Auto flight Flashcards
flight director (FD)
displays pitch and roll commands for the pilot to follow in order to achieve a specific flight trajectory
pilot chooses what they want the FD to achieve via the mode control panel (MCP)
FD components
MCP- shared with AP
FDC- flight director computer - older
FCC- flight control computer- newer, shared with AP. one for captain and FO and extra as backup
display- ADI or EADI
FD display
x-hairs or v-bar
displacement of bar shows directions & magnitude of control deflection required
does NOT show deviation from target flight path- shows you how to reach and maintain target flight path
why have an FD?
improves accuracy of flying
improves safety
reduces workload
FCC/FDC inputs
FMC MCP rad alt ADC IRS Nav radios
FCC/FDC outputs
EADI- (PFD)
FMA- flight mode annunciator
FD operation
allowed both FD's + AP's ON both FD's + AP's OFF FD's ON + AP'S OFF FD'S OFF + AP's ON
FD & AP modes
FD & AP mostly use same modes except: FD has take off mode, AP does not AP has landing mode, FD does not both FD's can be on at the same time, not normally possible for the AP
FMA’s tell you what modes are active
FD & off path
when off intended flight path FCC calculates optimum instantaneous path to regain the desired trajectory
FD is not a copy of ILS indication
FD gives no info about ILS deviation
the 3 axes
longitudinal axis (roll)- primary axis lateral axis (pitch) - secondary axis normal axis (yaw) - tertiary axis
single axis AP
provides stabilisation in roll
wing leveller
2 axis AP
provides stability about the primary & secondary axes
can capture and maintain heading & altitude
3 axis AP
stability about all axes
capable of:
co-ordinated turns
capture & maintain- headings, alt, vertical speed, IAS, Mach
capture and track: VOR radial, ILS, Auto land, follow FMS LNAV & VNAV
Stability vs Guidance
stability includes: wing level holding pitch attitude holding yaw damping these are not selectable modes they are active behind the scenes
everything else is guidance
Inner loop AP
up to x3 depending on AP axes
has an IRS
error detector- sends error signal to FCC
FCC- converts input error signal to output control command to servo based on control law
makes corrections
stabilises and controls
servomechanism
Inner loop feedback
control feedback- from servo actuator to FCC, check its actually moving
performance feedback- servo actuator to error detector
servo mechanism
small power input converted to a large power output in a strictly proportionate manner
Outer loop AP
inner loop still exists
outer- fakes an error signal which inner can correct in order to achieve a particular goal
outer loop provides guidance
AP components
sensors comparators computers amplifiers servo-actuators
parallel actuators
can move control surface through 100% of range
moves cockpit control column
series actuators
can move control surface through 100% of range
cockpit controls remain static
Size of control surface deflection depends on
size of the error
rate of deviation
rate of change of rate of deviation
CWS- control wheel steering
button on MCP activates it
gives pilot manual control of inner loop datum
pilot use the normal controls to set an attitude
inner loop then holds it
AP still considered to be on
Engaging AP
via button on MCP before engagement self check checks: pitch servo roll servo yaw damper trim servo IRS FCC if all good then it engages
disengaging AP
MCP button or button on control column or force controls
AP automatic synchronisation function
prevents control snatching during engagement
active whilst AP is off
purpose is to achieve smooth AP engagement
if it fails it may prevent AP engagement
Auto trim
active when AP on
ensures aircraft is in trim when AP is disconnected
smooth disengagement
Normal Law
always used unless there’s a problem
roll: converts bank into a roll rate command
pitch: converts pitch into a G or load factor command
Normal law protections
apply throughout the flight envelope pitch limits roll limits G limits high speed stability- gradual increase in attitude to reduce speed, can override high speed protection- abrupt increase in pitch to decrease speed low speed stability - can override low speed protection
Normal law ground mode
allows full deflection of controls whilst on the ground
Alternate law
no longer have AP pitch and roll are same as Normal protections reduced, only have: low speed stability high speed stability nothing that the pilot cant override
direct law
no AP
pitch & roll: direct relationship between elevator/ aileron deflection & control column
NO protections
legal requirement for AP
needed in single pilot operations in IFR or at Night
needs at least heading & altitude hold
FMA’s
main way of determining AP behaviour
active modes- green
armed modes- white or cyan - automatically activate when certain conditions are met
green box appears around FMA theres been a change and it shows for 10 seconds
lateral modes
HDG - hold heading put in MCP
VOR - tracks a VOR radial, switches to HDG overhead core of confusion until out other side
LOC mode- follows ILS localiser, intercept done on a fixed heading, uses radio deviation law to determine bank requirements
LNAV- follows FMS lateral profile. FMS gives the AP bank and heading commands to follow the programmed route
Rollout- after an auto land the AP will hold the runway centre line using ILS localiser
vertical modes
ALT hold
ALT AQ- alt acquire- smooth transition from climb/descent to level flight
V/S- target a certain vertical speed
LVL CHG- climb or descent change level
G/S- holds aircraft on ILS glide slope
VNAV- follows FMS vertical profile
FLARE- based on rad alt, flares on auto land
Flight Path Angle- like V/S mode but holds angle
auto throttle mode
N1- holds constant value of N1%, depends on temp and alt
IDLE
TOGA
MCT
SPEED- based on either MCP (pilot puts in) or FMC
What AT mode does LVL CHG use?
N1 mode- fixed N1 held
speed held constant by pitch
What AT mode does V/S use?
pitches to achieve vertical speed
auto throttle holds forward speed- MCP/VMC speed mode
prioritises required V/S so forward speed may suffer
what modes use the AT MCP/FMC speed mode?
V/S ALT hold ALT AQ VNAV Flight path angle
Auto-throttle provides…
provides automatic thrust control from start of take off (it can be used in take off) until landing
varies N1 and EPR depending on selected modes and phase of flight
Older aircraft auto throttle
use hydromechanical unit
MECU- main engine control unit
and a PMC- power management computer
newer aircraft auto throttle
uses FADEC- full authority digital engine control FADEC does: auto eng starts monitor limitations collects data for the instruments controls fuel flow to achieve N1 controls thrust reverser
Auto throttle capabilities
via various modes it can hold
mach no
IAS
N1
exam Q: can auto throttle be used to set a specific N1?
YES
if you disconnect it and set N1 manually via the lever
what will the low speed stall prevention do with the thrust ?
may be a system that auto engages TOGA thrust
Yaw damper
prevents dutch roll
it is NOT the AP rudder channel
2 or 3 for redundancy
Yaw damper & detection of dutch roll:
uses:
dedicated yaw rate gyro or/ IRS or/ nose mounted lateral accelerometer
ADC as an input
inputs added to pilot rudder inputs
2 or 3 for redundancy
can be in parallel or series with controls
can the auto land do the entire landing all the way down to a full stop?
YES pet
Auto land requirements:
crew qualified aircraft equipped equipment serviceable operator approved RWY has correct equipment
Minima
minimum visibility requirements at a certain height above the runway to be able to proceed
Approach ban
cannot proceed beyond the approach ban unless the required RVR has been reported
Alert height
100ft above runway most warning/ cautions are disabled aircraft only tells pilot about thing that prevent an auto land e.g: total AP failure RAD alt failure loss of ILS signal
auto land FLARE & ROLLOUT
flare- 40ft
rollout keeps centreline once touching down
how many AP systems are needed to do an auto land?
2
ensures there’s a cross checking occurring
Fail operational
more systems than needed i.e 3
one can fail and auto land can still take place
Fail passive
only 2 systems
if signals form them disagree it disconnects both of them
failure in fail passive results in a manual landing
will be no significant deviation from flight path as aircraft will be in trim
