Corrosion Prevention Aircraft Parked During Covid-19 Need Maintenance As Much As Those Still in Service

CORROSION PREVENTION AIRCRAFT PARKED DURING COVID-19 NEED MAINTENANCE AS MUCH AS THOSE STILL IN SERVICE

James Careless

o say that COVID- fleet out of service for an undetermined 19 has been bad period of time,” says Chuck Pottier, for the global president of Zip-Chem Products. airline business would be a serious understatement. Corrosion Doesn’t Spare Parked Aircraft T According to an October 2020 ICAO presentation, the pandemic’s full year (January-December Parking aircraft to save money is 2020) impact will slash gross passenger a risky proposition. This because operating revenues by up to $96 billion Above, Zip-Chem has multiple products to prevent or that airframes and their engines are worldwide, and reduce the overall slow corrosion. Below, Mankiewicz's experts say that highly complex pieces of technology in the right environment, parking aircraft short term number of seats offered by airlines up isn't detrimental to their exterior paint. Zip-Chem and that need to be regularly maintained, to 47 percent. Mankiewicz images. whether they are in daily service or indefinitely parked. In other words, “The pandemic has put a huge financial aircraft are not cars. An airliner strain on owners and operators, and cannot be left unattended for weeks they are doing what they can to reduce on the ground and then reentered spending,” says Emily Romblad, customer into service as if no time has elapsed. marketing manager with Celeste Industries Corporation. This includes parking aircraft This is an inconvenient truth that wherever they can. “Literally every carrier some airlines are doing their best to in the world has taken the majority of their ignore. They are so understandably

16 Aviation Maintenance | avm-mag.com | Winter 2020 AEROSPACE TECH WEEK 26/27 May 2021 | Toulouse, France | www.AerospaceTechWeek.com The natural environmental process of heating and cooling causes condensation which can result in corrosion. Daubert Cromwell image.

of the pandemic many operators corrosion, so it’s important to have repositioned planes to more routinely clean to prevent the buildup favorable dry environments,” says of corrosion causing contaminants.” a Boeing spokesperson. “This has also improved resource and material In fact, the long-term parking of availability for cleaning procedures aircraft has no negative influence and application of protective on their exterior paint, says aviation coatings.” coatings firm Mankiewicz. "UV radiation, humidity and temperature This says, aircraft still deteriorate differences are much lower on the over time in dry storage conditions. ground and therefore cannot harm desperate to staunch the financial They just do so at a slower rate, the protective outer layer," according bleeding that they are grounding especially if the cash-strapped airlines to information that the company aircraft first and leaving any that parked them fail to do required provided to Aviation Maintenance subsequent maintenance issues for a maintenance. For instance, “some magazine. "Resulting dirt can simply later date, hopefully when COVID-19 operators are opting to go longer be washed off and in the worst case has eased and air traffic is on the rise. between cleaning tasks or eliminating the outermost layer, the clear coat, the task altogether,” says Romblad. can even be polished." Unfortunately, this ‘park them “However, soils that build up on where you can’ approach increases the exterior can actually accelerate Engines At Risk During Parking the likelihood of corrosion in airframes and engines alike. This is Aircraft engines are particularly because “aircraft were being parked vulnerable to corrosion when parked wherever they could find room for extended periods of time, as is in what might be less than ideal the case for many aircraft during environments which could be hot and COVID-19. “This new form of humid,” says Jon Jacobson, Av-DEC’s ‘medium-term’ parking presents commercial technical sales team risks,” says Ed Barnes, ExxonMobil’s manager. ‘Hot and humid’ translates global chief engineer for Aviation into environmental conditions that Lubricants. The reason: “Aviation speed up corrosion on metal and turbine lubricants in commercial other aircraft materials. aircraft are overwhelmingly ester- based synthetic lubricants,” Barnes Mankiewicz has been offering corrosion protection Fortunately, “since the beginning for 17 years in cooperation with the Airbus Group. says. “These products have a natural Mankiewicz image.

Get your FREE subscription via ww.avm-mag.com/subscribe Aviation Maintenance | avm-mag.com | Winter 2020 17 Daubert Cromwell recommends using their Nox-Rust 1100 VCI Oil in enclosed spaces to ensure they are protected from corrosion. Daubert Cromwell image.

affinity for water and absorb water extended inactivity. Some of the COVID-19 were highlighted in vapor from the atmosphere at every most vulnerable surfaces – beyond July 2020, when the FAA released opportunity. Once contaminated those inside aircraft engines – are fuel Emergency Airworthiness Directive with water, turbine lubricants begin tanks, fuel and hydraulic lines. (EAD) 2020-16-51 for all parked to form corrosive acids, which can Boeing 737 Classic (CL) and Boeing become quite harmful to engine For instance, the cavity of air above 737 NextGeneration (NG) aircraft. It components over time.” the fluid line is called the ‘headspace’. applied to the engine bleed air fifth During normal operations the air stage check valve on the CFM56 Exposure to elevated water within the headspace, which may engines that power the 737CL contamination over time can also contain moisture is frequently (CFM56-3 series) and the 737NG loosen deposits inside the engine’s exchanged and exhausted. During (CFM56-7 series) on aircraft that were lubrication system, he noted. This idle periods air inside the headspace stored for seven or more consecutive can present issues during test flights, is not exchanged, and the moist air days. or when the aircraft is returned to remains trapped in the headspace. service. “This emergency AD was prompted “Throughout the day the airspace by four recent reports of single- Meanwhile, the practice of packing heats and cools,” says Scott Kotvis, engine shutdowns due to engine large numbers of parked aircraft Daubert Cromwell’s vice president bleed air 5th stage check valves being into whatever space is available of Global Business Development. stuck open,” says FAA EAD 2020-16- presents “an unusual challenge in “Each time it cools, moist warm air 51. “Corrosion of the engine bleed itself,” Barnes says. “This crowding condenses, creating water droplets air 5th stage check valve internal means engines cannot be operated that act as a corrosion electrolyte.” parts during airplane storage may or exercised and, consequently, water Airlines that use products like Daubert cause the valve to stick in the open contamination may accumulate in Cromwell’s Nox-Rust 1100 VCI Oil in position. If this valve opens normally their lubrication systems. Another such enclosures are protected from at takeoff power, it may become stuck challenge is personnel changes corrosion. But those that don’t may in the open position during flight and and ensuring there are enough experience headspace corrosion in fail to close when power is reduced people available to manage all this their aircraft, just by leaving them at top of descent, resulting in an maintenance work.” parked and doing nothing. unrecoverable compressor stall and the inability to restart the engine. Other Vulnerable Areas The Consequences Are Real Corrosion of these valves on both engines could result in a dual-engine Most aircraft systems are vulnerable The unexpected consequences power loss without the ability to to corrosion during periods of of storing aircraft quickly during restart.”

18 Aviation Maintenance | avm-mag.com | Winter 2020 AEROSPACE TECH WEEK 26/27 May 2021 | Toulouse, France | www.AerospaceTechWeek.com and then while on the ground until they are returned to service.

“Corrosion never sleeps, so if the aircraft is in storage of being flown it still needs to be on a corrosion protection program,” says Mark Pearson. He owns Learchem, which makes the ACF-50 (Anti-Corrosion Formula) lubricant that ‘creeps’ ACF-50 (Anti-Corrosion Formula) lubricant 'creeps’ into the tightest seams, lap joints, Zip-Chem recommends assessing the condition of into tight seams, lap joints and around rivet heads to and around rivet heads to displace every airframe and powerplant for corrosion issues displace moisture and corrosive ﬂ uids such as orange prior to parking it. Zip-Chem image. juice, Coke and salt water. Learchem image. moisture and corrosive fluids such as orange juice, Coke, and salt water. prone to corrosion,” says Boeing “Corrosion is like the insidious COVID spokesperson. “These tasks include In other words, the corrosion on 19 virus, except it causes havoc to the cleaning procedures, application these valves could lead to B737CLs airframe, avionics and engines rather of protective coatings and periodic and B737NG’s experiencing dual than to people,” he says. repeat inspections. Boeing guidelines engine failures in flight – just because also advise operators to cycle engines they had been parked for seven Pearson’s point is echoed by Zip- on a set schedule which helps consecutive days or more! Chem’s Pottier. “Airlines need to maintain the health of the engines assess the condition of every airframe and supporting components.” The life-saving remedy to and powerplant that they plan to park this problem was simple aircraft for corrosion issues that need to be Taking Care of Airframes Before maintenance, specifically “inspections addressed,” he says. The place to and During Storage of the engine bleed air 5th stage start this assessment is by referring check valve on each engine and to the specific Aircraft Maintenance When it comes to taking care of replacement of the engine bleed air Manual (AMM) guidelines developed airframes before and during storage, 5th stage check valve if any inspection by the OEM and is not passed,” says FAA EAD 2020- the operator's 16-51. The fact that maintenance engineering solved the problem underlines how staff “to protect important preventative maintenance and preserve is during COVID-19, both before an their aircraft for storage and subsequent return-to- service,” he says. In doing so, “they must be vigilant in the process.”

This approach is endorsed by Many operators have repositioned planes to more Boeing. “The favorable dry environments. Even so, aircraft can AMM Storage still deteriorate over time in dry storage conditions. Zip-Chem image. procedures (preservation aircraft is parked and then while it is tasks) provide sitting on the ground. detailed instructions Protecting Parked Aircraft Through on how to Preventative Maintenance adequately protect the If there is a moral to the tale above, areas of airframe it is that aircraft require preventative and engines maintenance prior to being parked, that may be

Get your FREE subscription via ww.avm-mag.com/subscribe Aviation Maintenance | avm-mag.com | Winter 2020 19 ROCOL says any corrosion that is detected during routine inspections of parked aircraft needs to be corrected immediately to stop it from progressing further. Protective compounds should be reapplied as required, like the ones ROCOL makes, shown above. ROCOL images.

Simon Parnell knows what he is “A visual inspection every seven considerations,” he says. “First, talking about. Parnell is aerospace days that includes bodywork and engines on parked aircraft need to be sales manager for ROCOL, which protective coverings will highlight periodically operated – long enough makes aerospace lubricants and any corrosion damage that needs to heat the lubricant and drive-off any corrosion protection products that to be addressed through further accumulated water contamination.” have been approved by commercial cleaning, corrosion removal and the and defense OEMs/operators such reapplication of corrosion protection The actual schedule for these as Airbus, Boeing, Rolls Royce compounds.” periodic operations can be and NATO. His company has also determined by consulting with engine given serious consideration to the That’s not all. A more detailed OEMs, and will vary depending on practice of parking aircraft during the inspection of the airframe should where the on-wing engines are being pandemic, and has formulated some be done every 14 days, with the stored. “For instance, if an aircraft sound advice. inspector paying close attention to is parked in a desert location it will wheel wells and landing gear. Any take longer for water to accumulate Before parking the aircraft, “the corrosion that is detected needs to be in the engine lubricant because of exterior should be thoroughly corrected immediately to stop it from lower ambient humidity,” says Barnes. washed, with particular attention paid progressing further, while protection “In this case, operating the engine to wheel wells and landing gear to compounds should be reapplied as for one hour every two weeks may ensure the complete removal of any required. “Taking these proactive be enough. However, thousands of contaminants such as runway ice or steps now together with a robust aircraft are parked today in non- snow removal compounds, sand and inspection routine will go a long way desert airports all over the world dirt to help prevent any corrosion to keeping valuable assets flight fit and their engines may require more issues,” says Parnell. “Once the for when they can be returned to frequent operation for various aircraft has been fully cleaned and any normal service,” says Parnell. reasons.” corrosion removed or treated, carry Fortunately, there are steps out usual lubrication procedures using Protecting the Engines that aircraft maintainers can take a general airframe grease or landing to check engine health on their gear grease then apply corrosion Maintaining aircraft engines is a own. Specifically, “we recommend protection compounds, particularly to top priority for ExxonMobil, and periodically testing the turbine oil unpainted metal parts.” something that Ed Barnes has thought for water (ppm) and monitoring the seriously about. total acid number (TAN), and then Once the aircraft has been parked, comparing these to the levels set regular maintenance is a must. “If “To prevent water contamination by the engine OEM,” Barnes says. possible, inspect each aircraft on and, in turn, the risk of corrosion, “ If the water cannot be eliminated a seven-day cycle,” Parnell says. there are a few maintenance by engine operation, and water

20 Aviation Maintenance | avm-mag.com | Winter 2020 AEROSPACE TECH WEEK 26/27 May 2021 | Toulouse, France | www.AerospaceTechWeek.com ppm or TAN are above engine provides effective moisture barrier and the potential corrosive effects OEM recommended limits, the while being easy to remove prior to if any might be seen in few years,” operator has a few choices: Find return-to-service. says Av-DEC’s Jacobson. “Also, a way to operate the engine more many of the aircraft that are currently frequently, periodically change the Lessons Learned parked due to Covid-19 and the lubricant to remove the water, or 737MAX grounding will need to be move to long-term preservation of The impact of parking aircraft re-inspected before they get put back the lubricant system by adding an quickly during COVID-19 has into service. As these inspections approved preservative chemical to the provided aircraft owners and occur new corrosion issues might be lubrication system.” operators with valuable lessons discovered on the aircraft.” about the importance of preventative Engine lip skins also need to maintenance. A case in point: “The The bottom line? “As extended be inspected and protected on a pandemic’s effects on commercial parking or storage has become the regular basis. “What some airlines aviation have underscored the norm for airlines during COVID- are starting to discover is that water vulnerability of turbine oil to water 19, we anticipate that those and moisture are getting trapped contamination, and the resulting operators that have implemented a underneath the cloth cover or degradation of the lubricant,” robust maintenance and corrosion plastic wrap that are covering their says ExxonMobil’s Barnes. “We protection regime will realize the engines in storage,” says Av-DEC’s recommend airlines continue their benefits of lower costs and shorter Jacobson. “This moisture can start focus on maintaining the integrity of lead-times to return fleets to flight,” to lead to corrosion on engine lip their turbine oil.” says ROCOL’s Parnell. “Overall, we skins, which can result in expensive would like to think that operators and time consuming repairs.” Other lessons may take a while will realize the value in using high According to Jacobson, there are a to make themselves apparent. For quality corrosion protection products few commercially options available instance, “many of the airlines are combined with a robust maintenance for sealing engine lip skins, such currently spraying disinfection spray regime at all times.” as Av-DEC’s SF2470 sealant that into their cabins between flights,

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