Flight Control Laws -1stepprep Flashcards
What is a flight control law?
A set of rules by which flight controls are governed
What are the 4 flight control laws?
- Normal Law
- Alternate Law
- Direct Law
- Abnormal Attitude law
Is Mechanical Backup a flight control law?
No
Its the absence of a law
How many flight control computers?
7
2 x FAC’s
2 x ELAC’s
3 x SEC’s
What does SEC 3 control?
SEC 3 only controls spoilers
What is the flight envelope in normal law?
30 deg NU
15 deg ND
67 deg L/R
How do you know you’re in normal law?
Green equal signs on the PFD at the flight envelope limits
What are the 5 protections in normal law?
1 . High Speed
- Pitch
- Roll
- G-load
- High Alpha
When will the aural alert occur in high speed protection?
At Vmo +4kts
When does high speed protection activate?
At Vmo +6kts
What happens when high speed protection activates?
- AP disconnect
- nose starts pitching up
- nose down trim inhibited
Can high speed protection be overridden by the pilots?
Yes,
will allow override to ~Vmo +15kts in case of TCAS RA.
As approach +15kts sidestick authority diminishes
What is roll protection in normal law?
-Cannot bank >67 deg
- Have positive spiral stability between 33-67 deg
ie. a/c returns to 33 deg when sidestick released
Will aircraft ever roll to wings level when AoB > 33 deg and sidestick released?
Yes,
If high speed protection is active to limit structural load
What is the relevance of 67 deg?
= 2.5g in level flight
G-load certification limit figure
In normal law the side stick is commanding…?
G-Load
AFT sidestick = +ve G
FWD sidestick =-ve G
Release stick -a/c holds pitch attitude
Normal Law pitch protection
30 deg NU
15 deg ND
What are your alpha protections?
- Alpha Prot
- Alpha MAX
- Alpha Floor
How is alpha Prot depicted on the PFD?
Top of Black and Amber checker bar
What is Alpha Prot?
Alpha Prot is the AoA where the FCC’s intervene to prevent stall
What happens at Alpha Prot?
ASAP
A oA is commanded by sidestick (normally G-load)
S poilers auto retract
A utopilot disconnects
Pitch Trim inhibited (nose up)
Alpha Max -how do you get there?
By continuing to pull fully aft through Alpha Prot
What is Alpha Max?
The Maximum AoA the ELAC’s will allow
What happens in Alpha max?
The aircraft holds the AoA just below critical stall
Is Alpha Max likely if alpha floor is working?
No,
Alpha floor will prevent you from getting to Alpha max
What is Alpha floor?
A PREDICTIVE function of the autothrust system to prevent low speed condition (stall)
Do you need to move through Alpha prot and alpha max to get to alpha floor?
No
How does alpha floor work?
By using the energy computers -the FAC’s
When is alpha floor available?
- autothrust available
- FAC’s available
What does the condition ‘A/THR available mean for alpha floor to be operable?
Does not need to be armed or active
Needs to not be:
- disconnected (A/THR instinctive disconnects pressed and held for >15secs inhibits A/THR for remainder of flight)
- MEL’d
- N1 mode
What items do the FAC’s give us?
YAWL
Y aw -trim (rudder)
- turn coordination
- travel limiter (rudder)
- yaw damper
A irspeed envelope
W indshear alerts -reactive
L ow energy warning
When is the Low energy warning available?
From 100’ RA -2000’RA, with
Flap 2, 3, Full
@ low speed
How do we get into Alternate law?
Failure of a system plus a redundancy
Dual failure of:
- Hydraulics
- ADIRS
- FCC’s
- Gernerators
- FAC 1+2
- ELAC 1+2 etc
And, after entering Abnormal Attitude Law
How do you know you’re in Alternate Law?
Amber crosses on the PFD
ECAM memo: ALT LAW: PROT LOST
What do you have in Alternate Law?
High/ Low Speed stability
G-load protection
What have you lost in Alternate Law?
All protections except g-load
What is High/Low speed stability
- A recommendation / overrideable
- Not a protection
- A/c generates gentle nose pitch up/down moments
Can the pilot override High/low speed stability?
Yes
Is the aircraft capable of stalling in Alternate Law?
Yes
What are the 3 modes available in normal law?
- Ground
- Flight
- Flare
Is Flare mode available in alternate law?
No -straight to direct law
How does the aircraft able to flare once in alternate mode?
By the aircraft going into direct law when:
- landing gear is selected down, and
- AP OFF
What is ground mode?
-Pitch and Roll have a direct relationship with sidestick movement
For flight control check and rotation into the air
What happens to ground mode once airborne in normal law?
transitions to flight mode over 5 secs
Why must you wait 5secs after lift off prior to engaging AP?
To allow a/c to transition from ground mode to flight mode
mode transition
What does the sidestick command in flight mode normal law?
Pitch: G-load demand
Roll: commands roll rate
What is the roll rate per sec in flight mode normal law with full sidestick L/R?
15 deg / sec
What does the sidestick command in flight mode alternate law?
Pitch -still G-load
Roll is now a direct relationship with control surfaces
not commanding roll rate
Flare mode is only available in ….?
Normal Law
Flare mode:
At 50ft RA…..
the ELAC’s memorise the pitch attitude.
the 50ft ELAC snapshot!
Flare Mode:
At 30ft RA
ELAC’s commands ~2deg ND pitch on memorised attitude over 8 secs
To counteract, the pilot flares aircraft with gentle nose up action
( a typical landing flare is 7 secs)
Why does the aircraft go from alternate law into direct law with landing gear down ?
So pilots can have a normal feel for landing because flare mode is lost in alternate law
How do you know you’re in direct law?
Amber USE MAN PITCH TRIM
What is Abnormal Attitude Law?
If normal design envelope is exceeded (pitch/roll by >2x) quickly or abruptly it gives the pilot control of the aircraft
ie +30/-15/67=+60/-30/134
What is the only protection in Abnormal Attitude Law?
G-Load protection
So the other protections do not hinder the pilot from recovering the a/c to a normal attitude
Once recovered from Abnormal Attitude Law phase, which flight control law will the a/c be in?
Alternate Law
But with Landing Flare Mode
So with gear down, stays in alternate law -does not go into direct law
What is Mechanical Back up?
The absence of all laws
Temporary state
How is the a/c controlled in mechanical back up?
rudder
pitch trim
differential thrust
What are the indications of Mechanical Backup?
Aircraft does not respond to sidestick
Amber X’s
Red MAN PITCH TRIM ONLY
No ECAM
How is the airspeed envelope generated?
By the FAC’s
Speed tape shows approximate speed for Alpha prot / Alpha max
Remember its based on an AoA, speeds are approaximate
Predictive function of the A/THR system
Clean wing, 210 kts, downwind, roll in bank, pull back on sidestick, +ve g-loads…..What happens in the event of an agressive decay in speed trend?
A/THR commands TOGA to prevent a low energy state.
FMA -A.FLOOR (1st column)
(never got near Alpha prot or Alpha max)
Alpha floor kicked in because it didn’t like what it saw in terms of energy
When does TOGA LOCK appear on the FMA
Anytime Alpha Floor activates and AoA is reduced
How do we get out of TOGA LK?
Click the IDP
Instinctive disconnect pb’s
(no need to match the doughnuts)
What is another way to get out of TOGA LK
not recommended!
Thrust levers to IDLE STOP
How do we know we’re in Ground mode?
-2 engines running
-PFD L angles in corners
Maltese cross
Are there any protections in Direct Law?
No
Is it possible to have AP functionality in Alternate Law?
Yes,
Depends on failure that you have
Can we go from Normal Law straight to Direct Law?
Yes,
Dual RA Failure
How do you know you’re in Abnormal Attitude Law?
Amber crosses on PFD
No ECAM memo
What does it mean if you have amber x’s on the PFD?
You are not in Normal Law!
How do you get into Mechanical Backup?
Loss of Pitch Control:
ELAC 1+2
SEC 1+2
(not SEC 3 -it only spoilers)
How many FCC’s control pitch?
4
ELAC 1+2
SEC 1+2
What is a better name for the FAC’s
RAC’s:
Rudder
AoA
Computer
YAWL
