Aircraft holdings explained: Breaking down the basics
Many of us have found ourselves aboard a plane executing repetitive turns in the sky or observed an aircraft circling a specific point.
While these manoeuvres might be perceived as either mildly irritating or amusing, it’s crucial to recognize that the act of flying over a particular area isn’t for the pleasure of pilots. Rather, it’s a response to various operational circumstances aimed at prioritising safety, albeit leading to increased emissions. In this series of blog articles, we will delve into the details of these aviation practices to gain a deeper understanding of the challenges and considerations involved in managing air traffic, providing a unique perspective on the controlled yet intricate choreography of aircraft navigating the vast expanse of the sky.
What is a holding?
In aviation, a holding or holding pattern is a designated flight path followed by an aircraft as it awaits clearance to proceed with landing at an airport. These patterns are typically used during situations such as air traffic congestion, adverse weather conditions, or when an aircraft is ahead of its scheduled arrival time. They were put in place to provide a systematic and safe means of delaying an aircraft’s approach or landing.
When a pilot is instructed to enter a holding pattern, they must follow specific instructions provided by air traffic control. This includes flying a racetrack-shaped pattern, maintaining a designated altitude, and executing turns at predetermined intervals. The goal is to keep the aircraft safely within a confined airspace while awaiting further instructions or clearance to proceed with the approach and landing.
Pilots use navigation equipment on board the aircraft, such as instruments based on radio signals or satellite navigation systems, to precisely follow the holding pattern. Effective communication between the pilot and air traffic control is crucial during this phase to ensure the safe and orderly management of air traffic in congested or challenging conditions. Once the aircraft receives clearance, the pilot exits the holding pattern and continues with the planned approach and landing.
Exploring the necessity of holdings
Holdings are implemented for various reasons, all aimed at ensuring the safety and efficient management of air traffic. Some common reasons for holding patterns include:
- Air Traffic Congestion: Holding patterns are often used when there is congestion at an airport, either on the ground or in the airspace. This helps air traffic controllers manage the flow of arriving aircraft, preventing overcrowding, and maintaining safe distances between planes.
- Weather Conditions: Adverse weather, such as low visibility, thunderstorms, or high winds, can impact the safe landing of aircraft. Holding patterns allow pilots to delay their approach until the weather conditions improve, ensuring a safe and controlled landing.
- Airspace Congestion: In busy airspace, especially in the vicinity of major airports, holding patterns may be employed to manage the overall flow of air traffic. This is crucial for preventing conflicts between arriving and departing flights.
- Runway Occupancy: If a runway is temporarily unavailable due to maintenance, an incident, or another reason, aircraft may be placed in holding patterns until the runway becomes operational again.
- Scheduling and Arrival Management: Air traffic controllers use holding patterns to manage the sequencing and timing of arriving flights. This is important for maintaining order in the airspace and allowing each aircraft to approach and land in a systematic manner.
- Unforeseen Circumstances: Emergencies, air traffic control issues, or other unforeseen circumstances may necessitate the use of holding patterns to provide controllers and pilots with time to assess the situation and make appropriate decisions.
- Airport Capacity Constraints: Some airports may have limited capacity to handle a large number of arrivals within a short time frame. Holding patterns can be implemented to regulate the flow of arriving aircraft, preventing bottlenecks, and ensuring a manageable rate of landings.
As such holding patterns are a dynamic tool in aviation, allowing for flexibility in managing air traffic under various conditions. They contribute to overall aviation safety by preventing congestion and facilitating efficient movements of aircraft in the sky and on the ground.
The operational aspects of holdings
While and aircraft is flying in a holding pattern, the airspace in which it is allowed to perform the turns is known as a ‘protected airspace’. This reserved or protected airspace ensures that there is a safe buffer zone around the aircraft, preventing conflicts with other air traffic. The concept of protected airspace is a critical aspect of air traffic management during holding procedures.
When air traffic controllers assign a holding pattern to an aircraft, they take into consideration factors such as the aircraft’s speed, the standard holding pattern dimensions, and the time it takes for the aircraft to complete a turn. Based on these factors, controllers establish a protected airspace around the aircraft to avoid collisions with other traffic.
Aircraft enters this space through what is known as a holding pattern and these patterns are classified into three main types, each distinguished by the entry method employed by the aircraft. The designated holding speed within a protected area is subject to variation based on regional distinctions, specific directives from air traffic control, and considerations related to airspace type, aircraft specifications, and local regulations.
Role of space-based ADS-B data for aviation data
Space-based aviation data with ADS-B data plays a pivotal role in spotting and understanding holdings by providing comprehensive information about aircraft movements and patterns. Satellite-based technologies contribute real-time data on the position, speed, and altitude of aircraft, offering a global perspective on air traffic. This data helps analysts identify holding patterns as aircraft circle specific points in the sky. Advanced data-driven digital twin models of air traffic coupled with post-flight analytics tools enables to develop future ATM capabilities. Such digital twins allow to prototype, analyze live and historical data and improve ATM operations quickly and safely, while reducing emissions. Additionally, space-based surveillance enhances the accuracy of tracking aircraft for air traffic controllers, allowing for more efficient management of air traffic such as, reducing separations, optimising flight paths and helping them enhance the awareness.