Boeing 737 MAX planes have been stuck on the ground now for five months. With the likelihood rising that they won’t return to service before the winter, some airlines may soon have to deal with the danger that the planes could literally become stuck to the ground.
Tires of planes that are parked for long periods of time can freeze to the tarmac during subzero weather, warns a Boeing maintenance manual for the previous generation of 737 aircraft. It advises maintenance workers to place sand or a coarse fiber mat under the tires and covers over the wheels and brake assemblies to protect them from the corrosive effects of rain and snow.
With the end of summer drawing closer, Air Canada is considering moving its 24 737 MAX planes south to the gentler climes of a desert storage yard, a spokesperson told Forbes. WestJet says it’s content to keep its 13 planes in Canada, spooling up the engines every week and taking them for a spin on the apron around their hangars.
Airlines have had 387 MAX planes sitting quietly at airports and storage facilities around the world since March, when the second of two horrific crashes led aviation authorities worldwide to ground Boeing’s best-selling plane. Boeing is storing roughly another 200 that it has assembled but can’t deliver.
Planes are built to move. Making sure these aren’t damaged from their prolonged grounding has become the mission of a small army of maintenance staff. The longer the planes’ wings are clipped, the more needs to be done. Among the main tools, as prescribed by the 737 manual: copious amounts of yellow 3M vinyl tape No. 471 to seal off gaps and sensors, and an array of lubricants.
Southwest Airlines, the largest operator of the 737 MAX, is storing its fleet of 34 planes in the dry heat of the high Mojave desert at an airfield in Victorville, California. Once a week, maintenance workers power up the Leap-1B engines, which their maker, CFM International, a partnership between General Electric and Safran, recommend should be idled for 15 to 20 minutes to vaporize any moisture that may have collected in the oil and fuel systems and to cover engine parts with a new coat of oil to prevent corrosion. Southwest technicians also boot up the flight computers and auxiliary power units weekly.
The doors of planes stored in the desert are generally opened during summer days so the cabins aren’t damaged by the heat, says David Querio, president of Ascent Aviation Services, which operates at Pinal Airpark in Arizona, one of the largest aircraft storage yards in the world.
Birds sometimes nest on a plane, and, rarely, an animal will take advantage of an open door to take up residence inside. “They’re removed the same day if they’re stupid enough to do that,” says Querio.
As the timeline for the 737 MAX’s return has receded further over the past few weeks, some airlines could decide to put their planes into a state of deeper storage, with the engines preserved and batteries and other sensitive parts removed, says Tim Zemanovic, president of the Minnesota aircraft disassembly firm Fillmore Aviation. Because it requires fewer regular maintenance tasks, this type of storage generally runs half the cost of active storage, at roughly $1,000 a month per plane, he says, but it means it would take more time to ready the planes to fly again when aviation regulators sign off on Boeing’s fixes for the 737 MAX.
In long-term storage, the engines, the single most valuable part on an airliner, are “pickled”: The oil is drained and replaced with an oil mixed with a corrosion prevention solution, and desiccant bags—larger versions of the moisture-removing silica packets put in consumer goods—are placed in the inlets, with gauges that monitor humidity levels. Then the ends are covered to keep out the elements, animals and insects, says Zemanovic, who used to run a storage and maintenance facility at Pinal Airpark.
When planes are dormant for more than two months, Boeing’s 737 maintenance manual calls for gaps in the fuselage to be sealed with vinyl tape and screens placed over drain holes. A protective coating is sprayed onto unpainted metal surfaces. The cabins go dark, with the window shades closed and cockpit windshields covered with aluminum foil tape or other reflective material. Cotton covers are put over the seats and runners protect the carpets.
Planes at a storage yard typically get visited at least once a day to make sure the exterior coverings are intact, says Querio.
The 737 manual lays out a schedule of maintenance procedures to be done at regular intervals that’s heavy on lubrication of myriad parts.
Every week the plane should be scanned for corrosion; every two weeks, electrical systems powered up for two hours. Every 30 days the plane should be moved a third of a wheel’s turn, to prevent the tires from getting flat spots; carpets and seats checked for mildew; and water drained from the sumps of fuel tanks to prevent growth of bacteria or fungi, which can have the consistency of mayonnaise and plug fuel filters.
Every 90 days, the flaps, rudder and other control services need to be exercised.
If the grounding extends to a year, the landing gear may need to be flexed, says Zemanovic, with the plane propped up on giant jacks placed under the wings and the nose. Boeing and Airbus recommend that some models should be restored to operating condition after a year before being shut down again, says Querio.
Boeing expects aviation regulators to sign off on its fixes for the 737 MAX and a revised training regime early in the fourth quarter, but given previous delays and new technical issues that have arisen over the past few months, some industry watchers think the plane’s return to service could slip further. Southwest Airlines has taken the 737 MAX off its flight schedule till January 5; Air Canada has scrubbed the plane through January 8.
A Southwest spokesman said that once the U.S. Federal Aviation Administration declares the model airworthy, the airline expects it will take 120 hours of work on each plane to get them ready to fly again, and 30 to 60 days for the airline’s whole fleet.
One giant task: cleaning the planes. Dust can collect inside planes stored in the desert if the doors are vented, requiring a thorough vacuuming, says Zemanovic, and if the storage facility doesn’t have a concrete wash pad with drains to properly dispose of large amounts of soapy water, workers may have no choice but to wipe down the plane by hand, a laborious process that he says could require a “couple hundred” man hours. Two necessities for the job: 27-foot high work platforms and a mammoth supply of cleaning wipes.