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Stainless belts key to aircraft decoy system

Edited by the Engineeringtalk editorial team Jan 23, 2002

Perforated stainless steel strips provided by Belt Technologies Europe are forming an essential component of aircraft self-protection systems manufactured by Saab Tech Electronics

Perforated stainless steel strips provided by Belt Technologies Europe are forming an essential component of highly sophisticated aircraft self-protection systems manufactured by Saab Tech Electronics AB.

The company manufactures BOL electronic countermeasure dispensers with the latest system currently undergoing tests with the US Military.

Belt Technologies has a ten year working relationship with Saab Tech Electronics (previously Celsius Tech) and has played a important role in electronic countermeasure product development with particular emphasis on the role of the perforated steel strip as a drive mechanism in the dispenser.

The advantages of simple and reliable physical off-board decoy flares for combat aircraft to confuse the enemy and avoid target lock-ons have been brought home to the general public over recent years with the wide media coverage of worldwide hostilities.

The effectiveness of such decoys continues to improve thanks to new pyrotechnic materials and methods of deployment.

Central to effective deployment has been the design of the BOL countermeasure dispenser from Saab Tech Electronics which has successfully built systems for aircraft such as the F14, Harrier Jump Jet and Saab Gripen.

When a redesign of the BOL countermeasure dispenser was begun in 1996 to improve its operational performance, the company once again turned to Belt Technologies for design advice.

The key feature of the latest countermeasures dispenser is that it can be inserted inside the missile carriers under aircraft wing tips, thereby avoiding the need to fix extra heavy equipment.

This integrated design was also more suitable in that it would not interfere with the aircraft's other defence or attack systems.

Each BOL dispenser has an elongated design and houses a long stack of countermeasure payload packs.

It operates with an electro mechanical drive mechanism consisting of two perforated stainless steel strips of unequal length on a three pulley system.

The system feeds the pack towards the rear of the dispenser where one pack at a time is separated from the stack and released into the airstream.

The performance and design of the drive mechanism is critical.

Arguably most importantly, the high strength to weight ratio of the steel strip helps to keep the weight of the dispenser as low as possible - as little as 19kg - thereby allowing a wider operating range for the aircraft as well as the potential to carry more missiles.

The steel belts have been specifically designed by Belt Technologies for this application.

Performance is guaranteed in terms of a very tight accumulation of tolerances of no more than 0.152mm over 40 pitches.

This ensures highly accurate and repeatable performance which is absolutely critical to successful deployment of countermeasures.

The width tolerance of the belt is also tighter than that required for more general applications and this has been achieved through the development of a dedicated special manufacturing process by Belt.

The inherent cleanliness of the stainless steel strips ensures that no particulate is generated during operation that may risk jamming the dispenser.

Operational performance is paramount and the steel strips are capable of withstanding extremes of temperature as the dispensers are mounted on the outside of the aircraft.