Why Do Aircraft Climb Steeply Right After Takeoff?

Aircraft typically follow a relatively steep climb profile during the initial climb-out phase for several technical and operational reasons. These reasons relate to performance requirements, safety, airspace management, and environmental considerations.

1. Aircraft Performance Requirements

During takeoff, aircraft operate at maximum or derated takeoff thrust, providing high climb performance. Key considerations include:

• Aircraft climb at approximately V2 + 10~20 knots, achieving the required initial climb gradient.

• To satisfy Obstacle Clearance Requirements, the aircraft must climb at a sufficient angle to safely clear any obstacles (e.g., trees, buildings, towers) beyond the departure runway.

• Regulatory requirements (e.g., ICAO Annex 6, EASA/FAA Ops Specs) mandate that the aircraft must maintain a minimum climb gradient even in the event of an engine failure (second segment climb).

2. Noise Abatement Procedures (NADP)

At airports located near populated areas:

• Noise Abatement Departure Procedures (NADP 1 and 2) are implemented.

• These procedures require the aircraft to maintain a relatively steep climb to minimize the ground-level noise footprint.

• For example, in NADP 1, the aircraft climbs to at least 800 feet AGL before any configuration or speed changes are made.

3. Airspace and ATC Requirements

At busy airports:

• Standard Instrument Departure (SID) procedures are designed to quickly transition aircraft into controlled airspace and separate departing aircraft from arriving traffic.

• Air Traffic Control (ATC) may require steeper climbs to ensure vertical and lateral separation between aircraft.

4. Climb Efficiency and Fuel Management

• At low altitudes, air density is higher, resulting in increased drag and higher fuel consumption.

• To optimize fuel efficiency, aircraft aim to reach cruise altitude as quickly and efficiently as possible, which involves following an optimum climb profile—often requiring a steep climb right after takeoff.

Summary

The primary technical reasons aircraft climb steeply right after takeoff are:

1. Obstacle clearance and safety requirements

2. Regulatory compliance for engine-out performance

3. Adherence to noise abatement procedures

4. Traffic separation and airspace structure

5. Fuel efficiency and performance optimization

For these reasons, aircraft execute a relatively steep climb immediately after takeoff in accordance with the departure procedure.