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Maintenance

Power curve

Future aircraft deliveries mean support requirements for the trusty CFM56 engine will continue to grow and develop. Ian Harbison spoke to the OEM and MRO providers to get their view of the market
 

CFM

Bill Brown, General Manager, CFM Marketing, says the engine manufacturer continues to look at upgrades to the engine, even though production will soon start to transition towards the next-generation LEAP family. Increasingly, however, any such upgrades will have to consider production costs to the company and installation costs to the operator. Of course, support for engines in service will not stop after the production transition – the company expects to be producing CFM56 spares until 2045.

 

One trend that is starting to have an impact, he says, is the growth of operators in harsh climatic conditions and/or emerging markets, such as China, India and the Middle East. These areas can carry the additional hazard of sand and dust ingestion from the air or from less-than-perfect runways. Despite this, about 50% of future aircraft deliveries are expected to go to these regions.

 

While GE Aviation introduced the Debris Rejection System on the GE90 (with doors located behind the booster, but ahead of the core, which are designed to collect material and pass it down the outside of the engine), he says these aircraft may make only one flight per day in tough conditions, as they head out to the more benign environments of Europe or North America. On the other hand, low-cost carriers in these regions operating CFM56-powered aircraft will be flying as many sectors per day as possible, thus facing an increased likelihood of engines suffering from ingestion problems.

 

One of the main hazards lies with dust and sand particles which can not only erode the leading edges of blades and vanes, but also block the cooling holes in blades, shrouds and nozzles. To understand the problem, the company has developed a special rig at one of its engine test sites that simulates this effect by injecting sand and dirt into the engine. This is proving successful, with engineers reporting that the rig is producing very close matches to real life conditions.

 

Improvements being made include better sealing (to prevent material entering in the first place), improved cooling hole patterns, and the redesign of the ducting (a 180º turn in a duct causes a loss of pressure that deposits material out of the airstream).

 

One of the most important benefits to come from these upgrade programmes is that the solution can be incorporated into new engines at the design stage, Brown says, and both the Debris Rejection System and harsh environment upgrades have already been seen in LEAP. Additionally, improvement programmes, such as Tech Insert and PEP for the -5B and the -7BE upgrade, are extending engine life. They also make older materials obsolete and so keep the spares market alive.

 

Brown says the CFM56 has the lowest maintenance cost in the business, at $100 per flight hour. Much of this comes from having a less complex, single stage high pressure turbine – an engine section that can account for 35 to 40% of costs – as well as from extended time on-wing. Data shows that engines are running to LLP limits at 20,000/25,000/35,000 cycles and 75% of the total fleet are yet to have a shop visit.

 

When they do come in for service, there is a wide choice of MRO facilities. Brown thinks there may actually be some overcapacity in the market at present. However, he does concede that the company’s policy of having a much more open network, compared with its competitors, is now being recognised by assessors as having a positive effect on the residual values of the CFM56. With competition lowering prices, this in turn reduces maintenance costs for operators. It also means engines stay in service longer, lowering the lifetime costs. The two partners, GE Aviation and Snecma, account for around 50% of overhauls but, even here, there is an element of competition to avoid the dangers of being perceived as too dominant.

 

As the number of older engines increases, changes have to be made to their maintenance requirements, with customers preferring to use repairs and refurbished materials. Incidentally, he points out, if the repairs are CFM-approved there is no effect on the engine’s TRUE status. He says the company operates in the open market to acquire materials but, as an OEM, it sometimes has a commercial advantage, as obtaining older engines for teardown can be included as part of a deal for new engines.

 

Aero Gulf

A new entrant into the CFM56 MRO market is Bahrain-based, Aero Gulf Group, which not only specialises in aviation, but also hospitality, real estate, food processing and catering. It purchased the former Pratt & Whitney Norway Engine Centre in Stavanger in 2013, renaming it the Aero Gulf Sola Engine Centre. With engine shop developments in Turkey and China, the facility fell outside the OEM’s strategy and was closed in 2012. In turn, it had been purchased by Pratt & Whitney in 2000 from the former Norwegian operator Braathens SAFE, so there has always been a good understanding of airline needs, says Glenford Marston, Manager Engineering & Operations for Aero Gulf.

 

At the time of the purchase, the shop employed about 190 people. It has been re-established and now has 80 staff, with a future head count of 125 and a capacity for 120 engines per year when fully operational. He says many of the former employees were snapped up by the oil and gas industry, in recognition of their skills, however the vast majority of the current staff consists of returnees. Those figures also show that the venture is intended to be much more efficient as they adopt more of a standard Lean approach to process improvement. >>


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