Airport Runway Surface Friction Testers

Friction Values

A Bangkok Airways ATR-72 passenger plane was substantially damaged when it skidded off the runway at the Thai resort island of Koh Samui in August in 2009. It was raining heavily. The airplane collided with a building previously used as a control tower but used for the fire brigade in 2009. Alas the pilot was killed.

Fortunately co-pilot, cabin crew and the 68 passengers survived, unfortunately four of them with injuries. The plane was damaged beyond repair and scrapped.

For its flight PG266 Krabi-Koh Samui, Bangkok Airways uses the ATR 72 – a twin-turboprop, short-haul regional airliner from the French-Italian aircraft manufacturer ATR. It is operated by a two-pilot crew and seats up to 74 passengers in a single-class configuration.

The plane skidded into a building previously used as a control tower and these days the base for the fire-fighters. An islander, who saw the accident, said that the nose of the plane crashed into the tower. The left wing hit the roof of a nearby utility building. Most of the damage to the plane was at the front.

The crash occurred at around 1415 local time (0715 GMT). Koh Samui lies some 480 km (290 miles) south of Bangkok. The airport runway was closed after the accident.

Friction is vital for a safe and efficient flow of people and goods, and to minimise and reduce the risk for accidents and incidents, says Fredrik Graflind, ASFT. Jetliners & airplanes, cars, trucks, buses, motorcycles all depend on friction between runway/road and wheels/tires.

 

Could Friction Measuring Have Helped to Avoid This Accident?

This is not for us to say, but rather something to be determined by the Accident Investigation Committee! Let us simply establish that fresh friction values, measured by a continuous friction tester from ASFT, immediately transferred to the control tower and announced to incoming aircraft pilots at least make pilots prepared for slipperiness and difficult braking in the case of nasty weather conditions. It can also help them decide to choose another airport for safe landing.

Friction is an Interaction Between Runway Conditions and Tire

Wet or dry, warm or cold, icy or snowy, surface material and surface wear interact with tires on the plane’s landing gear, says Fredrik Graflind, CEO at ASFT. The landing gear’s rubber quality, pattern and wear, pressure and temperature as well as strong winds and the efficiency of the brakes also influence braking results.

Major airports measure friction in windy or other hazardous conditions that may have an influence over braking efficiency. It is performed by a purpose designed vehicle travelling at 95 km/h during the measuring process. In a case as described here, the Routine Performance Manual in some airlines could well state that reduced brake efficiency occurs at values below

0.4 µ. Friction measuring is a procedure rarely applied at smaller airports. ASFT, however, is also developing technology matched to smaller budgets.

The New Generation Surface Friction Tester

Continuous Friction Measuring Equipment (CFME) is a sophisticated measuring system for both operational and calibration measurement. In the operational service, as an aid to ongoing air traffic, the immediate availability of the measuring system makes it possible to carry out measuring results as defined by ICAO and report the results to the traffic control in real time.

There is a wide choice of vehicles for the installation ranging from: Volvo V70 & FWD70, Skoda Octavia, Saab 9-5 wagon, VW Sharan, Ford Galaxy, Ford Taurus and trailer mounted systems. For temporary use we even offer a handheld friction tester unit. All systems are based on a stabile technology platform with high repeatability in measuring results.

For immediate announcements to pilots on incoming aircraft, friction values are transferred in real time to the control tower (Top). The ASFT continuous friction measuring technology can be built into a number of different vehicles (Middle) or trailer mounted (Bottom). ASFT is based on a reliable technology platform providing a high degree of repetitiveness.

Self-Wetting System

The Continuous Friction Measuring Equipment (CFME) can be equipped with a self wetting system. The system puts a strip of water on the runway surface immediately in front of the measuring wheel. The tank volume depends of the vehicle chosen. In case of the Volvo it is 600 litres, sufficient for measuring 8000 meters with a 1 mm water depth.

The ASFT Mark IV Rear-Axle System

This is a new generation of surface friction testers based on the highly successful MK II System. The rear-axle has a third smaller wheel on an arm (transmission arm) attached to it via three chains. This is the measuring wheel. The tyre has a material, shape and a tread which closely resembles those of a normal aircraft tyre. This gives friction readings that closely correlate with true friction values that are received from aircraft operations.

The measuring wheel is not attached to the body or chassis of the host vehicle. It is only connected to the rear-axle via a spring. This unique design allows the friction wheel to work without any disturbance from movements in the host vehicle. It also guarantees that the vertical ground pressure is absolutely constant at 1400 N. Independent research have over and over concluded that ASFT MK IV rear-axle have among the best correlation and repeatability in its industry.

 

New Generation Computer System (NG)

A fast, and reliable presentation of friction values measured is of utmost importance in order to secure safety. The ASFT New Generation (NG) Computer System ensures speed and accuracy.

ASFT New Generation (NG) Computer System combines all our knowledge about friction testing and adds new technology to make the handling and administration of measure results easier, faster and safer. We have added all the functionality that you can expect from a system designed today.

The main goals of Next Generation ASFT CFME have been

• Standard, reliable, proven techniques
• Traceability of measure results
• Authentication of operators
• Fast and easy assembly
• Ability to save GPS position of results
• Ability to perform remote support via internet
• Real time viewing of measuring

 

Early Ice Warning Systems

The Frensor is an active freezing point measuring device, allowing remote presentation of the actual freezing point, regardless of de-icing liquid used. Frensor heads can be installed in fixed clusters with several heads (left) or – for mobile use (right) – in an ASFT car for simultaneous, continuous friction measuring. Big photo courtesy of: Arne V. Petersen, Københavns Lufthavne A/S.


ASFT and Saab Security launches a partnership where ASFT and Saab Security cooperate in developing and marketing it-systems and products for weather monitoring at airports.

ASFT now offer computerised technology: for the detection of the freezing point, precipitation monitoring, ground frost measuring, ice warnings, systems for monitoring ice deposit growth as well as colour/IR camera systems. The technology is purpose built for stationary or mobile use.

With these systems, ASFT offer airports in frosty regions and authorities the technology to help save lives and cut costs.

ASFT supports the work for safe air traffic by developing state-of-the-art friction measuring equipment and products related to weather monitoring. We are the world’s leading manufacturer of continuous friction measuring equipment and our equipment has been approved by internationally recognised institutions. We supply friction measuring equipment that meet the need of any airport or contractor. Our continuous friction measuring equipment is used around the world at 250 airports. A more recent product is weather monitoring systems for airports and other major infrastructural objects. ASFT take ”happy landings” as seriously as you do!