A320 FLT CTRL Laws and Protections

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A320 FLT CTRL Laws & Protections General

Normal Law Alternate Law

Abnormal Attitude Law

Alternate Law (without reduced protection) Direct Law

Mechanical Backup

Load Factor Protection

High AOA Protection

Pitch Attitude Protection High Speed Protection Bank Angle Protection

Stall Warning

Low Speed Stability

High Speed Stability

Auto Turn Coordination Dutch Roll Damping Positive Static Stability

FLT CTRL Law reconfiguration acc. FCOM 1.27.30

Finish Presentation

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A320 FLT CTRL Laws & Protections Normal Law

Normal Law

Alternate Law

Mechanical Backup

High AOA Protection

         Stall Warning

Low Speed Stability

Auto Turn Coordination Dutch Roll Damping Positive Static Stability

FLT CTRL Law reconfiguration acc. FCOM 1.27.30 Finish Presentation   Overspeed Warning

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A320 FLT CTRL Laws & Protections Normal Law

Ground Mode

Flight Mode

Flare Mode

Pitch Control

• Direct relationship between sidestick deflection and elevator deflection • no auto trim

• Load factor demand • Auto trim available

• at 30ft in descent the system reduces attitude by 2° over 8 seconds

Lateral Control

• Sidestick commands aileron and roll spoiler depending of speed • After TakeOff smooth

transition to Flight Mode

• Roll rate demand • max. 15°/sec

• Same as in Flight Mode

• After touch down smooth transition to Ground Mode

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A320 FLT CTRL Laws & Protections Alternate Law

Normal Law

Alternate Law

Mechanical Backup

High AOA Protection

      Stall Warning

Low Speed Stability

Auto Turn Coordination

Dutch Roll Damping (limited) Positive Static Stability

Finish Presentation

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A320 FLT CTRL Laws & Protections Alternate Law

Ground Mode

Flight Mode

Landing Mode

Pitch Control

• Direct relationship between sidestick deflection and elevator deflection • no auto trim

• 5sec after landing active

• Load factor demand with less protections • Auto trim available

• At Gear down Flight Mode Direct Law • Direct stick

to- elevator-relationship

Lateral Control

transition to Flight Mode

• Roll direct • Yaw Damper

available with rudder deflection limited to +/-5° • Auto Turn Coordination lost • Same as in Flight Mode

• After touch down smooth transition to Ground Mode

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A320 FLT CTRL Laws & Protections Alternate Law

without reduced protection

Normal Law

Alternate Law

Alternate Law (without reduced protection)

Direct Law

Mechanical Backup

High AOA Protection



Stall Warning

Low Speed Stability

Auto Turn Coordination Dutch Roll Damping

Positive Static Stability

Finish Presentation

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A320 FLT CTRL Laws & Protections Alternate Law

without reduced protection

Ground Mode

Flight Mode

Landing Mode

Pitch Control

• Direct relationship between sidestick

deflection and elevator deflection

• no auto trim

• 5sec after landing active

• Load factor

demand with less protections

• Auto trim available

• No High Speed Stability

• No Low Speed Stability

• Only Load Factor Limitation

• At Gear down Flight Mode Direct Law • Direct stick

to- elevator-relationship

Lateral Control

• Roll direct • Yaw Damper available with rudder deflection • Same as in Flight Mode

• After touch down smooth transition to

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A320 FLT CTRL Laws & Protections Direct Law

Normal Law

Alternate Law

Alternate Law (without reduced protection)

Direct Law

Mechanical Backup



Stall Warning

Low Speed Stability

Finish Presentation

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A320 FLT CTRL Laws & Protections Direct Law

_{Direct Law is the lowest level of computer}

flight control.

_{Pilot inputs are sent to the control surfaces}

unmodified.

Because of the large number of failures required to degrade to Direct Law, it is unlikely to occur during normal flight.

_{It is most likely to be encountered when the}

landing gear is lowered after an inflight degradation to Alternate Law.

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A320 FLT CTRL Laws & Protections Direct Law

Ground Mode

Flight Mode

Flare Mode

Pitch Control

• direct stick to elevator

relationship • Direct stick to elevator relationship acc. slat/flap position

• No protections • No A-Floor active

• No Flare Mode

Lateral Control

• Direct stick to surface

relationship • Direct stick to surface relationship acc. slat/flap position • Max. roll rate:

clean 30°/sec

slats ext.  25°/sec • Yaw mechanical • No yaw damping • No Auto Turn Coordination • No auto trim • No Flare Mode

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A320 FLT CTRL Laws & Protections Mechanical Backup

Alternate Law

Mechanical Backup

High AOA Protection

Normal Law

Stall Warning

Low Speed Stability

Finish Presentation

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A320 FLT CTRL Laws & Protections Mechanical Backup

In the worst case of failures, such as complete loss of flight control computer power supply the aircraft will revert to Mechanical Backup Mode.

Ground Mode

Flight Mode

Flare Mode

Pitch Control

• No Ground Mode • Pitch control

manually by applying trim to the THS

• No Flare Mode

Lateral Control

• No Ground Mode • Pitch control

manually by applying trim to the THS

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A320 FLT CTRL Laws & Protections Mechanical Backup

In most cases

(e.g. by resetting the flight control computers) the flight crew will be able to recover from

mechanical backup to either alternate or direct law depending on type of failure.

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A320 FLT CTRL Laws & Protections Abnormal Attitude Law

Normal Law

Alternate Law

Mechanical Backup

High AOA Protection



Stall Warning

Low Speed Stability

Auto Turn Coordination

Dutch Roll Damping (limited) Positive Static Stability

Finish Presentation

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A320 FLT CTRL Laws & Protections Abnormal Attitude Law

If the aircraft under extreme conditions

leaves the protected envelope (e.g. flipover by severe turbulence), the

Abnormal Attitude Law becomes active.

That conditions are:

•Pitch > 50° or < 30°, •Bank > 125° •AOA > 30° or < 10° (A320), <15°(A319,A321) •Speed > 440kts or < 70-90kts (depending on pitch) •Mach > 0.91

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A320 FLT CTRL Laws & Protections Abnormal Attitude Law

Ground Mode

Flight Mode

Flare Mode

Pitch Control

• No Ground Mode • Load factor demand without protections except Load Factor Protection

• No Auto Trim

• No Flare Mode

Lateral Control

• No Ground Mode • Full authority Direct Law

• Yaw mechanical

• Auto Turn

Coordination lost

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A320 FLT CTRL Laws & Protections Abnormal Attitude Law

Ground Mode

Flight Mode

Flare Mode

Pitch Control

• No Ground Mode • Load factor demand without protections • Auto trim available

• No Flare Mode

Lateral Control

• No Ground Mode • Full authority Direct Law

• Yaw Alternate Law

 Roll direct

 Yaw Damper

available with rudder deflection limited to +/-5°

• Auto Turn

Coordination lost

• No Flare Mode

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DIRECT DIRECT

MECHANICAL

A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW : • Double ADR fail

(2nd_{not self detected}

VCAS or M disagree) • Triple ADR fail

• Double SFCC Slat channel fail (G+B) • Double HYD fail (G+B)

• Double self detected ADR failure

• Double ADR fail (2nd_not

self detected or AOA disagree

• Double ELAC fail • Double Aileron fail • THS jammed

• ELAC 2 + Blue HYD fail • ELAC 1 + Green HYD fail • ELAC 1 + Yellow HYD fail • One Elevator fail

• Double self detected IR fail

• Double FAC fail • Double HYD fail

(G+Y)

• Yaw damper fail

• EMER ELEC from RAT • Loss of all spoilers

• Triple SEC fail

• EMER ELEC CONFIG (on batteries) • Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : YAW :

ALT (REDUCED PROT) DIRECT

MECHANICAL

NORMAL NORMAL NORMAL

ALT

DIRECT DIRECT ALT

ALT (NO PROT) DIRECT

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ALT (REDUCED PROT) DIRECT MECHANICAL DIRECT DIRECT MECHANICAL

A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

• Double ADR fail (2nd_{not self detected}

(G+Y)

• Yaw damper fail

• Loss of all spoilers • Triple SEC fail

• EMER ELEC CONFIG (on batteries) • Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : NORMAL NORMAL NORMAL

ALT

DIRECT DIRECT ALT ALT (NO PROT)

DIRECT ALT

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A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

(G+Y)

• Yaw damper fail

• Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : YAW : NORMAL NORMAL NORMAL

ALT

DIRECT ALT

• EMER ELEC from RAT

• EMER ELEC CONFIG (on batteries)

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A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

(G+Y)

• Yaw damper fail

• Triple IR fail • RA fail, when

L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : NORMAL NORMAL NORMAL

ALT

DIRECT ALT • EMER ELEC CONFIG (on batteries) • Double IR fail (2nd_{not self} detected)

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DIRECT DIRECT

MECHANICAL

A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

(G+Y)

• Yaw damper fail

• Triple SEC fail

• EMER ELEC CONFIG (on batteries) • Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : YAW : NORMAL NORMAL NORMAL

ALT

DIRECT ALT

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MECHANICAL

A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

(G+Y)

• Yaw damper fail

• EMER ELEC CONFIG (on batteries) • Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : NORMAL NORMAL NORMAL

ALT

DIRECT ALT

DIRECT DIRECT

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DIRECT DIRECT

MECHANICAL ALT (REDUCED PROT)

DIRECT

MECHANICAL

A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW :

(G+Y)

• Yaw damper fail

• Triple SEC fail

• EMER ELEC CONFIG (on batteries) • Triple IR fail • Double IR fail (2nd_{not self} detected) • RA fail, when L/G down or in CONF2 if both LGCIU failed PITCH : ROLL : YAW : NORMAL NORMAL NORMAL

ALT

DIRECT DIRECT ALT

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A320 FLT CTRL Laws & Protections FLT CTRL Law Reconfiguration

PITCH: ROLL : YAW : PITCH : ROLL : NORMAL NORMAL NORMAL

ALT

(G+Y)

• Yaw damper fail

• EMER ELEC CONFIG (on batteries)

• Triple IR fail • RA fail, when L/G down or in CONF2 if both LGCIU failed

ALT (REDUCED PROT) DIRECT ALT DIRECT DIRECT MECHANICAL DIRECT DIRECT ALT ALT (REDUCED PROT)

DIRECT

MECHANICAL

• Double IR fail (2nd_{not self}

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A320 FLT CTRL Laws & Protections Load Factor Protection

The load factor is automatically limited to:

+2,5g to -1g for clean configuration

+2g to 0g for other than clean configuration

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A320 FLT CTRL Laws & Protections Bank Angle Protection

 _{at bank angle <= 33° constant roll rate with stick neutral}  positive spiral static stability for bank angle > 33°

 max bank angle 67°

 with AOA protection active max bank angle 45°

 _{with High Speed Protection active max bank angle 40°}  _{With bank angle > 45° autopilot and FD off}

 FD returns when bank angle < 40°

 Refer to FCOM 1.27.20

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A320 FLT CTRL Laws & Protections High AOA Protection

 If AOA > PROT the system switches to protection mode in which AOA is

proportional to sidestick deflection.

 Max AOA is αMAX

 at AOA = PROT + 1° the auto pilot switches off.

 v_PROT, VαMAX and VαFLOOR vary according to x-weight and configuration

 Refer to FCOM 1.27.20

 _{To deactivate AOA protection push sidestick} > 8° forward

> 0,5° forward and at least 0,5 sec if α<αMAX  _{Below 200ft AOA protection is deactvated if}

sidestick deflection is < half nose-up and actual α < PROT -2°

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A320 FLT CTRL Laws & Protections Low Speed Stability

 Low Speed Stability replaces normal AOA protection  Available at 5 kts to  stall warning speed + 10 kts  _{Introduction of gentle nose down signal}

 _{Audio stall warning is activated}  VαFLOOR protection inoperative  _{Modified PFD speed scale}

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A320 FLT CTRL Laws & Protections Stall Warning

 In low speed (at speed threshold below VLS) stall warning is activated at 1,03 VS1G

 Refer to FCOM 1.27.20; FCOM-NG / DSC / 27 / 20  Refer to FCTM OP-020

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A320 FLT CTRL Laws & Protections High Speed Protection

 _{a/c recovers automatically from high speed upset}

 activated at VMO/MMO depending from flight conditions (high acceleration, low pitch attitude)

 _{THS setting is limited between present position and 11°} nose-up

 _{Positive spiral static stability to 0° bank} max bank angle 40°

 autopilot deactivates

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A320 FLT CTRL Laws & Protections High Speed Stability

 Above VMO/MMO a nose-up demand is introduced to avoid excessive increase in speed.

 The pilot can override that demand.

 _{The aural overspeed warning remains available at} VMO+4 or MMO+0,006

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A320 FLT CTRL Laws & Protections Over Speed Warning

_{The aural overspeed warning remains available at} _V_MO_{+ 4 or}

MMO + 0,006

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A320 FLT CTRL Laws & Protections Pitch Attitude Protection

 30° nose-up in Config 0-3

progressively reduced to 25° at low speed  _{25° nose-up in Config FULL}

progressively reduced to 20° at low speed  _{15° nose-down}

 _{FD bars disappear at pitch > 25° up or < 13°} nose-down

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A320 FLT CTRL Laws & Protections Positive Static Stability

 An aircraft with positive spiral stability tends to roll out of a turn by itself if the controls are

centered.

 _{In other words the airplane reduces bank by itself aerodynamic configuration.}  According FCTM Operational Golden Rules No.1

“The aircraft can be flown like any other aircraft”

the A320 series shows basic aerodynamic characteristic of positive static stability.  p.e. in Normal Law: Neutral spiral stability up to 33° bank:

• Automatic pitch trim

• The bank angle is maintained when the sidestick is at neutral

 p.e. in Normal Law: Positive spiral stability restored above 33° bank: • No automatic pitch trim

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