How to Manage Overspeeds in The Cruise

HSP Activation, Recovery Methods, and Expert Techniques for A320 Pilots

Hey everyone and welcome back to this A320 Knowledge deep dive.

Overspeed events in cruise are a common yet often misunderstood challenge faced by pilots. Modern aircraft, especially those cruising at high altitudes, operate near their high-speed limits, making them susceptible to occasional overspeed situations. This article explores how to manage these events effectively and how applying the right techniques can prevent dangerous altitude deviations. Whether you are a seasoned pilot or just starting to understand cruise speed management, the following insights will help you master the art of handling overspeed conditions safely and efficiently.

Let’s dive right in.

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Insights at a Glance:

• Frequency of Overspeed Events: Overspeed occurrences are more frequent than many pilots realize, with one happening every 1,400 flights.

• Importance of Autopilot and Autothrust: Keeping these systems engaged is key to maintaining stability and minimizing workload during overspeed events.

• Speedbrakes Usage: Proper use of speedbrakes is crucial in controlling and mitigating overspeed situations without destabilizing the aircraft.

• High-Speed Protection (HSP): Understanding HSP activation and what to do when the autopilot disconnects is vital for safe recovery.

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Introduction

Flying at cruising altitude requires careful management of the aircraft’s speed to avoid overspeed events that can jeopardize flight safety. Temporary overspeed occurrences are not unusual in modern aircraft, especially with changing wind conditions during cruise. However, it's essential to distinguish between transient overspeed and situations that demand more significant corrective actions.

We’re going to delve into the nature of overspeed events in cruise, analyzing how the A320 is designed to handle these situations, and the techniques recommended to safely manage overspeed scenarios when they arise.

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Flight Data Analysis: A Deeper Look at Overspeed Events

Airbus has analyzed flight data from over a million flights to understand how often overspeed events occur and how pilots typically respond. The data reveals that there is an overspeed event every 1,400 flights, highlighting that this is a regular occurrence during flight operations. Interestingly, most overspeed events occur during the cruise phase, where the aircraft is subject to changing wind conditions and fluctuating airspeeds.

However, the study also reveals some concerning trends in how overspeed events are handled. Many pilots are not adhering strictly to the recommended procedures outlined in the Flight Crew Techniques Manual (FCTM). Key observations from the analysis include:

• Autopilot Disconnections: In 25% of overspeed events, pilots disconnect the autopilot and take manual control, which can lead to significant altitude deviations.

• Speed Target Not Reduced: In 30% of overspeed occurrences, pilots fail to reduce the speed target as they approach the maximum operating speed (VMAX), which increases the risk of exceeding safe limits.

• Underutilization of Speedbrakes: In 60% of overspeed events, speedbrakes are not used, even though they are one of the most effective tools for decelerating the aircraft.

These insights underscore the importance of understanding and applying the correct techniques during overspeed scenarios to prevent aircraft instability and ensure a safe flight path.

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Aircraft Capabilities: How The A320 Handles Overspeed

Airbus aircraft are designed with safety margins built into their speed limitations, providing ample time and resources for pilots to recover from overspeed situations. The VMO (Maximum Operating Speed) and MMO (Mach Maximum Operating) provide significant margins above the aircraft’s design limits. This means we do not need to panic when the aircraft reaches these speeds, as the aircraft is capable of handling it safely.

Key Aircraft Features:

• Robust Autopilot Systems: The autopilot system is designed to remain engaged during most overspeed events. Only in the case of a large or prolonged VMAX exceedance will the autopilot disengage automatically.

• Fly-By-Wire System: In Airbus fly-by-wire aircraft, when an overspeed event occurs, the autopilot will remain engaged as long as High Speed Protection (HSP) is not triggered. If HSP is activated, the autopilot disconnects, and the aircraft will automatically make a pitch-up input to slow down.

• Aircraft Inspection: Aircraft inspections are required only when the speed exceeds VMO by 20 knots (or MMO +0.04). Importantly, no significant issues have been found in post-overspeed inspections of A320 aircraft, demonstrating their resilience to such events.

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Recommended Techniques for Overspeed Management

The FCTM provides a set of recommended procedures for managing overspeed situations. Understanding and applying these techniques can help pilots prevent overspeed events from escalating, ultimately ensuring a safer and smoother flight.

Overspeed Prevention Technique

The primary goal is to prevent the aircraft from exceeding VMAX. To achieve this:

• Keep Autopilot and Autothrust ON: Maintaining these systems ensures the aircraft stays on the intended flight path. Autothrust will command idle thrust, reducing the chance of overspeed.

• Select a Lower Speed Target: Choosing a lower target speed creates a buffer between the current speed and VMAX, giving you more time to react.

• Monitor Speed Trend and Use Speedbrakes: Always keep an eye on the speed trend arrow. If it approaches or exceeds VMO/MMO, use the speedbrakes to decelerate the aircraft without destabilizing its trajectory.

Overspeed prevention technique

Overspeed Recovery Technique