How ILS Works | Instrument Landing System Explained | IFR Training

Summary

This video explains the Instrument Landing System (ILS) and how it helps pilots land safely, especially in poor visibility. It covers how ILS uses radio signals for both vertical (glide slope) and horizontal (localizer) guidance, as well as the use of VOR receivers to track the aircraft's position. The video also explores ILS approach charts, the role of marker beacons, and the significance of proper altitude and course adjustments. Through visual aids and step-by-step examples, it illustrates how pilots use these tools to align with the runway and execute a safe landing.

Takeaways

• 😀 The Instrument Landing System (ILS) helps pilots safely land in poor visibility by providing guidance via radio signals.
• 😀 ILS uses two main components: the glide slope for vertical guidance and the localizer for lateral guidance.
• 😀 The glide slope provides a three-degree descent path and is indicated by a needle on the aircraft’s navigation equipment.
• 😀 The localizer helps the aircraft stay centered on the runway's extended center line, with signals guiding lateral alignment.
• 😀 PAPI or VASI lights help pilots visually gauge their descent angle during approach, with a red-over-white signal indicating the correct glide path.
• 😀 The ILS system uses radio waves at different frequencies (90 Hz and 150 Hz) to guide the aircraft, similar to how VASI works with lights.
• 😀 The ILS approach is typically entered from below the glide slope to avoid false glide slopes created by ground reflections.
• 😀 Marker beacons, or DME/GPS, are used to indicate distance along the approach, with the outer marker signaling when the glide slope is intercepted.
• 😀 Aircraft must tune to the appropriate frequencies to receive ILS signals and align with both the localizer and glide slope.
• 😀 At a decision altitude (typically 200 feet AGL), pilots must decide whether to continue the approach or initiate a missed approach if visual contact is not established.
• 😀 The ILS approach chart provides all relevant frequencies, identifiers, and symbols, which pilots must interpret for a safe landing.

Q & A

What is the purpose of the Instrument Landing System (ILS)?

The ILS provides precise guidance to pilots during the final phase of flight, particularly in low-visibility conditions, by using radio signals to ensure exact alignment with the runway for a safe landing.

How does the VASI system help pilots during approach?

The VASI (Visual Approach Slope Indicator) system helps pilots by indicating whether they are too high, too low, or on the correct glide slope through a set of red and white lights, ensuring they remain on the proper descent path.

What is the difference between the glide slope and the localizer in ILS?

The glide slope provides vertical guidance to keep the aircraft on the correct descent angle, typically 3 degrees, while the localizer provides horizontal guidance to keep the aircraft aligned with the runway centerline.

How do the signals of the ILS system work to guide the aircraft?

The ILS system uses two radio frequencies, 90 Hz and 150 Hz, to transmit signals. The aircraft receives these signals and when they are perfectly overlapped, it indicates that the aircraft is on the correct approach path. Deviations from this signal help pilots adjust their course or altitude.

Why is it important to intercept the glide slope from below in an ILS approach?

Intercepting the glide slope from below is crucial to avoid potential false glide slopes caused by ground reflections, which can occur when the aircraft is too high during the approach.

What role does the VOR receiver play during an ILS approach?

The VOR (Very High Frequency Omnidirectional Range) receiver helps pilots interpret the ILS signals, such as the glide slope and localizer, by displaying needle indicators that guide the aircraft on both the vertical and horizontal approach paths.

How do marker beacons assist during an ILS approach?

Marker beacons, such as the outer and middle markers, help pilots determine their distance from the runway and key points during the approach. The outer marker usually indicates the point where the glide slope is intercepted.

What is the significance of the decision altitude in an ILS approach?

The decision altitude (usually 200 feet AGL) is the point at which pilots must decide whether to continue the approach and land or initiate a missed approach if they cannot see the runway or if conditions are not favorable.

What happens when the aircraft goes off-center from the localizer or glide slope during an ILS approach?

If the aircraft deviates from the center of the localizer or glide slope, the respective needle on the navigation equipment will show a deflection, signaling to the pilot that they need to correct their course or altitude to stay on the proper approach path.

How does the localizer signal change with the length of the runway?

The width of the localizer signal at the threshold of the runway is fixed at 700 feet, but the angle of the transmission varies depending on the length of the runway. Shorter runways will have a more angled localizer to ensure that the 700-foot width is maintained.