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Maintenance

Stop and go

In June, easyJet signed a 10-year wheels and brakes MRO agreement with UTC Aerospace Systems. Ian Harbison visited the London Service Centre where the work will be carried out
 

The London Service Centre is one of six worldwide that look after wheels and brakes manufactured by UTC Aerospace Systems (UTAS). Three are located in the US supporting the Americas; one in Hong Kong supporting Asia, and one in Australia. The UK Centre supports Europe, the Middle East and Africa from its location at Hemel Hempstead north of London and close to the M25 orbital motorway, providing easy access to all the major airports.

 

Howard English, Service Centre Manager, says the facility relocated about 18 months ago. As it was an empty building, the new layout could be organised from scratch for maximum efficiency, using the parent company’s ‘Achieving Competitive Excellence’ philosophy, a combination of Lean and good efficiency practices.

 

The customer base is more than 60 large airlines that have outsourced this type of work. For easyJet, which has been a customer since the start of its Airbus operations, the new contract added 100 A320neo aircraft. He explains that large fleets produce higher volumes, which is good for maintaining a constant flow of work. The wheels and brakes are from aircraft where UTAS is the OEM for the wheels and brakes, including Airbus (A320 Family, A330, A340 and, coming soon, the A350); Boeing (747-400, 747-8, 777 and 787); Bombardier (Q400); Embraer (ERJ 145) and Sukhoi (Superjet). The company is also the OEM supplier for the Embraer E-Jet E2. All of these use carbon brakes, which account for roughly 80% of the brake throughput, but older 737s and 757s still produce work on older generation steel brakes.

 

The London Service Centre sees around 14,000 wheels per year, plus 5,000 heat sinks and 2,500 brakes. The larger number of heat sinks is because, of the six centres, only London, Los Angeles and Hong Kong carry out this work, so units arrive separately.

 

More typically, complete wheel and brake assemblies arrive as a single unit, complete with tyres. The tyres are removed and sent for retreading, or replaced with new for redelivery. The wheels are then unbolted into two halves, cleaned, and given a visual inspection and an eddy current check to check for cracks. The brakes are removed and go through a similar process. If there are no problems, they are reassembled and shipped back to the airline with a turnaround time of a few days.

 

This is the usual process for the first three visits to the shop. On the fourth visit, it is time for an overhaul. For long haul aircraft, brake overhauls occur normally every 2-3 years, whilst for short haul aircraft, with greater utilisation, it is every 10-12 months.

 

The wheels have all paint removed (using a non-chemical plastic stripping medium) and checked for corrosion and damage. In addition to eddy current checks, they also undergo penetrant dye inspection. The same procedures are followed for the mechanical part of the brake.

 

For the carbon heat sink, the discs wear over time. A wear pin shows ground crew when the limit has been reached and the unit should be sent for overhaul. Usually, about 50% of the carbon discs will be replaced. This can be achieved with new items or with carbon material machined to size. Occasionally, the carbon has to be treated with a UTAS proprietary antioxidant protection system. While deicing fluids have become less of an environmental hazard, the greener chemical formulation can react with the heat sink material. It also affects the landing gear in some cases, he notes.

 

Overhaul turnaround time is typically about 5-10 days. One unusual aspect of the work is the electric braking system for the 787. This uses electric actuators to compress the discs instead of the more conventional pistons. The Centre can release actuators back to the airline if they have been checked and found serviceable, while unserviceable items have to be returned to the company’s Sensors and Integrated Systems division in the US. As a result, an exchange pool is held in Hemel Hempstead.

 

As that might cause logistical complications, English explains that the Centre is tied into the company’s Enterprise Resource Planning system. This allows the six centres to monitor progress, offload work in case of overcapacity at one location, and share inventory. This coordination, along with careful planning, means that AOGs are generally avoided.


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