As GPS Jamming Rises, Airports Are Reinvesting in Ground-Based ILS and DME

Availability of satellite navigation is not guaranteed and this is an increasing concern for aviation. There have been reports of GNSS jamming and spoofing events in several areas, but they do not make satellite navigation unusable everywhere; they are a reminder that aircraft need reliable backup options during approach. That’s why airports continue to invest in ground-based systems, working with an established ILS antenna manufacturer in India to maintain and upgrade equipment that does not depend on satellite signals.

Why Ground-Based Navaids Are Back in the Plan

GNSS jamming and spoofing may result in a localized degradation of the accuracy or availability of satellite positioning, often for a given time or area. This is a real operational problem, not a theoretical one, and aviation authorities are paying attention.

ILS and DME are ground based navigation aids and do not use satellite signals, so GNSS jamming and spoofing do not affect them. This makes them a useful complement to GNSS and not a full replacement. As GNSS-based systems have proliferated, many aviation authorities, including India’s Airports Authority of India, have continued to calibrate and install ILS and DME equipment” and add a link to an AAI, DGCA or ICAO source right after its of ILS and DME equipment, indicating the practical value of having both approaches together.

How ILS Localizer and Glide Slope Give Independent Guidance

·         ILS is not satellite based. It uses ground-based radio transmissions to give pilots lateral and vertical guidance to line up with the runway on approach the lateral and vertical guidance to line up with a runway on approach.

·         Localizer vs Glide Slope Roles

The localizer antenna provides lateral guidance to keep the aircraft on the extended runway centreline on approach. The glide slope glide path antenna gives vertical guidance and tells the pilot if the aircraft is on the correct path down to the runway threshold.

The two systems work together to guide the aircraft along a predetermined approach path. An ILS antenna transmits the required radio signals from the ground, allowing the system to provide guidance even when nearby satellite signals are being jammed or disrupted. Unlike GNSS-based navigation, ILS relies on ground-based radio signals rather than satellite positioning.

·         DME as a Position Backup When GNSS Is Denied

·         Distance Measuring Equipment (DME) gives pilots distance information by measuring the round-trip time between the aircraft’s interrogation and the ground station’s reply. The range data is used for navigation, approach procedures and other systems.

Siting, Category Goals and Flight Checks

Choosing airport navigation equipment is more than just checking the specifications of an antenna on a data sheet. The system performance is influenced by the runway and airport layout, antenna siting, obstruction and multipath considerations, the required ILS category, coverage requirements, equipment alignment, and local environmental conditions. Commissioning generally involves flight inspection or flight checks to verify that the installed system performs as required prior to use in operations.

·         Achievable ILS Category

·         The achievable ILS category is based on the entire system, not on any one component. Selecting an ILS antenna for a specific installation involves considering equipment performance, siting quality, signal integrity, monitoring capability, the runway environment and applicable aviation requirements. The antenna alone does not define the category; it is one part of a coordinated ILS system.

·         Materials and Wind Rating

 Airport antennas are exposed to harsh outdoor conditions for many years, so construction materials, mounting structure, corrosion resistance, mechanical strength and wind loading are all important. When choosing an ILS antenna supplier, these factors should be considered along with the antenna's performance and alignment requirements. A glide slope antenna, localizer antenna or high gain DME antenna not only has to meet performance requirements during initial testing but also maintain its mechanical and electrical performance through years of temperature changes, rain and wind exposure.

How Antenna Experts Supports Navaid Programs

Antenna Experts, New Delhi, is an ILS antenna manufacturer in India with 35+ years of experience in antenna design, backed by in-house design, manufacturing and testing capabilities. The company is certified ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018, registered NATO NCAGE and has export experience with installations in more than 60 countries.

Antenna Experts manufactures ILS antennas and related navaid antennas, where RF performance, mechanical construction, environmental durability and project-specific specifications are engineered together and related navaid antennas where the RF performance, mechanical construction, environmental durability and project specific specifications all have to be engineered together. That mix of in-house design and testing is important for airport programs where equipment needs to meet demanding technical requirements and withstand years of outdoor exposure.

FAQs

1.     Why keep ILS and DME if GPS exists?

In some conditions, GNSS can be subject to jamming or spoofing, so airports have ground-based systems such as ILS and DME that provide a form of navigation independent of satellite signals, and  support  operational continuity alongside GNSS, not instead of it.

2.                How does ILS work without satellites?

ILS uses ground-based radio transmissions from localizer and glide slope antennas to provide lateral and vertical guidance for the approach . ILS can be independent of any satellite input for positional information .

3.                Can DME back up GNSS navigation?

Partly. DME can support navigation when GNSS is degraded, especially when ranges from several stations are combined (DME/DME . DME provides radio-based range information from a ground station that can be used to support navigation in the event of GNSS degradation or unavailability. It provides useful range data as part of a larger system rather than replacing GNSS positioning on its own.

4.               What decides the achievable ILS category?

The category is based on the complete installation, including performance of the equipment, siting, signal quality, monitoring, the environment of the runway and applicable aviation requirements, not just the antenna used.

Planning Your Next ILS or DME Project

Airports and ANSPs planning new installations or upgrades can discuss antenna design, siting considerations and project-specific requirements, including ILS, DME and high gain ATC antenna needs, with Antenna Experts to support a system built to meet real operational needs.