Step-by-Step Landing Process Using Instrument Landing Systems

For passengers gazing out the window, the descent into an airport is a moment of anticipation. The engines throttle back, the flaps extend, and the ground slowly rises to meet the wheels. It feels seamless, almost magical. But inside the cockpit, this phase of flight is a rigorous exercise in precision, governed by strict procedures and advanced technology. 

During this phase, the pilots continuously scan their instruments. They check the Instrument Landing Systems indicators to ensure the plane isn't deviating from the center of the localizer or the glideslope. They also cross-check their altitude against distance measuring equipment (DME) to verify they are not too low. This redundancy is vital for preventing accidents.  

When visibility is poor—whether due to fog, rain, or night—pilots cannot rely on their eyes to judge the approach. Instead, they turn to a radio-based guidance method that has been the industry standard for decades. This system creates an invisible pathway in the sky, guiding the aircraft with pinpoint accuracy to the runway threshold.

Understanding how this process works demystifies the complexity of modern aviation. This article breaks down the landing sequence into clear, sequential steps, illustrating the intricate dance between pilot, machine, and ground infrastructure.

Phase 1: Preparation and Interception

The landing process begins long before the runway is in sight. It starts miles away, often while the aircraft is still cruising at a high altitude.

The Briefing

Before beginning the descent, the flight crew conducts a thorough approach briefing. They review the specific charts for the destination airport, noting the frequencies for the radio guidance, the runway length, and the "Decision Height" (the altitude at which they must abort the landing if they cannot see the runway). This ensures both pilots share a mental model of the upcoming maneuver.

Tuning the Radios

As the aircraft enters the terminal area (usually 30 to 50 miles out), the pilots tune the navigation radios to the specific frequency of the runway's guidance system. They also identify the Morse code identifier broadcast by the station to confirm they are locked onto the correct signal and not a nearby navaid.

The Intercept Vector

Air Traffic Control (ATC) plays a crucial role here. They vector (guide) the aircraft to a position where it can intercept the "localizer" signal. This is usually a point about 10 to 15 miles from the runway, at an angle of 30 degrees or less to the final approach course. The goal is to gently merge the aircraft onto the extended centerline of the runway.

Phase 2: capturing the Localizer (Lateral Guidance)

Once the aircraft is on the correct intercept heading, the first component of the system comes into play.

The Invisible Centerline

The localizer is a radio beam transmitted from the far end of the runway. It defines the horizontal center. As the aircraft flies into this beam, a needle on the pilot’s primary flight display (or the autopilot system) "comes alive." It moves from the side of the display toward the center.

Establishing the Course

The pilot or autopilot turns the aircraft to match the runway heading. The objective is to keep that needle perfectly centered. If it drifts left, the plane is too far right, and a correction is needed. At this stage, the aircraft is typically flying level at a fixed altitude (e.g., 3,000 feet), waiting to intercept the descent path.

Phase 3: Capturing the Glideslope (Vertical Guidance)

With the aircraft aligned horizontally, the next challenge is managing the descent. This is where the second critical signal, the glideslope, becomes active.

The Descent Path

The glideslope signal is transmitted from antennas located near the touchdown zone. It creates a vertical beam, usually angled at 3 degrees upward from the runway. On the cockpit display, a second indicator (often a diamond shape) appears. As the aircraft flies level toward the runway, this diamond will slowly move down from the top of the scale.

Glideslope Capture

When the diamond reaches the center of the scale, it means the aircraft is perfectly positioned on the descent path. The pilot (or autopilot) initiates the descent, configuring the aircraft for landing by lowering the landing gear and extending the flaps to generate lift at slower speeds. The aircraft now slides down this invisible ramp, maintaining a constant rate of descent.

Phase 4: The Stabilized Approach

From this point until the final moments, the focus is on stability. A "stabilized approach" is a critical safety concept in aviation. By 1,000 feet above the ground, the aircraft must be:

• Fully configured (gear down, flaps set).
• Aligned with the runway.
• Flying at the correct target speed.
• Descending at the correct rate.

Phase 5: The Decision Height (DH)

As the ground rushes closer, the crew approaches a critical altitude known as the Decision Height. This is the moment of truth.

Visual Confirmation

At this specific altitude (which varies based on the category of the approach, often 200 feet for standard operations), the pilot flying must look outside. To continue the landing, they must clearly see visual references—such as the approach lights or the runway markings.

"Continue" or "Go-Around"

The pilot monitoring calls out "Minimums."

• If the pilot flying sees the runway, they reply "Landing" and typically disconnect the autopilot to hand-fly the final few seconds (unless performing an autoland).
• If the runway is not visible due to fog or rain, the pilot must immediately announce "Go-Around," apply full power, and climb away to try again or divert to another airport.

Phase 6: Touchdown and Rollout

If the runway is in sight, the transition from instrument flying to visual flying occurs.

The Flare

Just above the runway (around 30 to 50 feet), the pilot gently pulls back on the control column. This raises the nose, arresting the descent rate for a smooth touchdown. The throttles are pulled to idle.

Rollout

Once the main wheels touch the concrete, the pilot deploys spoilers (panels on the wings) to dump lift and activates reverse thrust to slow down. Even during this ground phase, the localizer signal can still provide guidance to help keep the aircraft centered on the runway until it slows to taxi speed.

The Engineering Behind the Precision

While the pilots execute the procedure, the reliability of the entire process rests on the ground infrastructure. The radio signals must be unwavering, regardless of environmental conditions.

This is where advanced infrastructure design becomes essential. In regions with harsh climates, standard equipment can struggle. The sophisticated airport engineering Qatar utilizes at Hamad International Airport demonstrates how to secure these systems against extreme heat and humidity. By housing transmitters in climate-controlled shelters and using corrosion-resistant antenna arrays, engineers ensure that the guidance signal remains stable and precise, giving pilots the confidence they need to execute these steps safely, every single time.

Conclusion

The landing process using precision instruments is a testament to human ingenuity. It transforms a high-stakes, complex maneuver into a structured, repeatable series of steps. By breaking the landing down into phases—preparation, interception, stabilization, and decision—pilots can safely navigate through the most challenging weather conditions.

Next time you hear the landing gear extend while flying through a cloud layer, you can appreciate the intricate choreography happening in the cockpit and the robust technology on the ground guiding you safely home.