Greener on the Ground, Cleaner in the Sky

Environmentally friendly MRO can help an airline
become more eco-friendly after takeoff

Even if the environment is not alwaysfriendly to airlines, they try to be friendly to the environment. Airline maintenance departments and independent shops are cleaning things up—in the air by improving engine efficiency and reducing weight and drag on aircraft, and on the ground by many small changes. Air transport is a business, so much of the cleanup is done under the economic pressure of high-priced fuel or tougher regulation.

On the ground, SAS maintenance conforms to local laws on chemical use, water disposal and air quality that sometimes are stricter than even EU-wide regulations, notes Lars Andersen, director-environment & sustainability. It has reduced power consumption in offices, hangars and vehicles. Fortunately, SAS maintenance can use electricity generated by wind and water, plentiful in Scandinavia. The airline works hard to recycle both its aircraft and their parts. “This will become more and more important,” Andersen argues. “Aluminum and titanium are very energy intensive.”

SAS has added winglets to its 737s, generally those operating flights of more than 3 hr. where fuel savings are large and economics most attractive. Added weight and expense of retrofitting discourages winglets for short-haul flights. “If you add 250 kilos and it flies less than an hour, winglets can actually increase fuel consumption,” Andersen explains.

During off-wing overhauls the carrier will upgrade CFM56 engines on older 737s with a technical insert to improve fuel use and reduce nitrogen oxide emissions. Winglets and engine upgrades combined should cut fuel consumption and emissions by 3%-4%. It also has removed weight wherever possible; for example, by ending hot-meal service on some flights, thus shedding cooking equipment. Its short-term goal is reducing fuel used by existing types 6%-7% from 2005 to 2011. Through 2009 it achieved a 4.3% saving.

UPS Airlines Aircraft Maintenance and Engineering sends batteries to a metal reclamation facility where components are recycled. Used oils and Jet A are sent to a recycler, refined and sold on secondary markets. Used filters are drained so fluids can be reclaimed and metals recycled. Absorbent pads are recycled. UPS washes engines on all 757s, A300s, MD-11s and 767s and works with OEMs to reduce aircraft weight. For example, it collaborated with Airbus to cut the weight of cargo-handing systems on A300s and is doing the same with Boeing on 747-400s.

The cargo carrier has switched from fiberglass to Lexan containers, lowering container weight by 25% or 200 lb. each. The newest Lexan containers are half the weight of fiberglass models. In 2009, container lightening alone reduced fuel use by 700,000 gal. and CO2 emissions by enough to offset annual driving of 425 automobiles.

It is painting with a pre-treatment called PreKote, which replaces hazardous chemicals and eliminates a third coat of paint, saving 300 lb. per aircraft. It is experimenting with a new polyurethane topcoat less likely to degrade over time, thus requiring less repainting. All aircraft are washed and waxed every 90 days, reducing drag and fuel consumption.

Drag On Efficiency

Fuel-consuming drag has been reduced during maintenance checks by ensuring that gear doors are rigged properly with no gaps; setting flight controls, flaps, slats and speed brakes correctly, and installing fairings properly. Aerodynamic sealants are applied on repairs, cargo and gear doors. Maintenance and operational changes enabled UPS to emit only 1.42 lb. of CO2 per ATM in 2008 and it aims for 1.24 lb. by 2020—42% less than in 1990 and a 20% cut from 2005. Fuel burn is 6.73 gal. per 100 ATMs, a third less than in 1990, and it is shooting for 6.27 gal. by 2020.

In 2006 FedEx brought in an IATA Fuel Efficiency Gap Analysis team to review best practices in operations and maintenance. “We set up a meeting with me and other VPs,” recalls Robert Rachor, VP-planning and performance-air operations. “We were already doing some things, but not all.” The cargo carrier has cut fuel use by 3% by implementing FEGA recommendations. For example, it operated APUs only 0.64 hr. per flight in March 2010, saving 11,000 gal. of fuel annually. “And we were carrying too much fuel.” Excess fuel was trimmed, and engines were washed more frequently.

In maintenance, FedEx eliminated pneumatic leaks that waste engine power in flight. Its shops ensure rigging of control surfaces to eliminate extra drag. It considered adding winglets to its MD-10s but this required too much work on wings. Like UPS, FedEx has worked with container suppliers to get weights down.

The FEGA team revisited recently. “They said we were doing great in some areas but not in others,” Rachor says. The carrier has begun a second round of operational and maintenance improvements aimed at cutting fuel use another 1%.

Shops Propose, Airlines Decide

Engine-makers and overhaul shops are critical to environmental progress. Rolls-Royce spends $800 million a year on research and development. Two-thirds of that sum focuses on environmental effects: Fuel use, CO2 and NOx emissions and smoke. Research influences maintenance and modification of existing engines as well as design of new ones, says Mark Kerr, head of marketing services.

For example, Rolls developed the Trent 700EP, an enhancement package that reduces specific fuel consumption by more than 1%, enough to save $200,000 per year per aircraft. Similar packages are possible for other Rolls engines.

Customers looked to the manufacturer’s Total Care program chiefly to minimize maintenance cost and downtime until two years ago. Now they focus on lifecycle costs, including fuel costs. Best-practice shops develop workscope for overhauls that maintain high turbine gas temperature margins and minimize SFC.

A Rolls subsidiary, Operating Systems and Solutions, works with airlines to reduce fuel burn from the time aircraft are powered up in the morning until they are parked each evening. “They look at minutes on auxiliary power units, taxi time, thrust for takeoffs and other ways of improving fuel efficiency,” Kerr explains. He expects engine OEMs like Rolls, with their design expertise and data-management capabilities, to play an increasing role in fuel-management programs.

OSyS tracks and analyzes airline fuel burn, helping with both operational and engine-maintenance choices. Very few carriers do this well now, according to Customer Business Director Mark Goodhind, due to problems with data quality and availability. He estimates that OSyS analysis can identify an additional 1%-2% in fuel savings and prioritize implementation of IATA initiatives. It has eight airline customers and is seeing growing interest in the solution. The service supports all engines, not just Rolls products.

Snecma does environmental assessment of the entire engine cycle, from manufacture through operation, repair and retirement. Manufacture must conform to Europe’s Registration, Evaluation and Authorization of Chemicals rules, which restrict use of some chemicals and materials in its processes. For maintenance, Snecma develops workscopes that minimize fuel burn. “But workscope decisions are made by our customers,” acknowledges GM-Environmental Affairs Francis Couillard. Engine cleaning decisions also are made by airlines.

All Snecma repair facilities worldwide meet ISO 14000 standards for environmental management, including reduced water usage through prevention of leaks and processes to control energy and electricity. “We also measure our facilities’ CO2 footprint,” Couillard says. The company seeks new machinery to reduce energy consumption, replaces some solvents with eco-friendly chlorinated types and reuses aluminum for part coatings. It also is reducing acid consumed in baths and lessening solder weight to lighten engines and reduce fuel consumption.

Parts are reused as much as possible when engines are retired. To promote this goal, Snecma is part of Tarmac Aerosave, a French group that looks for ways to recycle parts, especially alloy parts, and of the US-based Aircraft Recycling Assn., which develops best practices for disassembly and recycling.

Full-service shops have broader opportunities to aid the environment. The single biggest fuel-saving program at Hong Kong Aircraft Engineering Co. is modifying 757s, 767s and older 737s with winglets, according to Marketing Manager William Davies. “Customers estimate these can save 5%-7% of fuel” on long-haul flights.

The Bare Necessity

There is controversy over another potential fuel saver, stripping paint off aircraft fuselages, leaving only brand insignia. “Taking paint off saves 1%-2% of weight, and if you fill in plates and cracks it should still be a slippy airplane,” Davies notes. But corrosion may increase, adding costs, so carriers still are experimenting with this choice. “They would love to get the weight off, but there needs to be a business case.”

On the ground, HAECO is shifting vehicles toward electric power. “We go at slow speeds over short distances, so hybrids and electrics are ideal at airports,” he says. This rule applies mostly to people-moving vehicles. Aircraft tractors require too much initial torque to dispense with diesel power.

Finally, the company works in state-of-the-art facilities with Leadership in Energy and Environmental Design lighting and in an environmentally easy climate. “We don’t have to retrofit like Europe because our hangars are only ten years old. And we do not have to air-condition or dehumidify hangars, like the Middle East,” Davies says.

Singapore may have a less temperate climate than Hong Kong but ST Aerospace is pushing aggressively to reduce environmental effects on the ground and in the air. “For example, improved engine testing helps minimize fuel use, especially at high-power runs,” notes former President Tay Kok Khiang, who retired last month. “Another example is nondestructive inspection of machining on landing gear parts. This requires stress relief of parts in an oven, which we do in batches to reduce fuel use.”

Common areas use reduced wattage whenever possible. Smaller compressors are used off-peak when fewer workers are present, and air-conditioning automatically shuts down when not needed. The engine shops rebalance temperatures to reduce electricity consumption and prevent uneven cooling. Air leakage is minimized by limited opening of main gates. Water is conserved with restrictors on pipes to control flow rates. Employees are trained and supervised on the most economic methods for washing engines and other parts after disassembly.

Controlling waste hinges on oversight of materials at the source, according to Tay. ST Aero is very strict about toxic-chemical storage, transportation and disposal. Residual fuels and scrapped parts are recycled. “We even recycle plastic blasting media used for paint removal,” he says. The company offers winglet modification and flush repairs that reduce drag compared with external repairs. And it can convert CFM56-5 engines from single annular combustors to dual annular combustors, saving fuel and cutting emissions.