Millimetre Wave Radar for Foreign Object Detection

FOD is an important security, safety, and quality control issue in any aviation environment; where small debris, loose objects and wildlife have the potential to cause damage to airport equipment and delays to runway operation.

Debris on runways and taxiways costs airlines and air forces millions each year in damage caused to aircraft. The most notorious incident was the Paris Concorde accident in 2000, in which a millimetre-thick piece of metal led to the deaths of 113 people and ultimately, the end of supersonic flights.

In 2019, aircraft manufacturer Boeing estimated that FOD costs the industry $4 billion a year. Additionally, we must consider the indirect costs to the aviation industry, such as flight delays, decreased fuel efficiency, workforce absences and not forgetting the cost of protracted legal cases.

Threats from FOD can comprise very small items where early detection is paramount, particularly on runways during take-off and landing, so risk to passenger safety is mitigated.

Airport workers are increasingly made acutely aware of the need to avoid FOD; especially after a recent case of a ladder slipping off the back of a maintenance truck on an active runway at Birmingham airport, where it sat for more than half an hour. Three aircraft landed, but luckily none of them hit the ladder. Such close calls are too risky – for operations, for lives and for the associated issues and costs mentioned above.

Plextek has applied its technology and engineering expertise to the problem, designing, developing, and deploying an effective, automatic FOD solution, which can be fixed or mobile.

Based on highly accurate millimetre wave radar technology, the fixed solution sits atop an 11-metre tower, monitoring for any debris 24-hours a day, and sending detection information to an Integrated Operating System within a minute. It can detect a 2.5cm object – as small as an M5 nut and bolt, for example - from 400m away, and will identify items such as stone, metal, plastic, rubber, glass, and organic matter.

The system can detect very small foreign objects at a range of +400m with very low false alarm rates. it has greatly enhanced situational awareness for detecting foreign objects to a very small size at short range, increasing airport runway safety and security.

The technology is designed to be low size, weight and power to reduce deployment cost and time to market and deliver maximum performance with 100% target illumination - even during early-stage development.

A bespoke system installation might take six to seven months but given current supply chain issues in the semiconductor market, installation may not take more than ten months, so close cooperation is key between Plextek and the buyer to facilitate progress.

The mobile version comprises a radar sensor and a military-grade Electro-Optical or Infra-Red camera (for night-time FOD) mounted atop a vehicle, which then drives around the site scanning for foreign objects.

The advantage of the mobile solution is that objects can be identified and dealt with in real time. The solution in both forms is weatherproof and will operate between -32 and 50C.

Operator console displays can be installed in multiple locations, with a minimum of four such consoles recommended. Data and images can be shared between the control tower, ground control and system operators and standby in real time.

Like any technical system, on-going maintenance is vital. While Plextek can provide maintenance, a foreign airport will benefit from a combination of remote and locally provided maintenance delivered via a technical support agreement, rather than via direct support.

Of course, Plextek provides full system documentation and operating manuals. Guidelines and training are also provided for any local airport maintenance team, to ensure ongoing smooth operations.

In terms of system reliability – or in the event of a power cut, operations can be performed for about 30 minutes through the system’s own UPS. If the power outage time is longer, procedures for stably turning off the system power must be performed What is the reliability of the system? For instance, what happens when the airport power goes down?

The system has obtained CE certification and reliability to US military (MIL-STD) standards – which include testing procedures designed to determine how equipment holds up under certain conditions — such as temperature, impact, vibration, humidity, and others — to ensure electrical stability.

How it works in a typical airport

System operation is complex, so separate training is delivered prior to live operations.

Methods of processing foreign objects found by the system need to be optimised for each airport – accounting for the different personnel, department and procedures present in every airport environment.

Under normal conditions, when the system's radar detects a foreign object, the camera automatically points to the object’s location.

The system operator checks this, determining the size and degree of danger. If immediate collection of any debris discovered is necessary, they contact the control tower to request the runway to be opened.

After the runway is opened, the operation team's vehicles are allowed to enter it, and can be dispatched to collect the FOD.

If the detected FOD is low risk and does not need to be collected, only a record of the detected object is left, and the alarm turned off.

Since these judgments and procedures differ from country to country and airport to airport, airport personnel who install and operate the system need to create a clearly defined process, specific to their own needs and requirements.

Plextek FOD Radar case study: Incheon Airport, Korea

The Challenge

Wave Tech, a Korean-based RF signal technology company, required a radar-based Foreign Object Detection system for airport runways, capable of rapidly detecting small debris in all weather conditions. They required a low-cost solution that could be easily deployed without compromising the high-performance necessary for reliable operation.

The Approach

Plextek produced a dual fixed and mobile antenna solution capable of detecting objects and movements from a fixed radar at 400m range for the airport.

We designed and mounted a fixed antenna along the runway for stationary scanning and detection. A mobile system, a 300mm antenna for rapid rotation, was also delivered, designed to be vehicle roof mounted to scan the runway while moving.

Enhancing the situational awareness of the technology involved using advanced signal processing algorithms to discriminate between wanted and unwanted signals and to separate detection of targets near each other.

The Outcome

Our mm-wave radar solution delivered 100% target illumination results in early-stage development tests, displaying accuracy and detection equivalent to a single fixed antenna.

The advanced design enabled our client to produce highly accurate FOD results with reduced deployment costs and time to market.

Plextek also delivers ongoing system maintenance, in the form of weekly, monthly, and semi-annual inspections.