What is ASR Approach – Overview of Airport Surveillance Radar
Airport Surveillance Radar (ASR) acts as essential infrastructure for air traffic controllers, enabling them to track aircraft movements within terminal areas up to 60 nautical miles away. This radar system proves especially valuable when other navigational aids fail, providing essential range and azimuth data that keeps aircraft safely separated and on course.
An ASR approach represents a non-precision procedure where Air Traffic Control assumes the role of navigator, providing lateral guidance through precise heading instructions. Controllers act as the pilot’s external reference, issuing specific headings to align the aircraft with the runway and creating a structured flight path that compensates for the system’s inherent lack of vertical guidance.
Within navigation systems like ForeFlight Mobile, ASR approaches appear as terminal procedures, sharing similarities with Precision Approach Radar (PAR) approaches. The key difference between them: ASR lacks the vertical guidance component that makes PAR more precise, which affects flight planning decisions.
Some airports use combined of navigational aids, such as the LOC/ASR approach. These hybrid procedures typically employ an offset localizer for the initial approach segment before transitioning to surveillance radar guidance for the final approach phase. For example, a LOC/ASR approach might employ the localizer for initial positioning before using radar guidance to execute a turn to final approach.
ASR approach charts provide detailed information, displaying critical information including minimum descent altitudes, missed approach points, and recommended headings. These standardized charts are essential for both pilots and controllers, maintaining situational awareness throughout the procedure and ensuring consistent execution despite the approach’s non-precision nature. Understanding ASR is important when traditional navigation aids falter or simply aren’t available.
Key Regulations Governing ASR Approaches
The Federal Aviation Administration maintains detailed regulations governing Airport Surveillance Radar approach execution. At the heart of these regulations lies the Air Traffic Control Order JO 7110.65, that details controller protocols for providing lateral guidance and monitoring aircraft during these approaches. This foundational order, combined with related terminal procedures’ documentation, provides the foundation for standardizing ASR procedures nationwide.
These regulations define the specific controller-pilot relationship during ASR approaches. They mandate standardized phraseology to ensure clear communication when margins for error are thin.
Safety is the top priority. Requirements govern aircraft separation and adherence to published minimums, creating consistent safety margins that protect lives.
The regulatory framework also sets protocols for missed approach procedures, including standard instructions and precise communication requirements. This ensures safe separation from terrain and obstacles when landing becomes impossible.
These regulations are mandatory for both controllers and pilots. This provides structure where each party clearly understands their responsibilities and limitations, standardizing ASR procedures across the entire national airspace system for consistent, reliable application.
Understanding ASR Approach Procedures
ASR approach execution follows a specific sequence. Initially, ATC vectors the aircraft to intercept the final approach course to position the aircraft for final approach. Throughout the approach, controllers monitor the aircraft’s position, continuously monitoring the aircraft’s position on their radar displays while providing real-time heading adjustments to maintain proper alignment with the extended runway centerline. These instructions typically include specific headings (“Turn right heading 095 degrees”) followed by position updates (“Five miles from runway, slightly right of course”).
Pilots need strong situational awareness during ASR approaches, building awareness of their position relative to the runway while executing ATC instructions with precision. This requires monitoring of critical instruments—the heading indicator and altimeter become their primary references—while simultaneously responding to ATC guidance. Without vertical guidance, pilots must manage their descent using distance information from ATC and any published altitude restrictions for guidance.
ASR approaches serve as backup procedures, typically deployed in specific scenarios, such as:
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When other navigational aids are unavailable due to equipment failures.
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When weather conditions are below minimums for other approach types.
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At airports with limited navigational infrastructure.
Final Approach Fix – Starting the Descent
The Final Approach Fix marks the transition point in any ASR approach—the moment when the final descent phase toward the runway officially begins. During ASR approaches, descent to the Minimum Descent Altitude is authorized at the FAF, unless the approach procedure includes altitude-limiting step-down fixes that must be observed along the final approach course.
When cleared to a fix where an approach begins, pilots should initiate the procedure near their expect-further-clearance (EFC) time or estimated time of arrival. However, if the clearance limit isn’t an approach fix, they must hold until the EFC before proceeding to one.
During an ASR approach, controllers provide altitude guidance, typically informing pilots when they’re crossing the FAF with phraseology such as “Crossing final approach fix.” This signals for pilots to begin their controlled descent from the final approach fix altitude toward the MDA.
Proper descent planning is essential at this juncture. Pilots must calculate and maintain an appropriate descent rate based on ground speed and the distance between the FAF and runway threshold to ensure a stable descent profile. This ensures the aircraft at the MDA before the missed approach point with sufficient time to acquire the runway visually. Controllers often provide recommended altitudes at each mile on final approach, helping in maintaining an appropriate descent profile without vertical guidance.
Minimum Descent Altitude (MDA) in ASR Approaches
The Minimum Descent Altitude is the safety threshold in ASR approaches, the lowest altitude that provides protection for pilots during this non-precision procedure. Unlike precision approaches that guide pilots smoothly to a decision height, ASR approaches require pilots to maintain the MDA, holding this altitude until reaching the missed approach point or establishing visual contact with the runway environment.
Reaching the MDA doesn’t require a missed approach. Pilots must maintain this altitude until they either acquire visual references for the runway or reach the missed approach point without visual contact.
The MDA serves as the minimum altitude of the final approach segment, ensuring terrain and obstacle clearance while the aircraft proceeds toward the runway. Controllers typically advise pilots when approaching the MDA with phraseology such as “Approaching minimum descent altitude,” maintaining situational awareness. Once established at the MDA, pilots must divide their attention between precise instrument scanning (to maintain altitude exactly) and vigilant external scanning (to identify the runway environment).
Weather conditions affect ASR approach execution at the MDA. Visibility must meet or exceed published minimums, providing pilots adequate time to transition from instrument references to visual references before reaching the missed approach point. This transition is important—pilots must have the runway environment clearly in sight to descend below the MDA for landing. If visual references cannot be established and maintained, pilots must execute the published missed approach procedure or as directed by ATC.
Missed Approach Procedures for ASR
The missed approach procedure provides the safety procedure of any ASR approach, providing pilots with specific escape instructions when visual contact cannot be established by the missed approach point. During an ASR approach, Air Traffic Control identifies this decision point with specific phraseology: “Missed approach point is (distance) miles from the runway.” As the aircraft reaches this predetermined location, controllers announce: “Over missed approach point. If runway not in sight, execute missed approach.”
When executing a missed approach during an ASR procedure, pilots must respond immediately, following either the published missed approach instructions or specific ATC directions. This typically involves an immediate climb to a safe altitude, followed by a series of turns or vectors that position the aircraft for another approach attempt or diversion to an alternate airport. Execute this transition immediately to ensure terrain and obstacle clearance.
If communication with ATC is lost, pilots must initiate lost communication procedures if no transmissions are received for:
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60 seconds while being vectored to final.
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15 seconds while on ASR final approach.
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5 seconds during a PAR final approach.
In such situations, pilots should proceed with the published instrument approach procedure (IAP) or previously coordinated instructions.
Preparation for a potential missed approach should begin during approach planning. Pilots should thoroughly review and brief the missed approach procedure during approach preparation, ensuring they understand the required climb gradient, heading, altitude restrictions, and any holding instructions. This preparation allows better execution if a missed approach becomes necessary. Additionally, pilots should configure their aircraft appropriately, considering factors such as power settings and aircraft configuration for quick transition from approach to climb when circumstances demand it.
Recommended Altitudes During ASR Approaches
During an ASR approach, altitude management is especially important due to this procedure’s non-precision nature. Unlike precision approaches that provide electronic vertical guidance, ASR approaches rely entirely on Air Traffic Control to assist pilots with maintaining appropriate descent profiles. To address this, controllers provide recommended altitudes at each mile marker, creating a step-down profile that ensures obstacle clearance throughout the approach.
This systematic guidance continues until the aircraft nears the runway, at which point the pilot should be established at or above the published MDA.
The recommended altitude system serves multiple safety functions:
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It helps pilots maintain a consistent and appropriate descent rate.
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It ensures adequate obstacle clearance at each point along the approach.
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It provides a structured framework for vertical navigation without an electronic glide path.
Pilots should request these recommended altitudes if ATC doesn’t automatically provide Themis not provided. This communication improves situational awareness and ensures compliance with the published procedure. When flying the approach, pilots should cross-reference these recommended altitudes with their instruments and approach charts, treating them as minimum crossing altitudes rather than mere targets. This adds safety margin, especially in challenging weather or at unfamiliar airports.
Using ATC’s recommended altitudes, pilots can conduct safe, stabilized approaches despite the inherent limitations of the ASR system.
ATC Instructions and Pilot Responsibilities in ASR
Pilots have important responsibilities throughout the ASR procedure. Foremost is the prompt and accurate execution of ATC’s heading instructions with precision. Unlike approaches where pilots navigate using onboard equipment, ASR approaches require pilots to relinquish directional control to ATC while maintaining full responsibility for aircraft performance and configuration. This requires clear radio discipline and communication between both parties.
Throughout the approach, controllers provide position updates such as “X miles from the runway, slightly right/left of course” to help pilots visualize their position in space. These updates typically occur at one-mile intervals on final approach, becoming more frequent as the aircraft nears the runway threshold. Pilots should acknowledge these communications promptly while maintaining focus on proper airspeed, descent rate, and aircraft configuration.
Altitude management is another pilot responsibility. While ATC provides recommended altitudes at specific distances from the runway, pilots must actively monitor their altimeters and vertical speed indicators to ensure compliance with these recommendations. If ATC doesn’t volunteer altitude information, pilots should proactively request it with a simple query: “Request recommended altitudes.” This coordination for vertical navigation helps compensate for the non-precision nature of ASR approaches.
Decision-making authority stays with the pilot-in-command, particularly regarding missed approach execution. When ATC announces “Over missed approach point,” pilots must immediately assess whether sufficient visual references exist to continue the approach safely. If not, they must execute the published or assigned missed approach procedure without hesitation. Action at the missed approach point is a critical responsibility during an ASR approach.
Successful ASR approach execution depends on coordination between ATC and pilots based on clear communication. By understanding and fulfilling their respective responsibilities, both parties can work within the limitations of this non-precision approach and achieve safe outcomes, even in challenging conditions when other navigational aids have failed.
Conclusion – Mastering ASR Approaches
Airport Surveillance Radar approaches require a specific skill set combining of technical precision and collaborative flying. These non-precision approaches rely on Air Traffic Control for navigation, providing lateral guidance that demands exceptional coordination between pilots and controllers.
Success in ASR approaches requires several key elements:
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Following ATC Instructions: Pilots must promptly and accurately follow heading instructions to align with the runway.
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Situational Awareness: Pilots must maintain awareness of position, altitude, and approach progress.
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Understanding Minimums: Knowing the published minimums for each ASR approach is critical, as they vary by location.
Pilots can improve their ASR skills through deliberate practice and thorough preparation, including:
Understanding ASR approaches expands a pilot’s operational flexibility and confidence. By developing the collaborative skills these approaches demand, pilots gain a useful tool for navigating challenging conditions and diverse airport environments safely when other navigation aids fail when conventional navigation aids are unavailable.