Aircraft Specific Questions: A320

A pack-off take-off involves temporarily switching off one or both air conditioning packs during takeoff to reduce engine bleed air demand. This provides several operational benefits:

• Improved engine performance, as more air is available for thrust instead of being diverted to the pneumatic system.
• Lower EGT during takeoff, which helps reduce engine wear and contributes to lower maintenance costs.
• Increased takeoff performance margins, especially useful in hot and high conditions, or on short or contaminated runways.

Typically, the packs are automatically re-engaged after takeoff, during the climb phase.

The FMA message 2 FD 2 means that Flight Director 2 (from FMGC 2) is active on both PFDs, indicating that FMGC 1 has failed.

In this case:
- FMGC 2 becomes the master FMGC, providing guidance to both flight directors.
- The message confirms that FD 1 is no longer available due to the FMGC 1 failure.
- Lateral and vertical guidance are now entirely based on FMGC 2 data.

SRS (Speed Reference System) mode provides vertical guidance through pitch control via the elevators, both during takeoff (SRS TO) and go-around (SRS GA). Although the logic is similar, there are key differences between the two:

During takeoff (SRS TO):
- Minimum vertical speed is protected at 120 ft/min, ensuring the aircraft maintains a positive climb gradient.
- Pitch angle is limited to 18° nose-up (or 22.5° in case of windshear).
- Speed target is limited to $V_{2}$ + 15 kt.

During go-around (SRS GA):
- Only a positive rate of climb is required (no specific minimum value).
- Same pitch protection as in TO: 18° max or 22.5° with windshear.
- Speed is protected to prevent exceeding VFE.
- Target speed is the greater of $V_{APP}$ or the speed at SRS engagement, limited to:
- 25 kt above VLS (15 kt if one engine inoperative),
- and 5 kt below $V_{MAX}$.

These protections ensure safe trajectory and speed management during both takeoff and go-around.

During an ILS CAT II manual landing, the autopilot must be disconnected by 80 ft AGL.

There are 3 TRs: TR1 supplies DC BUS 1, TR2 supplies DC BUS 2, and ESS TR can power the essential DC circuit from the emergency generator, if the engine and APU generators all fail, or if TR 1 or TR 2 fails.

When high speed protection activates (VMO/MMO exceeded), the flight control law introduces positive spiral static stability toward 0° bank (instead of 33° in normal law). With the sidestick released, the aircraft will return to wings level.

Additional effects include:
- The bank angle limit is reduced from 67° to 40°.
- Pitch-down authority is progressively reduced as speed increases above VMO/MMO.
- A permanent nose-up input is introduced to help recover the aircraft.

In a dive:
- If the sidestick is neutral, the aircraft will slightly overshoot VMO/MMO and return to the safe envelope.
- If full forward sidestick is maintained, the aircraft can exceed VMO by ~16 kt or MMO by ~0.04 Mach. At that point, pitch-down authority gradually reduces to zero, preventing further acceleration (though the aircraft does not stabilize at that speed).

These protections aim to recover the aircraft to safe flight without requiring pilot intervention.

When ACTs are installed, fuel is consumed in the following order:

1. ACT2 (if installed): fuel transfers into the center tank.
2. ACT1 (if installed): fuel transfers into the center tank.
3. Center tank: fuel is supplied to the engines via center tank pumps.
4. Inner wing tanks: each inner tank empties down to 750 kg.
5. Outer wing tanks: fuel transfers into the inner tanks to maintain the minimum level.

This sequence ensures center of gravity control and fuel management efficiency.

Current FL if flight time above FL300 > 30 min, FL300 if flight time above FL300 < 30 min, highest of FL150 and 7000 ft above take-off aerodrome if FL300 never exceeded, FL100 for Jet B.

On the A320 family configuration covered by this question, a dual loss of the GREEN and YELLOW hydraulic systems has the greatest impact on landing distance.

• Normal braking, powered by the GREEN system, is lost.
• Alternate braking, powered by the YELLOW system, is lost.
• Only the remaining brake-accumulator pressure is available for braking, without anti-skid.
• Both thrust reversers are unavailable: REV ENG 1 is powered by GREEN and REV ENG 2 by YELLOW.

The combination of limited accumulator braking, no anti-skid and no reverse thrust significantly increases the required landing distance.

This is a type-specific theoretical explanation. For operations, use the applicable ECAM/QRH/FCOM landing-distance data and the operator’s procedures.

Reference: Airbus Safety first — A320: Dual hydraulic loss.

With a green system failure, landing gear extension must be performed via gravity extension, and normal braking is lost. Alternate braking via the yellow system remains available. Anti-skid protection is still available provided yellow hydraulic pressure is present.

• A cabin altitude advisory is triggered when the cabin altitude exceeds approximately 8,800 ft.
• A cabin altitude warning (ECAM warning: CAB PR EXCESS CAB ALT) is triggered at around 9,550 ft.
• The passenger oxygen masks automatically deploy when cabin altitude reaches approximately 14,000 ft.