Understanding the Differences in Spoiler Operation Between Airbus A320 and Boeing 737

The Airbus A320 and Boeing 737 are two of the most popular and widely used commercial aircraft in the world today. While both aircraft feature spoiler systems to enhance their performance, there are notable differences in the way these spoilers operate. This article will delve into the reasons behind the seemingly slower spoiler operation in the Airbus A320 in comparison to the Boeing 737, exploring various design and operational factors.

Design Philosophy

Design Philosophy: Part of the reason for the difference in spoiler operation speed can be traced back to the design philosophies of the two manufacturers, Airbus and Boeing. Airbus, known for its advanced fly-by-wire systems, prioritizes smooth handling and passenger comfort over quick responses. This design choice often results in slower spoiler deployment to ensure stability and reduce abrupt changes in lift.

Aerodynamic Considerations

Aerodynamic Considerations: The Airbus A320's spoilers are designed to manage airflow and lift more gradually. This approach helps maintain control during critical phases of flight, such as landing and go-arounds. In contrast, the Boeing 737's spoilers may be designed for a quicker response, particularly in scenarios requiring rapid descent or sharp turns.

Control Systems

Control Systems: The control algorithms in the Airbus A320's fly-by-wire systems may include features that modulate spoiler deployment speed based on flight conditions. Conversely, the Boeing 737's control system may prioritize quicker response times, leading to faster spoiler deployment.

Operational Requirements

Operational Requirements: Different airlines and regulatory requirements can influence how quickly spoilers are deployed. The Airbus A320, emphasizing passenger comfort and smoothness, may be designed with slower deployment speeds to enhance this experience.

Structural Considerations

Structural Considerations: The size and design of the spoilers and the mechanisms that operate them can affect their deployment speed. The A320's spoilers might be larger or designed for different aerodynamic effects, necessitating slower operation to avoid structural stress.

Comparison of Spoiler Operation Logic

The spoiler operation logic for the Airbus A320 and Boeing 737 is quite different, adding another layer of complexity to understanding the operation differences. In the Boeing 737, the spoilers can only be deployed when both thrust levers are at idle position, and one main landing gear is compressed. Additionally, the red boxes in the picture below highlight the ground spoilers, while the yellow boxes show the flight spoilers.

However, in the Airbus A320, the process is more complex. For spoilers to be armed or not retracted:

Both main landing gears are on the ground. Both thrust levers are at or below idle or reverse is selected on one engine with the other thrust lever below MCT (Maximum Continuous Thrust).

When the spoilers are in the retracted position but not armed:

Both main landing gears are on the ground. Reverse is selected on at least one engine with the other thrust lever below MCT.

The Airbus A320 also features a partial spoiler extension called Phased Lift Dumping (PLD), which aims to accelerate full spoiler deployment. For spoiler extension:

One main landing gear is on the ground. Both thrust levers are at idle position.

For spoiler retraction:

One main landing gear is on the ground. Reverse is selected on at least one engine with the other thrust lever below MCT.

Note: In the A320, the wheel spin-up speed should be greater than 72 knots for spoiler extension, a threshold that is higher than the 60 knots required in the Boeing 737.

Delayed Spoiler Deflection in the A320

The delay in spoiler deflection observed in the A320 can be attributed to two primary factors:

Phased Lift Dumping (PLD): In the A320, when one wheel is detected on the ground, the spoilers only extend halfway due to PLD. Once the other gear is compressed, full extension occurs. This ensures stability and reduces structural stress. Wheel Spin-Up Speed: The A320 requires a wheel spin-up speed of 72 knots for spoiler extension, while the Boeing 737 only needs 60 knots. This difference results in a slower speed of deployment in the A320.

Final Thoughts

While both the Airbus A320 and Boeing 737 feature spoiler systems, the differences in their operation are a testament to the diverse design philosophies and operational requirements of these two manufacturers. Understanding these differences is crucial for pilots, technicians, and enthusiasts to appreciate and utilize the unique features of each aircraft effectively.