Unstable Approaches - Procedures & Risk Mitigation

Introduction

Approach and landing phases are among the most critical in flight operations, where any deviation from established parameters can significantly increase the risk of an accident. One of the most persistent threats during these phases is the occurrence of Unstabilized approaches. An Unstabilized approach occurs when the aircraft does not meet specific parameters of speed, descent rate, configuration, and alignment by a predetermined gate, usually 1,000 feet AGL in Instrument Meteorological Conditions (IMC) or 500 feet in Visual Meteorological Conditions (VMC). Failure to meet these conditions should necessitate an immediate go-around. However, continuation of an unstable approach often leads to serious consequences such as runway excursions, hard landings, loss of control, and even Controlled Flight Into Terrain (CFIT).

This article provides an in-depth exploration of the risks associated with Unstabilized approaches, supported by recent case studies and statistical insights. It also outlines effective mitigation strategies that can be implemented at the organizational, regulatory, and operational levels.

Scope and Impact of Unstabilized Approaches

Statistical evidence underscores the severity of this safety issue. According to the International Air Transport Association (IATA), Unstabilized approaches contributed to 26% of approach and landing accidents between 2016 and 2020. In 2020 alone, 29% of all accidents were linked to Unstabilized approaches. The Flight Safety Foundation further reported that between 1984 and 1997, 66% of 76 approach and landing accidents had unstable approach characteristics as a contributing factor.

Global Accident Dashboard 2024

The consequences of Unstabilized approaches are varied. Between 2016 and 2020, hard landings accounted for 36% of such outcomes, followed by runway/taxiway excursions (33%), tail strikes (12%), undershoots (10%), and other less frequent occurrences including Loss of Control In-flight (LOC-I), gear-up landings, and in-flight damage.

Factors Contributing to Unstable Approaches

Numerous factors increase the likelihood of an Unstabilized approach:

• Adverse Weather Conditions: Crosswinds, turbulence, low visibility, and wind shear can destabilize an otherwise well-planned approach.
• ATC Constraints: High approach speeds or late runway changes imposed by Air Traffic Control (ATC) often pressure pilots into rushed decisions.
• Commercial Pressure: Airline operational demands may subtly influence a pilot’s decision to continue an unstable approach rather than opting for a go-around.
• Human Factors: Fatigue, distraction, complacency, and poor communication can impair crew performance during critical moments 
• Operational and Cultural Challenges: Inconsistent Standard Operating Procedures (SOPs), lack of enforcement of go-around policies, and deficient safety cultures contribute significantly to continued unstable approaches.

Case Studies Highlighting the Risk

1. Air India Express B737 at Kozhikode (2020): The aircraft overran the runway and fell into a valley, killing both pilots and 19 passengers. The cause was the continuation of an Unstabilized approach and landing long despite the PM calling for a go-around.

2. Asiana Airlines Flight 214 (2013): A Boeing 777 crashed short of the runway at San Francisco due to improper speed management and a failure to go around during an unstable approach, resulting in three fatalities and numerous injuries.

3. ATR 76-600 at Jabalpur (2022): The aircraft overran the runway following a bounced landing resulting from an Unstabilized approach. The crew failed to initiate a go-around.

4. WestJet B738 at Halifax (2020): The aircraft overran the runway due to excessive approach speed and a failure to adhere to stabilisation criteria.

5. Caspian Airlines MD-83 at Mahshahr (2020): The aircraft overran the runway following a long landing during an Unstabilized approach. Poor judgment and failure to execute a go-around were cited.

These incidents reinforce the need for prompt recognition and action when the approach stability criteria are not met.

Analysis of Root Causes

A deeper analysis reveals patterns that transcend individual events:

• Continuation Bias: A psychological tendency to persist with an approach despite deviations, hoping to resolve issues before touchdown.

• Inadequate Monitoring: Many unstable approaches go unnoticed or uncorrected due to a lack of situational awareness or failure of the PM to challenge the PF effectively.

• Training Deficiencies: Training programs often emphasize completing landings rather than aborting for safety, conditioning pilots to avoid go-arounds unless absolutely necessary.

• CRM Breakdown: Poor Crew Resource Management (CRM) can lead to ineffective communication and decision-making under pressure.

Mitigation Strategies

To mitigate the risks of unstabilized approaches, a multi-layered strategy must be employed, encompassing procedural, cultural, and technological components.

1. Reinforcing SOPs and Stabilisation Gates

Airlines must adopt clear SOPs that define stabilization gates and mandate go-arounds when criteria are not met. This includes:

• Stabilisation by 1,000 feet AGL in IMC and 500 feet AGL in VMC.

• Mandatory callouts like “Stable,” “Unstable,” or “Go-Around” are made at the gate and any time deviation occurs.

2. Training Enhancements

Training programs should reflect real-world conditions and promote correct decision-making. Key aspects include:

• Simulator scenarios simulating high-pressure approaches.

• Regular reinforcement of go-around as a positive, safety-first action.

• Emphasis on early configuration and proactive energy management.

3. Technological Support

• Modern aircraft offer tools to assist in maintaining approach stability:

• Flight Data Monitoring (FDM) to detect unstable trends.

• Enhanced Ground Proximity Warning Systems (EGPWS) with glidepath deviation alerts.

• Utilization of HUDs for enhanced visibility and informed decision-making.

4. Organizational Safety Culture

Airlines must foster a culture where safety takes precedence over schedule. This includes:

• Non-punitive go-around policies.

•  Encouraging open reporting of unstable approaches.

• Promoting CRM practices that empower the PM to challenge or take over control if necessary.

5. Regulatory and ANSP Support

Regulators and Air Navigation Service Providers (ANSPs) can play a critical role:

• Avoid issuing last-minute runway changes.

• Provide a clear descent path and track mile information.

• Support operators through guidance and collaborative safety programs.

6. Awareness and Collaboration

Cross-functional collaboration improves effectiveness:

• Sharing data through regional safety groups and global platforms like IATA, FDX, or FAA ASIAS.

• Joint training programs involving pilots, dispatchers, and ATC personnel.

Conclusion

Unstabilized approaches remain a leading cause of accidents in commercial aviation. Yet, they are entirely preventable with the right combination of awareness, training, policy, and technology. The decision to go around must be normalized and reinforced as an integral part of professional airmanship. 

By fostering a safety-first environment that includes rigorous data analysis, ongoing simulator-based training, comprehensive standard operating procedures (SOPs), a strong safety culture, and organizational support, the industry can significantly reduce the frequency of unstable approaches.

Ultimately, recognizing a go-around as a proactive safety decision, rather than a failure, can reduce the industry’s most persistent cause of approach and landing accidents. Pilots must be trained, encouraged, and empowered to prioritize stability and safety above all else.

Remember: A landing is optional. A go-around is a reality.

Author: GR Mohan