4. Engines and ground operation
4.1 Warm-up and cool-down
These are engine figures, not airframe figures. The same A320 has different numbers depending on what is hanging under the wing.
| Warm-up | Cool-down | |
|---|---|---|
| CFM | 2 min | 3 min |
| IAE | 5 min | 3 min |
| neo | 5 min | 3 min |
4.2 Brake temperature and the brake fan
When to run it. Generally not before 5 minutes after landing. The exception is a landing where experience says the brakes will certainly pass 500 °C — then immediately after vacating.
When to stop it. Before taxiing onto the stand, where the turnaround allows — it is loud, and the noise lands on the ground crew rather than on the flight deck. Where the temperature is too high or the turnaround too short, leave it running.
Airbus procedure: any brake above 100 °C when taxi begins → brake fan on. Then cool as far as the time allows.
(M) Maximum brake temperature for takeoff is 150 °C.
The 300 °C figure is not the takeoff limit, and quoting it as one is a common error. It applies only where the brake fan was not used — a case that essentially does not arise in practice, because the fan is used. Fly to 150 °C.
4.3 De-icing and holdover
Holdover tables are reissued annually, because the fluid manufacturers keep improving the products. Tables exist for Type 2 and Type 4 fluids.
A holdover time cannot be looked up from the airport alone. There are around twenty different tables in circulation, and a single airport may have more than one fluid manufacturer on the field — so the table that applies depends on which fluid was actually sprayed on this airplane today.
The practical answer is a holdover tool rather than a printed table.
4.4 Noise abatement departure
Airport-dependent, and not inferable from the airport alone. The procedure is published in the arrival and departure information for the field. Different airlines use different values at the same airport, and there are arrangements made between individual airlines and individual airports.
The two standard profiles:
| Thrust reduction | Acceleration | |
|---|---|---|
| NADP 1 | 1,500 ft AGL | 3,000 ft AGL |
| NADP 2 | 1,000 ft AGL | 1,000 ft AGL |
NADP 1 keeps thrust longer and accelerates later, which moves noise away from close-in communities. NADP 2 cleans up earlier and is quieter further out. Which one applies is the airport's decision, not the crew's.