InstrumentationATPL

Andy / andy@bristol.gs

60 Questions - 1hour 30 mins

Temperature

Celsius and Kelvin 100C - 373K 0C - 273K -273C - 0K

Datums points of:

0F at the freezing point of salt water and;
100F at the average temperature of the human body

On the Fahrenheit scale:

Salt water freezes at 0F
Fresh water freezes at 32F
Fresh water boils at 212F

==Q. What is 9C expressed in Fahrenheit?== Formula: F = C x 9 / 5 + 32 OR use the CRP5 A. 48.2F

Temperature sensing in aviation

Mercury Thermometer - corrosive to airframes, not used much
Bimetallic Sensors
Resistance thermometers
thermocouples

Static Air Temperature and Total Air Temperature

total is dynamic temperature plus the static temperature. It is the SENSED temperature
Static Air Temp is the real air temp
Difference is caused by compression (ram rise) and friction
TAT = SAT + Ram Rise in Temp.

TAT = SAT (1 + 0.2 Kr x M2) Needs to be done in KELVIN!

==TAT will always be the same as OR higher than the SAT.==

==Q. Given M0.72, Measured impact Temp: -40C, Recovery factor (KR) = 0.9, What is the OAT?== A. -59C

Angle of Attack - angle of the chordline (alpha) to the relative airflow

AoA - Vane Sensor

vane is kept in place by the relative airflow but it is free to rate in airflow.
Electrically anti-iced.
Sends angle signal to indicator
Analogue

==Q. At what angle will the Vane sensor be at the 6 hour time in flight, compared to the 2 hour point?== A. further down, because the aircraft has lost weight and will require a greater AoA

AoA - Airflow direction detector

aka conical slotted probe
electrically anti-iced
rotates with the airflow
indicates on flight deck

==Q. What will be the angle of the airflow director in a climb?== A. C

AoA - Specific slaved pitot probe

indicates differential pressure

Total (pitot) pressure = static pressure + dynamic pressure

Pitot Tube

total pressure goes in
mounted away from boundary layer
electrically anti-iced
May include static measurement
Multi probes on large aircraft

Combination Pitot / Static Probe

Electrically anti-iced
Pitot angled for best PEC
Static minimising dynamic reading
Could still freeze behind heater

==Q. The pitot tube is attached to a mast as to:== A. to locate it outside the boundary layer

Static Port

One on early Cessna types
Two on most light aircraft
Errors cancel each other out
Multiple on large aircraft
May be heated
No dents/chips within that line

Multiple Sensors

Two pitot / static sensors
AoA vane
Temp probe
free of dent / chips

Alternate Static Source - Light Aircraft

Suspected static port blockage
Pull to admit cockpit air - airflow is slightly lower pressure, over reads slightly

Basics of an ADC, Large aircraft will have multiple ports and duplication for redundancy

Large AC Schematics

Duplication for redundancy
cross fed to cancel out errors
interchangeable parts
not all ports used on all stations
standby fed directily - bypassing ADC
no alternate static - pressurised

Pitot Static System Sensing Errors

Simple Altimeter

Aneroid Capsule
Static pressure fed
Partially evacuated capsule
Reacts to pressure changes
Subscale control to set QFE/QNH
Basically a barometer calibated to height

Blockages and leaks

Static port blocked - indication freezes, use alternate static source if possible, which will over read (a bit)

Errors

P - Position Error / Pressure Error
I - Instrument
T - Temperature
H - Hysteresis (degrading of the elasticity/sensitivity over time)
B - Barometric
L - Lag
O - Orographic
T - Transonic Jump (Supersonic airflow over the wing, to the shock wave. Causes instruments to jump (not in exam))

“High to low, careful go”

Altimeters

Subscale ranges

UK 800-1050hPa
US 950 -1050hPa

Pressure Altitude

Pressure altitude = Flight levels
standardised Flight Levels with altimeter set to 1013.25hPa set
True height of a pressure altitude goes up and down with temperature and surface pressure

LO: ‘the pressure altitude is the altitude in a standard atmosphere that corresponds to the actual static pressure’

Density Altitude

Pressure Altitude corrected for Temperature
Used for performance calculations

LO: ‘the density altitude is the altitude of the standard atmosphere which has the same air density as the actual conditions’

Sensitive Altimeter

two aneroid capsules
dual gearing to reduce friction (and lag)
has a vibrator to tap the back of the screen to prevent the stiction of the needles
capsules move a dial via a gearbox

Servo Assisted Altimeter

two or more capsules for sensitivity
Moves the I bar against an E bar which will detect / pick up the resistance / flow of the difference of the movement of the air gap between the E/I bar
Backdriven cam resets the I bar
Creates a current that drives a servo motor
motor drives gear to dial face

ADC Driven Systems - EFIS

Accurate indication inside pointer
Note hatched area on altitude
Tape translates behind pointer
FMS selected ALT at top (magenta)
QNH indication at bottom
hPa, in/Hg or STD through DCP

Accuracy Limits

20m or 60ft for altimeters with a test range of 0 to 9000m (0 to 30000ft) OR
25m or 80ft for altimeters with a test range of 0 to 1500m (0 to 50000ft)

The Simple VSI

Static air admitted to instrument into
Open capsule AND
Metered orifice
choke valve is there to restrict flow, to allow the measurement of the rate of change
Errors - think PITHBLOT
- Lag
- Pressure
- Instrument
Blocked - return to 0.

Instantaneous VSI

Overcomes lag
‘Dashpots’ cause immediate differential pressure (aka accelerometers)
Unreliable when load factor increases - steep turns >40deg AoB

Diaphragm ASI

Pitot air (dynamic and static) above
Static air below
Statics cancel each other out
Diaphragm movement is dynamic only
But diaphragm is affected by hysteresis Simple ASI
Pitot (dynamic and static) feed
Static Feed
Open capsule movement is dynamic only
Suitable system of linkages
indicates on calibrated scale
blocked pitot - PUD, Pitot blocked, underreads in a descent, POC, Pitot overreads in a climb.
blocked static - SOD, Static OverRead in a descent, SUC, Static blocked, underreads in a climb

Airspeed Indicator

VSO - Stuff out, stall speed MAUM landing config
VS1 - Stall speed MAUM, clean
VMCA - Minimum control speed, One engine Inop.
VYSE - Best vertical climb, single engine
VFE - Flaps Extended
VNO - Normal Operating
VNE - Never Exceed
VLO - Max Landing Gear Operating
VLE - Max landing gear extended
VREF - Landing Speed

IAS

whats on the instrument
subject to uncorrected position and instrument errors

IAS and CAS

PFD
IAS corrected for position and instrument errors
In an ADC CAS is calculated from dynamic pressure using a formula and corrections for position and instrument errors are applied
CAS is notmally displayed on the EFIS so here, IAS = CAS

300 knots - anything above and we will correct for compressibility.

CAS and EAS

CAS corrected for compressibility is EAS
Compressibility is a function of Mach number, which boils down to CAS and Pressure Altitude
So Car and Pressure altitiude derives EAS, or EAS and pressure altitude derives CAS
Compressibility is negligble below 300kt
At low speeds CAS = EAS
Compressibility correction is always negative so, as mach number increases CAS greater than or equal to EAS

EAS and TAS

EAS is the speed at ISA sea level where the dynamic pressure is the same as the TAS as altitude
So at ISA sea level EAS = TAS
The correction between EAS and TAS is for density or density altitude

==Q. FL400, OAT -56.5C, CAS 250kt, Determine the TAS== A. 475kts

==Q. FL250, OAT + 10C, CAS250kt, Determine the TAS== A. 395kts

The Machmeter

Doesn’t need temperature because we’re comparing TAS (temp dependant) with K (temp dependant too)
Pressure instrument
No temp input
Altitude capsule compensates
M = Pt - Ps/PS

ADC Driven IAS / Machmeter

VMO/MMO indicator in CAS
Moveable/ selectable bugs
Striped barber pole

EFIS MACH INDICATIONS

calculated by the ADC
Digitally displayed
normally near the CAS
All speed indications grouped together

MACH Calculation

Q. During a climb at a constant CAS, below the tropopause, what happens to TAS and Mach number? A. Tas and Mach both increase

Q. During a descent at a constant CAS through an isothermal layer what happens to the TAS and Mach? A. Both Decrease

If in an Isotherm, the T and M will be the same because its a layer of constant temp.

Q. Flying level at a constant CAS if the temperature increases what happens to the TAS and Mac Number? A. TAS Increases

Because the air is thinner, aircraft can move though easier, so TAS will increase.

ADC Inputs

Pitot
Static
TAT
AoA
Flap and Landing Gear position
Stored Aircraft Data

Modern systems are called an ADIRU

Gyroscopes

rigidity in space
precession at slower speeds

I REST TAXD, Always either 1 degree of freedom, or 2.

I -
R- Rate
E - Earth
S - Space
T - Tied
T - Turn
A - Attitude / Artificial Horizon
X - X
D - D.I

Precession

a force applied to a spinning gyroscope acts as if it is applied 90deg in direction of rotation

Rigidity in space

The spin axis of a gyro remains fixed in space
rigidity is directly proportional to rate of spin (RPM) & mass of rotor (angular momentum)
Angular momentum and therefore rigidity are increased by concentrating weight close to the rim

Sources of power

Pneumatic - air
- simple construction
- cheap(er)
- requires air supplier - restricted freedom
- possible contamination
Electrical
- constant spin rate
- greater rigidity
- greater freedom of movement
- case can be sealed against contamination

Wander Drift and topple combine to create Wander

Real wander - from imperfections
topple - wander in vertical spin axis 15 x cos(lat)
drift - wander in horizontal spin axis, at its maximum value at the poles. 15 x sin(lat)
Remember H / V are Earth Terms
15 x sin(lat)

Topple

zero topple at the poles
maximum topple at the equator
15 x cos(lat) - there’s an O in topple, whereas there’s an I in drift.

Transport Wander

only applied E/W, does not wander N/S
Is the change of angle between spin axis and true north
Calculation = Convergency

Apparent Wander

Earth Rotation
- Zero appart drift at equator
- max drift of 15deg/hour at the poles

D - No apparent topple E - Maximum apparent drift - 15deg per hour C - Topple - 15deg per hour B - Drift No apparent drift A - apparent drift and topple - drift at 15X sin lat - topple at 15 x cos lat

THe direction indicator

Erection System

Aircraft banks, tries to take gyro
we want it to stay in spin axis
some of the air is sideways
effect is 90deg later - precession

Errors of the DI

Real Wander
Gimballing Error
Earth Rotation
Transport Wander - compensated by the latitude nut

Latitude Nut:

The tilt in the gyro matches the tilt of the latitude and gives opposite precession to cancel out the apparent drift.

Artificial Horizon

the vertical reference unit of a three axis data generator
two degrees of freedom vertical - spin axis gyro
with its axis earth tied to the local vertical by an automatic erecting system

Servo Driven Attitude Indicator

Driven from remote vertical gyro
flight director command bars
ILS glideslope indication
Speed deviation indicator
May include Rad Alt info

Turn Indicator

Measures the rate of change of heading (not the yaw)
Rate Gyro
1 degree of freedom
Frame is controlled by two springs
spinning axis is parallel to the pitch axis, which is the lateral axis of the aircraft.
Errors
- calibration - TAS must be within around 5% of the calibrated value
- Pitch or looping error
  - steep turns are more pitch than yaw
- only indicates correctly at its calibrated rate
- typically rate 1 only

Rate 1 turn calculation

10% of TAS + 7

==Q. What angle of bank is required for a rate 1 turn at 120kt TAS?== A. 19 degree

Turn Indicator

Turn Co-ordinator

tilts the gyro up by 30deg
Makes it slightly more instantaneous in its indication
Always will have ‘no pitch indication’
electrically powered
balance ball

Rate Integrating Gyroscope

used in Inertial nav system
Can within a can - the gyro is positioned inside a can which is suspended with liquid inside another can. Allowing the inner can to rotate which can be picked up on the Y axis. Torque motor process bring back to null.

Magnetism

Laws of magnetism

like poles repel
unlike poles attract
the poles are not at the exact end of a magnet
- their position is governed by a ratio of magnetic length and width
- short distance in from the end of the magnets
every magnet is surrounding by a magnetic force
Unmagnetised - random alignment
Magnetised by:
- stroking with another magnet
- placing in a magnetic field
- Hammering
- Placing within a DC field
- Soft iron loses magnetism readily
- Hard iron keeps magnetism better.

Dip

Remove dip by sticking the magnet on a pivot to allow dip movement
compass mounted below a pendulum
CG below the pivot point

Isogonal - line of equal variation Agonic Line - A line of no variation Isocline - A line of Equal magnetic dip Aclinic Line - A line of zero magnetic dip

thick lines going up/down - 20degrees of dip per line

Direct Reading Compass

Sits in a silicon fluid
Bellows to account for expansion / contraction
Pendulous compass card
Reads back to front

Pendulum offsets dip, as seen
CG south of pivot, helps but gives up problems - acceleration errors and turning errors
ANDS in Northern Hemisphere
- Accelerate North
- Decelerate South
SAND in South Hemisphere
- South Accelerate
- North Decelerate

Acceleration Error

Offset CG

Turning Error

Rolling out on East / West?
- No real effect on compass
Rolling out North / South?
- Roll out early when turning north
- Roll out late when turning South
- UNOS - Underturn through North, Overshoot through South
- by 20-30 deg.
Needle tries to follow the field
Steep Turns
- Field at 90deg to compass, cannot align correctly
- ‘Equal to 180 on a 090 heading in a right turn’

Remote Indicating Compass

Validates the directional gyro against the compass
Combines the stability of a gyro with the accuracy of continuous magnetic monitoring
Comprises of:
- Gyro unit - horizontal, two degrees of freedom,
- Heading indicator
- Flux detector / valve
- Error detector
- Precession amplifier
Located in a wingtip / away from magnetic items

red highlighted area shows the re-erecting system. The two lines will connect to the bars when rotated to initiate the torque motor to re-align

Flux Valve

detects a change in magnetic force across each magnetic arm.
three soft iron arms
magnetic flux flows through them
air gap dictate path
damping fluid in the bowl
suspended in a universal joint
- 25deg freedom in pitch and roll, none in yaw!
- Can pivot up but is fixed to the aircraft azimuth

primary and secondary windings around the
487.5 Hz AC in excitation coil
AC fluctuations picked up in secondary coil, which will not include a steady earth field
Subtract 487.5 from this to determine magnetic heading
Then fed into an error detector (stators) and 1 rotor, current induced in rotor except at right angles to the field - that null point is north
‘Selsyn’ tells us when it is not so, 90deg out? = 90deg. (look at the smaller coil inside on second image).

Accurate to half a degree!

Cockpit indicator

Annunciator flicks to and fro
aka ‘dot crossing’

Cockpit Displays

Instrument T

Selected radial scan, based on master instrument (AI)
then Airspeed Indicator
then Alt
then Compass / Direction / Heading

Six Pack

Six pack analogue
Duplicated for each pilot (in larger aircraft)

EFIS - PFD / ND

Same as a six pack but all on one page
Also includes FMA (Flight Mode Annunciator)
indicates CAS because its coming from an ADC

Input Failures:

Faults generator by a signal generator
two sides constantly compare data
Red indications
- Windshear warning
- Pitch or roll greater that 3deg mismtach

Orange bar along VSI indicates rad alt
Green hash within altitude indicator shows under 10,000ft
Pitch limit eyebrows (just above 10deg) to show pitch limit.

Above image - taking off

10 second trend arrow - magenta arrow on the speed tape
THR HLD - boxed for 10 seconds to indicate recent change, then will look like the TO/GA indication
Above image - continuing takeoff
Flaps up indication along speed bar (green UP)
Rad alt is alive, filling the arc on the outside, above 1000ft it will go digital until disappearing at 2500ft.

Above image - autopilot engaged

Heavy boxes indicates within target altitude
Notice turn co-ord not in balance
CMD (under the heavy box within 1000ft) - signifies this PFD is command.

same colour conventions
selectable display styles/modes
variable range rings
can include WXR or TAWS - but never on the same screen.

Above image - Full Rose

ground speed / tas top left
TCAS off / bottom left in orange
Nav aid 1 - blue text bottom left and indications on the compass rose
Nav aid 2 - green VOR text on bottom right and on display
Waypoint and nav information magenta top right and deviation indicator magenta bar middle diagram
Track indicator - top of rose in blue, accounts for drift

Arc - track view, Rose - heading up, Plan - nav

Some may also have a Vertical Situation Indicator using the lower half of the nav display, includes terrain profile and can show whole or part of flight

Power Plant Monitoring

Engine Pressure Ratio
RPM
Temperatures
Pressures
Fuel Flow
Vibration

Mechanical Tachometers

Flexible shaft from the engine
turns a magnet in a cup eddy current ‘grabs’ aluminium cup, turns against a hair spring
limited by path length of 2m
best in straight line - friction
simple and cheap

Above image - Mechanical Tachometer

Yellow - cautionary limit (vibration)
Green - normal operating range
Red - maximum limit
Can include hobbs time indication
not time based on cruise RPM.

DC Tachometers

Same working principle as a dynamo light on a bike (magnet turning to produce electricity to create electricity to light a bike light)
Component measured drives tacho
tacho generated to instrument by wire
gauge is a voltmeter
calibrated in RPM
Voltage drops
Problems in exam:
- Line resistance
- The way in which we make DC

Above image - DC Gen

Lots of Coils
Multiple cutouts on commutator
Advantages:
- Simple
- Cheap
- No electrical supply needed
Disadvantages
- Sparking / Arcing
- Heat/Localised burning
- Interference on radios
Some sparking / generates static electricity which generates an electromagnetic force which interferes with instruments

Electrical Tachometer

does NOT spark / arc
Single phase AC generator
Electricity generated according to:
- Size of conductor
- Strength of magnetic field
- Speed / rate of cutting magnetic flux.
Gauge is still a voltmeter
Still have line loss issue

AC Three Phase Tachometers

aka ‘Induction Tacho’
Output is three phase - frequency is proportional to RPM
- Image driving away from a radio mast - still hear the radio because it measures frequency and not amplitude
Indicator is a 3 phase motor driving a drag cup
No line resistence
No sparking/arcing

Electronic Tacho (AC Phonic Wheel)

Toothed ferromagnetic wheel
passes coil of wire
generates single pulse of AC
counts the pulses of RPM

Rectifies the single AC current to a square wave of 1 / 0 Easier for EFIS, Also provides RPM to FADEC, Sine wave rectified to square wave

Synchroscope

synchronises engines
reduces noise/fatigue
works directly from RPM signal
Slave engines set to master RPM
- stator connected to slave
- rotor connected to master
Modern AC automated

Synchroscope

Synchronised - same RPM
Noise levels still quite high
Synchrophased - blade positions
No 2 Engine shown as master

Pressure Sensors

Gauge Pressure - calibrated against atmospheric
Absolute Pressure - calibrated against a vacuum
Absolute = Gauge + Atmospheric Pressure
Direct or Indirect indications
Elastic Pressure Sensing

Elastic Pressure Sensing

Capsule type
Low Pressures
More Sensitive
More Durable
single capsule - low pressure instrument
bellows - medium pressure instrument

Aneroid bellows - does not have an intake so atmospheric pressure alters the shape of the bellows Pressure Bellows - has an intake so that the pressure inside alters that shape of the bellows

Manifold Absolute Pressure - important because it measures absolute

Aneroid Bellows + Pressure Bellows = Absolute Pressure

Aneroid bellow measures ambient Pressure bellows measures suction.

Bourdon Tube

C shaped with oval cross section
Measures high pressure - tries to straighten out under pressure

Transducers - not in LO but is the modern pressure sensor and HAS popped up in the exam.

Mainly on hydraulic pressure systems
It pushes against a matrix which changes shape, the flow of electricity over this new shape determines the resistance (?) and change of voltage

Torquemeters

Measures twist
Oil pressure type
Spur cut gears have no side force
bevel cut gears exhibit a side force.

Expresses twist / torque in shaft

==Power = Torque x RPM==

Vibration Meter

No indication of the values, just an indication.
Uses two accelerometer -
Magnet on a spring - measures relative amplitude, frequency is filtered and amplified. Based on where the ball / spring is.

Fuel Measurement

Float Type Gauge (Volume measurement)

Float attached to rheostat
Changes current flow
Gauge is an ammeter
Accurate when almost empty
Volume Measurement
Affected by attitude

Capacitance Gauging System (Mass Measurement)

Depends on air gap, size of gap and dielectric
Charge depends on
- size of plates
- distance between the plates
- value of the dielectric
Current drives a torque motor which drives the gauge
Volume measurement
Compensating unit gives mass
Temp rises?
- Volume increase, density decreases
- dielectric constant reduces
- gauge reads the same
Measured in Farads (Capacitance)
Dielectric values
- Air = 1
- Fuel = 2
- Water = around 81

Capacitance = E x A / D

E = Dielectric Value A = Area of the plates D = Distance between the plates

A and D are fixed by design

E varies according to the substance.

Fuel Flow Measurement

Volume Flow
- Litres per hour
- Gallons per hour
Mass Flow
- Kilgrams per hour
- Pounds per hour
Fuel Used
- Flow integrated over time
Fuel flow measured just before the engine

Why do we suck fuel rather than blow it?

If we blow and theres a hole in the pipe it will leak. However if we suck it just sucks fuel and doesn’t leak fuel. Think negative pressure.

Fuel flow measurement - volume / AC

Impeller turns a small magnet which pass an induction coil which generates pulses of AC.

Also a mechanical version:

Angle is measured of the door which measured the flow. Includes a PRV incase door jams.

Mass Flow / AC

AC motor drives impeller
Swirl gives angular momentum
Reaction turbine senses momentum
Requires Power

Electronic Measurement

Fuel indications - Airbus ECAM

Flight Recording

Solid state memory mounted in a shock resistant case
underwater locating beacon good for 3 miles / 90 days
Cockpit area microphone
control unit with auto/on, test, erase, and a headset jack.

Missing - Yaw data is excluded.

Radar Altimeters

Calibrated to read 0 on the ground - account for the landing gear and the length of the cables
Works in SHF, Centimetric band, Modulates from 4200 to 4400MHz
Frequency difference indicates true height
Accurate to +/- 2ft up to 500ft
Higher sweep rate at lower altitudes
Accurate to +/- 1.5% above 500ft
Req for Autoland CAT III
GPWS
TCAS

Cockpit Displays:

vertical scale or round dial
Must indicate 0 - 2500ft
May indicate more
Bugs to set decision height
Expanded scale closer to the ground

Ground Proximity Warning Systems

Four variants
- GPWS
- EGPWS (Enhanced GPWS)
- TAWS (Terrain Awareness System)
- HTAWS (Heli TAWS)

GPWS - ICAO annex 6

GPWS on all aeroplanes on public transport > 5700kg, >9 passenger seats (greater than 9 doesnt include 9, so must be 10 or greater)
System must provide distinctive audio signal, and may have Visual Alerts
5 basic modes of operation
May have additional callouts
- Height
- Bank
- Windshear
Aeroplanes greater than 15000kg and over 30 passenger seats MUST have EGPWS

GPWS Inputs RAF Navigator R - Rad Alt A - ADC (Pressure Speed, Mach) F - Flaps, Gear N - Nav Receiver (ILS Glideslope)

GPWS Warnings and Alerts

Range 2500ft to 50ft
Hard Warning - red, requires immediate climb
Soft Alert - yellow, requires a corrective response.
Flap and Gear alerts may be inhibited

Not taught but found elsewhere online

Mnemonic: ==STD GirlFriend? Good Man Be Wrapped!==

Enhanced Ground Proximity Warning Systems

World Terrain Database
- No expiry date for validity
Obstacle Database
- 28 days
Display uses mainly Green, Amber or Red
- Amber, Red - may not be able to avoid terrain
- Magenta - terrain not in the database (think large expanses we don’t go to - Sahara, Siberia etc)
Positional accuracy essential
- Required Navigational Performance
- Actual Navigational Performance
- RNP10 = accuracy within 10nm either side of track
- RNP0.3 = accuracy within 0.3nm either side of track

==Q. When installed, a TAWS must be coupled to:== A. A three-dimensional world terrain database

TAWS and WXR mutually exclusive, use similar colours. Must check the TERR in blue to determine which is which.

Traffic Collision Avoidance Systems

Transponder based system
- transmits an interrogation
- responds to an interrogation
TCAS 1 = Traffic Advisory
TCAS 2 = Resolution Advisory
Vertical Separation only
Lateral not yet accurate enough
EU Ops Requirement
- Passenger aircraft with over 19 seats and 5700kg TOM
Inputs:
- S - Mode S Transponder
- C - Configuration of aircraft (flaps/gear)
- A - Air data computer
- R - Rad Alt (No RA below 1000ft)
- I - Inertial Reference System

Q. Why would you use TA only? A. Might not have the performance to climb

Data Links

ACARS (Aircraft Addressing & Reporting System)
CPDLC (Controller Pilot Data Link Communication)
ADS-B (Automatic Dependant Surveillance Broadcast)
- ADS-B In - Receives data from ground stations
- ADS-B Out - transmits data from aircraft
FANS (Future Air Navigation Systems)
D-ATIS (Datalink transmitted ATIS messages)

Onboard Datalink Comms

Multi function control display unit
Communications Management Unit
Communication Unit (VHF HF Satcom)
HF - slowest
VHR - medium
SATCOM/AMSS - fast

MCDU

Autoflight

FD + AP + AT + FMC

Flight Director - provides the instantaneous path to reach the selected radial

on glideslope - bar and diamond centered

Basic Autopilot

requirements for Single Pilot IFR
- Altitude Hold
- Heading Hold
Stability system
- Stability & trim
- pitch trim as a minimum

Types and Levels of Controls

Stability

positive static stability - hit the bowl the ball will return back
negative static stability - hit the bowl and the ball will not return back
Dynamic stability is impossible without static stability

For Autoflight we need:

Sensors - to detect altitude and changes
Computers - to work it all out
Comparator - to compare what we have with what we need.
Amplifiers - to convert data into the signals
Servos / actuators - to move the control surfaces

Horrible question - no longer in the exams, B is the answer.

Autopilot engagement is inhibited if:

Electrical supply faulty
Roll control knob is not centred
Synchronisation fault
Attitude reference unit fault

Mach Trim

Only operates at high mach numbers
shockwaves reduce downwash, increasing longitudinal stability, causing nose to pitch down,

Yaw Damper

prevents Dutch Roll
Aircraft with greater lateral stability than directional can suffer from a periodic motion called ‘Dutch Roll’

Can be stand alone or integrated with another system

Autothrottle

Maintains selected
- Airspeed
- Mach Number
- N1
- EPR

LNAV/VNAV

VOR & Localiser (VOR/LOC)

Radial selected on rotary knob
VOR LOC pushlight selected
White - armed
Green - engaged
Automatically engages when valid signal received from VOR/LOC
Captures and maintains the radial or centreline

LOC - Airfield, VOR - Elsewhere

Cone of Confusion - Affects VOR and LOC, Over Station Sensor ignores confusing signals, AP switches to heading hold until leaving cone of silence, re-engages on reciprocal

Vertical Speed Control

Engaged with VS pushlight
Rate up or down on thumbwheel
Viewed in window above
Active until a higher mode selected

Altitude Acquire

Selected on rotary knob
Rate set using V/S
On reaching, ALT HOLD engages

Altitude Alerting

Heading Hold

Pushlight selection
Rotary Selection knob
heading appears in window above

Approach Mode:

APP pushlight selected
Arms or Engages
Other CMD (A/B) engaged
Enables ‘Fail Passive’ for Autoland

==Fail Operational - if you get a failure, you remain operational Fail Passive== - If we fail it will PASS back to you (not quite what it means but )

Flight Envelope Protection

Flight Management Computer Systems

// The whole system is the FMS but the blue box SHOULD rather be labelled as FMC

IDENT PAGE:

POS INIT:

ROUTE:

PERF INIT:

Takeoff Ref:

FMS Route Flying:

Principle behind this isn’t complicated, it’s essentially just Speed = Distance / Time
First integration - multiply acceleration x time = ==speed==
Second integration - multiply speed x time = ==distance==

Calculating latitude change is easy, because we’re on a great circle. Because 1nm is 1minute of latitude and 60nm is 1 degree of latitude.

Longitudinal change is slightly harder because we will sense East/West acceleration.

Integrate twice gives distances E/W Only at the equator
Need to work out Change of Longitude from the DEPARTURE formula

change of longitude = departure x secant of the latitude

Early systems had an actual gear.

Stable Platform INS

INS is a stable platform - stays level whilst the aircraft moves around it in a gimbal array
East Gyro & North Gyro
2 accelerometers N/S and E/W
Gyros N/S, E/W and Azimuth
Platform finds level and N
Stays N aligned and level - aircraft manoeuvres around it but the platform stays still.