy. The transmitter/receiver generates a Continuous Wave (CW) signal
varying from 4250 to 4350 MHz modulated at 100 MHz

83 81

ICAO Problem Statement related to ‘5G’ ICAO Problem Statement related to ‘5G’
▪ Radar altimeters (RA), operating at 4.2-4.4 GHz, are the only sensors onboard a civil aircraft which provide
a direct measurement of the clearance height of the aircraft over the terrain or other obstacles (i.e. the
Above Ground Level - AGL - information).
▪ The RA systems’ input is required and used by many aircraft systems when AGL is below 2500 ft. Any
failures or interruptions of these sensors can therefore lead to incidents with catastrophic outcome,
potentially resulting in multiple fatalities. The radar altimeters also play a crucial role in providing situational
awareness to the flight crew.
▪ The measurements from the radar altimeters are also used by Automatic Flight Guidance and Control
Systems (AFGCS) during instrument approaches, and to control the display of information from other
systems, such as Predictive Wind Shear (PWS), the Engine-Indicating and Crew-Alerting System (EICAS),
and Electronic Centralized Aircraft Monitoring (ECAM) systems, to the flight crew.
▪ There is a major risk that 5G telecommunications systems in the 3.7–3.98 GHz band will cause harmful
interference to radar altimeters on all types of civil aircraft—including commercial transport airplanes;
business, regional, and general aviation airplanes; and both transport and general aviation helicopters. If
there is no proper mitigation, this risk has the potential for broad impacts to aviation operations in the
United States as well as in other regions where the 5G network is being implemented next to the 4.2-4.4
GHz frequency band.
84 82
 Primary Flight Display (Airbus) LRRA – Radio Altimeter – Typical installation

87 85

TAWS / EGPWS – Callouts LRRA – Radio Altimeter – Typical Displays

Possible callouts – not all implemented on each aircraft!

88 86
 Boeing 737-800 Primary Flight Display (Airbus)

Flight Mode Annunciator

Flight Director

91 89
https://youtu.be/2SNKo7JYLL4

EBBR – LVP Chart

• Critical Area
• Sensitive Area

92 90
https://youtu.be/trEuAwRnsOY
 Airbus – « Dragon Fly » ILS Sensitive & Critical Areas

▪ Toulouse, 12 January 2023 – Airbus UpNext, a

wholly owned subsidiary of Airbus, has started
▪ ILS critical area. An area of defined dimensions about the localizer and glide path
testing new, on ground and in-flight, pilot assistance
antennas where vehicles, including aircraft, are excluded during all ILS operations.
technologies on an A350-1000 test aircraft.
▪ Note.— The critical area is protected because the presence of vehicles and/or aircraft
▪ Known as DragonFly, the technologies being
inside its boundaries will cause unacceptable disturbance to the ILS signal-in-space.
demonstrated include automated emergency
diversion in cruise, automatic landing and taxi ▪ ILS sensitive area. An area extending beyond the critical area where the parking
assistance and are aimed at evaluating the and/or movement of vehicles, including aircraft, is controlled to prevent the
feasibility and pertinence of further exploring possibility of unacceptable interference to the ILS signal during ILS operations.
autonomous flight systems in support of safer and
▪ Note.— The sensitive area is protected against interference caused by large moving
more efficient operations.
objects outside the critical area but still normally within the airfield boundary.

95 93

94
https://youtu.be/IyYxbiZ1FCQ