What is the difference between NADP 1 and NADP 2?

In real-world aviation, NADP 1 reduces noise close to the airport by keeping the take-off configuration and a relatively steep climb until the higher acceleration altitude. NADP 2 reduces noise farther along the departure track by lowering the nose, accelerating and retracting flaps earlier. Neither is a universal fixed profile.

NADP means Noise Abatement Departure Procedure. The useful cockpit shorthand is: NADP 1 reduces thrust early but cleans up later; NADP 2 starts accelerating and cleaning up earlier.

NADP 1 vs NADP 2 at a glance

The often-quoted ICAO specimen uses changes beginning no lower than 800 ft above aerodrome elevation, with 3,000 ft AAE as the upper reference point for acceleration or transition. Those figures are not permission to ignore an airport chart, aircraft procedure or operator-specific altitude.

What happens during each noise-abatement procedure?

Both procedures normally begin with the approved take-off thrust, configuration and climb speed, commonly within V2 plus 10 to 20 knots, until the minimum noise-abatement initiation altitude.

NADP 1 sequence

1. Initial climb: maintain the take-off configuration and approved take-off climb speed.
2. Thrust reduction: at the specified altitude, reduce from take-off thrust to the approved climb or noise-abatement thrust setting.
3. Configuration held: continue climbing at roughly the same target speed, leaving flaps and slats in take-off configuration.
4. Delayed acceleration: at the higher acceleration altitude, lower the pitch smoothly, accelerate and retract flaps or slats on their normal speed schedule.

This keeps the aircraft higher over communities near the departure end, although it retains the drag of the take-off configuration for longer.

NADP 2 sequence

1. Initial climb: use the same basic take-off configuration and approved climb speed.
2. Earlier acceleration: at the specified altitude, reduce pitch while maintaining a positive climb and accelerate towards the clean-up speed.
3. Earlier retraction: retract flaps and slats progressively as the aircraft reaches the required manoeuvring or retraction speeds.
4. Thrust reduction: reduce thrust at the approved point during this acceleration segment, without compromising safe acceleration or required climb performance.

“Thrust reduction” does not mean closing the thrust levers or selecting idle. It means changing to an approved climb setting. The wider post-take-off climb sequence and its safety priorities still apply.

Which noise-abatement procedure should a pilot use?

Pilots use the procedure specified by the airport, operator and approved aircraft procedures; NADP 1 or NADP 2 is not normally an improvised cockpit choice.

• Check the departure chart and local noise notes for a named procedure or exact thrust-reduction and acceleration altitudes.
• Apply the operator's aircraft-specific speed, thrust and flap schedule.
• Confirm that the profile satisfies obstacle-clearance and SID climb-gradient requirements.
• Use the applicable abnormal or performance procedure if an engine failure, windshear warning, terrain conflict or other safety issue makes the noise profile unsuitable.

A local procedure may resemble NADP 1 or NADP 2 without using that label, and operators may implement the same concept with different altitudes. The published and approved instructions always take precedence over generic 800 ft and 3,000 ft examples.

How does an NADP work with a SID?

An NADP mainly governs thrust, speed, pitch and configuration, while a SID defines the departure route and may add altitude, speed and climb restrictions.

The two are flown together. A turn restriction, minimum climb gradient or waypoint altitude does not disappear because a noise-abatement profile is active. Our guides to interpreting altitude and speed notes on departure charts and flying a published SID in a simulator cover that chart-to-cockpit workflow.

How do you set NADP 1 or NADP 2 in a flight simulator?

In a simulated airliner, reproduce the charted thrust-reduction and acceleration altitudes rather than looking for a universal NADP switch.

1. Read the departure notes: identify the required procedure, initiation altitude, acceleration altitude and any speed or turn restrictions.
2. Enter the vertical profile: where the aircraft supports it, set the relevant thrust-reduction and acceleration fields, sometimes shown together as THR RED/ACC.
3. Check the altitude reference: a chart may state height above aerodrome elevation, while the flight-management system may expect a barometric altitude above mean sea level. Do not add the airport elevation unless the aircraft's entry convention requires it.
4. Monitor the sequence: verify thrust reduction, acceleration and flap retraction rather than assuming the automation has interpreted the entries correctly.

Some simplified simulator aircraft combine these events or do not model separate entries. In that case, fly the approved sequence manually using the aircraft's normal speed and configuration limits.

What mistakes cause the wrong NADP profile?

The most common errors are reversing the two procedures or treating the ICAO example altitudes as universal requirements.

• Using 3,000 ft indicated when the instruction means 3,000 ft above aerodrome elevation.
• Retracting every flap stage at the acceleration altitude instead of following the aircraft's speed schedule.
• Reducing thrust too far because “cutback” is mistaken for idle thrust.
• Accelerating early during NADP 1, which defeats its close-in noise objective.
• Holding take-off configuration to the higher altitude during NADP 2, which effectively turns it into the wrong profile.
• Following a noise procedure despite an engine failure, windshear escape manoeuvre or other condition requiring maximum safe performance.

The reliable memory aid is: NADP 1—thrust back, clean up later; NADP 2—accelerate and clean up earlier.